Recent advances in analytical tools including more sensitive detection techniques have led to the discovery of microbial biosignatures in ultra-low biomass samples such as the oceanic lithosphere. Here, energy fluxes are low and microbial life has adapted to the slow cycling of sparsely available food and nutrient sources along cracks and fissures and the access to Earths chemical energy through water-rock interactions. Nevertheless, our understanding of the habitability of Earths lithosphere and potential connections to the surface world are still in its infancy. Rock-hosted microbes produce unique biosignatures such as diether and tetraether lipids produced by both bacteria and archaea. These lipid biomarkers can be used to trace chemo(litho)trophic life in extant, but also in past ecosystems due to their exceptional preservation as chemical fossils in mineral precipitates. Here, we present lipid data from a diverse set of past and present lithospheric habitats, ranging from the lower ocean crust to active and inactive hydrothermal vents and subsurface mantle rocks to terrestrial ophiolites in order to explore the diversity and abundance of microbes found in these systems. Furthermore, we will discuss the approaches we currently have in place to elucidate microbial metabolisms, microbe-mineral interactions and their potential roles in global geochemical cycles.

Iron (Fe) plays an important role in aquatic environments as an essential, often biolimiting micronutrient but at very high concentrations can potentially be toxic. Consequently, microbes have evolved capabilities to influence Fe bioavailability through production of organic molecules, so called ligands, which can enhance iron bioavailability or be used for detoxification mechanisms. Hydrothermal vents represent a major source of Fe to the oceans and host specialized microbes that are likely capable of influencing Fe speciation through ligands. Through abiotic decomposition of marine dissolved organic matter (DOM) or abiotic synthesis, hydrothermal systems might themselves constitute an additional source of Fe-binding ligands. Iron complexation in these systems is likely crucial in mediating Fe distribution to the water column but the interdependencies are still not well understood. Here we present first insights from experiments that incubated hydrothermal plume microbes in an artificial seawater dilution over a range of different Fe concentrations. The results show how variable Fe levels in conjunction with dissolved organics control Fe-binding ligand systematics and ultimately how this relates to the structure of the microbial community. At lower Fe concentrations the final community structure is more diverse with certain Epsilonproteobacteria as the most dominant group. Overall, ligand concentrations remain relatively low but the diversity of documented Fe-binding DOM formulas is high. In contrast, high Fe incubations are dominated by a group of Gammaproteobacteria and show high ligand concentrations but a very limited diversity of Fe formulas. These findings are further discussed in context of DOM characteristics and ligand stability constants.

A novel hydrothermal system was discovered at the summit of the underwater Tagoro volcano at 89–120 m depth after the 2011–2012 eruption, characterized by the low-temperature venting of Fe-rich fluids that produced a seafloor draped by extensive Fe-flocculate deposits. The basanite-hornitos are capped by mm- to cm-thick hydrothermally derived Fe-oxyhydroxide sediment and contain micro-cracks and degasification vesicles filled by sulfides (mostly pyrite) and covered by sulfur-oxidizing bacterial mats. Electron microprobe studies on Fe-oxyhydroxide crusts show the presence of various organomineral structures, mainly twisted stalks and sheaths covered by iron-silica deposits, reflecting microbial iron-oxidation from the hydrothermal fluids. Sequencing of 16S rRNA genes also reveals the presence of other microorganisms involved in sulfur and methane cycles. Samples collected from hornito chimneys contain silicified microorganisms coated by Fe-rich precipitates. The rapid silicification may have been indirectly promoted by microorganisms acting as nucleation sites. We suggest that this type of hydrothermal deposits might be more frequent than presently reported to occur in submarine volcanoes. The discovery of this mineralization system and associated microbiota identifies a potential Fe-based chemosynthetic ecosystem, which typically have been studied at spreading centers and arc volcanoes. This underscores the importance of geomicrobiological interactions in shaping mineral deposits on Earth today, and in the geological past. This hydrothermal system provides an excellent laboratory to study the formation and evolution of newly formed hydrothermal deposits and their association with microbiota at an intraplate hot-spot volcanic edifice under low-temperature, shallow-water conditions.

At magma-poor rifted margins, serpentinization of lherzolitic mantle rocks releases molecular hydrogen (H₂) that supports chemosynthesis-based deep life. Until now, however, H₂ fluxes in these systems remain largely unquantified. To help closing this knowledge gap we investigated serpentinization and H₂ production using drill core samples from the West Iberia margin (Ocean Drilling Program Leg 103, Hole 637A).

The mostly lherzolitic samples are strongly serpentinized, consist of serpentine with little magnetite, and are generally brucite-free. Serpentine can be uncommonly Fe-rich, with X_Mg = Mg/(Mg+Fe) < 0.8, and exhibits distinct compositional trends towards a cronstedtite endmember. Bulk rock and silicate fraction Fe(III)/∑Fe ratios range from 0.6–0.92 and 0.58–0.8, respectively. Our data show that more than 2/3 of the ferric Fe is accounted for by Fe(III)-serpentine. Mass balance and thermodynamic calculations suggest that the initial serpentinization of the samples at temperatures of <200°C likely produced about 100–250 mmol H₂ per kg rock, which is 2–3 times more than previously estimated. The cold, late-stage weathering of the serpentinites at the seafloor caused additional H2 formation.

Owing to generally lower geothermal gradients, the amounts of H₂ produced under conditions close to/within the habitable zone at magma-poor margins are likely larger than those at slow-spreading mid-ocean ridges. These settings may hence be particularly suitable environments for hydrogenotrophic microbial life.

The observation of oxidized arc melts has led to a discussion about the redox conditions during the dehydration reactions of serpentinites in subduction zones. The discussed range of oxygen fugacities (fO₂) between+5 and -2 log units relatively to the QFM buffer allows sulfur to be present either as oxidized or reduced species.

This work investigates the development of the fO₂ with serpentines form the western part of the island Elba in Italy. We compared observations of opaque mineral phases and silicates with thermodynamic models. The opaque mineral phases have previously shown to be a good indicator for the redox conditons during the hydration of ultramafic rocks.

The samples have faced different metamorphic grades during the contact metamorphism of the 6.9 Ma Mt. Capanne pluton up to the Amphibole-facies. The peak assemblage shows the paragenesis of prograde grown anthophyllite and olivine. The omnipresence of magnetite between 500 °C and 650 °C indicates an fO₂ above the QFM buffer at these temperatures. However, the fO₂ does not exceeded the Mt-Hm buffer because hematite has not formed. The maximum fO₂ is 2 log units above the QFM buffer and limited due to the ubiquitous presence of pentlandite in the serpentinites. The most abundant paragenesis of pentlandite-magnetite-heazlewoodite and pentlandite-magnetite-pyrrhotite is in equilibrium with 0.01-0.1 mol/kg H₂S. Combined with the low sulfur concentrations below 200 ppm in the bulk rock composition a loss of sulfur as a reduced species in the form of H₂S is indicated.

Marine Isotope Stage (MIS) 3 represents a critical interval for understading the response of terretrial environments to rapid climate change driven by orbital focring. As the primary constituent of loess and a major driver in global climate forcing, mineral dust serves as a proxy that allows for direct comparison of loess data with chronologically better resolved ice and lake records. Motivated by the recent emergence of high-resolution magnetic and sedimentological data on European loess-paleosol profiles, we explore advances and drawbacks in comparing regional paleoenvironmental response to millennial-scale climate variability during last glacial cycle. We show that the Lower Danube loess preserves a convincing paleoclimate record that closely tracks the Greenland interstadials/stadials (GI/GS) during MIS 3. To explore regional patterns of change, we focus in comparing loess records with better-established lacustrine and marine records from southeastern Europe. As reliable chronological control is the major limiting factor in exploring the full MIS 3 paleoclimate potential of loess records, we also discuss regional implications in defining an improved loess chronostratigraphic framework based on several lines of chronological evidence, and especially loess tephrochronology.

Loess-paleosol sequences (LPSs) are valuable paleoclimate archives capable to record Pleistocene climate changes. Since the past decades, LPSs of the famous Chinese Loess Plateau and the Danube Basins were investigated by means of rock magnetic and paleomagnetic properties. Less attention is so far paid to Ukrainian LPSs, which are unique in Europe in terms of their large distribution, thickness (up to 60 m) and stratigraphic completeness. Since the alternation of loess and paleosol complexes is caused by the Earth’s orbital parameters, spectral analysis is a method of choice to investigate the imprint of the Milanković cyclicity capable to modify the mineral magnetic composition inside LPSs as a result of alternations of interglacials and glacials.

We present the first conducted spectral analysis of the recently investigated Ukrainian LPS at Roksolany, covering the past 1 Myrs (Hlavatskyi & Bakhmutov in Geol. Quart. 64(3):723–753, 2020). We use independent age control by means of paleomagnetic reversals (e.g., the detected Matuyama–Brunhes boundary) and preserved tephra layers. Since the detailed correlation of the well-known Roksolany tephra layer remains – based on missing geochemical data – questionable in age determination, we test different possibilities derived from wavelet analysis and eccentricity correlation. Furthermore, we reconstruct paleoclimate patterns of the interglacials reflected by magnetic susceptibility variations. Comparison of the results obtained from one the most representative loess archives in Ukraine with those in the Middle- and Lower Danube Basin provides implications for holistic understanding SE European Pleistocene climate evolution.

The research was partly supported by the NRFU grant 2020.02/0406.

At present, it is difficult to obtain numerical astronomy solutions prior to 50 Ma , which should be two reasons for this. First, the solar system's chaotic behavior, namely, small initial disturbances will greatly affect the results of the numerical model of the earth orbit. Second, we do not fully understand the evolution history of the Earth-Moon separation, that is the distance versus time series. Recently, a new method called "TimeOptMCMC" has been successfully applied to invert the paleo-astronomical parameters of Cenozoic (~55Ma) and Proterozoic (~1400Ma). However, only two case studies cannot show the complete evolution process, and there is a lack of suitable way to model and discuss the Earth-Moon separation process.

Therefore, in this study, we perform TimeOptMCMC analysis on four well-studied sections’ proxy sequences to enrich the eccentricity and precession estimates in Paleozoic and Proterozoic. At the same time, we innovatively use a simple continuous Markov monotone stochastic process to reconstruct the Earth-Moon separation history from 2465 Ma to present. Meanwhile, based on the reconstructed Earth-Moon separation simulations, we calculate the tidal drag factor which represents the history of tidal dissipation in the Earth-Moon system.

Our results improve the estimates of palaeoastronomical parameters in the Paleozoic and Proterozoic, providing results with good constraints for tuning cyclostratigraphy in ancient era. Further, we corroborate the previous inference that the Earth-Moon system has a long-term low tidal dissipation, give the Earth-Moon system’s dissipation history trend with stepwise characteristic at large scale, and provide a comparison with other tidal models.

Lake Ohrid (North Macedonia/Albania) is Europe’s oldest lake and thus is a valuable archive for changes of local (hydro)climate during the last 1.36 million years (e.g., Wagner et al. 2019). During an International Continental Scientific Drilling Program campaign in 2013, geophysical downhole logging by the Leibniz Institute for Applied Geophysics acquired continuous datasets of physical properties. Additionally, sediment cores from four sites were obtained, the deepest with a length of 570 m (Wagner et al. 2014).

Investigations of half-precession (HP) cycles (~9,000 – 12,000 years) have been given a subordinate role in previous cyclostratographic studies. Here we focus on HP-signals in Lake Ohrid and investigate the temporal variability of this signal over the last one million years. Next to a connection of HP-cycles to interglacials, we see a more pronounced HP-signal in the younger part of several proxy records.

We relate the results from Lake Ohrid to a variety of proxy records from the European mainland and marine records. The HP-signal is to some extent present in all of the investigated sites and exhibits similarities, but also differences to the Lake Ohrid-records.

HP-cycles are a relevant part of natural climate variability - also in Europe - and allow a more detailed investigation of sedimentary systems.

References:

Wagner, Bernd, et al. "The SCOPSCO drilling project recovers more than 1.2 million years of history from Lake Ohrid." Scientific Drilling 17 (2014): 19-29.

Wagner, Bernd, et al. "Mediterranean winter rainfall in phase with African monsoons during the past 1.36 million years." Nature 573.7773 (2019): 256-260.

The scientific discipline "geology" has relied on outcrops as the primary source of information since its beginnings. The initial equipment to analyse the rocks in these outcrops was simple: hammer, hand lens, compass, and diluted HCL. Topographic maps proved useful to find the location of the outcrop. Fieldbooks and material for sketching were – and are – used to document the findings. The documentation was further improved by cameras which became available for everyone in the second part of the 20^th century. With the beginning of the 21^st century handheld GPS systems became common and hence simplified the localisation. Soon thereafter, smartphones, with their integrated GPS and growing versatility due to a plethora of installable apps unified all the aforementioned analogue tools into one compact device.

In the second decade of the 21^st century drone-technology became popular. These devices enabled an entirely different view on the outcrops. Structure-from-motion-techniques allow for uncomplicated construction of 3D models. Now, that access to mobile internet is given everywhere (except the Eifel), digital and virtual content can be created and accessed everywhere. The smartphone app OutcropWizard combines all the recent advances in technological development. The basic approach of OutcropWizard is to show and geological highlights worldwide and to enable everybody to contribute content to this project.

Even though a smartphone can fulfil most of the tasks, it still cannot replace a hammer. We suggest being loyal to our tradition and carry this piece of equipment as it has been done since the dawn of geology.

Introducing concepts of 3D geology to students can be difficult. While 2D geological maps and pictures are well supplemented by 3D animations and movies in presentation slides, for most students, a true hands on experience with 3D data is only possible in computing labs.

On the other hand, Augmented Reality (AR) is a rising technology that is very accessible by being available on popular handheld devices such as smartphones and tablets. With the development of an app that allows for collaborative viewing of 3D geological models in AR, further concepts to improve education in geosciences have been explored.

With simpler and more direct access to 3D geomodels, students could browse through a catalog of models (e.g. different fault types) whenever they want to refresh their knowledge before the next exam. Teachers could guide larger audiences through a 3D model by highlighting individual parts while every member of the audience visualizes and explores the model on their own device. For smaller study or project groups, models can be discussed while being visualized in the same location and the same state in a shared AR session.

Although these concepts have not yet been applied in day to day education, they pose potential to greatly improve the accessibility of 3D geological data for students and offer ways to enrich the communication of teachers. The author is in contact with the Freiberg University of Mining and Technology to exchange ideas and hopefully apply them in practice soon.

Geoscience teaching has not kept up with technology. The ability to visualize objects in 3D is fundamental in geology, and yet we have hardly integrated any 3D tools in our courses, even though such tools have been available for years. Apart from occasional tests carried out by individuals, there has been no widespread effort to use the latest technology in the classroom and the field. Covid restrictions on travel thus simply accelerated a project we were already working on: the creation of a collection of 3D models of rocks and outcrops to be used as a training aid in the classroom. We expanded the original concept to include also a full 3D virtual environment for students to carry out field exercises.

We have created 3D models of hand samples from our rock collection, and 3D models of key outcrops at several field locations that we normally use in both Spain and Germany, using both hand held cameras and a small drone. Image processing to produce scaled and georeferenced models was done with Metashape Pro. We then used 3DVista Pro to produce immersive virtual field trips. This software allows linking our 3D models, which are stored on public platforms, with videos, photos, maps, text, and realistic sounds for each field scene. A training module in the form of quizzes and game-like features can be incorporated too. The reception from students has been positive, and we plan to keep using these tools extensively even after the covid crisis is over.

GEOWiki@LMU is a constantly growing open platform for the promotion of practical and research-oriented knowledge acquisition elaborated by and for students of earth sciences. The contents are developed by students in courses or on their own initiative in interdisciplinary teams. All topics are discussed in weekly editorial online-meetings and revised in close collaboration with lecturers.

One of the main goals is to provide information on methods relevant to geosciences. Focus is on field, preparation and analytical methods. GEOWiki@LMU offers students a quick overview with helpful practical hints, provides references to relevant literature and links to the courses at LMU where these methods are taught. In addition, there are online tutorials for students, e.g. polarization microscopy. In the so-called GExikOn, articles are currently being created on the topics of rocks, minerals and soils. In addition, the subsection GEOWiki@School is under construction. It deals with school education and can be used by students and teachers. All articles are interlinked with each other.

GEOWiki@LMU can be used flexibly and is constantly further developed. Outstanding is the own initiative of the students working in the GEOWiki-Team. They give decisive impulses for the selection and structure of the topics, write the articles and are involved in acquisition of funding. All graphics, icons and videos are created by students. In addition, the website is programmed by students: what doesn't fit is made to fit.

The content is optimized for mobile devices, so information can be accessed spontaneously in the field, laboratory or comfortably on the couch.

Remnants of pre-Cadomian rocks are scarce in the Variscides including the Bohemian Massif. In the latter, numerous Variscan metamorphosed Mesoproterozoic and Early Neoproterozoic sediments and granitoids are contained in the Drosendorf Unit (DU) in Lower Austria. Here, we present U-Pb zircon ages for two orthogneisses from this unit showing even older magmatic formation ages of 2.10 Ga and 2.05 Ga. These granitoid gneisses with volcanic-arc and within-plate characteristics belong to the oldest rocks known from the Central European Variscides: the Gaberkirche Gneiss (~2.1 Ga), occurring as a relatively small, ~0.3 km² orthogneiss body near Drosendorf, and the Schallaburg Gneiss (~2.05 Ga) located in the south-eastern outskirts of the Bohemian Massif near Melk, where it forms two small bodies with a total area of ~2.5 km².

Although tectonically incorporated into the Moldanubian Zone (Armorica) during the Variscan orogeny, the DU likely represents a part of the Brunovistulian Terrane (BT), which lay north of the Rheic Ocean before the Variscan collisional events. Rare Palaeoproterozoic remnants have also been identified in other parts of the BT in the Velké-Vrbno Dome and the Rzeszotary Horst, the latter being interpreted as a tectonic splinter from north of the Tornquist Line. However, the Meso- to Neoproterozoic rocks of the DU typically show a detrital and inherited Palaeoproterozoic zircon signal, and may thus have been originally associated with a Palaeoproterozoic basement. This could be an important new aspect for future palaeogeographic interpretations.

The Saxothuringian Zone of the Central European Variscides preserves the sedimentary record of the post-Cadomian shelf and an Early Carboniferous synorogenic basin. Thus, this area reflects the transition from a passive continental margin setting to an active plate boundary zone. Particularly the record of the so called “Wrench-and-Thrust Zone” (WTZ) can be regarded as the connecting link between the Peri-Gondwana shelf and the Variscan orogen. The WTZ separates the complex metamorphic stack of the Erzgebirge-Fichtelgebirge Zone to the SE and the Paleozoic lithologies of the Schwarzburg Antiform to the NW. Compared with the adjacent Schwarzburg area, the WTZ differs in two essential points: i) It contains the record of a Late Devonian phase of bimodal magmatism, and ii) it experienced Early Carboniferous stacking that was partially related to a greenschist facies metamorphic overprint. Based on detailed studies such as structural mapping and 3D-modeling we propose the tectono-sedimentary evolution of the WTZ as follows. Late Devonian strike-slip faulting dissected the inner shelf of the W-African promontory of the Gondwana plate, culminating in localized and short-lived magmatism. Continued sedimentation on the segmented shelf is indicated by facies variations and prevailed until the onset of synorogenic sedimentation in the Tournaisean. Due to ongoing Gondwana – Laurussia plate convergence, first collisional tectonics, (D1) occurred in the Middle Viséan and led to SW-directed nappe stacking and the juxtaposition of low grade and non-metamorphic lithologies. The evolved synorogenic basin has been overfilled c. 10 Myrs after the D1 deformation. Late orogenic (N)NW-(S)SE-directed transpression finally overprinted the entire area.

Ancient plate boundary processes define the first order architecture of consolidated continental crust. Therefore, regional tectonic features allow for the reconstruction of plate tectonic processes. Here we explain the Paleozoic tectonics of various orogens of Europe and both Americas in terms of the Pannotia – Pangea supercontinent cycle. Early Paleozoic separation of Gondwana and Siberia from the eastern and western edges of North America, respectively, is compensated by convergent tectonics at plate boundaries surrounding the East-European Craton, eventually leading to the Scandian orogeny of the Caledonides and the initial formation of the Uralides. The complex opening scenario transformed passive continental margins into active ones and culminated in the Ordovician Taconian and Famatinian accretionary orogenies at the Peri-Laurentian margin and at the South American edge of Gondwana, respectively. The final assembly of western Pangea is characterized by the prolonged and diachronous closure of the Rheic Ocean (~400-270 Ma). Continental collision started within the Variscan - Acadian segment of the Gondwana – Laurussia plate boundary zone. Subsequent zipper-style suturing affected the Gondwanan Mauretanides and the conjugate Laurentian margin from north to south. In the Appalachians, previously accreted island arc terranes were affected by Alleghanian thrusting. The Ouachita – Marathon – Sonora fold-and-thrust belts of southern Laurentia evolved from the transformation of a vast continental shelf area into a collision zone. Slab pull as major plate driving force is sufficient to explain the entire Pannotia – Western Pangea supercontinent cycle for the proposed scenario.

Earthquake hazard assessment is crucial for different planning tasks, including the search for a German nuclear waste repository. Germany is located in an intraplate setting with a low level of seismicity and the seismically active faults are incompletely known. To solve this problem, seismotectonic regions (SR) of assumed uniform seismicity can be defined and used as a basis to define seismic area sources to be used in seismic hazard analyses. We have elaborated a new concept for a transparent implementation of geological data. Our basic assumption is that the intensity of past geologic deformation controls the propensity of an area for renewed fault slip and earthquakes. Based on a compilation of published geological maps we analyzed the post-Variscan (<300 Ma) evolution of Germany´s fault network and created maps of geologic deformation intensity for six time slices. The time slice maps were superimposed to give a map of total deformation intensity. Regions of similar total geologic deformation intensity define SR. Comparison of these geology-based SR with recent seismicity (1000 years) shows good correlation in Cenozoic rifts (Lower Rhine, Upper Rhine, Eger grabens) and fair correlation of sparser seismicity in areas of strong and repeated Mesozoic deformation (particularly the “Mesozoic inversion belt” of central Germany). However, the prominent earthquake clusters of Brabant and the Swabian Jura occur in “stable” areas of little past deformation. We conclude that regional geology is a valuable source of information for seismotectonic regionalizations but should initially be analyzed separately from recent seismicity to avoid circular reasoning.

Geological maps are important products of geological work that display results of generations of field geologists’ work. Most original geological maps are generated and utilized at local scales. At regional scales, geological maps have gained in practical significance ever since William Smith’s 1815 geological map of England exemplified the powerful nature of mapping and correlating strata beyond local scales. However, by comparison, geological maps compiled at continental-scales appear to be of limited use outside of geological circles. Often, they are oversized which inhibits their practical use, so they decorate our geoscience hallways and lecture halls for their beautiful colors and their general esthetic appearance. Few outsiders can even read these maps. Their special color-coding, the multiple non-diverging color schemes and their complex legends further inhibit non-geologists from being able to recognize the enormous knowledge stored in these maps. I present an analysis of continent-scale geological maps by visualizing time not represented by the rock record (hiatus) and by examining the dimensions of hiatal surfaces at interregional scales. The maps yield great variability in dimensions and space-time patterns of hiatal surfaces, a behavior which is to be expected in light of interregional-scale processes induced by both, the plate and the plume mode of mantle convection. However, to test models of mantle convection rigorously, the temporal resolution of continent-scale maps must be increased to stages level, i.e., the scale at which tectonic processes take place.

The requirements for radiological protection regarding radioactive substances in water intended for human consumption are established in the Council Directive 2013/51/EURATOM of 22 October 2013. In Portugal, the Directive was transposed to the Decree-Law 152/2017, of December 7, which states that the entities managing water supply must establish a quality control program based on a risk assessment. The risk assessment must consider the results of previous monitoring programs of both groundwater and surface water sources and the results of radionuclides measured in raw water, among others.

To aid the entities managing water supply, risk maps of radon (Rn-222), uranium (U-238 and U-234), radium (Ra-226) and polonium (Po-210) were developed for mainland Portugal by the Laboratory of Natural Radioactivity of University of Coimbra using: (i) results from measurements performed in water samples retrieved from the database of the national regulation authority responsible for water and waste services (ERSAR); (ii) the terrestrial gamma dose rate map at the scale of 1:1 000 000; (iii) uranium concentration (n = 2681) and (iv) radium activity concentration (n = 609) measured in bedrock samples. ERSAR’s database comprises radon (n = 9473), gross alpha and beta (n = 10500), Po-210 (n = 1188), Ra-226 (n = 1143), U-234 (n = 1127) and U-238 (n = 1129) results from 5874 distinct groundwater and surface water sources. In this work, data are presented, methods and challenges for risk mapping of radon and terrestrial radionuclides in water samples are discussed.

Radon (Rn)is a naturally occurring, radioactive gas that is considered an indoor air pollutant. Due to its negative effects on human health, a Germany-wide "Radon Potential Action Plan" was implemented based on the European Directive for Radiation Protection (2013/59/Euratom).

As part of this action plan, areas with high geogenic Rn potential (GRP) need to be determined and surveyed. GRP is based on the measured soil gas Rn concentration and the soil gas permeability indicating higher availability of Rn and hence, a higher potential for elevated indoor Rn concentration. Based on former studies of the Federal Office for Radiation Protection, a medium-to low GRP for the state of Hesse was estimated. Locally high variations in the south are found, primarily due to the Odenwald-Mountain-Range.

Based on the geological diversity and its major impact on the GRP, this study tried to include geological small-scale variations, to estimate an urban GRP map for Darmstadt. For this, 134 measurements of soil gas Rn concentration were used as well as a soil gas permeability map with a resolution of 100 km². The geological classification is based on the Hessian geological map 1:25 000, showing 55 petrographic classes for Darmstadt, from which 16 are represented by GRP calculations showing the highest GRP for silt with 41.39. The other classes are following the tendency that acidic plutonic rocks show higher GRP (18.4), metamorphic rocks medium (10.1), and clastic sediments lower GRP (6.1).

It is a well-known fact that the city of Cluj-Napoca in Romania has a diverse geological stratification, based on the geological data and studies performed on the soil by geologists. Also, the measurements and studies performed of radon in soil conclude the fact that in certain parts, the geological formations lead to a higher concentration of geogenic radon, thus making the soil in this area a radon prone hotspot. The following presentation aims to show the correlations between the radon prone geological areas and the accumulation of high concentrations (indoor radon) in different types of buildings, regarding a few examples of residential buildings like houses and big building categories such as public institutions. The studies performed so far show different accumulation between buildings, but even the way that certain buildings were built in the same area where the soil has a high radon potential. This shows that even if the population builds in high radon prone areas, there is a way to build buildings, following radon building guidelines to limit the diffusion of radon trough out the foundation of the building or even blocking it completely.

There are three key factors when talking about a high radon concentration risk exposure indoors, that are the following: the radon potential in the soil where the building is built, the way and techniques used to build the certain building and the way the building is used on a daily bases.

With the new Radiation Protection Act, the EU member states are required to identify so-called "radon prone areas". In Germany, the federal states are accounting for this task. An important source of information, inter alia, are maps describing the geogenic radon potential (GRP) provided by the Federal Office for Radiation Protection (BfS). Those maps are modelled using measured radon concentrations and permeabilities as well as geological information. Overall, the availability of such data increased significantly in recent times. Consequently, this has resulted in several versions of GRP maps over the last approx. 25 years.

The present study is aiming to assess the evolution of GRP maps available for the federal state of Hesse and to derive “difference maps” that show changes over time. One of the goals is to define the minimum data requirements for a robust prognosis of the GRP. The current GRP map with a resolution of 10 x 10 km is crosschecked with regional geological information in order to reveal possible inconsistencies between the modelled GRP and the geological setting. Finally, for a set of radon measurements underlying the current GRP map of Hesse, soil samples have been taken and analysed regarding their content of Pb214/Ra226 as well as the radon emanation under laboratory conditions in order to investigate if measured concentrations in the field can be explained by in situ conditions. Both regional geological information and soil samples help in the interpretation of the GRP and the difference maps, respectively.

Ukraine is known as a uranium mining country located in the Central-Eastern Europe. The authors have been studying radioecological situation within the Central Ukrainian Uranium Province where the uranium deposits are located (operated, dormant and perspective ones) for more than 10 years already. Radioecological research, including the radon emanations from soils, allowed us allocating radon-hazardous areas associated with uranium mineralization.

The recently studied Mykhailivska ore area (south-eastern part of the Ukrainian Shield) is a unique one in terms of the location of two different types of uranium deposits here. One type is an endogenous deposit represented by the main ore body and almost 20 smaller ore anomalous. The other type belongs to exogenous infiltration uranium deposits type of Paleogene epoch uranium ore formation. The area of 15 km x 20 km was explored and more than 150 measurements of radon flux density (RFD) were made.

The measurement RFD is based on the determination of the activity of radon accumulated due to the inflow of a known area from the soil surface, in a measuring chamber or sampler during pumping with a blower for 5 minutes. The exposure time of one sample is 20 minutes. Areas adjacent to uranium ore manifestations are characterized by increased levels of radon exhalation, which is typical for areas containing uranium minerals.

High and average radon-prone areas were outlined and maps of radon anomalies prepared.

Geological interpretation is supposed to be used while further planned uranium extraction through method of underground leaching within the researched territory.

The area of the Upper Rhine Graben (URG) is known for its geothermal potential. However, the recent interest for lithium co-production from geothermal brines raises questions about the quantification and dynamics of fluid flow paths in the geothermal system at the basin scale. This study aims to better understand the impact of the fluid circulation on the temperature field evolution and on the fluid recharge by performing a 3D thermal basin modeling.

The Buntsandstein group sandstones, constituted by early Triassic fluvial to playa-lake deposits are one of the targeted reservoir layers for geothermal and lithium co-production. They overlay permo-carboniferous deposits and the the crystalline variscan basement. The basement inherited structural network plays an important role on heat distribution and flow pathways on the graben shoulders and within the basement. Faults control also the lateral and vertical reservoir connections and fluid mixing, and thus need to be integrated into the burial model.

In this study, the focus is made on the northern part of the URG between the cities of Haguenau (France) and Frankfurt (Germany). A new structural model and the geometry of twelve sedimentary layers are implemented in TemisFlow® software. The thermal simulation included both conductive and advective heat transfer. The model integrates the Tertiary rift event from 46 Ma to 23 Ma, by coupling the lithosphere with the depositional evolution. The influence of permeability heterogeneity in the crystalline basement, the role of the main graben border faults, and some selected internal faults on the fluid flow were also investigated. The model is calibrated with the available temperature measurement data, vitrinite reflectance data and temperature maps at different depths or horizons.

As a result, the simulations show that the thermal structure of the Eastern part of the URG is mainly controlled by conductive heat transfer, and directly related to the burial. Modeling outputs also highlight the impact of the basement heterogeneity on hydrothermal circulation and the temperature field of the Western part of the URG.

Energy generated from geothermal systems is a good alternative to non-renewable fossil fuels and plays an important role in reducing greenhouse gas emissions. Geothermal energy is generated from the inner parts of the earth as tangible heat. The geothermal energy is distributed between the host rock and the natural fluid contained in fractures and pore spaces of the rocks in the earth's crust. Suitable areas for the exploitation of geothermal energy are related to tectonic activities and hot spots of the earth, which have signs of surface activities such as hot springs, geysers and volcanic rocks. Iran, under the influence of these tectonic and volcanic activities, has large sources of geothermal energy. A geothermal power plant with a capacity of 5 MWe is being built in the Meshkinshahr volcanic zone in the northwest Iran. This research aims to evaluate these resources for electricity generation by studying the available data obtained from the surface and subsurface exploration activities for the entire country. The results of exploratory studies in five provinces of Iran have led to introduction of 35 potential geothermal areas. Among them, the subsurface data of the northwest of Sabalan reveals that this area has a potential electricity generation capacity of about 50 MW. Further investigations and investments are required in particular in the zones where there exist high-temperature hot springs. Therefore, the capacity of electricity generation in this field would be significantly increased.

Achieving a (?) reliable geological model is the foremost step in all underground resource assessments. However, regarding the sparsity of data and lack of knowledge, a spectrum of solutions makes more sense compared to a single deterministic model. It this study, a probabilistic geological modeler (Gempy) is used to understand the effect of existing uncertainty in the data representing subsurface layers and faults. A synthetic single fault model in which both the layers and fault are perturbed is designed. Random numbers are used for perturbation to prevent from any bias. In the first round of uncertainty analysis, thickness of reservoir layer in the footwall and location of the faults are perturbed. In the next round, dip and direction of fault are considered to be uncertain. In each of two rounds, 20 geological realization are resulted to act as a framework for later numerical simulations. After perturbing different elements of the synthetic geological setting and generating mesh (using GMSH) for each scenario (40 ones), TIGER code is exerted to simulate the tracer flow path. All the three packages are open source and availability of Gempy and GMSH in Python ecosystem facilitates the transfer from structural models to a high quality mesh. A doublet system (one injection and one production well) penetrating a geothermal reservoir is simulated in this study. In the base model, only the production well is passing through the fault but adding uncertainty to location of the fault resulted in having realization in which both wells penetrate the fault. Through simulating the tracer path for all geological realizations, sensitivity of results to the location of the fault is clearly observed. Statistical analyses revealed and numerically quantified the effect of structural uncertainty on the flow properties of a doublet system in a geothermal reservoir.

To achieve the Paris Agreement's goal of maximum global warming by 2 degrees, CO₂ reduction is indispensable. Space heating for residential, service and industrial buildings amounts to 26% of EU's final energy consumption with about 3347 TWh/a. Approximately 75% of the heat produced is generated by fossil fuels with high CO₂ emissions. Those Emissions can be reduced by implementation of renewable energy sources, such as deep geothermal energy.

As Part of the Interreg NWE project “DGE-ROLLOUT - Roll-out of Deep Geothermal Energy in NWE” a heat demand map of North-West Europe is developed to determine the spatial heat demand distribution of residential, service and industrial buildings. Subsequently limiting factors including subsurface geology and energy infrastructures are used to identify potential production areas for deep geothermal energy. In addition, potential supply areas of deep geothermal power plants by given annual heat production are estimated. The results will show that there is a great potential for CO₂ reduction through the use of deep geothermal energy, especially in densely populated and heat consuming areas.

Efficient fluid flow and circulation are important for an economically viable geothermal reservoir. One type of underexplored reservoir for high-temperature geothermal exploitation is a crustal fault zone, where hot fluids from depths corresponding to the brittle-ductile transition are brought to the surface via crustal-scale, permeable fault zones. To better understand the evolving permeability of reservoir rock during deformation in the brittle regime—fault formation and sliding on the fault—we performed triaxial experiments on samples of well-characterised Lanhélin granite (France) in which we measured the permeability of the sample during deformation to large strains (up to an axial strain of about 0.1). We first thermally-stressed our samples to 700 °C to ensure their permeability was sufficiently high to measure on reasonable laboratory timescales. Experiments were performed on water-saturated samples (pore fluid pressure = 10 MPa), at effective pressures of 10, 30, and 50 MPa (corresponding to a maximum depth of about 3 km), and at ambient laboratory temperatures. Our data show that sample permeability decreased (by about an order of magnitude) prior to macroscopic shear failure, as the closure of pre-existing microcracks outweighed the formation of new microcracks during loading up to the peak stress. Sample permeability increased following fracture formation (by about a factor of two). Sliding on the fracture to large strains (corresponding to a fault displacement of ~7 mm) did not appreciably change the permeability of the sample, and therefore the permeability of the fracture did not fall below that of the host-rock. Although the permeability of the sample at the frictional sliding stress was lower at a higher effective pressure (by about an order of magnitude between 10 and 50 MPa), the evolution of sample permeability was qualitatively similar for effective pressures of 10−50 MPa. We now plan to use the results of this experimental study to inform numerical modelling designed to explore the influence of macroscopic fractures on fluid flow within a fractured geothermal reservoir.

Reducing the cost of drilling is crucial to economically extract deep geothermal energy as drilling costs can reach up to 70% of the total investment budget (Tester et al. 2006). Unfortunately, traditional mechanical rotary drilling is often far too expensive to enable economical geothermal energy extraction from many deep geologic settings due to the amount of energy rotary drilling requires and due to its significant drill bit wear, causing long, unproductive tripping times to exchange worn drill heads (Schiegg et al. 2015). To reduce deep geothermal drilling costs, novel drilling technologies are required, such as Plasma Pulse Geo Drilling (PPGD) as well as thermal spallation, laser, and microwave drilling, to name a few (Woskov et al. 2014; Buckstegge et al. 2016; Vogler et al. 2020; Walsh et al. 2020).

PPGD is a so-called contact-less drilling technology that uses high-voltage electricity pulses >200 kV that last for ∼2 microseconds to fracture the rock, thereby drilling without mechanical abrasion, reducing/eliminating costly, unproductive tripping times and requiring less energy to break the rock than rotary drilling. Experimentally, Anders et al. 2017 found that PPGD is ∼17% cheaper than mechanical rotary drilling. Analytical studies by Rodland 2012 and Schiegg et al. 2015 suggested that further research could possibly reduce PPGD drilling costs by as much as ∼90% of current mechanical rotary drilling costs. Nonetheless, the fundamental physics that underlies the PPGD process is still poorly understood, and the feasibility of PPGD under deep wellbore conditions requires further investigations. (Zhu et al. 2021) investigated numerically how the local electric breakdown in pores can lead to electric breakdown occurrence across the entire rock sample. Numerically, Ezzat et al. 2021 found that the plasma pressure generated due to the localized electric breakdown in rock pores is high enough to induce rock fracturing for specific conditions, resulting in drilling success.

Here, we present our preliminary numerical modeling results concerning the influence of rock pore characteristics, such as pore fluid, shape, and size on the localized electric breakdown of rock. Our goal is to eventually use these results to further increase the efficiency, and thus, further reduce the costs, of PPGD. Our results show that PPGD is facilitated if the rock pores are filled with a gas and not with water, which is consistent with the experimental findings of Lisitsyn et al. 1998 and Inoue et al. 1999. Also, our results suggest that larger pore sizes and smaller pore pressures are more favorable for PPGD. These findings are valid until ∼1 MPa pore pressure. To extend our model to cover higher pressure ranges, further physical lab experiments are required that investigate the electric breakdown of air at high gas pressures >1 MPa.

References

Anders,-E.-et-al.-(2017).-“Electric-Impulse-Drilling:-The-Future-of-Drilling-Technology-Begins-Now”. In:-36th-International-Conference-on-Ocean,-Offshore-&-Arctic-Engineering.-Vol.-8.

Buckstegge,-F.-et-al.-(2016).-“Advanced-Rock-Drilling-Technologies-Using-High-Laser-Power”.-In:-Physics-Procedia-83,-pp.-336–343.

Ezzat,-M.-et-al.-(2021).-“Simulating-Plasma-Formation-in-Pores-under-Short-Electric-Pulses-for-Plasma-Pulse-Geo-Drilling-(PPGD)”.-In:-Energies-14.16,-p.-4717.

Inoue,-H.-et-al.-(1999).-“Pulsed-Electric-Breakdown-and-Destruction-of-Granite”.-In:-Japanese-Journal-of-Applied-Physics-38.Part-1,-No.-11,-pp.-6502–6505.

Lisitsyn,-I.-V.-et-al.-(1998).-“Breakdown-and-destruction-of-heterogeneous-solid-dielectrics-by-high-voltage-pulses”.-In:-Journal-of-Applied-Physics-84.11,-pp.-6262–6267.

Rodland,-A.-(2012).-“Deep-Geothermal-Energy;-Photonics-for-Harvesting”.-In:-Proceedings-SwissphotonicsWorkshop:-Photonics-for-Deep-Geothermal-Energy-Harvesting,-pp.-125–129.

Schiegg,-H.-O.-et-al.-(2015).-“Electro-pulse-boring-(EPB):-Novel-super-deep-drilling-technology-for-low-cost-electricity”.-In:-Journal-of-Earth-Science-26.1,-pp.-37–46.

Tester,-J.-et-al.-(2006).-The-Future-of-Geothermal-Energy.-Impact-of-Enhanced-Geothermal-Systems-(EGS)-on-the-United-States-in-the-21st-Century.-Idaho-National-Laboratory.

Vogler,-D.-et-al.-(2020).-“A-numerical-investigation-into-key-factors-controlling-hard-rock-excavation-via-electropulse-stimulation”.-In:-Journal-of-Rock-Mechanics-and-Geotechnical-Engineering.

Walsh,-S.-D.-et-al.-(2020).-“Simulating-electropulse-fracture-of-granitic-rock”.-In:-International-Journal-of-Rock-Mechanics-and-Mining-Sciences-128,-p.-104238.

Woskov,-P.-P.-et-al.-(2014).-“Penetrating-rock-with-intense-millimeter-waves”.-In:-2014-39th-International-Conference-on-Infrared,-Millimeter,-and-Terahertz-waves-(IRMMW-THz),-pp.-1–2.

Zhu,-X.-et-al.-(2021).-“On-the-Mechanism-of-High-Voltage-Pulsed-Fragmentation-from-Electrical-Breakdown-Process”.-In:-Rock-Mechanics-and-Rock-Engineering,-pp.-1–24.2

Over the past fifteen years, Bavaria has become a hotspot for deep geothermal utilization in Europe. There are now 24 plants operating in the Molasse Basin that provide climate-friendly heat, electricity and cooling. For example, the state capital plans to cover its district heating supply in a climate-neutral manner and largely from deep geothermal energy by 2040. However, the use of deep geothermal energy is not limited to Munich.

The demand for space heating and hot water calculated in this study is just under 160 TWh. A total of 99 district heating demand areas in Bavaria were identified where district heating is a potential supply technology. These areas correspond to almost 50% of the total heat demand in Bavaria. According to the estimates, the deep geothermal potential in the Molasse Basin alone could supply 80% of the district heating demand (7655 MWth). To raise the enormous potential, theoretically about 500 doublets, i.e. production and injection wells, would be necessary.

The discovery of further geothermal wells, and thus the basic prerequisite for the economic success of deep geothermal energy, can be predicted comparatively well for the Molasse Basin. However, there are significant local differences in terms of predictability. Comparatively good well-finding forecasts are given in particular in Munich, south of Munich and in the eastern Molasse, where there is already a comparatively high number of successful wells today.

Geothermal energy is particularly strong in base load supply. The prerequisite for operating a deep geothermal plant economically is that the heat can be purchased in sufficient quantities via a district heating network. In many parts of the Molasse Basin, particularly favorable geothermal conditions exist, but these do not directly coincide with heat consumers on the surface. In these cases, there is the possibility of using interconnected pipelines to transport the heat to the consumers, thus optimally exploiting the potential. The construction of larger interconnectors increases the amount of geothermal energy extracted and consequently its share in the heat supply - the number of required plants is minimized. If fossil fuels are displaced from the heating network, large amounts of CO2 can be saved - about two million tons per year in the case of base load coverage by deep geothermal energy. The analyses show that the interconnection pipelines can also have a positive effect on the heat generation costs and increase the reliability of plants.

The implementation of a deep geothermal project involves high investment costs. These costs are further increased by the construction of larger interconnectors. However, for interconnection pipelines across municipalities to transport green district heating to neighboring municipalities and beyond, there are currently no equivalent funding mechanisms available as there are for on-site heat production. The technology will become economically attractive for municipalities or investors when the initial costs, especially for drilling, network expansion or interconnection pipelines, become lower and can be supported by society.

Delft geothermal project (DAPwell) is a planned geothermal well doublet, where relatively cold water is going to be injected through one well into a low enthalpy geothermal reservoir to produce hot water from the other well. The volume of the cold water around the injection well will increase over time and, in the end, result in a thermal breakthrough. Thus, it is essential to trace the time-lapse change in the volume of the cold water to monitor the DAPwell efficiently. The invaded reservoir volume by the cold water is associated with a decrease in the pore fluid temperature and salinity. This increases the electrical resistivity of the geothermal reservoir, where the cold front is located. Hence, estimating the time-lapse change in the electrical resistivity of the geothermal reservoir can be used to identify the distribution of the cold water. From a theoretical point of view, the controlled-source electromagnetic (CSEM) method can be used to get information about the change in the electrical resistivity within the geothermal reservoir. In this study, we investigate the feasibility of monitoring a geoelectric model of the DAPwell using land CSEM forward modelling. The optimal source frequency is also investigated as well as the optimal source-receiver offset.

A subsurface model of the DAPwell is illuminated by a horizontal electric dipole source, which emits a sinusoidal field with many frequencies. Based on the numerical experiments, surface measurements do not pick up sufficient time-lapse signal to use them for field applications. On the other hand, the difference in the z-component of the electric field, recorded in a borehole that crosses the reservoir, allows for a feasible detection of the electrical resistivity changes within the geothermal reservoir. However, it is not determined yet if the spatial distribution of the cold water can be adequately revealed from the electric field responses, or this needs to be done through CSEM inversion.

The residential sector consumes a significant amount of energy globally, with the majority being produced through the use of fossil fuels. Residential microgeneration technologies, such as photovoltaic systems and micro wind turbines for electricity production, and solar thermal systems, biomass boilers, and heat pumps for thermal needs, offer an alternative for reducing fossil fuel consumption.

In this respect, the present study aims to examine the determinants of market acceptance of residential ground source heat pump systems in Greece, through a comparison between potential adopters, and potential non-adopters of the system. Factors taken into account include socio-economic characteristics, dwelling characteristics, spatial characteristics, environmental awareness and behavior, as well as perceptions towards system-related attributes.

The collection of data was performed in 2019, through a web-based questionnaire. In total, 451 responses were collected. The statistical analysis, performed through SPSS 20, included a descriptive statistics analysis, a Categorical Principal Component Analysis (CatPCA) to categorize the system-related attributes, and a binary logistic regression –on the basis of the two groups (potential adopters, and potential non-adopters of the system).

The system-related attributes seen as the most significant, include functional reliability, system lifetime, and operation & maintenance costs. Based on the CatPCA, the attributes can be categorized into four groups, namely, convenience, market conditions, costs, and performance. The binary logistic regression model indicates that factors affecting market acceptance of residential ground source heat pump systems include socioeconomic characteristics (gender, age, income), and dwelling characteristics [size, and presence of senior residents (i.e,, older than 65 years)].

The present work, offering new empirical findings concerning the determinants of market acceptance of residential ground source heat pump systems, provides information to policymakers and marketers for the design of tailored actions that can foster the further market diffusion of these systems.

The nature of the tectonic processes that shaped the early Earth remain unresolved, hampered not only by the sparse Early Archaean crustal rock record, but also by the dearth of tangible mantle samples (e.g., xenoliths and diamonds) older than 3 Ga. Investigating the Archaean mantle provides a complementary foil to the knowledge gleaned from the early Earth crust, and can be used to trace the onset of crustal recycling, but also to evaluate the secular evolution of Earth’s mantle regarding its temperature and composition including redox state.

We have conducted an in-situ carbon and nitrogen isotope study of “confirmed” Archaean diamonds from the 3.0 – 2.8 Ga Witwatersrand Supergroup of the Kaapvaal craton in South Africa [1]. While the absolute formation age of the placer diamonds is unknown, nitrogen aggregation suggests diamond residence within the upper mantle for 10 - 400 Myr. Coupled with the depositional age of the Archaean basin, the Witwatersrand diamonds may have formed in the mantle as early as 3.5 Ga, before their transport via kimberlite-like magmatism to Earth’s surface during formation of the Kaapvaal craton.

The d¹⁵N values of 0.5 to +2.7 ‰ determined for the Witwatersrand diamonds are higher than both the ancient and modern mantle (-5 ‰), and overlap with positive d¹⁵N values shown by >3 Ga old Kaapvaal sedimentary rocks. The diamond carbon isotope ratios (d¹³C of -5.7 to -3 ‰) are mantle-like, but increases in d¹³C values from core to rim suggest that the Witwatersrand diamonds formed from relatively oxidised fluids containing CO₂ rather than CH₄. It follows that oxidised CHO-fluids containing recycled crustal nitrogen were present in the upper mantle possibly prior to 3.5 Ga. This observation suggests operation of subduction-style tectonics during the inception of craton formation in the Eo- to Palaeoarchaean. It also implies that the Early Archaean upper mantle was not more reducing than at the present, in alignment with new evidence for an oxidised CO₂-rich early Earth atmosphere created by mantle outgassing.

[1] Smart KA, Tappe S, Stern RA, Webb SJ and Ashwal LD. 2016. Early Archaean tectonics and mantle redox recorded in Witwatersrand diamonds. Nature Geoscience, v. 9, p. 255–259.

The oldest volcanic rocks exposed on Malekula Island, now belonging to the New Hebrides Island Arc, formed in the Upper Eocene to Middle Miocene Vitiaz Island Arc, Southwest Pacific. They are thought to have formed contemporaneously with Fiji and the Izu-Bonin-Mariana (IBM) arc during westward subduction initiation of the Pacific beneath the Indo-Australian Plate [e.g., 1]. To test this hypothesis with regard to the mantle source compositions and contributions from the subducting slab, we provide major- and trace element data combined with Hf, Nd, and Pb isotopes for twenty-seven volcanic rocks of Malekula Island. Our results show that Malekula lavas display similar magma types, i.e., boninite-series rocks, island arc basalts, and MORB-type tholeiites, to the earliest volcanic rocks of Fiji and the IBM arc resembling the sequential stratigraphy of the IBM system [2], rather than the interlayered stratigraphy of early arc rocks on Fiji [3].

Moreover, Malekula lavas display a change in Hf-Nd isotope composition from isotopically ‘Indian’, similar to the IBM arc [4, 5], to mainly ‘Pacific’, like on Fiji [3]. We interpret this progressive change in mantle source composition to reflect the propagation of ‘Pacific’ South Fiji Basin spreading into the Vitiaz Arc. Hence, the Malekula lava succession provides a link between subduction initiation in the Northwest and Southwest Pacific.

[1] Hall (2002) J Asian Earth Sci 20. [2] Ishizuka et al. (2011) EPSL 306. [3] Todd et al. (2012) EPSL 335-336. [4] Reagan et al. (2010) G³11(3). [5] Li et al. (2019) EPSL 518.

Phase changes in the mantle have long been known to play a major role for convection in a one-component mantle. When considering cases with depleted ambient upper mantle and upwelling mantle either chemically or mechanically enriched with basaltic crust, very complex density-difference histories are possible for a wide range of realistic temperature-composition scenarios. We explore the ascent of enriched mantle plumes in ambient mantle using combined thermodynamic and themomechanical modelling. Plumes are unlikely to feel a blocking effect from the negative Clapeyron slope of the 660 phase transition due to excessive buoyancy in the uppermost lower mantle. Hot plumes cross the phases transition at temperatures above the negative slope segment and are even promoted. Instead, they may stall and spread in the upper mantle transition zone for significant periods of time, as this depth is characterized by negative thermal expansion for mantle compositions at elevated temperatures. With time, both, the cooling plume and the heating ambient mantle experience density reduction and secondary plumes can spawn from that domain. These secondary plumes may show large lateral offsets from the deep plume stem and show complex and divers geochemical signatures.

We present phase diagrams of variously enriched and depleted mantle rocks down to 800 kilometers depth and explore density as the parameter governing convection and compositional stratification. Some results are surprising and not all are included in present concepts and models:

(1) Primitive and enriched mantle compositions are buoyant in the uppermost lower mantle compared to depleted mantle, especially, when they are warmer, but also at identical temperatures. Hence, if the upper mantle is depleted compared to the lower, a petrological lower-upper-mantle boundary (LUMB) can be expected several tens of kilometers below the seismic one.

(2) Depleted compositions show the slope-break of the 660 phase transitions at higher temperatures. Hence, the uppermost lower mantle would be an excellent trap for very hot depleted mantle, which could be relevant for komatiite generation.

(3) Primitive and enriched compositions experience negative thermal expansion at high temperatures in the upper MTZ, i.e. they display a density minimum at slightly elevated temperatures. The dynamic consequences for plume rise are enormous and explored in a complementary contribution (Vesterholt and Nagel).

The key phase for effects above is garnet, which (1) is stable in the uppermost lower mantle, (2) relatively dens in the upper, but buoyant in the lower mantle, and (3) may become more abundant with temperature. Depending on bulk rock composition, garnet is stable in the uppermost 70-150 kilometers of the lower mantle causing a reversal of the expected density-order in that depth interval. Our present work includes studying seismic footprints of stratification scenarios.

Speleothems are secondary cave carbonate deposits and an established terrestrial paleoclimate archive. Moreover, they have the potential to record conditions in the ecosystem overlying the cave, particularly the vegetation and soil. Coupled records of paleoclimate and -ecological information from a single speleothem would be an invaluable source of information to understand the past and future sensitivity of terrestrial ecosystems to climate change, particularly under the lens of anthropogenic forcing. In order to develop proxies that record unambiguous and quantifiable ecosystem processes, it is necessary to i) understand and characterize how processes in the soil-karst-cave system will affect geochemical tracers that may be sensitive to ecosystem conditions, and ii) develop transfer functions and frameworks that allow the interpretation of such tracers in speleothems over time periods longer than observations.

In this talk, I will discuss ways to approach these problems using different methods. I will show how combining multiple proxy measurements and forward modeling can be used to quantify the temperature sensitivity of soil respiration in the past from speleothem δ¹³C records. Finally, I will discuss the potential of speleothem organic carbon isotopes (δ¹³C and ¹⁴C) as direct tracers for surface ecosystem conditions, and the challenges and opportunities associated with these measurements.

Changes in the surface ocean pH and temperature caused by the uptake of anthropogenic CO₂ are posing a threat to calcifying marine organisms. Recent studies have observed significant impacts on coral reef ecosystems with impaired carbonate skeletal growth and decreased calcification due to acidifying oceans. The current coverage of observations for the northwestern Cuban coastal waters provides an incomplete picture of natural climate variability over interannual to interdecadal timescales, showing the need for high resolution climate archives. Cuba is situated between densely populated landmasses of North and South America offering a unique environment to study multiple aspects of anthropogenic activity across the region as well as their interconnectivity. Sub-seasonally resolved sea surface temperature (SST), δ¹⁸O of seawater, and carbonate chemistry parameters were reconstructed from a massive Siderastrea siderea coral from Cuba’s northwestern coast through a multi-proxy approach since the preindustrial era. Trace element ratios as proxies of SST indicate no significant increase in temperature over the past 160 years since 1845. Over the same time period, coral skeletal δ¹¹B ratio decreased by ca. 1.6 ‰, translating into a decrease of 0.1 on the pH scale, reflecting the acidification of the northwestern Cuban coastal waters. Furthermore, an accelerating depletion of coral δ¹³C from the 1850s to 2005 of 1.5 ‰ demonstrates the changes in seawater CO₂ with an anthropogenic imprint due to increased fossil fuel combustion. Further investigation and the comparison to trace elements indicate possible baseline shifts in regional seawater carbonate chemistry that has been affected by anthropogenic activity.

High-resolution speleothem paleoclimate records with annual to seasonal resolution are helpful for detailed analysis of climatic changes with limited duration (e.g., volcanic climate impacts), but also for longer-duration events (e.g., at 8.2 ka or 4.2 ka). A high resolution paleoclimate data set is also mandatory for meaningful comparison with archaeological or historical records.

Low stalagmite growth rates could impede the acquisition of high-resolution isotope data with the classical micro-milling approach and isotope ratio mass spectrometry (IRMS) analysis. We therefore compared secondary ionization mass spectrometry (SIMS) stable isotope measurements at 7-15 µm resolution with the lower-resolution micro-milling results at 90 µm steps. For the investigated stalagmite from Kleine Teufelshöhle (Frankonia, Germany) the SIMS resolution corresponds to annual resolution, whereas IRMS only reaches a 4-13 year resolution.

Albeit a constant offset, SIMS and IRMS δ¹⁸O data match very well (r = 0.61, p < 0.001, n = 84). This significant correspondence suggests that SIMS stable isotope analysis could be a promising alternative for high-resolution carbonate studies. An adjacent second δ¹⁸O SIMS profile reproduced high-resolution features (r=0.59, p < 0.001, n = 982) and allows a detailed assessment of paleoclimate variability on an annual scale and a comparison with independent climate records, e.g., weather information from historical documents or tree rings.

Stalagmite δ¹⁸O trends closely follow the low-frequency fluctuations of a regional tree-ring record (Land et al., 2019), additionally constraining the stalagmite chronology. The different climate sensitivities of both records enable a more robust and detailed discussion of paleoclimatic variations.

A cave monitoring sets the basis of speleothem studies. It helps to understand changing cave conditions on seasonal scale and site-specific geochemical differences such as hydrological conditions and heterogeneities in bedrock respectively. Here we present a set of parameters measured in La Vallina Cave (NW Iberian Speleothem Archive, NISA). Over the course of 16 months cave air conditions (pCO₂ and δ¹³C) were examined to understand calcite precipitation, ventilation processes and mixing of soil air and atmospheric air. From stalactitic soda straws the δ¹³C_DIC of dripwater was determined to learn about the carbon cycle in the overlaying soil and karst driven by seasonal vegetation and microbial degradation changes. We capture seasonal changes in δ¹³C_DIC independent of degassing/PCP effects. Further, the δ¹⁸O and δD composition of dripwater and hydrology help to understand water reservoir and recharge processes related to precipitation. Finally, the elemental geochemistry of dripwater was investigated by analyzing 16 elements. We present data of commonly used elements such as Mg, Sr, Ca or Ba but also elements sparsely reported in cave dripwater monitoring studies such as Y, Na or As. Controlling factors are related to bedrock leaching, particulate import and potentially redox conditions.

Here, we map a series of stalagmites from Asturias, Spain, by laser ablation inductively-coupled-plasma mass spectrometry and confocal laser scanning (fluorescence) microscopy and discuss the origins of trace element and fluorescence variations. Seasonal banding is evident with both methods and may be attributed to lignins/humic acids based on fluorescence absorption and emission characteristics.
Some lateral variations in fluorescence present as saw-tooth “spires” and demonstrate disruptions of seasonal banding, corroborated by trace element variations (most prominently Mg and Na). Such features likely reflect the differential partitioning of trace elements by sectoral zoning as a result of low supersaturation and/or high organic matter load, combined with the effects of dissolved organic matter on the calcite growth surface and the association of each element with colloidal organic matter. The lateral variability of trace elements demonstrates the pitfalls of obtaining trace element information from one-dimensional transects without prior reconnaissance mapping. It is, however, possible that traditional drilling with ~1 mm holes homogenizes these features and provides reliable trace element estimates.

Geoscience has a key role in adressing the challenges of sustainability, yet in German schools a regular subject such as Earth sciences does not exist. Teacher feel uncomfortable with teaching the content and unless an infrastructure for geoscience education - including educational research and systematic teacher training - is implemented in all 16 German states this situation is unlikely to change. Thus geoscience outreach activities play an important role in informing the society about the processes that determine the continuous development of the Earth as a system. Can they also contribute towards geoscience school education?

The 3D digital model of the outcrop „Devils Table“ (https://digitalgeology.de/der-teufelstisch) was used for instruction in an applied science course called „Geoscience“ with students aged 14-16 years. The aim of this small exploratory investigation was to find out, whether the students were able to identify the rocks characteristics only using the model and to what extend they deduced sensible conclusions about the development of the landscape from their observations. After that, the students received the information provided by the scientist online and were asked to verify their own assumption rsp. to identify and correct misconceptions.

All students showed interest in the task and developed their understanding of the Earth as a dynamic system. The learning outcomes and challenges will be presented and suggestions discussed that can help to enable teacher and students without geoscience background to profit from the digital outcrop models.

The Geowindow offers an infrastructure to create analog models in geographic contexts, it is a “test tube” for visualization; not only of static images but also to display processes in the Earth system. Thus, it is an interactive teaching and learning device for all Earth Sciences.

Due to their enormous temporal and spatial dimensions, most of the complex structures and processes in the context of the earth´s systems and cycles cannot be observed directly. In addition, many geoscientific phenomena remain hidden below the surface.

The Geowindow is an innovative tool for geography lessons allowing to visualizing dynamic and systematic processes of the Earth system. The potential to simulate human impacts on different scales offers a wide range to support an education for sustainable development.

During the last years, the Geowindow has been further developed in a professional way. It offers the experimental infrastructure for modelling many geoscientific structures and processes and is suitable as a teaching and learning tool for all types of schools, as well as for earth science courses in higher education.

The presentation introduces the technical features and various methodological options of the Geowindow. Secondly, we will demonstrate how a geowindow can be used to model different geoscientific processes like the formation of coal, the formation of groundwater or the Eruption of a stratovolcano.

Eventually, we present our project website, which provides tutorials, demonstrations, movies and written guides to support the classroom implementation.

Geosciences only play a minor role in today’s German and Austrian school curricula, although being strongly related to important topics such as climate change and sustainability of resources. The Mineralogical Science Kit (Mineralogischer Lehrkoffer ‘mileko’) aims at bringing back geoscientific and mineralogical contents into STEAM-fields (science, technology, engineering, art, mathematics) by linking mineralogy to regular teaching subjects.

In 5 different modules pupils can not only discover the world of rocks and minerals but also get an understanding of important principles and processes such as redox reactions when extracting copper from ore (chemistry), the density of rocks which can be linked to the structure of the Earth’s interior (physics, geography), or how the inner structure of materials affects their outer appearance by exploring natural crystalline bodies and their geometry (chemistry, mathematics).

Since 2014, about 650 boxes were produced and sent to schools and museums all over Germany. 2020 marked the starting point for the implementation of a rent-a-scientist-program as well as a network of lending stations, where boxes can be borrowed by schools or be used to host workshops for teachers and pupils in-house. In 2021, the development of a video format is planned that will improve and expand the applicability of the Mineralogical Science Kit by presenting relevant geoscientific topics to a wider public.

This new digital format combined with presence activities like workshops and school visits will enhance discussions between children, teachers and scientific experts resulting in knowledge transfer from the scientific community to the public.

A new Geosciences campus will be built in central Munich, that will also house an innovative exhibition on geosciences, the Forum der Geowissenschaften. A team of scientists, curators and museum educators has started to plan the exhibition in the last year.

Currently, a catalogue of topics for the forthcoming permanent exhibition is being prepared. As the topics that we as experts find most interesting do not always coincide with the interests of the public, potential visitors should be involved in the planning process. Therefore, we have conducted an online survey to ask the audience which topics they would like to see in the future Forum der Geowissenschaften.

Participants were asked to rate a wide range of topics according to their interest on a Likert-scale reaching from ‛highly interested’ to ‛not interested’. Moreover, participants were invited to indicate other topics which they find interesting. The survey was distributed via several digital platforms to reach a broad audience and received more than 750 responses. First results indicate variations in interest regarding different age groups, but also between educators and scientists.

Overall, the survey provides a large database about the targeted audiences that will help to refine the exhibition concept. We assume for example, that topics might be rated with low-interest due to insufficient and ineffective communication in the past. Therefore, we aim to create new curiosity for these topics by adopting modern approaches to science communication.

Traditional geological field education includes organized trips of large student groups to geological outcrops. Typically, instructors guide students to outcrops and give (mini-)lectures, such that the students’ notes consist of the provided verbal summaries instead of one’s own sketches and descriptions of outcrops, often leading to poor reports. In 2020, the Covid-19 pandemic prevented group-travel to geological sites, which halted such forms of teaching. To continue field education despite the contact-restrictions, I designed an alternative way of field-based learning through proactive engagement of students in trip planning, site selection, outcrop study, discussion and report writing. The concept involves (1) geotope-sites provided by survey offices (e.g., Geotoprecherche LfU Bayern), because they contain precise outcrop locations and just the right amount of relevant geological information allowing students to visit geotopes of their personal interest on their own. It also involves (2) a shared project on GOOGLE EARTH WEB to which students post field photos, sketches and text, which they present in (3) in the weekly zoom-seminars (geotope seminar). Instructors provide feedback and stimulate discussion among participants based on the presented field observations. The resulting sketches and reports are of higher quality because they are exclusively based on the student’s concentrated work at the outcrop (only 2 per day), although no instructor accompanied any student in the field. The geotope seminar accommodates day trips, multi-day field exercises and mapping projects for geoscience students of all ages and interests. Geotope courses could be offered to the broader public if site access is secured.

Many attempts up to today exist to transfer geosciences to the general public. Some started at the beginning of the 20th century. It is surprising that only since the beginning of the 21st century with the formation of the European Geoparks Network in 2000 and the Global Geoparks Network in 2004, a new, consequent professional way of transfering geosciences was implemented. This includes information, education, geotourism, sustainable development of territories and at sites, e.g. Messel Pit World Heritage Site. These activities have opened people’s minds that landscapes are not „ugly, dirty and dead“. A starting signal was given to explain geoscientific phenomena with discovery activities, enthusiasm, passion and fun for children as well as for adults. Holistic views were initiated and not only fossil or mineral collections presented. By marketing beautiful landscapes, aesthetics of volcanos or reef limestone areas with caves, the interest of large amounts of visitors was raised. A key option however, found during about 18 years of geoscience knowledge transfer is to link up having fun within landscapes, with rocks, fossils and to enjoy a better understanding of where people live. Hands on activities have been reduced to zero during the pandemic of 2020. But why Earth is dynamic, changes landscapes and homes of people, this can be transmitted by edutainment games. An important aspect of this is geo-gamification: virtual and or by hands on, for „Generation Z“, as a key to attract students and too make people aware about the exciting planet Earth we live on.

Hydrothermal activity, triggered by endogenic processes, distributes and redistributes organic matter through diffuse flow networks and may lead to a production of organic matter via abiotic synthesis. Today, hydrothermal seepage, especially at seafloor spreading zones, induces oases for diverse microbial communities in otherwise relatively hostile environments. Furthermore, hydrothermal fluids can deliver organic molecules as building blocks and/or substrates for primeval microorganisms and thus probably played a central role in the emergence of life on Earth. In this talk I will briefly outline evidence for traces of early life on Earth associated with hydrothermal processes from the 3.5 Ga old Dresser Formation (Pilbara, Western Australia). Recent findings strongly support the idea that microbial life in the Dresser Formation was linked to, and perhaps locally fuelled by, hydrothermal seepage. I will demonstrate that integrative study designs including analytical imaging techniques (e.g., Raman spectroscopy), biogeochemical approaches (e.g., catalytic hydropyrolysis and gas chromatography – mass spectrometry), stable isotope analysis and experimental approaches provide important insights into the complex interplay between biological and abiotic processes in early Archean hydrothermal habitats. Thus, they allow us to catch a glimpse into the earliest record of life on Earth.

Modern hydrothermal vents provide diverse environments for microorganisms. Here there is a large phylogenetic and physiological diversity of bacteria and archaea, occurring in a wide range habitats. An assumption is that similar communities of microorganisms have been present on Earth for an extremely long time, given that there is direct evidence of marine hydrothermal activity going back to the Archaean eon (which began 4 billion years ago), and the hypothesis that life may have originated in these environments. In this presentation I will review the fossil record of microorganisms at hydrothermal vents, focussing on volcanogenic massive sulfides (VMS), which formed at high temperature vents, and jaspers (iron-silica rocks), which formed at low-temperature, sulfide-poor vents. Occurrences of microorganisms in VMS go back to the Paleoarchean and in jaspers to the Eoarchaean (3.770, or possibly 4.280, billion years ago), with the latter being the possibly the oldest organisms yet discovered on Earth. These very early dates suggest that life may have been possible on Mars during its equivalent aged warmer period, and that life may be found at putative hydrothermal sites on the icy moons with liquid oceans (e.g. Europa and Enceladus).

The Moodies Group (~3.2 Ga) of the Barberton Greenstone Belt is one of the oldest and best-preserved shallow-water siliciclastic sequences. It also harbors one of the largest occurrences of Paleoarchean microbial mats and the oldest record of early Earth-Moon dynamics. The extent (ca. 40 km * 70 km), lithologic and alluvial-to-prodeltaic facies diversity (incl. paleosols, pedogenic concretions and microbial mats etc.) , good outcrop, and excellent preservation of Moodies strata allows the recognition of mappable systems tracts and sequence-stratigraphic surfaces. However, the lack of biostratigraphic constraints and the nonactualistic Archean surface conditions (absence of vegetation, aggressive chemical weathering, oceanic composition and temperatures, climate, tides) challenge the applicability of sequence-stratigraphic concepts. Well-studied Moodies strata north of the Inyoka Fault zone can be readily subdivided into several 3rd-order parasequence sets. Lower Moodies strata are characterized by an overall increase in accommodation space relative to sediment supply and comparative tectonic quiescence, whereas upper Moodies strata (above a basinwide volcanic unit) record an overfilled basin. Much less is known about the Moodies south of the Inyoka fault zone where the Masenjane Range exposes a section 600-2000 m thick of largely northeastward-prograding, coastal, deltaic and estuarine strata. They record at least five 4th-order shoaling-upward parasequences. Stacking patterns, paleocurrents and provenance indicators show an overall northeastward progradation of facies, likely controlled by local tectonothermal drivers, as evidenced by several syndepositional shallow sills, stockworks, and syndepositional normal faults. These may have been regionally related to the tightening and rotation of the Onverwacht Anticline and the formation of other paleogeographic features.

Geological evidence suggests liquid water on the earth's surface as early as 4.4 Ga when the faint young Sun only radiated about 70 % of its modern power output. At this point, Earth should have been a global snowball if it possessed atmospheric properties similar to those of modern Earth. An extreme atmospheric greenhouse effect, an initially more massive Sun, release of heat acquired during the accretion process of protoplanetary material, and radioactivity of early Earth material have been proposed as reservoirs or traps for heat. We explored the possibility that the new-born Moon, which formed about 69 Ma after the ignition of the Sun, generated extreme tidal friction - and therefore heat - in the Hadean and the Archean earth. We show that the Earth-Moon system has lost about 3 × 10^31 J (99 % of its initial mechanical energy budget) as tidal heat. Tidal heating of about 10 W/m^2 through the surface on a time scale of 100 Myr could have accounted for a temperature increase of up to 5 degrees Celsius on early Earth. Tidal heating alone does not solve the faint-young-sun paradox but it could have played a key role in combination with other effects. Future studies of the interplay of tidal heating, the evolution of the solar power output, and the atmospheric (greenhouse) effects on early Earth could help in solving the faint-young-sun paradox, particularly if tied to geologic evidence.
Details published in
Heller et al. (2021) accepted by Paläontologische Zeitung, PDF pre-print: https://arxiv.org/abs/2007.03423

The sole Archean data point to reconstruct past orbital parameters of the Earth’s moon is from the Moodies Group (ca. 3.22 Ga) of the Barberton Greenstone Belt. From time-series analysis of tidal bundles of a subaqueous sand wave, Eriksson and Simpson (2000) suggested that the Moon’s anomalistic month at 3.2 Ga was closer to 20 days than the present 27.5 days. This is in apparent accordance with models of orbital mechanics which place the Archean Moon in a closer orbit with a shorter period, resulting in stronger tidal action. Although our reexamination of the site confirmed that the sandstone bed in question is likely a subaqueous dune, mud clasts, channel-margin slumps, laterally aggrading channel fills and bidirectional paleocurrents suggest that this bedform was likely located in a major nearshore channel; it thus risks incompleteness. Remeasurements of foresets along the published traverse, perpendicular to bedding, failed to show consistent spectral peaks. Larger data sets acquired along additional traverses parallel to bedding along the 20.5 m-wide exposure are affected by zones of minor faulting, uneven outcrop weathering, changing illumination, weather, and observer bias. Our most robust measurements show a distinct periodicity peak of approximately 14, removed by Eriksson and Simpson (2000) in the original data, and are interpreted to be due to a lunar month of about 28 Earth days, as today. This estimate agrees well with Earth-Moon dynamic models which consider the conservation of angular momentum and place the Archaean Moon in a nearer orbit, rotating faster around a faster-spinning Earth.

Water bearing adits form a historic near-surface underground drainage and outflow systems whose functionality is of considerable importance in many mining areas all over the world. Water bearing adits are technical structures that have often been in place and in operation for more than two centuries. In most cases, they are no longer accessible directly behind the tunnel portal. Therefore, stable hydraulic, geotechnical and rock mechanical conditions are important, otherwise the hydraulic system would collapse.

In recent years, the Research Centre of Post-Mining has investigated the current situation of a large number of water bearing adits in the southern Ruhr area/Germany. To understand the interaction with the groundwater- systems hydrochemical parameters were analysed, the rate of discharge and of precipitation compared. An essential step is the spatiotemporal evaluation of available mine survey maps of the water bearing adits and the hydraulically connected mine workings. This is needed in order to determine the catchment area of a water bearing adits within the groundwater-system.

To further enhance the process understanding the results from monitoring-stations, special depth-dependent hydrochemical sampling campaigns in former shafts and infiltration/tracer tests in ditches/local streams were integrated. The entire data fusion happened in 3D geological/hydrogeological subsurface models. This integrated subsurface understanding is now the enabler for the implementation of a risk monitoring and management system for this sensitive system of water bearing adits.

Mine water rebound in German hard coal mine areas operated by RAG AG under the leadership of RAG Foundation is a showcase for post-mining associated research. It is a long-term, cost intensive and multidisciplinary project affecting highly populated urban areas like the Ruhr District. RAG is facing long-term liabilities as regulatory framework for the rebound process. Currently, mine water is pumped from levels down to 1200 meters to be discharged into local rivers. In the vicinity, monitoring water wells were drilled to identify any hydraulic potential changes in the overburden sections in support of the project’s risk assessment. Mine water management issues comprise control and forecast of mine water levels including to determine a financially and environmentally sustainable level. Mine water treatment, evaluating hydraulic barriers, but most importantly, protecting groundwater for domestic use and even more critical, regional drinking water reservoirs are mandatory prerequisites. We identified natural hydrochemical tracers, worked on in-situ processes affecting mine water chemistry and progressed with petrophysical measurements on core material including clay mineralogy screening to deliver a first step towards an integrative monitoring approach to manage such liabilities. A suite of own and literature-based hydrogeochemical and petrophysical data are presented to better describe the regional hydrology and geology.

Due to the cessation of coal mining in Germany, mine water management in the former coal districts is subject to change and of environmental and economic significance. Since there is no technical need to drain the abandoned coal mines, mine water levels rise. As a result, subsurface rock pore pressures rise changing the subsurface effective stress regime. This may induce local ground movements and activate mining-related and natural fault zones.

In order to develop a better understanding of the processes and their interaction, FloodRisk applies an interdisciplinary approach involving geological, geomechanical, geodetic, and geophysical methods. For this purpose, former German coal districts in the Saarland, Ruhr area, and Ibbenbüren serve as suitable study areas.

Based on a geological 3D subsurface model complemented by petrophysical (porosity and permeability) and structural data (fracture network characterization), geomechanical properties such as slip and dilation tendencies of faults were calculated. These data give insights into the expected fault behaviour under assumed stress conditions and provide a basis for the localisation of suitable areas for soil gas measurements (²²²Rn, ²²⁰Rn, CO₂, O₂, H₂, S, CH₄) using recently developed economic sensors. Simultaneously, seismic events and ground movements are continuously monitored using seismic network, GNSS, Nivellement, and InSAR data and subsequently compared with the evolution of mine water levels. These multidisciplinary observations will be combined in a conceptual model on flood-induced ground movements and seismicity. This enables the deduction of operations for future mine flooding and the establishment of an optimised reservoir management.

After operation of hard coal mines has been terminated in Germany, many of the mines are being flooded. In the project “FloodRisk: Earthquakes, uplift, and long-term liabilities – risk minimization during mine flooding”, the consequences of the rising mine water levels are investigated from a multidisciplinary perspective. Geodetic, geophysical, geomechanical and geological approaches are combined to develop a conceptional model for flooding induced surface displacements and seismicity. Saarland, Ruhr area and Ibbenbüren have been chosen as exemplary investigation areas.

The DMT GmbH & Co. KG (DMT) and the Geodetic Institute Karlsruhe (GIK) contribute to the project by analyzing surveying and InSAR data. DMT installs ten low-cost GNSS-Sensors near Bergwerk Ost and includes them in DMT SAFEGUARD, a proprietary GNSS monitoring system, that provides an integrated evaluation and provision service. GIK is analyzing InSAR data from Sentinel 1a/b and intends to combine GNSS, levelling and InSAR data from different orbits to derive 3D displacements. Challenges that are typical for mining areas as the spatially as well as temporally diverse displacement patterns demand for new solutions in InSAR processing. The so found displacements of the earth’s surface will be integrated with geomechanical modeling in the final phase of the project. In this presentation, the goals, challenges and approaches of FloodRisk with regard to geodesy are discussed and first results are shown.

FloodRisk is an interdisciplinary project focusing on the effects of mine water level rise in abandoned coal mine regions in Germany. Such effects are heterogeneous ground uplift, stress changes due to the change in pore pressure and the reactivation of potential faults. One of the most directly measurable effects is the induced micro seismicity.
In this study the relationship between mine water rise, fluid-induced stress changes and induced seismicity in the Haus Aden dewatering area in the eastern Ruhr area (Germany) will be investigated in more detail. For this purpose, we operate a network of short period seismic stations in the region of the former "Bergwerk Ost" colliery, which had the highest seismicity rate in the Ruhr area during active underground coal mining (closed 2010).
Level of induced seismicity started again when pumps were shut down (mid 2019). We were able to detect and localise more than 1000 microseismic events in magnitude range between -0.7 and 2.6 Mlv. Many of these events are spatially clustered and some show quite high waveform similarity. This allows relative localisation and can increase the accuracy of the location. The depth location of the earthquakes, within the limits of localisation accuracy, agrees very well with the distribution of seismicity at the time of active mining. The measured temporal trend of the mine water level shows a strong correlation with the temporal evolution of the observed micro seismicity.

The task of this European research project (PostMinQuake) is to identify mechanisms, relevant parameters and dependencies causing post-mining seismicity for several European coal regions.

When closing an underground coalmine, the mine water raises by stopping mine water pumping, which can lead to micro seismic events due to the final change of the geomechanical stress-regime.

The consortium partners (FZN-THGA, GFZ, BRGM, INERIS, CMI, SUT, SRK, IGN, Green Gas, DIAMO) will collect and analyse information from the coal basins Gardanne (France) and Upper Silesia (Czech Republic and Poland). In Germany, we will focus in the Ruhr Basin and Ibbenbüren (North-West Germany), which are places with centuries of hard coal mining history and where mining ceased in 2018.

In order to detect the processes that cause micro-seismicity, we are gathering information in the basins regarding geology; mining methods and monitoring protocols; and post-mining situation and seismicity.

This information will be analysed to identify similar approaches to develop a synthesis of good practices, compulsory and desired improvements, as well as an post-mining seismicity map for post-mining seismicity diagnosis. We also aim to develop a Ground Motion Prediction Equation, and the elaboration of criteria of hazard rating.

The final guideline could help the mining industry and decision-making bodies to manage the risks of post-mining micro seismicity, also of interest in old petroleum reservoirs when used to storage H2 or even for geothermal energy.

Acknowledgements: The Research Fund for Coal and Steel funds the PostMinQuake project under the grant agreement No 899192.

The transboundary Cuvelai-Etosha Basin (Namibia/ Angola) is a semi-arid region. Rising population and water demand increase the stress on already scarce water resources. The local aquifers, the perched KOH-0 and the deeper KOH-1 are of limited use, the former due to low yields and microbiological issues, the latter due to often brackish water. A previously unknown deep freshwater aquifer, KOH-2, with high yield and good water quality was discovered at the end of the 1990s. This new resource is a game changer for the region. Therefore, the geological framework of the CEB and its hydrogeological conditions were investigated by detailed geological (core drilling), geophysical (TEM) and hydrogeological studies.

The geological background of the KOH-2 is an inland mega-fan system, reaching from the Angolan highlands in the north down to the Etosha Pan. A 400 m cored borehole revealed three distinct depositional sequences, which cover the last 60 Ma. The lower Olukonda Formation (270-400 m) has poor well yields due to a high degree of heterogeneity. It is overlain by the Andoni Formation, of which the KOH-2 (170-270 m) forms the lower part. The transition between the formations is marked by distinct geochemical changes, indicating different source areas. The KOH-2 is overlain by a sequence of aquitards and aquifers (KOH-1 (80-110 m), KOH-0).

The sedimentology of mega-fans strongly affects the distribution and hydraulic properties of aquifers and aquitards. This knowledge will be useful for the further exploration and sustainable development of the KOH-2.

Due to limited availability of surface water, many arid and semi-arid countries have to rely on their groundwater resources. Despite the quasi-absence of present-day replenishment, some of these aquifers contain large amounts of water that was recharged during wetter periods in the past. Although these recharge events often occurred several thousand years ago, some of these so-called fossil aquifer systems exhibit considerable hydraulic gradients and flow towards their discharge areas, even without pumping. As a result, these systems have more discharge than recharge and are therefore not in steady state, which makes their modelling, in particular the calibration, very challenging. Probably the most relevant explanation for this phenomenon is the long groundwater residence time and the associated long-term head decay of the paleo-recharge mounds.

In this study, we propose a possible approach to deal with this phenomenon during model calibration. Moreover, we analyse the effect of considering and ignoring fossil gradients on aquifer parameterization for the Upper Mega Aquifer system on the Arabian Peninsula.

Further details can be found in a related publication (Schulz et al., 2017).

References

Schulz S, Walther M, Michelsen N, Rausch R, Dirks H, Al-Saud M, Merz R, Kolditz O, Schüth C. 2017. Improving large-scale groundwater models by considering fossil gradients. Advances in Water Resources 103: 32–43 DOI: 10.1016/j.advwatres.2017.02.010

The Yarmouk River is the primary tributary to the Jordan River and a strategic transboundary freshwater resource of Syria, Jordan, and Israel. In the past decades, the Yarmouk watershed has been extensively exploited by the riparian with the construction of dams including the Al-Wehda and Adassiyeh dams. The operation of the dams is guided by international water agreements between Jordan and Israel and Jordan and Syria and control the flux of the Yarmouk River.

Repeated sampling over 16 years revealed variable flow paths towards certain wells over time as documented by variable REE-pattern and δ¹⁸O, δD and ⁸⁷Sr/⁸⁶Sr signatures of groundwater and lead to new insight with respect to sources of groundwater, their flow patterns and salinization in the Yarmouk basin. The conjoint interpretation of water table fluctuations indicate unexpected interactions of the river with the major groundwater resources of the entire region. 2D transient numerical simulations of coupled fluid flow and heat transport processes are used to investigate the impact of (i) a zone of hydraulic anisotropy and (ii) abstraction on hydraulic heads and temperature profiles in the shallow aquifers. The models support the geochemical indicated existence of a structural feature along the principle axis of the gorge, which hydraulically connects groundwaters in both flanks, while cross flow of groundwaters is prevented. That implies a subsurface anisotropic zone, which lets the gorge act as a complex conduit-barrier system where adjacent N-S and S-N flow-fields confluence and get drained towards the Jordan Rift.

Faults are common geological structures distributed at various depths within the Earth with different behaviors: from seismic to aseismic. The frictional stability of faults is linked to the properties of asperities that make the contact between fault surfaces. Investigating the interaction between asperities and their link with the frictional stability of faults aims at a better understanding of the intrinsic relationships between the observations of earthquake swarms and the slow local aseismic transient. Here we propose an experimental approach, which allows a customized interface sliding slowly under a well-controlled normal load, to study this problem. This interface consists of asperities modeled by poly-methyl-methacrylate (PMMA) balls in a softer, polymer base representing the parts of the fault that are easily deformed, facing a transparent flat PMMA plate. We employ a high-resolution camera for in-situ optical monitoring of the local deformation of the interface while loaded. We also attach acoustic sensors to capture the dynamics events attesting to local dynamic ruptures. We connect our observations with a mechanical model derived from a high-precision topography of the customized interface. We investigate the effects of various internal parameters of natural fault systems, including the size and density of asperities, their rigidity or the contrast of rigidity compared to the base, on the evolution of the frictional stability under variable normal load and of the behavior of the population of asperities at the transition between seismic and aseismic slip. Our results, bring new observations on the mechanics of swarm and fault transient.

At the Äspö hard rock underground laboratory in Sweden, six in situ hydraulic fracturing experiments took place at 410 m depth. A multistage hydraulic fracturing approach is tested with a low environmental impact, e.g., induced seismicity. The idea is to mitigate induced seismicity and preserve the permeability enhancement process under safe conditions. The fractures are initiated by two different injection systems (conventional and progressive). An extensive sensor array is installed at level 410 m, including simultaneous measurements of acoustic emissions, electric self-potential, and electromagnetic radiation sensors. The monitoring catalog includes more than 4300 acoustic emission events with estimated magnitudes from the continuous monitoring setup (in-situ sensors between 1-100 kHz). The experiment borehole F1 is drilled in the direction of Shmin, perpendicular to the expected fracture plane. Two electromagnetic radiation sensors are installed and aligned to (i) Shmin and (ii) the expected fracture plane with a sampling rate of 1 Hz and a frequency range between 35-50 kHz. The self-potential sensors are installed at level 410 with a distance of 50-75 m from the borehole F1, including nine measuring probes and one base probe. A second self-potential setup is deployed at level 280 m in the far-field with a distance of 150-200 m from F1. The self-potential data were measured with a sampling rate of 1 Hz. For the first time (to our knowledge), the electric and electromagnetic monitoring results of two hydraulic stimulation at mine-scale are presented. The results are discussed, including the different injection types (one conventional and one progressive experiment) and the acoustic emission events. The self-potential results reveal increases in amplitude during both hydraulic fracturing experiments at both depth levels. A second increase in the self-potential was observed only during the conventional injection and only at level 280 m. This is consistent with the results of the acoustic emission catalog, which show a larger number and larger magnitude of events during conventional injection experiments. The changes in the electromagnetic field are predominantly in the direction of Shmin during both the conventional and the progressive injection experiments.

In Central Europe, the largest geothermal potential resides in the crystalline basement rock with important hotspots in tectonically stressed areas. To better harvest this energy form under sustainable, predictable and efficient conditions, new focused, scientific driven strategies are needed. Similar to other geo-technologies, the complex processes in the subsurface need to be investigated in large-scale facilities to ensure environmental sustainability.

The proposed new underground research laboratory GeoLaB (Geothermal Laboratory in the Crystalline Basement) will address the fundamental challenges of reservoir technology and borehole safety. The specific objectives of GeoLaB are 1) to perform controlled high flow rate experiments, CHFE, in fractured rock, 2) to integrate multi-disciplinary research to solve key questions related to flow regime under high flow rates, or higher efficiency in reservoir engineering, 3) risk mitigation by developing and calibrating smart stimulation technologies without creating seismic hazard, and 4) to develop save and efficient borehole installations using innovative monitoring concepts. Planned experiments will significantly contribute to our understanding of processes associated with increased flow rates in crystalline rock. The application and development of cutting-edge tools for monitoring and analyzing will yield fundamental findings, which are of major importance for safe and ecologically-sustainable usage of geothermal energy and further subsurface resources. As an interdisciplinary and international research platform, GeoLaB will cooperate with the German Research Foundation (DFG), universities, industrial partners, and professional organizations to foster synergies and technological and scientific innovations.

GeoLaB is designed as a generic underground research laboratory in the crystalline rock adjacent to the Rhine Graben, one of the most prominent geothermal hotspots in Germany. GeoLaB is an analogue site representative of the world‘s most widespread geothermal reservoir rock, the crystalline basement. In an initial phase, the suitability of a site for GeoLaB located either in the Black Forest or the Odenwald, will be proven by geological, geophysical, and geochemical drilling exploration. At the selected site, a two km long gallery will be excavated, tapping individual caverns, from which controlled, high flow rate experiments will be conducted. The experiments will be continuously monitored from multiple wells, drilled from the underground laboratory or from the surface. This will create a unique 4D-benchmark dataset of thermal, hydraulic, chemical and mechanical parameters. A virtual reality concept accompanies the development of the complex infrastructure concept from the very beginning, supporting the infrastructure set-up and the scientific experiments in planning, documentation and analysis.

GeoLaB will become a cornerstone for the target-oriented development of the enormous geothermal resource. With its worldwide unique geothermal laboratory setting, GeoLaB allows for cutting-edge research, associating fundamental to applied research for reservoir technology and borehole safety, bridging laboratory to field scale experiments and connecting renewable energy research to social perception. GeoLaB comprises a novel approach that will shape research in earth science for the next generations of students and scientists.

One of the most important actions to limit climate change is to decrease worldwide CO₂ emissions. A large contributor to worldwide CO₂ emissions is the production of heat. Therefore, the recently started transition from fossil based fuels to renewable heat sources is of great importance. Renewable heat sources like geothermal and solar energy often exhibit a temporal mismatch between the availability and demand of heat. Excess heat is available in summer while the heat demand cannot be fulfilled in winter. A solution for this problem is to use heat storage facilities that are able to bridge the gap between winter and summer. Given the needed storage capacity for these systems, high temperature aquifer thermal energy storage (HT-ATES) is one of the best options to do so. At the TU Delft, a combined geothermal well with a HT-ATES installation is currently being prepared. The system is designed to provide the district heating network of the university and possibly a part of the city with renewable heat, and, is set up as a research facility to foster future research.

The performance and feasibility of HT-ATES systems is affected by many factors as previous research showed. Understanding which factors are important, and how these factors impact the project feasibility, would provide a solid basis for future HT-ATES feasibility studies and foster the future use of HT-ATES systems, ultimately resulting in are more rapid reduction of CO₂ emissions. However, while low temperature ATES systems are regarded a mature technique, only limited experience is available with HT-ATES. Higher storage temperature and larger storage capacity cause technical challenges and variable performance, resulting in an uncertain business case.

Therefore, we determined the most important conditions that influence the feasibility of HT-ATES and performed a feasibility study for the TU Delft HT-ATES project. Our study shows that the integration of HT-ATES together with a geothermal well on the TU Delft campus is feasible, both technically and financially. Most importantly, the use of HT-ATES leads to twice as much CO₂ savings compared to the stand alone geothermal well.

At this moment, the project is in the next, more detailed phase, of the feasibility study to optimize the HT-ATES design and decrease project uncertainty. The feasibility of the project is strongly linked to the performance of the HT-ATES system, which is unclear because of uncertainties regarding the characteristics of the subsurface. Therefore, we are currently working on subsurface characterization by means of drilling, sampling and logging activities and aim to determine which layer(s) are most suitable for placement of well screens for the and determine appropriate, generic, methods for subsurface characterization for HT-ATES systems. In this presentation we will discuss the learning outcomes of the feasibility study for future studies and present our current effort in developing the HT-ATES project.

Agriport A7 is a large-scale greenhouse area in Middenmeer in the Netherlands. The local energy company ECW provides geothermal heat (92ºC, from 2 km depth) to the greenhouses through a heating network. The geothermal systems have significant overcapacity in the summer period while in winter they can provide only ~25% of the heat demand, resulting in a strong dependence on fossil fuels. ECW has built a full-scale High Temperature Aquifer Thermal Energy Storage (HT-ATES) system, which facilitates the large-scale storage of surplus heat (overcapacity in summer) and its recovery in winter time. HT-ATES improves the yearly net heat production of geothermal systems hence reduces GHG emissions.

The full-scale HT-ATES doublet well system allows the storage of heat in an unconsolidated sand aquifer at nearly 400 m depth, with a maximum flow rate of 150 m³/h. Each summer, up to 28,000 MWh of thermal energy (>100.000 GJ) can be stored, the bulk of which is recovered in winter.

The HT-ATES system is an innovation that takes place at the edge of technology. The depth (360-380 mbgs) and the temperature of 85 degrees Celsius offered technical and legal challenges that had to be overcome. On a technical level, the standardized well design for ‘regular’ ATES systems (< 25 ^oC, <200 mbgs) needed to be reconsidered entirely. Components of both the well and the surface installations must withstand the combination of high temperatures, saline groundwater and high pressures. Knowledge and experience from both the ATES and Geothermal sector were combined to get to a suitable design.

The reliability of the HT-ATES system finds root in the knowledge and experience available from thousands of lower temperature ATES systems that have been successfully built and operated in the Netherlands over the last decades. Risks identified in former small-scale HT-ATES pilot-projects were investigated within the HEATSTORE context, and the results contribute to the quality of the full-scale HT-ATES system. The test drilling performed in 2019 has offered a detailed image of the subsurface properties and the risks associated with it. A highly detailed system was designed, and successfully installed. Clogging risks are tackled by a special CO2 dosing unit and groundwater will be monitored on chemical and microbial changes.

In the second quarter of 2021, the installation of the HT-ATES has been completed and the system has been taken into operation. During the test period, samples were taken from the groundwater and analysed on the chemical composition and microbiological content. Also temperature profiles were made during the injection of heat into the aquifer. The first results are very promising and gives valuable information about the effects of an HT-ATES on the aquifer and environment.

The subsurface conditions of the Upper Rhine Graben are favorable for the development of novel geothermal utilization concepts. In particular, they allow optimization of energy use with flexible heat production and storage scenarios. A first potential analysis revealed an enormous storage potential of formerly used and well-explored oil fields. The involvement of former hydrocarbon reservoirs as components of geothermal concepts perfectly symbolizes the transition from the fossil-fuel age to the use of carbon-neutral renewable energies.

The proposed DeepStor concept takes advantage of these preconditions. The comprehensive geothermal concept is tailored to the Campus North of the Karlsruhe Institute of Technology (KIT) that is located in the central-eastern Upper Rhine Graben. It includes multi-level utilization with heat recovery from the deep Mesozoic reservoirs (associated GeoHeat project) and seasonal high-temperature heat storage in the Tertiary Sandstones above (DeepStor project). The KIT Campus North Campus offers good prerequisites for the concept implementation with extraction, seasonal storage and distribution of heat from deep geothermal energy: The underground of the campus is characterized by the largest known heat anomaly in Germany, with temperatures exceeding 100 °C at a depth of 2 km. An existing area-wide local heating network allows for heat distribution. In the long term, the concept provides for the coverage of a significant part of the basic heat load of the KIT Campus North in a climate-neutral way.

The scientific DeepStor storage project represents the first stage in the step-by-step development of deep geothermal energy utilization at the KIT Campus North. The targeted reservoirs involve the same Tertiary strata from which hydrocarbons have been extracted until the 1990s. Initially, the high-temperature thermal storage reservoir will be fed from cogeneration as well as current renewable waste heat from scientific infrastructures such as the biomass pilot facility "bioliq". The overarching scientific goal of the first DeepStor phase is the establishment of a scientific demonstrator to validate the technical feasibility of high-temperature heat storage in the deep underground. In the associated GECKO project, a transdisciplinary approach with natural and social sciences is pursued to develop concepts for deep geothermal energy usage on KIT Campus North in a co-design process with the local population.

Geothermal energy extraction through closed systems is a secure approach responding to the global heating demand without contaminating subsurface water and causing seismic events. However, the generated power of conventional closed systems is much lower than those of open systems. Therefore, this study is dedicated to planning a novel closed system, which can produce a significant amount of thermal power. For this purpose, the performance of a single closed-loop deep system with a lengthy horizontal extension is preliminarily assessed. Based on the achieved results, it is feasible to produce roughly 3 MW thermal power while operating with thermosiphon flow. It is a big step forward in designing a new type of closed geothermal system that operates without pumping power and produces a considerable amount of thermal power, comparable to the power generation of open systems. Nevertheless, the low ratio of generated power to the total length of the wellbores and long payback period are big barriers to the spread of this system. Therefore, in the next step of this research project, enhancing the lateral heat exchange area by designing multilateral closed deep systems is proposed to increase this ratio. It is demonstrated that operation with multilateral systems can remarkably improve the performance of the system. Hence, working with multilateral systems is more reasonable than operating with several single systems to generate the same amount of power. However, it requires an extensive sensitivity analysis for different numbers of lateral wellbores and flow rates to identify the best operation scenarios. Additionally, some criteria are set as functions of extraction temperature, produced power, and relative drilling expenses to define successful cases. The interpretation of the results revealed that a successful project requires a specific relation between local vertical and horizontal flow rates. Finally, it is found that the long-term performance of a multilateral system can be predicted as a function of its short-term behavior.

Climate change requires immediate action, and for sustainable development, and uninterrupted energy supply is necessary. Since anthropogenic emission of CO2 in the atmosphere has a major role in climate change, carbon negative energy solutions are the necessity of the time. Geothermal energy is one such renewable source that can assist in achieving an economic solution to low carbon energy. Engineered geothermal systems or enhanced geothermal systems (EGS) are more suitable from an industrial perspective and can supply uninterrupted energy supply for a long duration. In conventional EGS systems, water is the heat transfer fluid. However, the use of supercritical CO₂ as the heat-carrying fluid has significant advantages over water including less chemical reactivity, low fluid viscosity, and comparatively higher thermal conductivity for shallow systems. Fluid loss is the major issue in any EGS operation. However, CO₂ loss during the EGS operation could lead to carbon geosequestration, and therefore a carbon-negative energy solution is possible when using CO₂ in EGS operations. A case study of Soultz-sous-Forêts geothermal site is considered in this work to investigate the feasibility of CO₂ usage as the heat-carrying medium. Soultz-sous-Forêts is present in the Upper Rhine Graben, France. Geologically Soultz-sous-Forêts geothermal site comprises three layers: 1.5 km of thick quarternary and tertiary sediments, 350 m thick Buntsandstein and the basement is granite. Presently, three wells (GPK-3, GPK-4: injection wells, and GPK-2: production well) are operating at this site up to a depth of approximately 5 km. In this work, a three-dimensional Soultz-sous-Forêts site is considered with five major faults. In the present model, supercritical CO₂ is injected through GPK3 and GPK4 and produced using GPK-2. This work investigates the coupled hydro-thermal processes occurring in the fractures and the rock matrix. The local thermal non-equilibrium (LTNE) approach is considered to account for the heat exchange between the rock matrix and supercritical CO₂ flowing through the faults. Recent studies have reported fluid loss along the wellbore casing in all three wells. Therefore, a wellbore leakage model is also coupled along these well trajectories and its impact on final production temperature is assessed. Results obtained from different injection rate strategy at different injection temperature indicates that even 100 years of geothermal energy extraction operation will not have much impact on the production well temperature and therefore, a sustainable energy supply is feasible at the Soultz-sous-Forêts site.

Understanding climate and human impacts on water storage is critical for sustainable water-resources management. Here we assessed causes of total water storage (TWS) variability from GRACE satellites by comparison with climate forcing, particularly droughts and irrigation water use, in major aquifers in the U.S.. Results show that long-term variability in TWS from 2002 – 2020 tracked by GRACE satellites is dominated by interannual variability in most of the major aquifers. Low TWS trends in the humid eastern U.S. are linked to low drought intensity. Although irrigation pumpage in the humid Mississippi Embayment aquifer exceeded that in the semiarid California Central Valley, a surprising lack of TWS depletion in Mississippi is attributed to streamflow capture. Marked depletion in the southwestern Central Valley and south-central High Plains totaled ~90 km³, about three times greater than the capacity of Lake Mead, the largest U.S. reservoir. Depletion in the Central Valley was driven by long-term droughts (≤5 years) amplified by increased groundwater irrigation. Low or slightly rising TWS trends in the northwestern (Columbia and Snake Basins) U.S. are attributed to dampening of drought impacts by mostly surface water irrigation. GRACE satellite data highlight synergies between climate and irrigation, resulting in little impact on TWS in the humid east, amplifyied TWS depletion in the semiarid southwest and southcentral U.S., and dampened TWS depletion in the northwest and north central U.S.. Sustainable groundwater management benefits from conjunctive use of surface water and groundwater, inefficient surface water irrigation promoting groundwater recharge, efficient groundwater irrigation minimizing depletion, and increasing managed aquifer recharge.

Located between the Pacific Ring of Fire and Alpide Belt, Vietnam possesses significant potential geothermal resources, with more than 300 hot spring sites with temperatures from 40^oC to 100^oC have been detected in the territory. Based on available data, Vietnam is estimated to have a geothermal potential of up to 400 MW power generation. A pilot 25MW power plant was constructed in 2013 in Đakrông - Quảng Tri Province, central of Vietnam.

From geothermal measurements in oil and gas exploration boreholes, heat flow anomalies have been identified that are higher than the average heat flow of the Earth 100 mW/m2 in the Southeast of the Red River Delta (at a depth of 3,000 m temperature reaches more than 140^oC) and coastal Binh Thuan (volcanic activity in Tro island in 1923) has an area of hundreds of square kilometers.

High heat flow anomalies have been identified in some places like Phu Tho, Hue, Quang Ngai, Kon Tum, associated with active tectonic geological structures and have many hot water eruptions on the surface. Therefore, geothermal resources in Vietnam are prosperous, belonging to low to medium potential heat sources, with conditions for small capacity power generation.

In Politburo's resolutions regarding the national electricity development plan, Vietnam will develop breakthrough mechanisms and policies to encourage and promote renewable energy sources, with the capacity of renewable energy plants reaching 30% by 2030 and 40% by 2045. Overall assessment of geothermal energy's potential and development orientation will be established; then deploy several application models and conduct experimental exploits to evaluate the effectiveness. Geothermal energy can be as base-load electricity and offers an opportunity for a country with naturally free-resource and less dependence on fossil fuel. To jump-start the geothermal exploitation rather than solely relying on knowledge, introducing the techniques outside Vietnam is needed.

For the resource development, geothermal systems need to be improved to increase the profitability of the investment. One aspect to support this aim is the reservoir productivity, a key parameter, which depends on the hydraulic and mechanical properties of the reservoir formation. In order to develop possible improvement strategies for the profitability enhancement of geothermal reservoirs and/or nuclear waste repositories, hydraulic and mechanical properties of artificial generated fractures were investigated. The importance of the fracture geometry yields the fracture network of the geothermal system. As a result, the influence of stress exerted on single fractures was exploited. Hereby, the fracture aperture represents a key parameter for several other parameters such as the fracture permeability and fracture stiffness. Therefore, experiments of progressive and constant cyclic loading were performed to analyze the fluid flow inside of fractured rock samples from geothermal reservoirs. The specimens analyzed in this research project are the Odenwald Granodiorite which was extracted from the Bergstrasse in Heppenheim, Germany, and the Cornwall Granite from the St. Austell pluton in Cornwall, England. The progressive cyclic loading test (PCL) was performed with confining pressure maxima of 15 MPa, 30 MPa, 45 MPa, and 60 MPa. Within the constant cyclic loading test (CCL), the maximum pressure was raised up to 60 MPa to ensure reproducibility. Axial and lateral strain deformation were measured with LVDT extensometers to calculate the fracture and matrix deformation. Fracture stiffness, -permeability, and -closure were evaluated from the collected dataset. Moreover, the fracture geometry was taken into account by 3D surface scans to display fracture aperture distribution and to model the change in surface structure and its impact on the fracture behavior. The fracture stiffness visualized for both granitoids is similar in terms of values and behavior, despite their different origin and, respectively, their petrographical composition. Moreover, the PCL displayed a linear trend of the fracture stiffness in the 1st cycle and before exceeding the previous stress maximum. This feature transformed into a non-linear trend when exceeding the previous stress level. The transition seems to be related to a stress-memory effect and the behavior of the ‘Kaiser effect’ for acoustic emissions. Both features were additionally detected in the fracture permeability results. The outcome of a similar research by Kluge et al. (underreview) with the Flechtingen Sandstone shows the same characteristics in a different domain for the fracture stiffness, -permeability, and –closure values. Last but not least, the fracture permeability reduction turned out very similar in the PCL and the CCL test, a result that contrasts the outcome of Kluge et al. (under review). Experimental and theoretical results on single fractured rock specimens are discussed and display the importance of fracture stiffness on geothermal systems.

We provided an approach to estimate hydraulic diffusivity of a single fault by solving the linear diffusion equation in a partly open rough fracture under drained conditions when applying small pressure drop fluctuations (10^-5 Pa) along the fault. In contrast to the traditional calculation for the fracture hydraulic diffusivity using parameters such as hydraulic aperture, fluid compressibility, fluid viscosity, we here directly used time-dependent pressure profile p(x, y, t) to match the analytical solution for an equivalent parallel plate model, which contains hydraulic diffusivity as unknown. The method considered transient pressure diffusion process, which might give a more accurate value for hydraulic diffusivity compared to traditionally calculated one. Our results under large closure (hydraulic diffusivities are of orders 10^2 m2/s – 10^4 m^2/s) are consistent with the values derived from analysis of some earthquake sequences (Noir et al., 1997; Antonioli et al., 2005; Malagnini et al., 2012; Dempsey and Riffault, 2019; Schmittbuhl et al, 2021). Those earthquakes were assumed to be triggered by the diffusion of pore pressure perturbation in a fractured medium, and the seismicity migration was then evidenced to be compatible with pore pressure relaxation. The hydraulic diffusivity estimated by Noir et al. (1997) for the 1989 Dobi earthquake sequence of Central Afar ranges between 10^3 – 10^4 m^2/s, which corresponds to the characteristic width (i.e., effective aperture) 1 mm - 3 cm. The consistency with our results indicates that our model might be used to predict potential earthquake migration, in particular, when a single fault path dominates the fluid flow. Compared to diffusivities estimated from direct hydraulic tests, the values obtained from our simulations are somehow large. The discrepancy could be attributed to several aspects: the diffusivity from direct hydraulic test is commonly affected by fracture networks instead of a single fault, and combines matrix diffusivity and fracture diffusivity (Ortiz R et al., 2013; Sayler et al., 2018), which lower the value. In addition, it also depends on temperature, mineral sealing, fault movement and tested methods, e.g., lower hydraulic diffusivities were observed in constant rate tests than periodic tests (Guiltinan and Becker, 2015). In cases that fluid flow was dominated by a constrained planar fracture., e.g., Sayler et al. (2018), it was evidenced that flow between an interval with large diffusivities (up to 10^3 m^2/s). We also compare our results to the hydraulic diffusivity assessment for the recent Strasbourg earthquake sequence: 25 m^2/s (Schmittbuhl et al, 2021). Our approach can be extended to estimate hydraulic diffusivity for fracture networks when considering roughness (varied aperture distribution) for each fracture (Haagenson and Rajaram, 2021).

For two-phase geothermal resource, Organic Rankine Cycle (ORC) based binary plant is often applied for power production. In this work, a network topology was built with the Thermal Engineering Systems in Python (TESPy) software to simulate the stationary operation of the ORC plant. With this topology, the performance of nine different working fluids are compared. From the thermodynamic perspective, the gross and net power output is optimized respectively. Results show that R600 has the highest gross power output of 17.55MW, while R245fa has the highest net power output of 12.93MW. However, the turbine inlet temperatures for these two working fluids need to be designed at the upper limit of 131℃. It is also found that R245ca and R601a (Isopentane) require the heat exchange rates of IHE to be larger than 1.51MW and 0.99MW to satisfy the re-injection temperature limit, which are smaller than the R600 (6.7MW) and R245fa (6.0MW) cases. Besides, in order to establish a stable ORC plant, the lower geo-steam fraction, the working fluid with lower critical state is preferred. The workflow for the ORC design and optimization in this work is generic, and can be further applied to thermo-economic investigation.

DeepStor is an experimental facility with the goal to investigate High Temperature Aquifer Thermal Energy Storage (HT-ATES) systems at KIT Campus North. The operational seismic monitoring of DeepStor includes a network of five broadband and one borehole seismometer. In addition, we plan to install a scientific monitoring network with low-cost seismometers (such as the Raspberry Shake and the Quakesaver Hidra) to test innovative monitoring methods and for a Citizen Science project.

Ambient noise tomography and coda wave interferometry are being used increasingly to image and monitor geothermal reservoirs. Especially in locations with a high anthropogenic noise level, such as the Oberrheingraben, these methods could potentially provide valuable insights in the evolution of the storage acquifer during injection/production cycles. Our monitoring approach focuses on the use of a larger number of these low-cost sensors instead of fewer and more expensive broadband instruments (Large-N approach). With the broadband network and established monitoring methods as a benchmark, DeepStor provides the ideal testing ground to explore the benefits of a dense network of low-cost sensors.

The Citizen Science project will build on the successful Gecko project, which involved the public in the conceptualization of geothermal energy usage. A major conclusion from the Gecko workshops was the importance of transparent monitoring processes for the acceptance of geothermal energy usage. Consequently, we plan to involve the communities around KIT Campus North in the monitoring of DeepStor by distributing sensors for radon and seismicity. To ensure trust in the monitoring process, we will follow open data practice and investigate options to make the data easily accessible and understandable.

During the Quaternary, large ice sheets repeatedly formed and retreated over continental North America and northern Europe, which in turn caused fluctuations in global sea level by up to 120 m. This caused substantial changes to the Earth's surface, changing the distribution of land, continental ice sheets, and ocean. I demonstrate a technique we use to reconstruct ice sheets and paleotopography, and its application for the past 800000 years. I show that with the use of observations from glacial geology and ice extent chronology, it is possible to determine the history of the ice sheet configuration even prior to the Last Glacial Maximum (19000-26000 years ago). During Marine Isotope Stage 3 (57000-27000 years ago), when there are few constraints on sea level, we determined that sea level was between about 25-50 m lower than present, substantially higher than estimates based on marine benthic oxygen proxies. We also determined that global sea level during the Last Glacial Maximum was about -115 m, about 15 m higher than previous estimates. This shows that it is possible that, given the current constraints on sea level, that past ice sheet configuration may be an non-unique problem. The growing community efforts to standardize and compile datasets on past sea level bring an opportunity to reduce the uncertainty on ice sheet configuration, and extend our reconstructions further into the past (such as the last interglacial).

Polar plankton plays a large role in global carbon cycling. There is a significant lack of knowledge of these biotas, however. The main goal of our project is to understand how plankton and oceans interacted in the past during the Eocene/Oligocene (E/O) transition, when significant climate shifts happened. We use a multiproxy approach by combining microfossils and geochemical data. Our study includes the first-ever comprehensive surveys of both diatom and radiolarian plankton diversity (siliceous protists dominating the preserved microfossil record in polar regions). We analyze abundance, diversity, speciation, and extinction rates between 40 and 30 Ma. This plankton data, correlated togeochemical and sedimentological proxies of ocean conditions and carbon pump activity, geographic water masses, and nutrient export data will contribute to global syntheses to determine the global significance and role of plankton in climate change at the E/O transition.

Our data comes from several deep-sea drilling Sites from the Atlantic and the Indian Ocean sectors of the Southern Ocean: 689, Weddell Sea; 511 and 1090, near the Atlantic sector polar front; and Indian sector 748, Kerguelen Plateau.

Our results show a latitudinally differentiated pattern of paleoceanographic and productivity change. Episodes of increased Southern Ocean productivity occurred well prior to the E/O boundary within the late Eocene, beginning at ca 36-37 Ma. Diversity of siliceous plankton increased with productivity, and shows major episodes of evolutionary turnoverin the late Eocene and at the E/O boundary correlated to productivity and temperature change.

Southern Ocean paleoceanography provides key insights into how iron fertilization and oceanic productivity developed through Pleistocene ice-ages and their role in influencing the carbon cycle. We report the first high-resolution record of dust deposition and ocean productivity for the Antarctic Zone, close to the main dust source, Patagonia. Our deep-ocean records cover the last 1.5 Ma, thus doubling that from Antarctic ice-cores. We find a ≥10-fold increase in dust deposition during glacials and a ≤5-fold increase in ocean productivity during interglacials. This antiphasing persisted throughout the last 25 glacial cycles. Dust deposition became more widespread across the Mid-Pleistocene Transition (MPT) and, at ~0.9 Ma, dominant ice-age cycles changed from 40,000 to 100,000-years, suggesting more severe glaciations thereafter. Productivity was intermediate pre-MPT, lowest during the MPT and highest since 0.4 Ma. Glacials experienced extended sea-ice cover, reduced bottom-water export and Weddell Gyre dynamics, which helped lower atmospheric CO₂ levels.

The reconstruction of past Antarctic sea ice coverage through the application of diatom assemblages is often hampered in near coastal environments due to silica dissolution effects. The more recently established approach of using highly branched isoprenoid biomarkers to identify past sea ice conditions seems a valid method to overcome this limitation and that may also provide insight into ice-shelf dynamics. Here, we evaluate the so-called PIPSO₂₅ index applied to modern surface sediments from the Amundsen Sea, the Drake Passage and Bransfield Strait, and the Weddell Sea. The comparison of biomarker-based sea ice estimates with satellite-derived sea ice concentrations supports the potential of the proxy approach. In a next step, we generated biomarker records using two sediment cores from the western and eastern Weddell Sea to track sea ice variability over late Pleistocene glacial-interglacial cycles. Consideration of additional data such as XRF and multi-sensor core logging records as well as micropaleontological investigations enables a comprehensive assessment of the environmental changes in the Weddell Sea in response to large-scale climate transitions. While magnetic susceptibility and density data obtained for both cores display similar patterns, we note distinct differences between the biomarker records highlighting local feedback mechanisms affecting sea ice cover.

The Muskau Arch in the border triangle of Brandenburg-Saxony-Poland is a push moraine that was folded up by the Muskau Glacier during the second Elster surge about 340,000 years ago. In the process, it folded the underlying strata to a depth of approx. 270–290m. It is considered one of the best examples worldwide of large-scale glaciotectonic deformation. As a result of the compression, lignite, glass sands and clays, were pushed to the surface, and a flourishing raw material extraction and processing industry developed between 1840 and 1970. Today, the region is an attractive natural area with 300 to 400 partly coloured post-mining lakes and has developed into a diversified cultural landscape. Numerous projects in the area aim to carry on this closely linked geological and industrial heritage and make it tangible for the people in the region. For example, the narrow-gauge railway once built to transport goods and supply the factories is now operating again since the 1980s as a museum railway to tell the story of the forest railway and the former industrial region. Large open-cast mines that shaped the landscape for a long period are now being recultivated, taking into account their glacial history and incorporating relics in the form of erratic boulders as design elements. Former industrial buildings, such as the old brickworks in Klein Kölzig, are also being integrated into the sustainable development of the region and nowadays serve as Geopark's office on the one hand and illustrate industrial processes of brick production on the other.

The sustainable use of geological resources is a management task, demand and challenge. When the European Geoparks Network was founded in 2000, a new view fell on geosites, geotopes, former quarries as resource areas of rocks and energy provider. Their contribution to regional economic development during their active use has been enormous. Only few scientists identified unique scientific value for geosites or geotopes, e.g. for Messel Pit World Heritage Site, Hesse, Germany with the need for protection for and by the global community. Other scientists with far sightedness directed the view onto a new use: geotourism, education and sustainable development. Their initiative started the first geo-trails in territories called geoparks. Infrastructures were restored and directed into a new use. Not only one geo-trail was created. By the positive acceptance of the population the new infrastructure was now used for their weekend walk. Eyes were opened on the formation history of a landscape, cultural connections were identified. An amazing development followed during the last twenty years. Today UNESCO Global Geoparks have a set of trails serving a variety of topics. Their management involves different measures. Maintenance after creation, as well as up dating and marketing are challenging management tasks. A speciality is using infrastructure of former quarries as geotourism highlight for guided tours. Connecting them with visitor requirements leads to modern geotourism products. They finally result in new or larger economic income with sustainable results like new jobs, income and benefits by e.g. selling products of the region or geoproducts presented in this contribution.

When it comes to the mining and use of local geological raw materials, a reflexive, sometimes undifferentiated social rejection arises. The ore, hydrocarbon and coal consumption have now been reduced through recycling and the use of alternative energies or have been replaced by imported products. The last open-cast lignite mine in Schöningen was closed in 2016, the last Harz ore mine in Bad Grund in 1992 and the last iron ore mining in the Salzgitter area in 1976. Petroleum is now only produced to a small extent at a few points in the northern Braunschweig region. At the same time, the consumption of resources such as sand, gravel, solid rock (especially limestone, gypsum) and water continues on a high level. The quarrying of building stone has been almost completely ceased. Some raw materials are imported to avoid the conflict over mining, to take advantage of low labor costs abroad, or simply because they are no longer available in sufficient quantities. In terms of sustainability, there is overall significant potential for improvement. In the further planning of mining sites and quarries, special protection of the groundwater reservoir is of outstanding importance. The lecture describes examples from the UNESCO Global Geopark Harz . Braunschweiger Land . Ostfalen.

The company Evers und Co GmbH operates two gravel plants in Süpplingen and Uhry / Helmstedt district and thus produces various sands and gravel, topsoil, mineral mixtures and concrete aggregates, among other things. It is also active in the recycling sector, e.g. producing recycled mineral mixtures. An important aspect of sustainability is that the unconsolidated rock for construction work in the region has only short transport routes. This saves massive amounts of CO₂. The yield from the extracted unconsolidated rock is already over 90%. Attempts with sludge recovery, filtering and drying are currently being worked on to process and also use the unused residue from quartz powder and clay minerals. During processing, as much process water as possible is treated and reused. After mining, the pit areas are either directly used as lakes or succession areas for nature conservation or recultivated as farm land.

The geological heritage provides a particularly effective pedagogical tool to engage school students with climate change through on site exploration in UNESCO Global Geoparks. Geological data provides invaluable opportunities to create authentic experiences for school children to understand the consequences of climate change.

The Petrified Forest in Lesvos Island UNESCO Global Geopark shows abundant evidences for past climate change as it reveals information about the composition of the palaeoflora (an important indicator of the past climatic and environmental conditions and their changes) the last 20 million years. At the same time the Lesvos Petrified Forest is an area where the petrified flora coexists with today’s flora. This characteristic provides unique opportunities for school children to explore the consequences of climate changes.

In this paper is presented the educational program “Climate change: Learning about the consequences by studying the Petrified Forest of Lesvos” and the educational materials that have been designed to educate school students on climate change issues. Through a variety of educational activities, pupils are encouraged to explore the consequences of climate change, to think critically, formulate arguments, evaluate solutions and choices, and take action. Geological data, palaeoflora and today flora and their diversity are used as the main pedagogical tools during the educational programme.

The educational role of historical mining sights for sustainable use of geological ressources – examples from the UNESCO Global Geopark Bergstraße-Odenwald

In a Geopark, historical mining sights can act as showcase for landscape modification and education for sustainable development (ESD). As elements of the recent cultivated landscape, they provide an excellent motive to discuss aspects of utilization of geological raw materials in actual products, their provenance and related mining and processing. In addition, deep insights into visitor mines and historical mining landscapes by guided tours open the view to environmental consequences of historical mining up to now (e. g. with respect to soil erosion processes), awareness of human impact on our planet earth. Thus the processes of sustainable development and awareness building can be established easily.

The UNESCO Global Geopark Bergstraße-Odenwald realizes this strategy by a strong cooperation with the voluntary „Mining Research Group Odenwald“. Due to intense contacts with departments of monument protection and universities, the working group is able to carry out professional interdisciplinary research on historical mining and cultural landscape evolution in the Geopark region. On the other hand, the Geopark’s network enables preservation projects within the local mining landscapes, development of information panels and the operation of an own visitor mine. This scientific, geo-touristic and educational infrastructure is presented to the public by guided tours dealing with results of actual research and experimental archaeology events. In this context, ESD is the predominant concern.

All activities are reported at the Geopark´s network platform, within its calendar of events, and in online and print media. This combination of networking, local expertise, citizen science and collaboration with governmental institutions enables the reflection of the Global Agenda 2030 from a holistic point of view and also deeply rooted with the Geopark inhabitants and visitors appreciation.

Stromatolites are laminated, presumably microbial, structures, consisting largely of an authigenic precipitate, and manifest the appearance of microbial life in the geological rock record at least 3.4 Ga ago. Thus, stromatolites provide unique geochemical archives of aqueous environments on Earth and their habitability. It is, however, still incompletely understood under which physico-chemical conditions stromatolites formed and how these environments changed with the co-evolution of the atmosphere-hydrosphere-lithosphere systems through deep time.

This contribution targets the potential and pitfalls of emerging and established isotope applications to stromatolites based on improved and newly developed analytical and technical facilities in the last decades. I will provide an overview of present data and the interpretation of novel applications of stable and radiogenic isotope systems in stromatolites. Although the behaviour and fractionation processes of different isotope systems in stromatolites and microbial mats are sometimes incompletely understood, the different isotope proxies have the unique potential to better understand and reconstruct microbial habitats through deep time. Primarily, radiogenic isotopes are used to directly date stromatolites and determine the source of elements in ancient stromatolite environments; stable isotopes are used to understand redox conditions, metal availability, and (biogenic) metal cycling processes in microbial habitats. I provide insights into different isotope applications and their future perspectives to bridge the gap between geochemistry and microbiology and better understand the evolution of microbial life in stromatolite-forming environments on Earth and beyond.

The global record of early life is only poorly preserved, but has an ark in the 3.2 Ga Moodies Group of the Barberton Greenstone Belt, South Africa and Eswatini. It preserves silicified photosynthetic and sulfate-reducing metabolic signatures in sandstone-dominated, terrestrial to shallow-marine strata. Large fluid-escape structures are common in thick-bedded kerogen-laminated sandstones of (sub-)tidal facies. We document and interpret silicified, massive and laminated carbonate aggregates and beds, both of likely microbial origin, within and on top of these syndepositional and early diagenetic features, not previously described from Archean shallow-water fluid-escape structures. We distinguish three morphotypes: (1) cm-scale, silicified, bulbous aggregates aligned within fluid-escape conduits; (2) up to dm-scale, dolomitized, finely-laminated conical and tabular mounds on top of the conduits; (3) cm-scale, isolated, silicified, finely-laminated, stromatolitic aggregates. In-situ SIMS isotope analyses from traverses across the best-preserved laminae of a mound yielded δ¹³C_(PDB) values relative to a dolomite standard of -2.5 to 0.5‰, and -3.5 to 4.0‰ for δ³⁴S_(VCDT) from diagenetic rims of nearby detrital pyrite grains, respectively. Values and ranges are consistent with a near-complete hydrothermal alteration. Facies context, location within and on top of the fluid-escape structures, stromatolitic morphology, and carbonate composition suggest that robust microbial communities utilized one or several carbon-based redox pathways in this siliciclastic tidal setting. Methanogens, methanotrophs, sulfate reducers and photosynthesizers may have colonized these tidal-zone sand volcanoes at 3.2 Ga, collectively forming a diverse microbial community.

The Earth’s atmosphere was without free oxygen until the Great Oxygenation Event, thought to have been driven by oxygenic photosynthesis. The expansion of early Cyanobacteria was proposed to be restricted by the lack of bioavailable nitrogen. The effects of an anoxic Archean atmosphere on the growth of a the nitrogen fixing Cyanobacterium Nostoc sp. PCC7524 was compared to control cultures grown under present day atmospheric levels (PAL) of O₂ and CO₂. Additionally, we assessed how the early Archean atmosphere affected the gas diffusion barrier, consisting of heterocyte glycolipids, of the heterocyte and the ability of early Cyanobacteria to fix N₂.

While no significant changes were observed for growth rates under N-depleted conditions in the experimental and control atmospheres, upregulation of the C- and N₂-fixation associated genes, were observed under Archean conditions relative to PAL. This correlated with increased levels of the C-fixing Rubisco protein and O₂ production. The glycogen and protein content of the Archean endpoint culture material showed raised levels of these long-term storage compounds compared to those grown under PAL conditions. No significant changes in the heterocyte glycolipid content or composition was observed.

This data suggests that diazotrophic Cyanobacteria were able to fix nitrogen and carbon more efficiently under the anoxic conditions of the Archean, thereby releasing more biologically available carbon and nitrogen into the immediate environment than under PAL conditions. The fact that no significant changes in the heterocyte glycolipid content occurred suggests they are suitable biomarkers for cyanobacterial N₂-fixation in geological records.

Archean Cyanobacteria oxygenated Earth’s atmosphere during the Great Oxygenation Event (GOE) through the action of oxygenic photosynthesis. The photosynthetic apparatus relies on metalloproteins, many of which contain iron. Cyanobacteria use several specific transporters to meet their high iron requirements. In the ferruginous anoxic Archean ocean, the FeoABC transporter was thought to be the primary means of Fe(II) uptake.

Our goal is to investigate the distribution of inorganic iron uptake mechanisms among Cyanobacteria and to determine the emergence of core iron receptors in the Cyanobacterial lineage.

Essential iron uptake transporters and regulators were identified in 125 Cyanobacteria using in silico analysis. We reconstructed the Baysean phylogeny of the Fe(II) receptor FeoB, the high affinity Fe(III) permease, FutB, and cyanobacterial FTR1. Additionally, the arrival of these iron receptors in the Cyanobacterial lineage was timed using a molecular clock. The expression of cftr1 (Pse7367_Rs12485), furA (Pse7367_Rs06445) and cyoC (Pse7367_Rs00935) was determined by quantitative RT-PCR against the reference gene, rpoC1 (Pse7367_Rs07505), in the basal clade cyanobacterium Pseudanabaena PCC7367, grown under simulated Archean conditions.

Genome analysis shows an absence of the high affinity Fe(II) transporter, FeoB, in most basal Cyanobacteria. Moreover, evolutionary dating timed the arrival of FeoB, cFTR1 and FutB in the cyanobacterial lineage during the Proterozoic. Furthermore, cftr1 is constitutively expressed in Pseudanabaena PCC7367, even after the addition of Fe(II).

This study highlights the need for a reappraisal of iron uptake systems in early Cyanobacteria, as Fe(II) does not appear to have been their primary source of iron in the ferruginous Archean oceans.

Cyanobacteria are able to conduct oxygenic photosynthesis and are thought to have been responsible for the Great Oxygenation Event (GOE). The effect of increasing levels of atmospheric O₂ on the physiology of Cyanobacteria is unknown. Cyanobacteria produce toxic superoxide ions during photosynthesis through the hydrolysis of water. In this project, we investigate the expression of the Superoxide Dismutase (SOD) enzyme, which is responsible for eliminating the superoxide ion, in an ancestral marine species, Pseudanabaena sp. PCC7367.

Growth curves based on Chlorophyll a and protein content were conducted under an anoxic atmosphere representing the ‘Archean’, and one representing Present Atmospheric Levels (PAL) of CO₂ and O₂. Expression of SOD genes was monitored over a day: night cycle, in conjunction with measuring oxygen release. The activity of the enzymes was assessed using native gel assays.

The growth rate for Pseudanabaena sp. PCC7367 was highest for cultures grown under the anoxic atmosphere suggesting that modern levels of atmospheric O₂ impair the growth of Cyanobacteria compared to the ‘Archean’ atmosphere. SOD gene expression was highest during the day when O₂ levels were at their highest. Relative gene expression under both atmospheres was not significantly different, suggesting that the expression of SOD depends on cellular O₂ production rather than atmospheric O_2. Enzyme activity assays confirmed the synthesis of the SODs.

In conclusion, this study suggests that increased atmospheric O₂ levels would not have restricted the spread of Cyanobacteria as they would have required SODs once they acquired the ability to conduct oxygenic photosynthesis.

The so-called Permian – Triassic mass extinction was followed by a prolonged period of ecological recovery that lasted until the Middle Triassic. Triassic stromatolites from the Germanic Basin seem to be an important part of the puzzle, but have barely been investigated so far. Here we analyzed late Anisian (upper Middle Muschelkalk) stromatolites from across the Germanic Basin by combining petrographic approaches (optical microscopy, micro X-ray fluorescence, Raman imaging) and geochemical analyses (sedimentary hydrocarbons, stable carbon and oxygen isotopes). Paleontological and sedimentological evidence, such as Placunopsis bivalves, intraclasts and disrupted laminated fabrics, indicate that the stromatolites formed in subtidal, shallow marine settings. This interpretation is consistent with δ¹³C_carb of about -2.1 ‰ to -0.4 ‰. Remarkably, the stromatolites are composed of microbes (perhaps cyanobacteria and sulfate reducing bacteria) and metazoans (non-spicular demosponges, Placunopsis bivalves, and/or Spirobis-like worm tubes). Therefore, they should more correctly be referred to as microbe-metazoan build-ups. They are characterized by diverse lamination types, including planar, wavy, domal and conical ones. Microbial mats likely played an important role in forming the planar and wavy laminations. Domal and conical laminations commonly show clotted to peloidal features and mesh-like fabrics, attributed to fossilized non-spicular demosponges. In the light of our findings, it appears plausible that the involved organisms benefited from elevated salinities. Another possibility is that the mutualistic relationship between microbes and non-spicular demosponges enabled these organisms to fill ecological niches cleared by the Permian – Triassic Crisis and maintain their advantage until the Middle Triassic.

Soil gas surveys (e.g. ²²²Rn, CO₂, O₂ etc.) are very well known in diverse backgrounds such as the detection of geological faults, prediction of earthquakes or monitoring of gas contamination risks at building sites. Risk monitoring using soil gases in the frame of mine flooding is a quite new field of application currently investigated in the frame of the German BMBF funded project FloodRisk. Analogies to some of the classical soil gas applications highlight a relevant potential for technology transfer to the mining industry. Flooding of closed-down mines can induce ground movements and earthquakes that can potentially be monitored with soil gases provided that site-specific characteristics meet soil gas survey requirements. Such relevant requirements, as well as standard soil gas methods used, but in particular also first steps for new, low-cost sensor developments for permanent soil gas monitoring will be presented in this contribution.

Since coal mining in the Ruhr Area has been ceased, mine water drainage is gradually reduced leading to the rise of formation water and groundwater levels. Rising mine water levels increase the pore pressure and induce stress changes in the subsurface, which may reactivate natural and/or mining-related faults and fractures. As part of the interdisciplinary FloodRisk project, which aims to enhance the understanding of the geomechanical coupling of increased pore pressure and heterogeneous ground movements, we present a geological km-scale 3D model of a former mining area hosted in the Upper Carboniferous. Fault and horizon geometries are constructed based on coal seam mappings from the Geological Survey of NRW.

Beside the integration of petrophysical data, a discrete fracture network model (DFN) is implemented to capture the fracture network of the subsurface. Therefore, Upper Carboniferous outcrops were studied by UAV-derived 3D outcrop models to analyse fracture parameters. Fracture network characterization revealed five dominant fracture sets with striking orientations of N-S, NE-SW, ENE-WSW, WNW-ESE and NW-SE. Calculated dilation tendencies provide information on which fracture sets are likely to contribute to fluid flow in the subsurface. A DFN model is stochastically modelled based on these “effective” fracture sets and will be the basis for the construction of a simulation model.

Geomonitoring of mining processes is a very current topic. Geomonitoring uses modern surface and subsurface methods observing the Earth’s surface. “Digital Twin” is a research project whose main goal is to use methods to detect surface and subsurface trends in post-mining areas and relate them to environment processes (e.g. climate changes). An important aspect it to distinguish between environment and artificial/mining influences and effects. The research area of this project is the closed Prosper-Haniel coal mine. The project uses modern research methods and instruments ranging from modelling the geological subsurface in order to visualize the model in three-dimensional space. Through a spatiotemporal analysis of available satellite data and verify the results, in-situ mapping using a mobile GIS application or copter flights with multispectral and thermal sensors are deployed. Each of the sensors play an important role in project “Digital Twin”, but collaboration and combination of different domains allows a broader view of the problems of environmental and geoscientific processes.

The TRIM4Post-Mining project aims to develop an integrated information modeling system to support decision-making and planning during the transition from coal exploitation to a re-vitalized post-mining landscape, enabling infrastructure development for agricultural and industrial uses and contributing to the recovery of energy and materials from coal mining dumps. This modeling system will be composed of a high-resolution spatiotemporal database founded on state-of-the-art multi-scale and multi-sensor monitoring technologies to characterize dynamical processes in coal waste dumps related to timely dependent deformation and geochemical processes. To test this approach, the European consortium formed by experts from industry and academia (FZN-THGA, TUBAF, TU DELFT, MIBRAG, Beak Consultants, Spectral Industries, and Eijkelkamp SonicsSampdrill) will compile and analyze data from the Schleenhain Mine dump in Leipzig, Germany. In this context, comprehensive spatiotemporal data analytics, feature extraction, and predictive modeling will be developed to target potential contamination areas and forecast the waste dump dynamics. All the up-to-date data and models will be embedded in an interactive planning system based on Virtual Reality and Augmented Reality technology forming a TRIM – Transition Information Modelling System that guarantees efficient and transparent communication of planning scenarios in terms of residual risks, technical feasibility, environmental and social impact between all key stakeholders.

The potassium mine Burggraf-Bernsdorf was established between 1911 and 1913. It was situated at the southwestern flank of the Roßleben saddle (Sachsen-Anhalt) and belonged to the “Unstrut Kalirevier”. About 300.000 tons of carnallitite were extracted. The mined cavity was about 175.000 m³. Due to a reorganization of the German potassium industry the mine was closed in 1921.

After a 40 year long period of quietness the abandoned mine was investigated for its suitability as an underground gas storage facility (UGS). The project was regarded as a large-scale test firstly. Safety criteria were developed and investigations were conducted in the fields of rock mechanics, explosion hazards and of physicochemical interactions. The storage phase started in 1970 after installation of an effective seal into both shafts. Due to the small capacity the UGS was used as a buffer store of the regional gas grid. About 1,4 billion m³ of gas were handled during the operating phase.

In 2014 the operator decided to close the UGS due to the high wetness of the produced gas and the complexity of a refitting of the facility. Several methods were checked to abandon the UGS. Dry abandonment was compared with flooding with different media. Aspects of rock mechanics, of leaching kinetics and of environmental studies were considered during this procedure. The abandonment of the mine, the removal of the casing and the backfilling of the shafts happened between 2018 and 2020. A five year long monitoring period will finalize the history of the multifunctional mine Burggraf-Bernsdorf.

The Emscher, formerly discredited as the "Köttelbecke", is being renaturalised at great expense by the EMSCHERGENOSSENSCHAFT / LIPPEVERBAND in the course of post-mining activities. In addition to the Emscher Canal as the central structure, this primarily affects the Emscher itself and the receiving waters in the catchment area, such as the Boye. River areas that have been redesigned to be close to nature are to be gradually transformed into functioning natural areas.

Today the project faces the challenges of climate change. The question arises whether the Emscher can be supplied with enough water from the catchment area in the future to achieve the ambitious goals? FZN is tackling this question on behalf of EGLV together with its partner EFTAS. A complex data mix of sentinel satellite data, special multicopter sensor technology, in situ sensors and soil samples are fused in a model test to calibrate each other. This will result in a better hydro(geo)logical process understanding of the catchment over a hydrological year. The aim is to obtain area-wide, but reliable statements via the satellite level to be able to transfer the model test to other catchments.

The lecture presents first results from the copter and in situ level. It describes the procedure and approaches for the experimental setup and the evaluations. In this context, inexpensive RFID/NFC data loggers from the greenhouse sector are tested for the first time to see how they can contribute to the overall hydrogeological/geological understanding as a future in situ component.

In drylands, stormwater is often collected in surface basins and subsequently stored in shallow aquifers via infiltration to cope with water scarcity. These groundwater recharge schemes are often accompanied by high evaporation rates and hygiene problems due to low infiltration rates, which are a consequence of clogging layers on the topsoil and the presence of a thick vadose zone. The present study aims to develop a conceptual solution to increase groundwater recharge rates in stormwater harvesting systems. The efficiency of vadose-zone wells and infiltration trenches is tested using numerical models and sensitivity analyses. The constructed models are conceptualised in the dams built in the channel of ephemeral streams (wadis) and validated utilising analytical equations. The modelling demonstrated that the employment of vadose-zone wells and infiltration trenches contribute to starting the recharge 2250–8100% faster than via infiltration from the wadi dam bed surface. Furthermore, recharge rates are predominantly affected by well length and trench depth as per the sensitivity analyses. In terms of recharge quantity, the well is the most efficient solution contributing to infiltrating up to 1642% more water than an equivalent area of the wadi dam bed surface and between 336 and 825% more than a trench. Moreover, the well can provide the highest cumulative recharge per unit cost and high recharge rates when there are space limitations. The use of analytical equations proved the adequacy of the developed numerical models. The techniques explored can significantly improve groundwater recharge, providing practical solutions to enhance water availability in drylands.

Sustainable groundwater use is commonly linked to groundwater recharge: If the long-term average of withdrawals is not higher than the inflows, the groundwater use is considered sustainable. In arid environments, natural inflows are small, but the amount of groundwater-in-storage might be large. Potential groundwater withdrawals cannot be referred to the small inflows only. Hence, the determination of groundwater-in-storage volumes and their exploitable parts, respectively, is of high importance.

In this study regional aquifer systems, like they exist on the Arabian Peninsula or in North Africa, are considered. Options and limits in the determination of groundwater-in-storage are investigated.

For the assessment of groundwater-in-storage the determination of aquifer geometry and storativity (under confined and unconfined conditions) are essential. Exploration, data interpretation, and knowledge of aquifer genesis allow for accurate determination of aquifer geometry. In contrast, determination of storage coefficients is difficult. Firstly, the logarithmic relation between storativity and drawdown makes determination from pumping tests indifferent. In regional aquifer systems, exploitable groundwater volumes relate to confined conditions, where the uncertainty of the storage coefficient may range over an order of magnitude. Secondly, there is also a lack in data interpretation: known heterogeneities in lithology, or assumable changes with increasing aquifer depth are rarely translated into corresponding distributions of storage coefficients.

Herewith, we want to emphasize the importance of the assessment of groundwater-in-storage and the related storage coefficients. Increasing occurrence of dry seasons lead to use of groundwater-in-storage in humid environments, too. Consideration of groundwater-in-storage is hence important for both arid and humid environments.

Effective implementation of sustainable water resources management is one of the daunting tasks in most parts of the world. The Pra Basin has a high economic importance, hosting most of Ghana’s mineral resources, including gold, bauxite, iron, manganese, and diamonds. Currently, the basin is faced with several water resources management issues, especially pollution arising from the discharge of untreated waste into water bodies and illegal artisanal mining. Considering this background, the present study aims to determine the geochemical processes controlling the Pra Basin’s groundwater chemistry and provide the baseline information for groundwater management. A total of 65 groundwater samples sourced from boreholes (depths >30 m) were analysed for their physico-chemical parameters. Hierarchical cluster analysis and inverse geochemical modelling were applied to the hydrochemical data to investigate the sources of variation in groundwater hydrochemistry in the area. Three major geochemical processes were determined as drivers for groundwater chemical evolution: dissolution of carbonates, weathering of silicates and ion exchange. Inverse modelling underlines the dissolution of primary biotite, dolomite, halite, plagioclase, and precipitation of secondary calcite and gypsum as the apparent dominating reactions, reflecting the general groundwater chemistry in the basin. Groundwater evolves, namely from CaHCO₃ to NaHCO₃, and finally into NaCl water along its flow path. The presented results improve our understanding of the hydrochemical controls of the groundwater resources and support the design and implementation of sustainable water resources management strategies for the Pra Basin.

The water providers of Jordan are constantly seeking to find new water resources to supply the public. Water table depths of up to 250 m, dry aquifers and saline waters make it increasingly difficult to successfully strike exploitable groundwater. We provided geoelectrical measurements for the exploration of a new well field area and set up a preliminary a-priori model for the interpretation of the geoelectrical results. Borehole geophysical logs, data on salinity content and subsurface interpretations greatly helped to get a detailed mapping of subsurface structures in the pilot area. To improve drilling success, geoelectrical investigation should be regarded as a mandatory step in the exploration process for new boreholes in Jordan.
The sustainability of groundwater use started to be challenged in the 80es when the first deep water wells were drilled. In addition, pump capacities increased and groundwater-based irrigated agriculture expanded since then. However, there are still big challenges that need to be addressed at national level. This includes improving operation and maintenance of well fields, basic well monitoring in order to increase energy efficiency to bring rising costs of water production under control. Through support of the Jordanian Ministry of Water and Irrigation, the BGR aims at improving the sustainable management of groundwater resources.