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.