Palaeo-environments at the Batagay site in West Beringia during the late Quaternary

Climate change influences all ecosystems on all levels. Understanding the geological lessons of the Quaternary could provide valuable information for managing future environmental variations. Climatic changes in the past triggered alteration of past environments. The consequences of past alterations are widely documented in palaeontological records.
Permafrost deposits, which underlie vast areas of Asia, provide valuable information for reconstructing past ecological events. Most permafrost exposures studied in Russia are situated in the coastal lowlands of northeastern Siberia, whereas reports of inland archives are scarse. The syngenetic permafrost deposits of the Batagay outcrop preserve valuable data about the palaeo- environment of the Yana Highlands of inland Beringia. The former subcontinent of Beringia connected Eurasia and America during low sea-level stands and hosted a now extinct biome—the mammoth‒steppe. To unravel the environmental history of West Beringia, the Batagay permafrost sequence was investigated.
The first part of the thesis (chapter 2) reports the first sedimentological results and provides a stratigraphical and temporal framework of the sequence. The stratigraphy comprises five units, including two ice complexes, two sand units and one woody layer. OSL and AMS dating suggest that the sequence started to accumulate during the late Middle Pleistocene and extends through the Late Pleistocene, with interruptions and erosional events. The depositional processes were climatically and seasonally controlled. Stratigraphical, cryolithological and geochronological data are significant for later palaeontological investigations.
The second part of the thesis (chapter 3) presents the palaeo-environmental reconstruction at the Batagay site during marine isotope stages (MIS) 6‒2. Plant macrofossil, palynological, entomological, and charcoal analyses were performed on 41 samples from the Batagay outcrop. The palaeo-vegetation of the two climatic extremes of the Late Pleistocene—the Last Interglacial (LIG) and the Last Glacial Maximum (LGM)—are described in detail based on exceptionally fossil-rich samples. The palaeo-environmental reconstruction suggests that meadow steppes were a significant vegetation type during the LIG and formed the primary vegetation during the LGM. Cold-resistant tundra‒steppe communities were mostly lacking at the site during the studied period, whereas larch was locally present in the Yana Highlands throughout the Late Pleistocene. Palaeontological data indicate that the Yana Highlands were a northern refugium for larch, steppe communities, and herbivores. That larch stands and meadow steppes persisted at the site from MIS 6 to 2 indicates environmental stability in the region. The magnitude of climatic continentality changed during the late Quaternary, but warm growing season and low precipitation fluctuations were insufficient to effect fundamental shifts in plant communities in the Yana Highlands.
The third part of the thesis (chapter 4) discusses the phylogeographical history of the endemic steppe plant Stellaria jacutica found in the LIG fossil assemblage. A finding of this single seed proves that modern steppes of the Yana Highlands did not establish as late as in the Holocene. Instead, they are relics of a formerly closed central Siberian–northeast Yakutian steppe belt.
Overall, the data obtained from the inland Batagay outcrop differ from those previously reported from coastal permafrost sections. Thus, the results of this thesis provide valuable information about the evolution of vegetation in continental settings of West Beringia.