Stages of the Late Quaternary environment of NE Siberian lowlands during the last 200 ka Permafrost records from northern Yakutia

• Main Authors: Schirrmeister, Lutz, Wetterich, Sebastian, Grosse, Guido, Andreev, Andrei, Kienast, F., Meyer, Hanno
• Format: Conference Object
• Language: unknown
• Published: 2008
• Subjects: Ice; laptev; Laptev Sea; permafrost; Thermokarst; Tundra; wedge*; Yakutia
• Online Access: https://epic.awi.de/id/eprint/18632/; https://epic.awi.de/id/eprint/18632/1/Sch2008n.pdf; https://hdl.handle.net/10013/epic.30275; https://hdl.handle.net/10013/epic.30275.d001

Permafrost sequences in Yakutian coastal lowlands preserved palaeoenvironmental records of the last 200 ka. Several stages could be separated using a multiproxy study approach. Because the study region is separated by the neotectonically active rift zone between the North American and Eurasian continental plates, the available stratigraphical records are different between the plate regions. Middle Pleistocene deposits areonly exposed along the Dimitrii Laptev Strait, the eastern part of the study region and situated on the North American plate. The identified pre-Eemian cold period (>200 to 130 ka) was subdivided into a stadial-interstadial alternation and is characterized by ice-rich deposits with thick syngenetic ice wedges (older Ice Complex formation) as well as loess-like flood plain deposits. The following Eemian warming resulted in thawing of ice-rich deposits and the formation of ice wedge casts and thermokarst depressions filled with subaerial and lacustrine deposits. Pollen-based reconstructionsshow that summer temperatures during the Eemian climate optimum were at least 4-5°C higher than today. However, plant macrofossils point to summer temperatures even 10°C higher. The vegetation changed from open steppe-like associations at the beginning of the Eemian to shrub tundra during the optimum, and to tundra-like associations at the transition to the following glacial stage. During the Early Weichselian, loess-like floodplain accumulation, shallow water bodies, and very sparse vegetation were characteristic features in the Laptev Strait region on the North American plateedge. In contrast, the records west of the plate boundary, in the central and western Laptev Sea regions, cover less than the last 100 ka. Here, the Early Weichselian palaeoenvironment was characterized by wide fluvial runoff plains in front of the low mountain ridges. The comparably rare bioindicators reflect the existence of a tundrasteppe environment during the time of deposition.Strong changes in all environmental conditions are ...