Numerous coastal exposures and cores of permafrost deposits have been studied in the lowlands surrounding the Laptevs and East Siberian seas since 1998 within the Russian-German Science Cooperation «SYSTEM LAPTEVS SEA». The reconstruction of palaeoenvironment dynamics of these non-glaciated arctic lowlands are based on geochronological, palaeoecological, sedimentological and geocryological studies. Permafrost aggradation and degradation triggered by Quaternary climate changes are the most important regional processes of landscape evolution. The presented composite sequences illustrate the various palaeoenvironmental stages within the last 200,000 years. Sharp sedimentary discontinuities, probably caused by seismotectonic events, as well as long-term gradual transitions in sedimentary environments have been described. There is also a clear stratigraphic difference between the eastern part of the region (New Siberian Islands, the Dimitry Laptev Strait) and the western area (Lena Delta, the Lena-Anabar lowland).

We will summarize our new palaeoenvironmental results and stratigraphic conclusions starting from Late Saalian (Taz) Ice Complex deposits on Bol'shoy Lyakhovsky Island, the reconstruction of records from Eemian (Kazantsevo) ice wedge casts, and Early Weichselian (Zyryanka) floodplain deposits there. In the western Laptev Sea region, discernible permafrost sequences are younger. They begin with Early Weichselian (Zyryanka) fluvial deposits reflecting active runoff in front of the main mountain chains (the Kharaulakh, Chekanovsky and Pronchshishev ranges) between 100 to 60 kyr BP.

The onset of the ubiquitous Yedoma formation is time-transgressive within the range of 80 to 28 kyr BP, depending on the locality. Depositional environments were probably similar for these ice-rich permafrost sediments in flat and poorly drained lowlands. Whereas Yedoma sequences of New Siberian Islands are not younger than 28 kyr, other sequences (e.g. at Bykovsky Peninsula) reflect a time span up to the final Late Pleistocene. Despite the ongoing discussion about the Karginsky Interstadial (c. 50-25 kyr BP) records in Siberia there is clear evidence for environmental variations during this period in the studied area. Even if the MIS 3 interstadial period in northern Yakutia was not strongly pronounced, the obtained terrestrial record reflects the global trend of climate changes of this period.

New data from sandy deposits of the Arga Complex in the western Lena Delta testify to their synchroneity with Yedoma and fluvial deposits in front of the Chekanovsky Range.

The strongest environmental impact on the Laptev Sea margins is connected with the regional permafrost degradation in response to the Holocene warming and the simultaneous sea level rise. It has resulted in the formation of numerous thermokarst depressions, flooding of the shelf, and in general reorganisation of hydrological regime. Thermokarst depressions seem to have appeared earlier on New Siberian Islands as compared to the western Laptev Sea region. The regional Holocene Thermal Optimum is documented in paleoecological records at about 9-7 kyr BP.

Reference:

Schirrmeister L., Hubberten H.-W., Andreev A., Grosse G., Kienast F., Meyert H., Siegert Ch., Schwamborn G., Kunitsky V., Kuznetsova T., Derevyagyn A., Kuzmina S. Late Quaternary landscape dynamics of non-glaciated arctic Siberia: results of eight years study of the Laptevs Sea coastal lowlands. Correlation of Pleistocene Events in the Russian North. International Workshop Abstracts. 4-6 December 2006. Saint-Petersburg, 2006, p. 82.