Intriguing climatic shifts in a 90 kyr long lake record from the Timan Ridge in northern Russia

¹Mona Henriksen, ¹Jan Mangerud, ²Alexei Matiouchkov, ³Andrew Murray, ⁴Aage Paus, ¹John Inge Svendsen

INTRIGUING CLIMATIC SHIFTS IN A 90 KYR LONG LAKE RECORD FROM THE TIMAN RIDGE IN NORTHERN RUSSIA

1) Department of Earth Science, University of Bergen, Bergen, Norway mona.henriksen@geo.uib.no, jan.mangerud@geo.uib.no, john.svendsen@geo.uib.no

2) A.P. Karpinsky Russian Geological Research Institute (VSEGEI), St. Petersburg, Russia alexei_matiouchkov@vsegei.ru

3) Nordic Laboratory for Luminescence Dating, Department of Earth Sciences, University of Aarhus, Roskilde, Denmark andrew.murray@risoe.dk

4) Department of Biology, University of Bergen, Bergen, Norway aage.paus@bot.uib.no

A 22 m long core record of lacustrine sediments that was obtained from the basin of Lake Yamozero on the Timan Ridge in northern Russia has provided intriguing climatic shifts during the last glacial cycle. An overall shallowing of the lake is reflected in the lower part of the cores where the minerogenic sediment changes into a gyttja that accumulated in a shallow lake. The changing pollen composition in these lower strata indicates a transition from glacial steppe vegetation to interstadial shrub-tundra. These organic beds are capped by a well-defined layer of compact silty clay deposited in relative deep water under climatic conditions at least as warm as today with surrounding spruce forest.

Judged from the pollen assemblages, this unit represent the last interglacial period, i.e. the Eemian. However, a series of OSL dates contradict this possibility and rather suggest that the warm interval corresponds to the Early Weichselian Odderade interstadial (MIS 5a). If correct, the latter age model implies that the summers during this interstadial were just as warm as in a normal interglacial of this part of Europe. Furthermore, the high lake level suggests a high groundwater table and probably a relatively humid climate.

The upper contact of the silty clay is an erosional surface that most likely formed during a period when the lake floor became subaerially exposed, suggesting that the basin dried out. The sediment directly above seems to reflect a reversal to much colder conditions. During the Middle Weichselian (c. 70-40 kyr) a long sequence of laminated silt accumulated under fluctuating climatic conditions. Following a second gap the lake basin was filled up again around 18 kyr. This part of the sequence includes the Lateglacial Interstadial and Younger Dryas with Holocene gyttja at the top.

Reference:

Henriksen M., Mangerud J., Matiouchkov A., Murray A., Paus A., Svendsen J.-I. Intriguing climatic shifts in a 90 kyr long lake record from the Timan Ridge in northern Russia . Correlation of Pleistocene Events in the Russian North. International Workshop Abstracts. 4-6 December 2006. Saint-Petersburg, 2006, p. 40.