QUATERNARY DEPOSITS OF NEW SIBEIRIA ISLAND (RUSSIAN ARCTIC)
BASILYAN, ALEXANDER . Geologycal Institute RAS, Moscow, Russia.
Nikolskiy, Pavel A. Geologycal Institute RAS, Moscow, Russia.
In 2000 and 2001, the reconnaissance were undertaken on New Sibeiria Island (East-Siberian Sea) within the Russian-US Project "Zhokhov-2000". In order to reveal the quaternary history of the New Siberia Island, development of fauna and flora and search for the ancient man traces, a significant part of the Island was investigated.
The surface of New Siberian Island is about completely covered by genetically different quaternary deposits. The only exception is the restricted outcrops of the underlying folded Meso-Cenozoic rocks.
In general, sequence of the quaternary deposits consists of marine deposits, which are overlayed by terrestrial deposits. Lower marine deposits are dislocated. During the Quaternary, probably up to the beginning of the Late Pleistocene, the moste territory of the Island was submerged below the sea level. Three sedimentation cycles of marine deposits are identified by sea level oscillations. In the lower one, Arctica islandica (the Atlantic species of mollusks) is encountered. Its penetration such eastward shows climate warming in the early Quaternary. Numerous shells of Astarte (Tridonta) borealis and Astarte (Nicania) montagui are typical of the second cycle. An analysis of mollusk fauna and the character of lamination of enclosing deposits indicate a change of the sedimentation depth between 0 to 35-50 m. The cycles are separated by a peat interlayer formed under the sub-aquatic conditions. The sub-horizontal deposits of the regression part of the third cycle outcrope everywhere on New Siberian Island from the sea level up to the 20-30 m. Of mollusks in these deposits, only Portlandia arctica is encountered. This species can stand strong freshening.
In the Late Pleistocene, due to active tectonic movements and the eustatic sea regression accompanied with cooling, the shallow water parts of the shelf were dried. Simultaneously an Ice Complex deposits(dusty deposits with multiple ice wedges) have being forming at its surface following the development of erosion network. Terrestrial deposits are not dislocatet. Numerous late Pleistocene mammal bones are associated with these deposits. The age of fauna shows that Ice Complex deposition started at the beginning of late Pleistocene. The formation of an Ice Complex was completed around 10 kyr BP.
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