Geological nvestigations in the Chukchi Sea and the adjacent areas of the Arctic Ocean during the RUSALCA-2009 expedition

Abstract

The Joint Russian-American LongTerm Census of the Arctic Project (RUSALCA) started in Novem� ber of 2003 for the longterm monitoring of the Arctic environment. The studied region comprises poorly studied areas of the Chukchi Sea and the adjacent seg� ment of the Arctic Ocean near the Russia-United States boundary. This area is characterized by maximal rates of the environmental changes in the Arctic dur� ing the last decades, which is expressed, for example, in the enhanced ice melting (Fig. 1). Therefore, this project was aimed at the longterm monitoring of the Arctic environment and searching for the factors responsible for these changes. In this connection, of importance is the testing of different hypotheses explaining such significant environmental changes in the region under consideration. The main of these hypotheses are the increased water and heat exchange via the Bering Strait, the strengthened air heat transfer in the northern direction, and the upwelling of rela� tively warm intermediate Atlantic waters, which pene� trate into the eastern Arctic Ocean along the Eurasian continental slope. There is also an assumption con� cerning the activated geological processes in this region based on the development of a graben-rift sys� tem of nearmeridional and nearlatitudinal riftogenic structures in the Chukchi Sea (Fig. 1) formed in the Mesozoic and activated in the Late Cenozoic. This system is best studied in the socalled Chukchi Gra� ben, a neotectonic structure extending from eastern Chukotka in the south to at least the Herald Trench in the Chukchi Sea in the north (Fig. 1). Its onshore part studied in eastern Chukotka (the Kolyuchino- Mechigment zone) hosts Late Cenozoic volcanics and many hydrothermal vents with a discharging water temperature up to 97