The Problems of Tectonic Reconstructions in the Arcticand New Paleomagnetic Data for the New Siberian Islands

Valery Vernikovsky

Key words: paleomagnetic reconstructions, New Siberian Islands, Arctic The current structure of the Arctic Ocean is determined by: the relative position of Eurasia and North America; the location and structures of microcontinents and main terranes of the Arctida paleocontinent; and the opening of the Amerasian (J-K) and Eurasian (Pg-N) basins. Along with geological and geochronological data, in order to create evolutionary models and paleogeodynamic reconstructions for the Arctic region for the entire Neoproterozoic-Phanerozoic time interval one must use paleomagnetic data that will allow the determination of the relative position of paleocontinents and terranes at particular moments in time. Unfortunately such data for the main structures of the Arctic are extremely scarce, and virtually nonexistent for the eastern part of the Arctic. The New Siberian terrane is one of the key structures of the Arctic. However, many issues related to its structure, margins and formation history are under vivid discussion. Among the problems discussed is its initial appurtenance to the marginal structures of Siberia or North America, as well as the position of the western margin of the Chukotka-Alaska terrane, which could include the New Siberian terrane. At the same time it is inferred that this very important boundary can divide the New Siberian block in two fragments by passing between the Anzhu and De Long islands or between the Kotelny and Faddey islands. The comparison of newly obtained paleomagnetic directions for the Ordovician series of the studied islands distinctly shows their similarity in stratigraphic coordinates and is an indication of the tectonic unity of the territory of the Anzhu and De Long archipelagos. Their relative position at the beginning of the Paleozoic did not differ from their current position. On the geosphere the calculated virtual geomagnetic poles form a trend line, in which the Middle Ordovician (465 Ma) pole of Bennett Island is located between the Early Ordovician (475 Ma) pole, calculated for the Ayan formation rocks and the Ordovician-Silurian (440 Ma) pole for rocks of the Terutekh and Urasin formations of Kotelny Island. Judging from this apparent polar wander path in the Early Paleozoic the New Siberian block was slowly and steadily drifting in the subtropical area of the Earth with insignificant clockwise rotation (latitudinal drift was less than 4 cm/year, rotation – up to 2 deg./m.y.). These first paleomagnetic data, obtained for well dated Early Paleozoic sedimentary rocks of the Kotelny and Bennett Islands, let us assume that the rocks of the Anzhu and De Long archipelagos formed in the same New Siberian terrane, that is to say, on the same basement at least from the Early Ordovician.

AAPG Search and Discovery Article #90177©3P Arctic, Polar Petroleum Potential Conference & Exhibition, Stavanger, Norway, October 15-18, 2013