SMSPS Stephan Mueller Special Publication Series SMSPS Stephan Mueller Spec. Publ. Ser. 1868-4564 Copernicus Publications Göttingen, Germany 10.5194/smsps-4-243-2009 Age and paleomagnetism of the Okhotsk-Chukotka Volcanic Belt (OCVB) near Lake El'gygytgyn, Chukotka, Russia Stone D. B. 1 Layer P. W. 1 Raikevich M. I. 2 Geophysical Institute, University of Alaska, Fairbanks, Alaska, 99775, USA Northeast Interdisciplinary Research Institute, 16 Portavaya St., Magadan, 685010, Russia 17 09 2009 4 243 260 Copyright: © 2009 D. B. Stone et al. 2009 © European Geosciences Union 2009 This article is available from https://smsps.copernicus.org/articles/4/243/2009/smsps-4-243-2009.html The full text article is available as a PDF file from https://smsps.copernicus.org/articles/4/243/2009/smsps-4-243-2009.pdf

Paleomagnetic results from the upper two thirds of the whole section of the Okhotsk-Chukotka Volcanic Belt (OCVB) volcanics exposed in the area around Lake El'gygytgyn, Chukotka yield stable, consistent magnetic vectors and well-preserved reversed directions. The magnetostratigraphy and <sup>40</sup>Ar/<sup>39</sup>Ar geochronologic data reported here indicate that the sampled OCVB volcanics were erupted between about 90 and 67 Ma, and show no significant change in the apparent pole position over that time. The OCVB extends from northeast China, across Northeast Russia to the Bering Straight. This belt is made up of both extrusive and intrusive rocks, with the extrusive rocks and their associated sediments being dominant. The whole belt important in interpreting the paleogeography of the region because it overlies many of the accreted terranes of Northeast Russia. Most importantly, it overlies parts of the Chukotka-Alaska block which is thought to have moved out of the Arctic Ocean region, as well as terranes accreted from the south. These latter terranes have been rafted northwards on the paleo-plates of the Pacific, implying that the present relative paleogeography of all of the terranes overlain by the OCVB were essentially in place by 67 Ma, and possibly as early as 90 Ma. However, comparing our paleomagnetic pole position for the OCVB with those for North America and Eurasia (a proxy for Siberia) shows a statistically significant displacement of the OCVB pole to the south west. This implies that not only the OCVB, but the underlying terranes of northeast Russia, experienced southerly displacement with respect to the Siberian and North American platforms since the Late Cretaceous.

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