NORTH AMERICAN-BERING PLATE BOUNDARY: NEW PALEOMAGNETIC DATA ON LATE CRETACEOUS VOLCANIC ROCKS OF CENTRAL CHUKOTKA
I.E. Lebedev1, V.E. Pavlov1, P.L. Tikhomirov1, A.M. Pasenko1, U.S. Efremova2
1Schmidt Institute of Physics of the Earth, Russian Academy of Sciences, Moscow, Russia
2Institute of the Earth’s Crust, Siberian Branch of the Russian Academy of Sciences, Irkutsk, Russia
Keywords: North-East of Eurasia, Bering Sea region, Okhotsk-Chukotka volcanic belt, Valunistoe deposit, paleomagnetism, geochronology.
Abstract
This paper presents new geochronological and paleomagnetic data that support the idea of later termination of magmatism in the Okhotsk-Chukotka Volcanic Belt (OCVB) within the East Chukotka flank zone than previously thought. It also allows the calculation of a new paleomagnetic pole (78.6°N, 212.2°E, A95= 4.7°, N=104) with an age of ~72 Ma for the vicinity of the Valunistoe deposit. Combined with paleomagnetic data previously obtained by us for the Kupol deposit area, the new results lead to the following conclusions: 1. The studied areas (the "Kupol" and "Valunistoe" location) have experienced relatively small, but statistically significant, displacements relative to the North American plate during the time interval from the Late Cretaceous to the present. 2. The "Kupol" location is rotated counterclockwise by several to a few tens of degrees relative to the North American plate, while the "Valunistoe" location is displaced relative to this plate in latitude by a distance of at least several hundred kilometers. 3. Based on the obtained data, we propose a model, building on the existing Bering Sea region model of Redfield and Fitzgerald (1993), according to which the "Kupol" and "Valunistoe" locations belong to the boundary area between the North American plate and the Bering plate, represented by a series of tectonic blocks. The tectonic block to which the "Valunistoe" location belongs is one of the westernmost blocks grouped into the Bering plate, while the "Kupol" location belongs to the easternmost regions of the Chukotka deformed margin of the North American plate. Deformations arising in the interaction of these tectonic blocks in the region under consideration are mainly diffuse. The Trans-Bering Seismic Belt appears to be a potential area where the discussed deformations may be most concentrated.
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