HR: 15:10h
AN: GP43C-07    [Abstracts]
TI: Siberian Arctic Continental Margin: Constraints and Uncertainties of Plate Tectonic Models
AU: * Drachev, S S
EM: drachev@newfields.ru
AF: New Fields Ventures Ltd./P.P. Shirshov Institute of Oceanology, 77/1, Sadovnicheskaya Nab. , Moscow, 115035 Russian Federation
AB: Siberian Arctic Continental Margin (SACM) reveals a complicated tectonic history resulted from three major events: (1) Mesozoic collisions of various allochtonous blocks with Paleo-Siberian continental margin, (2) Opening of Canada Basin, and (3) Opening of Eurasia Basin. Despite considerable progress was achieved in the past 15 years owing to CDP seismic reflection surveys and satellite observations, some major points of SACM's structure and history are still poorly understood. According to the most accepted model, opening of the Canada Basin led to separation and counterclockwise rotation of North Alaskan-Chukchi Microplate until it collided with Siberian/Omolon margin along South Anyui Suture. However, the time and geometry of the opening are not properly constrained yet. Uniform rotation of North Alaskan-Chukchi Microplate by 66 deg. causes a significant overlap in the East Siberian Sea that cannot be explained by later extension of the SACM. Accepted age of the basin opening is 130-80 Ma, however, geological data show that South Anyui Suture was already completely closed by Aptian. In contrast, Cretaceous flood basalts suggest even later opening of the Canada Basin, which may have begun around 125 Ma. Chukchi Borderland, when remained at its present position, prevents closure of the Amerasia Basin. We suggest it was conjugated to what now the northeastern margin of East Siberian Sea is. Then it was detached from the SACM and moved to the present-day position during spreading episodes within the Arctic basins. However, the time of this event is unconstrained yet. Late Cretaceous-Cenozoic extension of the SACM was related to opening of the Eurasia Basin, and, probably, North Atlantic and Labrador Sea. It led to significant modification of SACM's initial architecture and created several profound rift systems. Extension of northern Laptev Shelf totals at least 190 km, which is about 47 % of the total divergence within adjacent Eurasia Basin. The northern East Siberian and Chukchi seas and Chukchi Borderland are the best candidates to account for some 200 km of the "missing extension". Using all available data we have revised structure and geological history of the SACM and speculated its relationships to the Canadian Arctic Margin in a "pre-Canada Basin" Arctic.
DE: 8105 Continental margins and sedimentary basins
DE: 8109 Continental tectonics--extensional (0905)
DE: 8157 Plate motions--past (3040)
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2004 AGU Fall Meeting