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Tectonic Development of the Amerasian Basin with Implications for Surrounding Arctic Regions

Winefield, Peter 5; Worrall, Dan 1; Bergman, Steven *1; Steffens, Gary S.4; Van Oosterhout, Cees 2; DiMarco, Michael 4; Hafkenscheid, Edith 2; Wannier, Mario 2; Ross, Malcolm I.1; Bishop, Andrew 1; Homza, Thomas X.3; Scheidemann, Robert 4
(1) Shell International E&P, Houston, TX.
(2) Shell International E&P, Hague, Netherlands.
(3) Shell Exploration & Production Co, Anchorage, AK.
(4) Shell Exploration & Production Co, Houston, TX.
(5) Shell Petroleum Development Co, Lagos, Nigeria.

The tectonic development of the Circum-Arctic region has long been debated due to its physical remoteness, complexity, scale and relative paucity of subsurface data. In particular, the Amerasian (Canada) Basin remains a geological enigma. Although most prevailing models favor a rotational movement of Arctic Alaska/E Siberia away from the Canadian Arctic Islands, the details and timing remain unclear and most resulting reconstructions fail to explain the evolution of the Chukchi Borderlands - a key element.

Using regional geology, seismic and well control with newly compiled potential field data, a new tectonic model is proposed that has significant impact on timing and opening of the Amerasian (Canada) and surrounding Circum Arctic regions. The model highlights the formation of the Amerasian Basin in the mid to late Jurassic when a continental block consisting of northern Alaska and a portion of East Siberia rifted away from the Canadian Arctic Islands around a pole of rotation in the onshore Richardson Mountains region. This region has subsequently been overprinted by deformation in the NE Brooks Range orogen. The Chukchi Borderlands consists of highly extended continental crust that rifted away and rotated from East Siberia during this Jurassic rifting event. An early Jurassic palinspastic restoration provides a tight and compelling pre-rift fit of the two conjugate margins. Whereas previous models invoked an Early Cretaceous opening of the Amerasian Basin marked by the LCU (Lower Cretaceous Unconformity) defining the rift-drift transition, the LCU represents a flexural unconformity related to Brookian thrusting in our model to explain the observed magnetic anomaly data.

A selection of paleogeographic maps across the Circum-Arctic are presented ranging from the early Triassic to Paleocene-Eocene times. The maps were created using key stratigraphic and structural data restored to their paleo-positions via PaleoGISTM. In addition, a Circum-Arctic stratigraphic chart was compiled from various sources to validate and constrain the proposed tectonic model and resultant maps. This process facilitated regional basin tectonic analysis and extrapolation of proven reservoir and source rock trends into under-explored or data-poor areas highlighting potential ‘white-space’ areas for future exploration.


AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California