An Integrated Tectonic Model for the Amerasian (Canada) Basin and Surrounding Arctic Regions

Peter Winefield³, Dan Worrall¹, Steven Bergman¹, Gary S. Steffens¹, Cees van Oosterhout², Edith Hafkenscheid², Michael DiMarco¹, Malcolm Ross¹, Mario Wannier², and Andrew Bishop^1
1Shell International Exploration & Production, Houston, TX.
²Shell International Exploration & Production, The Hague, Netherlands.
³Shell Petroleum Development Co. of Nigeria, 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 the resulting reconstructions fail to incorporate the Chukchi Borderlands - a key constraint.

Using regional geology, seismic and well control with newly compiled potential field data, a new tectonic reconstruction addresses most outstanding issues relating to the development of the Amerasian Basin. This has a major impact on the paleo-geographic evolution of the entire Circum-Arctic. Key elements of the proposed model are outlined in this presentation.

The Amerasian Basin formed in the mid to late Jurassic when a continental block consisting of northern Alaska and a portion of E. Siberia rifted away from the Canadian Arctic Islands around a pole of rotation in the onshore Mackenzie Delta region. This zone has subsequently been overthrust by the NE Brooks Range orogen. The Chukchi Borderlands consists of highly extended continental crust that rifted away from the E. Siberia during this Jurassic rifting event. An early Jurassic palinspastic restoration provides a tight and compelling pre-rift fit of the two conjugate margins. Based on available magnetic data, we propose that the oceanic crust of the Amerasian Basin formed between ~160-135 Ma whereas previous models have interpreted the Lower Cretaceous Unconformity (LCU) as the breakup unconformity. In our model, the LCU represents a flexural unconformity.

Seafloor spreading ceased with the closure of the Anyui Ocean and the formation of the S. Anyui Suture along the southern margin of the western Alaska-E. Siberia block. As spreading waned, a large igneous province developed in the region of the Alpha-Mendeleev Ridge concurrent with thermally driven uplift beneath Alaska and Chukotka manifested by emplacement of widespread magmatic rocks and formation of extensional basins.

Lastly, the Siberian affinities of Paleozoic carbonate platform strata in Alaska and E. Siberia have been an outstanding issue with the proposal of a rotational tectonic model for Amerasian Basin. We propose a new delineation of the suture related to the Late Silurian to Middle Devonian Innuitian orogeny that resolves this issue.

 

AAPG Search and Discovery Article #90130©2011 3P Arctic, The Polar Petroleum Potential Conference & Exhibition, Halifax, Nova Scotia, Canada, 30 August-2 September, 2011.

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