Chukchi Edges Project - Geophysical constraints on the history of the Amerasia Basin

Abstract

The geological history of the Amerasia Basin is poorly understood, in part due to the lack of identified plate boundaries within it. These boundaries must exist to explain the basin history. Identification of these structures will make it possible to reconstruct the development of the basin, which will substantially improve our understanding of the surrounding continents. The Chukchi Borderland, a block of extended continental crust embedded in the Canada Basin, figures prominently in all tectonic models proposed for the opening of the Amerasia Basin. The Chukchi cannot be simply reconstructed back to any of the nearby continental shelves. It complicates any model for the Mesozoic opening of the Amerasia Basin. According to the commonly accepted model, the Canada Basin opened like a pair of scissors. This was accomplished by a counter-clockwise rotation of the North Alaskan-Chukchi micro-plate (Arctic Alaska Plate) by 66 degrees. The micro-plate collided with the Siberian margin. Most of the existing models for the development of the Amerasia Basin accept the basic pattern of scissors-like or, classically, the “windshield wiper” opening for the basin. This theory finds some support in the identification of a possible relict mid-ocean ridge axis in the central Canada Basin. Since the continental Chukchi Borderland creates a space problem for any simple opening model, the greatest differences between models revolve around how to accommodate that block. Fundamental differences among the proposed models include the paleo-location of the Chukchi Borderland as well as whether the Borderland is a single entity or is instead comprised of small terranes which behaved as independent microplates. A consequence of these models is the prediction that the Chukchi Borderland is distinct from the Chukchi Shelf. During the Chukchi Edges cruise on board the RV Marcus G. Langseth, we collected multi-channel seismic reflection, swath bathymetry, gravity, magnetics and sonobuoy refraction data across the transition from the Chukchi Shelf to the Borderland. These data will establish new constraints on the timing and distribution of deformation in the development of the Amerasia Basin and provide a test of the windshield wiper model of basin opening.