Arctic Ocean spreading models and their significance for understanding Late Palaeozoic and Mesozoic sediment dispersal patterns in the Arctic

The Arctic Ocean contains two deep-water oceanic basins: the Eurasia Basin opened during Cenozoic time, with a spreading history that is well-constrained by linear magnetic anomalies; the Amerasia Basin is considered to have opened predominantly during Cretaceous time but there is no easily interpretable pattern of magnetic anomalies and the origins of several component features are controversial. Consequently, the mechanism responsible for opening the Amerasia Basin is disputed. One of the most important variables in spreading models is the origin of the Alpha-Mendeleev Ridge. This ridge is the largest submarine bathymetric elevation in the Arctic Ocean and crosses the Amerasia Basin from Ellesmere Island to the Siberian continental shelf.

The widely supported ‘Alaska rotation model’ involves opening of the Amerasia Basin by counterclockwise rotation of an Alaska-Chukotka block away from the Canadian Arctic margin around a pole situated in the Mackenzie Delta region. Supporters of this model generally favour an oceanic hotspot origin for the Alpha-Mendeleev Ridge. However, although hotspot-related basaltic igneous rocks are probably an important component of the Alpha-Mendeleev Ridge, new geophysical data suggest that the ridge may be, at least partially, underlain by extended and intruded continental crust. Although the presence of continental crust does not preclude the simple Alaska rotation mechanism, the complex bathymetry of the Alpha-Mendeleev Ridge, and the need to accommodate the Chukchi Borderland in reconstructions points to a more complex spreading history in the central Arctic Ocean. As changes of spreading geometry in the presence of a hotspot are conditions favourable to creating microcontinental fragments, the presence of continental crust within the Alpha-Mendeleev Ridge is therefore compatible with a multi-stage opening history. However, the details of this opening history remain elusive.

Different spreading mechanisms in the Amerasia Basin imply profoundly different geological histories for the surrounding shelves. Northerly-derived Late Palaeozoic and Mesozoic sediments are recognised in a number of Arctic basins on these shelves, necessitating sediment derivation from the area now occupied by the Arctic Ocean. As a consequence, a central Arctic landmass has been depicted on many palaeogeographic reconstructions prior to opening of the Arctic Ocean. However, because pieces of this putative former landmass (or landmasses) are now fragmented around the margins of the Arctic Ocean, their pre-drift configuration can only be truly understood once spreading geometries for the Amerasia Basin are properly constrained. Conversely, the ability to identify and characterise the component pieces of a pre-drift central Arctic landmass will provide data with which to refine Arctic Ocean spreading models. Here we report research that seeks to combine geophysical studies of the Amerasia Basin with provenance analysis of northerly-derived clastic sediment on surrounding shelves in an attempt to provide these constraints.