Re-evaluating the Amerasian Basin Tectonic and Sedimentation History with New Geophysical Data

David Mosher

New wave geophysical data acquisition in the high Arctic permits re-evaluation of the Amerasian Basin tectonic and sedimentologic history. In the past seven years, 15,480 line-km of new seismic reflection data and coincident refraction data and >38,000 line-km of shipborne gravity data and >50,000 line-km of airborne gravity and magnetic anomaly data were acquired in Amerasian Basin and over Lomonosov Ridge by Canadian, US and Danish expeditions.These new data support a limited rotational opening model for southern CA Basin around a pole located about 64.6 deg N and 130.8 deg W. Gravity and basement structure data reveal a central basement ridge and valley. Coincident symmetric magnetic anomalies and blocky basement morphology are consistent with an extinct spreading center. Refraction data show oceanic crustal velocities within this zone. To the flanks, crustal velocities suggest significant areas of stretched serpentinized continental crust. Basement elevations within the CA Basin deepen to the south, where sediment thicknesses exceed 15 km. The sedimentary sequence thins to the north and west. The seafloor and underlying sedimentary succession of CA Basin is remarkably flat-lying. Reflections correlate across the basin and on-lap bathymetric and basement highs. Isopach maps reveal three distinct depositional patterns, documenting the migration of sediment sources during the basin’s history. Initially, Early to mid Cretaceous synrift and orogenic sediments derived from the Alaska and Mackenzie-Beaufort margins. This unit onlaps underlying unconformities with a younging trend towards Alpha and Northwind ridges. Sediment source direction shifted to the Canadian Arctic Archipelago margin for the Eocene and Oligocene due to uplift of Arctic islands during the Eurekan Orogeny. The final stage of sedimentation appears to be from the Mackenzie-Beaufort region for the Miocene and Pliocene when drainage patterns shifted to the Mackenzie Valley. Upturned reflections at onlap positions may indicate syn-depositional subsidence. There is little evidence, at least at a regional seismic data scale, of contemporaneous or post-depositional sediment reworking, suggesting little large-scale geostrophic or thermohaline-driven bottom current activity.

AAPG Search and Discovery Article #90177©3P Arctic, Polar Petroleum Potential Conference & Exhibition, Stavanger, Norway, October 15-18, 2013