Crustal structure and tectonics of the southeastern Beaufort Sea continental margin

Abstract

The structure of the southeast margin of the Canada Basin is synthesized from seismic reflection and refraction profiles in the southern Beaufort Sea and Mackenzie Delta, interpreted in conjunction with potential field data and the exploration seismic data base. The present margin was formed in the Jura‐Cretaceous and comprises a complex pattern of rifted and transform faulted crustal segments. Thinning in the upper crust is bounded by the Eskimo Lakes Fault Zone (ELFZ), a series of extensional listric normal faults, and is controlled by preexisting structures. Lower crustal thinning and the transition to oceanic crust occurs outboard of the ELFZ. A thick (up to 16 km) Late Jurassic and younger synrift and postrift sedimentary succession overlies oceanic crust in the eastern part of the Canadian Beaufort Sea and thinned continental crust between the Mackenzie Delta and Alaska. Tertiary faulting in the sedimentary basin appears to be related to the crustal structure. Present‐day seismicity in the southern Beaufort Sea is essentially limited to the area underlain by oceanic crust. Abrupt along‐strike changes in crustal affinity and degree of thinning allow the recognition of a NW‐trending transform fault. Regional gravity data, dominated by a series of coastline parallel highs, are used to extrapolate crustal features to the northeast along the Canadian polar continental margin. It is inferred that the Canadian polar margin consists of a number of 250‐to‐350‐km‐long stretched crustal segments separated by possible fracture zones. The orientation of the analogous tranform fault identified in the southeastern Beaufort Sea offers the possibility of kinematic constraints on models of ocean floor development within Canada Basin.