CRUSTAL STRUCTURE AND TECTONICS OF THE SOUTHEASTERN BEAUFORT SEA CONTINENTAL-MARGIN

The structure of the southeast maring of the Canada Basin is synthesiz ed from seismic reflection and refraction profiles in the southern Bea fort Sea and Mackenzie Delta, interpreted in conjunction with potentia l field data and the exploration seismic data base. The present margin was formed in th Jura-Cretaceous and comprises a complex pattern of r ifted and transform faulted crustal segments. Thinning in the upper cr ust is bounded by the Eskimo Lakes Fault Zones (ELFZ), a series of ext ensional listric normal faults, and is controlled by preexisting struc tures. Lowe crustal thinning and the transition to oceanic crust occur s outboard of the ELFZ. A thick (up to 16 km) Late Jurassic and younge r synrift and postrift sedimentary succession overlies oceanic crust i n the eastern part of the Canadian Beaufort Sea and thinned continenta l crust between the Mackenzie Delta and Alaska. Tertiary faulting in t he sedimentary basin appears to be related to the crustal structure. P resent-day seismicity in the southern Beaufort Sea is essentially limi ted to the area underlain by oceanic crust. Abrupt along-strike cahnge s in crustal affinity and degree of thinning allow the recognition of a Nw-trending transform fault. Regional gravity data, dominated by a s eries of coastline parallel highs, are used to extrapolate crustal fea tures to the northeast along the Canadian polar continential margin. I t is inferred that the Canadian polar margin consists of a number of 2 50-to-350-km-long stretched crustal segments separated by possible fra cture zones. The orientation of the analogous transform fault identifi ed in the southeastern Beaufort eea offer the possibility of kinematic constraints on models of ocean floor development within Canada Basin.