Middle to Late Miocene Slope Failure and the Generation of a Regional Unconformity Beneath the Western Scotian Slope, Eastern Canada

摘要

The global greenhouse to icehouse transition that occurred during the middle Cenozoic marked a major shift in the geological and oceanographic conditions in the northwest Atlantic Ocean. During this transition, strong contour currents developed and sediment input to the North American Basin increased. These events were coeval with the development of regional unconformities within the basin and along the basin margins. This study examines a widespread, Middle to Late Miocene-age unconformity preserved below the western Scotian margin and demonstrates that it is primarily the product of erosion by regional submarine mass movement, although bottom currents and channel development may have played a role in its formation. The mass-transport deposits are among the largest reported in the literature. Despite the presence of a steep upper slope in the study area, the erosion is not due to mass-wasting initiated on the upper slope, but rather erosion and seabed failure initiated on the lower slope and continental rise, followed by failure retrogression. It is suggested that salt tectonics and bottom-current activity contributed to sediment failure.