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Regional Depositional Setting of the West Orphan Basin; The Importance of Contour Current Processes on Stratigraphic Trap Generation in a Hybrid Depositional System


We have completed a regional study of the Canadian Atlantic Margin to better understand the geologic evolution and hydrocarbon prospectivity of the West Orphan Basin (WOB). The WOB is interpreted to have been initiated through extension beginning in the late Jurassic resulting in a set of extensional and trans-tensional rift basins. Ongoing extension in the early Cretaceous then stepped outboard into the Atlantic opening which set up deep water conditions across Orphan basin. As a result of the opening of the north Atlantic during in the Eocene, Arctic-derived, boreal waters begin to interact with warm central/southern Atlantic systems. The resulting circulation system set up a series of shelf parallel contour currents, which transported, deposited and eroded sediment across thousands of kilometers of the Eastern North America seaboard. Regional mapping identified a series of slope-parallel migrating sediment drifts, which migrated and infilled slope accommodation created by the opening and subsidence of the Atlantic. Within the WOB, the location and geometry of contourite drifts created a terraced slope-to-basin floor architecture, and depositional profile upon which the turbidity current-sourced Eo/Oligocene, Cape Freels Fan (CFF) was deposited. 2D and 3D seismic mapping in the WOB reveals evidence for strong and persistent slope parallel currents throughout the Tertiary interval in the form of plastered and separated drifts, sediment wave fields, erosional toe-of-slope moats, and extensive mega-furrows. The CFF shows stratigraphic evidence for both turbidity and contour currents. Hence, the depositional history of the CFF (Ephesus) is that of a hybrid system that records the interaction of simultaneous north-south oriented contour currents and west-east oriented sandy turbidity currents. The contour currents can be shown to have interacted with, and modified the primary depositional architecture of the fan and were important processes for the formation of stratigraphic traps.