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Using Seismic Expression of Contourite Drifts to understand Mud-Dominated Depositional Systems: Insights from the Newfoundland Ridge, Offshore Canada

Boyle, Patrick R.; Romans, Brian W.; Scientists, IODP Expedition 342

Bathymetric contour parallel currents play a significant role in the shaping of continental margins and deep-sea sedimentation. Mud to fine sand-dominated oceanic sedimentary drifts deposited by these currents (contourites) display unique seismic expressions related to their evolution. The Newfoundland Ridge in the northwest Atlantic Ocean intersects one of these abyssal contour currents, the Deep Western Boundary Current, providing the ideal setting for significant and long-lived deposition of contourites. A grid of 2-D seismic-reflection profiles combined with nine IODP (Exp 342) drill sites provides a unique opportunity to link seismic-scale geometries of contourite drift deposits to abundant core data. Sediment cores spanning from the middle Eocene to the Pleistocene, reaching seafloor to subsurface depths of approximately 250 m, provide lithologic and chronologic control on seismic stratigraphic interpretations. This integrated dataset affords the ability to map these deposits and hence the Deep Western Boundary Current through both time and space.

Stratal geometries of several contourite drift deposits have been identified and mapped using 2-D seismic data. Seismic stratigraphic mapping indicates distinct changes in contourite morphologies, which are interpreted to reflect changing dynamics of current energy through time. For example, seismic facies interpreted as up-current migrating mudwave deposits are more common in younger (post-Oligocene) strata that reflect relatively high current energy. Linking seismic stratigraphic interpretations with lithologic and chronologic data allows for a better understanding of the stratigraphic evolution of these drifts deposits. Increased familiarity with deep-sea sedimentation such as contourite drift construction contributes to the fundamentals necessary to understand mud-dominated depositional systems. Improved concepts related to the depositional dynamics and resulting stratigraphic architecture of mud-dominated systems is increasingly important with continued interest in the exploration and development of shale plays.


AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013