Linking Shelf and Slope Deposits Outboard the Sable Subbasin, Offshore Nova Scotia: Improved Understanding of Cretaceous Fluvial-Deltaic Systems, Shelf-Edge Trajectories, and Equivalent Deepwater Strata

The Cretaceous shelf to slope transition outboard the Sable Subbasin, offshore Nova Scotia, Canada, is often inadequately imaged and therefore poorly understood. In part this is because of the complex structural geology across this important boundary. Even the simple mapping of shelf-edge trajectories has been problematic and there is significant uncertainty about how to correlate shelf strata onto the equivalent slope. Consequently, there has been disagreement about paleogeography and shelf-slope gross depositional environments. In this poster we present two composite seismic sections to be used as type sections for the central and western Sable Subbasin and to aid correlation of seismic markers across the Cretaceous shelf-slope transition. Line locations were carefully chosen to intersect features commonly found at or near shelf breaks, such as offlap geometries and canyon heads. These profiles also avoid salt structures and areas affected by large amounts of listric faulting while still remaining within the coverage of 3D seismic data. These lines demonstrate that high confidence correlations to deep water are still possible when care is taken to select a route that avoids geologic features that degrade seismic imaging. Seismic geomorphology of fluvial-deltaic deposits from 3D seismic surveys, and identification of numerous canyon heads aids in our interpretation of shelf-edge trajectories through time. On the slope, 3D seismic attributes coupled with time-thickness maps have been used to identify sediment transport corridors interpreted to connect to shelf margin canyon systems. This work, coupled with our improved understanding of slope morphology at the time of deposition, provides a clearer understanding of the five existing Cretaceous deepwater well penetrations outboard the Sable Subbasin. These results can be used to guide deepwater exploration off Nova Scotia.

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California