Three-Dimensional Variation in High-Relief Shelf Margin Clinoform Architecture With Implications for Sediment Delivery to the Deep-Sea, Cretaceous Alaskan North Slope
Clinoform architecture and stratigraphic evolution provides critical insight into the history of shelf margins, including paleogeographic reconstructions and the prediction of sandstone reservoirs. Recent emphasis has been placed on shelf-edge processes and growth patterns, margin morphology, and phases of sediment delivery beyond the shelf-edge. Due to data limitations, related to outcrop exposure or limited seismic coverage (e.g., 2D data), many efforts have focused on depositional dip-oriented cross-sections of clinoforms without ability to rigorously consider along-strike variation in shelf margin character. Expansive 3D seismic data allows for enhanced spatial investigations of clinoform growth and deep-sea sediment delivery. Cretaceous deposits of the Colville Basin, N. Alaska are the focus of this study, and are characterized by clinoforms that propagated along the axis of a retroarc foreland basin. Over thirty clinoforms are documented in the 1500 km2 seismic survey, preserving a gross stratal thickness of over 3500 m. Multiple scales of clinoforms are seen, encompassing strata that preserve 250-900 m estimated paleo-shelf margin relief. Clinoform evolution was both qualitiatively and quantitatively described using a series of metrics (e.g., slope rugosity, clinothem thickness, shelf-edge trajectory). These data vary along strike and provide a platform to consider margin development in a 3D framework. Furthermore, there is apparent correlation between these parameters and toeset strata thickness. For example, thin clinothem intervals are associated with an elevated degree of slope rugosity and relatively voluminous basin floor accumulation; thick clinothem intervals are associated with smoother clinoforms and more limited toeset deposits. In addition, where clinothems are associated with increased progradation, they tend to correspond to smooth surfaces and limited toeset strata volume; where clinothems are associated with higher amounts of either aggradation or degradation, surfaces tend to be more rugose and associated with increased toeset strata volume. At a gross scale, along strike variability in clinoform characteristics is interpreted to correspond with varying locations of enhanced basinward sediment transfer. We consider that the 3D interaction of variables such as sediment supply, subsidence, sedimentation rate, delta lobe switching and RSL changes influence along-strike morphology of slope systems and resultant stratigraphic architecture.
AAPG Datapages/Search and Discovery Article #90291 ©2017 AAPG Annual Convention and Exhibition, Houston, Texas, April 2-5, 2017