Well and seismic data in the National Petroleum Reserve in Alaska (NPRA) demonstrate that the Jurassic-Lower Cretaceous Kingak Shale is present throughout NPRA. Several southward offlapping depositional sequences within the Kingak culminate in an ultimate shelf margin in southern NPRA, across which the formation thins dramatically. However the exact limit of the formation is obscured by frontal structures associated with Brooks Range tectonism. We propose that these changes in Kingak facies and stratigraphic architecture influenced the frontal structures of the Brooks Range foothills during Brookian thrusting and folding, and control an abrupt change in detachment level. The ramp in this area underlies the Carbon Creek anticline. This prominent northwest-southeast trending fold marks a change in structural grain in the foothills region of southwestern NPRA from east-west trending anticlines to the south.