Regional to Subregional Facies Architecture of River-Dominated Deltas in The Alberta Subsurface, Upper Cretaceous Dunvegan Formation

Abstract The Dunvegan Formation (mid-Cenomanian) comprises a thick clastic wedge deposited in the West Alberta foreland basin. This wedge consists of a complex series of interbedded shales, siltstones, and sandstones and has been subdivided into seven allomembers (A-G), each separated by widespread flooding surfaces. Allomember E consists of four offlapping, shingled, heterolithic sedimentary units that progressively built seaward to the southeast. Isolith maps of the sandstones within these shingles reveal deltaic morphologies consisting of well-developed sandy depositional lobes fed by sandy distributary channels separated by mudstone-dominated interchannel and interlobe areas. The plan-view morphologies and facies successions in the lobes are typical of prograding river-dominated delta fronts. Superposition of sandbodies within each shingle reveals the autocyclic fashion in which the sedimentary basin was filled. The arcai pattern and scale of overlapping depositional delta lobes are similar to those of the Mississippi delta during the last 5 ka.