Architecture and Facies Analysis of Allomember F, Upper Cretaceous Horseshoe Canyon Formation, Drumheller, Alberta

Mixed-influence, marginal-marine deposits are typified by complex heterogeneous architectures that are challenging to model in the subsurface. Utilization of modern and outcrop analogs can serve to mitigate these limitations. Marginal-marine successions of the Horseshoe Canyon Fm near Drumheller, Alberta are well exposed in laterally continuous outcrops for 15 km down depositional dip and 3.5 km along depositional strike. This study uses 30 outcrop sections from Allomember F along the Red Deer River and Willow Creek and 4 subsurface cores to classify the deposits in terms of facies and to identify element complexes (EC). Depositional environments are interpreted to record a variety of marginal-marine, paralic, and coastal environments that include: wave-dominated, fluvial-influenced, tide-affected deltaic deposits (FA1); tidal-fluvial channels (FA2); wave-dominated, tide-influenced, fluvial-affected shoreface (FA3); and, delta plain/terrestrial deposits (FA4). The deposits are characterized using the WAVE Classification scheme. Using this process-based approach, FA1 is subdivided and categorized into two element complexes, namely a Fw (t) lobe complex and a Wf (t) mouthbar complex. FA2 is designated as a Ft channelized complex. FA3 is categorized as a Wtf beach complex. FA4 can be subdivided into multiple element complexes representing terrestrial deposits. Overall, the paleoshoreline forms a Wtf or Wft Element Complex Assemblage.