Abstract

Upper Devonian Leduc Formation reef-edge outcrops in the Alberta Rocky Mountains serve as natural workshops for modelling reef-edge morphologies. The study area extends from latitude 52° to 54° N in the Front Ranges of the Rocky Mountains. To the east, low angle seismic anomalies of questionable interpretation were noticed in the deep autochthonous Woodbend interval. The purpose of this study was to develop outcrop reef-edge models at a scale which could be compared directly to seismic anomalies. Previous outcrop studies had indicated a variety of shelf-to-basin transitions or reef margin styles but had displayed them at extremely exaggerated vertical scales. Published diagrams for the Ancient Wall, N.W. Miette, S.E. Miette, Cripple Creek and Hummingbird exposures were replotted to a common scale. Reef-edge models for Job Creek and Wapiabi Gap illustrated in this paper are the results of Shell’s geological fieldwork. The models compiled showed a variety of reef-edge morphologies with true reef slopes ranging from 10 to 20°. Seismic anomalies were displayed at the same scale as the geological models. Visual comparison of outcrop reef-edge models to seismic anomalies allowed the anomalies to be interpreted as reef-edges of specific types. Subsequent drilling of two anomalies has shown them to be Leduc reef build-ups.