Calcilutites with abundant stromatopores, corals and amphiporids.

Abstract of ref. 2125:
The Duhamel reef is an isolated Upper Devonian Leduc Formation limestone bioherm, situated immediately NNE of the Bashaw reef complex in south-central Alberta. Although Duhamel has a relatively small basal area (less than 12 km2), this reef rises some 275 m above the platform facies. From seismic data it is interpreted that there is a raised peripheral reef rim that appears to be elevated about 25 m relative to the interior of the reef. Although late-stage accretionary growth about the periphery of the reef complex may have contributed to its development, the raised rim at Duhamel is interpreted to be principally of secondary origin. Optimal hydrocarbon recovery could be realized if all production wells were drilled into the raised reef rim. The Duhamel example shows that even relatively small Leduc reefs can exhibit raised rims and that these rims may be seismically visible. 