Abstract

A shelf-edge coral-stromatoporoid reef complex occurs on the southwestern margin of the Pragian-Emsian carbonate platform partially exposed in the western Ogilvie Mountains of east-central Alaska and adjacent Yukon. The reef complex occurs along a 5 km long east-west trend on the south side of Hard Luck Creek. Where studied in detail on the north flank of Squaw Mountain the reef complex consists of an initial Renalcis boundstone core facies overlain by a bioherm containing abundant in situ colonial corals and stromatoporoids. The Renalcis boundstone core facies overlain by a bioherm containing abundant in situ colonial corals and stromatoporoids. The Renalcis boundstone overlies cross-bedded pelletal and encrinoidal grainstone and represents substrate stabilization of actively shifting sand shoals prior to skeletal metazoan colonization.

The coral-stromatoporoid bioherm is unbedded to massive bedded with reef framework composed of from 50 to 70 percent hemispherical colonial corals and lesser quantities of tabular and lamellar stromatoporoids. The dominant coral within the bioherm is the rugosan genus Xystriphyllum with the rugosan genus Spongophyllum and the tabulate genus Favosites as accessory reef builders. In-place and overturned corals are commonly capped by stromatoporoid framestone to bindstone, especially near the top of the reef complex. Reef framework voids are filled with angular to rounded fine to coarse grained skeletal sediment which includes coral, stromatoporoid, pelmatozoan and molluscan shell debris.

Exposures of reef foreslope facies situated to the northwest of the Squaw Mountain reef locality suggest that the reef trend extended to the northwest. Penecontemporaneous with reef growth were shelf margin crinoid thickets in inter-reef areas.