100 m thick.
Reef talus (corals), forereef limestones (corals), reef margin (stromatopores), reef flat (grainstones with micritization).
Almost no fossils in situ.

Abstract of ref. 1503:
Early Devonian limestones of Ellesmere, Bathurst, and smaller islands between them in the Canadian Arctic Archipelago contain a diverse fauna of stromatoporoid sponges. This fauna provides the best evidence in North    America of the early recovery phase of this reef-building group from a diversity low at the Silurian/Devonian boundary, a recovery that lead to its diversity peak in Givetian time. Stromatoporoids from the lower member of the Blue Fiord Formation locally form large reefal masses. Well preserved stromatoporoids also occur less abundantly: 1. in the top of the underlying Eids Formation, 2. in the upper member of the Blue Fiord Formation, 3. in the Disappointment Bay Formation, which is correlative of the upper Blue Fiord, and, 4. in the overlying Bird Fiord Formation, and a correlative unnamed formation, both of which span the Lower/Middle Devonian boundary. The stratigraphic distribution of these stromatoporoids can be accurately determined according to conodont biostratigraphy as spanning the dehiscence to partitus (Emsian to basal Eifelian) conodont zones. Common occurrences of Stromatoporella perannulata, Stictostroma gorriense, Habrostroma proxilaminatum, and Parallelopora campbelli in the arctic fauna and southern Ontario and the adjacent United States, indicate that the Detroit River Group is of similar Emsian age, and that the Eastern Americas realm was open to migration from the Arctic. Similarity of species with the Emsian faunas of Russia, Australia and China suggests the cosmopolitan and equatorial distribution of stromatoporoids in Emsian time and opens possibilities for using the group in correlation. The fauna is therefore important in establishing both the evolution of the order and also its geographic distribution in Early Devonian time. Twenty-five    species (assigned to 22 genera) are described. The species concept used is a broad one and the range of variation in each taxon is documented. New species described are: Gerronostroma septentrionalis, Anostylostroma anfractum,    Pseudoactinodictyon conglutinatum, Stictostroma? nunavutense, Clathrocoilona vexata, Stromatopora hensoni. The morphologic limits of the following genera are considered in the description of species: Plectostroma, Aculatostroma and Atelodictyon, Clathrocoilona, Salairella and Syringostromella. The range of Trupetostroma is extended downward into Emsian strata. 