Lower Devonian brachiopod communities of the northern Canadian Cordillera

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Abstract
The N Canadian Cordillera can be divided into 3 more or less parallel arrayed lithofacies, which from E to W correspond to progressively deepening waters. The shallow water, yellow, or orange-weathering carbonates occupy essentially the E half of the region and NW Yukon. Shallowest water carbonates yield fairly abundant ostracoderm faunas, ostracodes, and little else. Slightly deeper water carbonates contain brachiopod faunas rich in individuals but low in generic diversity. The name Howellella- Protathyris Community is applied to the Lower Lochkovian shallow water faunas: the Sieberella-Nymphorhynchia-Athyrhynchus Community is the approximate Upper Pragian-Zlichovian equivalent. Deep water calcareous shales and limestones occupy a narrow band and yield faunas rich both in number and diversity. These faunas are designated the Skenidioides-Sprigerina-Vagrania Community and are recognized through the entire Lower Devonian interval. An intermediate depth fauna from Upper Pragian and Zlichovian dark carbonates is probably recognizable in NW Yukon, and termed the Strophochonetes-Proreticularia-receptaculitid Community. The widespread deep water graptolitic shales and carbonates contain a rich fauna of graptolites and relatively rare trilobite, sponge, and brachiopod faunas.