ABSTRACT

In stratigraphically ascending order, the Early Paleozoic sequence consists of Lower Cambrian clastics with minor carbonates, recessive Upper Cambrian mudstones, and resistant Lower Ordovician cherty dolomites, and Upper Ordovician carbonates. The latter are well dated in all sections by the "Arctic Coral fauna." The former sequences are very poorly fossiliferous and dating is based on sparse collections of Olenellus, Dresbachian brachiopods, and trilobites of the Leiostegium-Kainella Zone. Major facies variations are absent within this basal sedimentary package.

A gradual carbonate-shale transition occurs within the Lower, as well as Upper, Silurian Series. The former displays a lateral change from mainly restricted carbonates with a sparse ostracod-brachiopod fauna to open marine limestones and shales with a rich and varied trilobite-brachiopod-graptolite assemblage. Upper Silurian sediments range from restricted ostracod-bearing carbonates to open marine limestones and shales with the Atrypella scheii fauna. Apparently, most of the Middle Silurian is absent.

An abrupt carbonate-shale transition is assigned to the earliest Devonian.

Extensive faunal collections, from closely-spaced measured outcrop sections straddling these transitions, indicate conformable relations from Late Middle Silurian into Early Devonian and contribute to the definition of the Siluro-Devonian boundary. Intercalations of shelly and graptolitic sequences render the area particularly interesting.

The various carbonate facies indicate a progression from restricted shelf to normal marine basinal deposits.

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