Abstract

The carbonate shelf, shelf edge, and outer shelf basin were the sites of deposition of a facies complex that shifted in response to transgressive-regressive (T-R) cycles. In the Silurian-Lochkovian, three T-R cycles are identified, and seven are identified from mid–Lower Devonian (Pragian) to high Upper Devonian (middle Famennian). The last of these produced a thick, upward-deepening sequence truncated above by a Famennian-lower Kinderhookian hiatus, due to foreland effects of the Antler orogeny. The middle and upper members of the Pilot Shale compose an eighth cycle, which spans the Devonian-Mississippian boundary on the carbonate shelf.

Most of the short-lived T-R cycles resulted from rapid deepening and progradation of the carbonate-shelf edge. Exceptions occurred during the late Early Devonian, when the carbonate-shelf edge was a ramp, and during the Taghanic and Frasnian onlaps, when transgressions are known to have been strong. The dolomite front tended to coincide approximately with the carbonate-shelf edge, but it was situated cratonward during extensive onlaps and basinward during the pre–Middle Devonian regression.

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