Abstract

The Lower Devonian Corridor Member of the Camsell Formation consists of a brightly color banded cyclic sequence of peritidal carbonate rocks deposited on the western continental shelf of North America. These color bands may be resolved into a suite of seven lithotypes reflecting deposition in a variety of shallow subtidal, intertidal and supratidal environments. Correlatable marker beds are not present and there are no obvious correlations between the sequences of lithotypes exposed in four closely spaced sections. Lateral facies changes between lithotypes were observed. Markov analysis of these lithotype sequences indicates that neither shallowing upward nor deepening upward sequences predominate. Instead these sequences are oscillatory with vertically adjoining lithotypes reflecting deposition from laterally adjacent depositional environments.

A tidal flat island model for carbonate shelf deposition is more appropriate than the linear shoreline depositional models as an explanation for the origin of Corridor strata. Tidal flat islands are ideally suited to produce oscillatory peritidal depositional cycles of local extent. Islands may have grown by means of lateral progradation until the subaerially exposed island interiors were inundated when subsidence caused them to fall below sea-level. The presence of dolomite sands reworked from tidal flat carbonates cemented by dolomite that formed the source of these sands indicates that dolomite cementation and dolomitization of Corridor rocks was synsedimentary. Beach rock cementation by dolomite may have stabilized these islands and expedited the growth of low beach berms above high tide.