An inferred sea level curve from carbonate depositional facies of the Middle Cambrian Elbrook Formation, western Maryland, U.S.A

Approximately 500 m of the Upper Member of the Elbrook Formation exposed along the Chesapeake and Ohio Canal in western Maryland can be divided into four depositional subfacies each up to a few meters thick. The four subfacies comprise thin-bedded dolomitic mudstones peloidal/oolitic grainstones ribbon-laminated limestone/dolomite interbeds, and microbially influenced thrombolites and stromatolites. Elbrook Formation subfacies are, in turn, organized into cyclic and non-cyclic facies. Approximately the lower third of the measured section comprises cyclic repetitions of most of the rock types organized into shallowing-upwards successions up to 10 m thick. The depositional environments: subtidal sand shoals associated with algal patch reefs; subtidal to intertidal mixed sand-mud flats; and intertidal mudflats associated with algal patch reefs. Upsection, the cyclic facies is replaced by a non-cyclic facies dominated by microbial bioherms up to tens of meters in thickness. These were apparently deposited over a completely subtidal shelf that rarely aggraded to sea level. A sea level curve developed for this portion of the Elbrook Formation does not match curves developed for the same time interval (Spencer & Demicco, 2002) from other portions of North America.