ALGAE AND MICROPROBLEMATICA OF MUSTOE REEF, SILURIAN KEYSER FORMATION, MUSTOE, VIRGINIA

Mustoe Reef in the Silurian Keyser Formation provides an opportunity to investigate habitats within Silurian reef core facies in the Appalachians. The occurrence and distribution of algal and problematical microfossils on the surface of the reef and within reef cavities reveals information about their ecology. The late Silurian reef exposed at Mustoe, Highland County, Virginia consists of a stromatoporoid and coral reef core associated with flank facies. A diverse assemblage occurs in grainstone/packstone pockets between the stromatoporoid and coral framestone and boundstone core, predominantly consisting of fragments of crinoids, brachiopods, bryozoans, ostracods, and molluscs. Crinoid holdfasts are locally important encrusters on the stromatoporoids and corals. Numerous algal and microprobematical taxa occur within the debris as well as encrusting surfaces on the top of the reef and within cryptic habitats. Calcispheres and codiacean and dasycladacean algae are scattered within the debris that fills pockets within the reef. Most of these occur as small grains, except for a possible receptaculitid. Cyanophytes such as Hedstroemia occur encrusting stromatoporoid surfaces. Probable serpulid tubes encrust grains and surfaces, especially crinoid holdfasts and tabulate coral, but are also present in cryptic cavities that are floored with lime packstone and filled with clear calcite cement. The tubes frequently encrust the upper surface of cavities, hanging pendant from the roof. In summary, the codiacean and dasycladacean algae were dwellers living on the surface of the reef and contributed to sediment fill. Cyanophytes encrusted the surface of the reef and became part of or encased in the framework. The serpulids were encrusters that took advantage of the hard substrate and could live in cryptic habitats.