Trilobite faunas from Upper Cambrian microbial reefs in the Central Appalachians

Trilobites from thrombolitic reefs in the Ore Hill Member of the Upper Camb rian Gatesburg Formation are assigned to (in ascending order) the Psudosara togia magna, Cliffia lataegenae, and Irvingella major Subzones of the Elvin ia Zone. These reef faunas contrast markedly with those from coeval off-ree f grainstones (tempestites), representing separate biofacies rather than bi ostratinomic variants. Associated lithologies suggest that the fauna of the P. magna Subzone at the base of the member comprises a biofacies associate d with shallower microbial reef environments than those occupied by faunas in the overlying C. lataegenae Subzone. Reefs in the C. lataegenae Subzone yield a Fauna dominated by Buttsia drabensis, extending the documented rang e of catillicephalid abundance in microbial reef biofacies downward into th e highest strata of the Steptoean Stage. This reef fauna also includes seve ral new taxa, including Cheilocephalus quadratus new species (described her ein), an atypical species of Cheilocephalus with catillicephalid-like crani dial features. The fauna in off-reef tempestites low in the C. lataegenae S ubzone contains the genera that characterize the Xenocheilus-Kindbladia Bio facies, expanding the known environmental and geographic range of that biof acies. Sulcocephalus, typically a minor component of faunas in the I. major Subzone, dominates the fauna in reefs within this subzone such that a dist inct Sulcocephalus Biofacies can be recognized immediately above the extinc tion horizon that defines the base of the Sunwaptan Stage.