RELATIONSHIP OF THE EARLY PERMIAN BILK CREEK FORMATION (BLACK ROCK TERRANE) TO OTHER EARLY PERMIAN TERRANES ALONG THE WESTERN AND NORTHWESTERN MARGIN OF PANGEA BASED ON BRACHIOPOD BIOGEOGRAPHY

Early Permian brachiopod faunas of the Bilk Creek Limestone of the Bilk Creek Mountains of Northwestern Nevada, which is known to be part of the accreted terrane know as the Black Rock terranes, were collected in the summer of 2006. The brachiopod faunas of the Bilk Creek have been compared statistically with other known Early Permian rocks deposited along northwestern and western Pangea. Analysis of over 900 individuals of 22 brachiopod species from the Bilk Creek Limestone was done using multivariate analysis in the software program PAST. Analysis showed that the Bilk Creek brachiopod fauna was similar to that of the Eastern Klamath and Quesnellia terranes when using the Euclidean and Raup-Crick similarity measures. When using the Simpson similarity measure, the Bilk Creek fauna is isolated from all other terranes of Western and Northwestern Pangea. Consequently, multivariate analysis shows that the Bilk Creek fauna has some ties with the fauna of the Eastern Klamath terrane. This is to be expected, as previous studies (Kenter and Wardlaw, 1981; Jones 1990) suggest that the Eastern Klamath terrane and the Black Rock terrane were deposited in the same basin, with the Black Rock terrane being further from the volcanic arc. Overall, while some compositional overlap exists the Bilk Creek brachiopod fauna is clearly distinct from faunas of the Boreal and Tethyan realms of Pangea, Suggesting that mid-latitude oceanic/arc communities were not merely intermediate between their high and low-latitude counterparts in the Early Permian.