A LINK BETWEEN LATEST EDIACARAN BIOTIC ASSEMBLAGES GLOBALLY: NEW FOSSIL FINDS FROM THE LOWER MEMBER OF THE WOOD CANYON FORMATION IN DEATH VALLEY

A distinct, temporally-restricted latest Ediacaran (~550-541 Ma) biotic assemblage exists, but it remains unclear if this reflects biological turnover and evolutionary progression within the late Ediacaran, or if it instead represents environmental, taphonomic, or biogeographic biases. Distinguishing between these possibilities has been limited by a dearth of late Ediacaran fossil localities that are well-constrained temporally and that contain overlapping assemblages. For example, though the late Ediacaran Nama Assemblage in Namibia is thought to be correlative to the Gaojiashan Assemblage in China, each of these assemblages preserves a markedly different biota.

Here, we report new fossils from latest Ediacaran strata within the lower Member of the Wood Canyon Formation in Death Valley that establish a link between latest Ediacaran assemblages globally. This newly described assemblage of fossils includes three-dimensional preservation of soft-bodied Erniettomorphs, similar to those in the Nama Assemblage, as well as cast and molds and secondary pyritization of a variety of tubular fossils, similar to those in the Gaojiashan Assemblage. This is the first report of many of these fossils occurring in the same stratigraphic section, providing a biostratigraphic link between latest Ediacaran assemblages found in Namibia, South China, Siberia, Brazil, and Paraguay. Therefore, the Wood Canyon Assemblage supports the theory that a distinct latest Ediacaran faunal assemblage is the result of true biotic turnover during the end of the Ediacaran Period, prior to the Precambrian-Cambrian boundary.