ORGANIC-WALLED MICROFOSSILS FROM NEOPROTEROZOIC CAP CARBONATE UNITS AND ASSOCIATED STRATA OF THE WESTERN UNITED STATES

Although Neoproterozoic cap carbonate units and associated siliciclastic strata record a time of global change, they are little studied paleontologically. Preliminary paleontologic results from such strata in the western U.S. reveal acantomorphic acritarchs from argillite in a cap carbonate interval and probable organic-walled microfossils from cap-dolostone units.

Well preserved organic-walled microfossils have been recovered (via hydrofluoric acid maceration) from a green argillite in the (<665 Ma) Scout Mountain Member of the Pocatello Formation. The assemblage of small (~10 – 30 micron dia.) acanthomorphic acritarchs appears to be monospecific. The recovery of microfossils from a green argillite encourages continued study of traditionally unexplored lithotypes in post-Sturtian strata.

Dark material, morphologically consistent with organic-walled microfossils, has been recovered from Neoproterozoic cap carbonate units of the western U.S. Material was recovered via hydrochloric acid maceration techniques modified from Armstrong and Brasier (2005). Although the material appears organic in nature, a mineral origin cannot be discounted based on morphology alone. Currently, scanning electron microscopy is being used to analyze the elemental composition of the material to further constrain its origin.