Seafloor precipitates and carbon-isotope stratigraphy from the neoproterozoic Scout Mountain member of the Pocatello Formation, Southeast Idaho: Implications for neoproterozoic Earth history.

摘要

A 'carbonate and marble' unit tops the Scout Mountain Member of the Neoproterozoic Pocatello Formation. It contains unusual carbonate textures and records negative delta13C values similar to Neoproterozoic "cap carbonates", but no glacial strata have been recognized directly underlying this unit, and it does not conform to generally accepted glacial intervals. It may be an actual cap carbonate in the absence of an underlying glaciogenic diamictite, thus representing the aftermath of an unrecognized glaciation. Alternatively, it may be a cap-like carbonate produced by non-glacial processes.; Analysis of radiometric constraints on Neoproterozoic glacial successions worldwide shows that Neoproterozoic glaciations happened more than twice and were not synchronous. As only two glaciations are currently recognized in the Pocatello succession, it is plausible that the carbonate and marble represents additional glaciation, and previous correlations along the Cordillera may need to be reconsidered.