NEW STRATIGRAPHIC AND ISOTOPIC CONSTRAINTS ON THE CRYOGENIAN -- EDIACARAN STRATA OF DEATH VALLEY REGION

The Death Valley region of California has long been recognized as containing one of the best exposed, albeit structurally dismembered, Cryogenian–Ediacaran successions on the globe, and perhaps the most complete section on Laurentia. Sparse geochronology has hindered construction and testing of hypotheses regarding many of the hallmark geological events of this time period. In addition, the single-most continuous belt of Cryogenian–Ediacaran outcrops in Death Valley, the Panamint Range structural block, has remained largely unstudied in detail. Research has generally focused on the eastern and southern parts of Death Valley outcrop belt because of ease of access and lesser tectonothermal overprinting relative to the Panamints.. Our new data comprises detailed mapping and measured sections to which we have tied a high-resolution sampling scheme in order to construct a C-isotope stratigraphy. We have concentrated on the Kingston Peak and Noonday Formations in the Panamints, the two units in the Death Valley region that contain a record of the climatic extremes of Neoproterozoic time. Our findings show that the C-isotopic trends in the Panamints match to within 1-2‰ reproducibility those established for correlative strata in the unmetamorphosed sections elsewhere in Death Valley. In addition, both the lithostratigraphic and chemostratigraphic datasets reveal the positions of major disconformities in the eastern and southern Death Valley sections. Our data permit us to confidently link to global C-isotopic trends, particularly the troughs and the peaks which denote the C-isotope excursions associated with the Snowball Earth glaciations and their aftermath. In particular, the much more complete stratigraphy present in the Panamint successions records the history of Precambrian tectonism relative to global C-isotopic excursions, and insight into the number and character of Snowball Earth glaciations preserved in these strata.