Late Neoproterozoic Glaciation: Discrete Global Climate Events or One Extended Glacial Epoch with a Climate Record Preserved by Rifting

A thick succession of Precambrian strata in the Death Valley region of southeastern California records a common Late Neoproterozoic association between rifting and glaciation. The Kingston Peak Formation has been interpreted to record distinct Sturtian and terminal Proterozoic Marinoan glacial events with accompanying cap carbonates and separated by an interglacial interval. Detailed field studies of an eastern facies assemblage demonstrate a correlative and conformable record of glacially-influenced rift sediments between correlative surfaces bounding the apparent interglacial interval in the west. This relationship suggests a shift in the locus of rifting and glaciation to the east and not a discrete glacial event synchronous with other Sturtian intervals.

In both eastern and western facies assemblages the Kingston Peak Formation is preserved as uplift-derived wedges filling extensional grabens whose stratigraphy is dominated by rifting. In the east this succession includes a diminishing but continuous glacial signal throughout the section. The coincidence of the Neoproterozoic climate signal preserved in tectonic basins has significant implications for the completeness of Earth's ancient glacial record. Glacigenic diamictites developed due to diachronous local tectonism provide no direct evidence of global climate in these local areas and are then diagnostic of local creation of accommodation space.

The contradiction between the Snowball Earth model of two distinct synchronous worldwide glaciations and the stratigraphic record of Death Valley along with a growing body of other pre-Marinoan glacial intervals suggests the Cryogenian Period was a long-lived period of diachronous glaciations terminated suddenly by a global deglacial event with demonstrably unique geochemical implications. A possible way to reconcile both diachroneity of Sturtian glacials and the inability to correlate lower carbonates with confidence is that the Cryogenian period is a prolonged cold interval making local climate records more sensitive to uplift by being prone to glaciation. This provides the semblance of multiple ice ages.