A PORPOISING CRYOGENIAN BASIN IN THE PANAMINT RANGE, CALIFORNIA

In the Panamint Range, which forms the western flank of Death Valley, California, spectacularly exposed Cryogenian (ca. 717-635 Ma) strata of the Kingston Peak Formation include two distinct diamictites of the putative Sturtian and Marinoan snowball Earth glaciations. These glacial deposits are separated by up to 1 km of mixed carbonate and siliciclastic strata deposited during the ca. 660-640 Ma Cryogenian non-glacial interlude. Here, combining mapping with stratigraphic, sedimentological, geochemical, and geochronological datasets, we present a transect of the Kingston Peak Formation across the Panamint Range to place this strata in a regional depositional and tectonic framework and integrate it with other Cryogenian stratigraphic records globally.

The results of this study highlight two major unconformities within the non-glacial interlude strata (South Park Member) of the Panamint Range that formed as the result of sequential structural uplift and exhumation of opposite sides of this Cryogenian basin. The timing of this apparent basin inversion is calibrated by U-Pb LA-ICPMS maximum detrital zircon dates from strata bound by these unconformities, as well as by global stratigraphic correlations using chemostratigraphy and lithostratigraphy. These data represent the first Cryogenian geochronological constraints reported from Death Valley and confirm active tectonism in southwest Laurentia during the deposition of the South Park Member of the Kingston Peak Formation. The styles of successive burial and exhumation and of basin inversion are consistent with yo-yo tectonics or “porpoising” that involve both lateral and vertical displacement, suggesting that Cryogenian sedimentation was accommodated within pull-apart basins in a wrench zone of a strike-slip margin, rather than within a true rift basin. This compels a revised age model for the break-up of the supercontinent Rodinia on the southwestern margin of Laurentia, with subsidence models indicating that significant crustal thinning did not occur until the late Ediacaran, ~100 Myrs later.