Neoproterozoic ice sheets and olistoliths: multiple glacial cycles in the Kingston Peak Formation, California

Abstract

The Kingston Peak Formation is a diamictite-bearing succession that crops out in the Death Valley region, California, USA. An exceptionally thick (>1.5 km) outcrop belt in its type area (the Kingston Range) provides clear insights into the dynamics of mid-Cryogenian (‘Sturtian’) ice sheets in Laurentia. Seven detailed logs allow the lateral and vertical distribution of facies associations to be assessed. We recognize (1) diamictite facies association (ice-proximal glacigenic debris flows), (2) lonestone-bearing facies association (ice-marginal hemipelagic deposits and low-density gravity flows with iceberg rafting), (3) pebble to boulder conglomerate facies association (ice-proximal cogenetic glacigenic debris flows and high-density turbidites), (4) megaclast facies association (olistostrome and hemipelagic sediments subject to ice-rafting), and (5) interbedded heterolithics facies association (low-density turbidites and hemipelagic deposits). The stratigraphic motif allows three glacial cycles to be inferred across the range. Ice-minimum conditions interrupting the Kingston Peak succession are associated with the development of an olistostrome complex, succeeded by a thick accumulation of boulder conglomerates deposited during ice readvance. The data testify to a strong glacial influence on sedimentation within this ancient subaqueous succession, and to highly dynamic ice sheet behaviour with clear glacial cycles during the Sturtian glaciation.