A tale of two rift shoulders, and two ice masses: the Cryogenian glaciated margin of Death Valley, California

Abstract

The Death Valley area of California, USA, exposes an outstanding record of a Neoproterozoic 15 (Cryogenian) glaciated margin: the Kingston Peak Formation. Despite the quality of exposure, however, the 16 outcrops of glaciogenic strata are fragmentary, forming isolated, laterally offset outcrop belts at the western 17 extremity of the Basin and Range province. Excellent evidence for glacially modulated sedimentation includes (i) 18 ice-rafted dropstones in most ranges, (ii) thick diamictites bearing a variety of exotic (extrabasinal) clasts, (iii) 19 striated clasts, and (iv) local occurrences of glacitectonic deformation structures at the basin margins. In tandem 20 with this, there is a distinct signature of slope collapse processes in many ranges, including (i) up to km-scale 21 olistoliths, (ii) extensional growth fault arrays, (iii) dramatic proximal-distal thickness changes and (iv) basalt 22 occurrences. New sedimentological observations reinforce long-held views of rifting superimposed on glaciation 23(or vice versa), with both processes contributing to a complex record whereby rift and glacial processes vie for 24 stratigraphic supremacy. We consider that a mechanism of diamictite accumulation in a series of rift-shoulder 25 minibasins produced greatly contrasting successions across the Death Valley area, under the incontrovertible 26 influence of hinterland ice sheets.

A slippery slope for Cryogenian diamictites?

“…(c) A continuous sedimentary log, modified after Le Heron et al. (), through the upper part of the Kingston Peak Formation in the southern Kingston Range, showing the intimate association between boulder bearing diamictite, dropstone‐bearing heterolithics, and graded conglomerates and sandstones…”

“…The reader is referred to Le Heron et al. () for a review of this issue. The map presented herein (Figure ) only slightly modifies the earlier work of Wright ().…”

“…This region was mapped by Wright (1974), who divided the Kingston Peak Formation into mapping units pꞒk1-pꞒk4, later reassigned as KP1-KP4 by Mrofka and Kennedy (2011). The reader is referred to Le Heron et al (2019) for a review of this issue. The map presented herein ( Figure 2) only slightly modifies the earlier work of Wright (1974).…”

“…Cryogenian diamictites occur in the Kingston Peak Formation of the Panamint Range, to the west of Death Valley (Petterson, Prave, & Wernicke, ), and in a suite of disconnected outcrops to the southeast of Death Valley (Le Heron, Busfield, Ali, Vandyk, & Tofaif, ). Key glaciogenic indicators comprise faceted, striated clasts and delicate dropstone textures, with local evidence for glaciotectonic deformation (Busfield & Le Heron, and references therein).…”

Syn‐rift mass flow generated ‘tectonofacies’ and ‘tectonosequences’ of the Kingston Peak Formation, Death Valley, California, and their bearing on supposed Neoproterozoic panglacial climates

“…More recent work emphasizes the subaqueous setting of most of the Kingston Peak Formation and interprets the matrix‐supported clast‐rich facies as debrites that reworked glacial debris downslope from a partially‐floating ice margin that also released icebergs into the basin which dropped clasts onto the basin floor (Le Heron et al. , 2014, 2016, 2019; Busfield & Heron, 2016; Le Heron & Busfield, 2016; Tofaif et al. , 2019).…”