Multiple intercalations of glacially derived and slope-derived diamictites testify to the drawbacks of correlating Neoproterozoic diamictites more widely, but shed new light on the close interrelationship of these processes in the Cryogenian world. In the Neoproterozoic of Death Valley, California (USA), rifting of Rodinia occurred concomitantly with a major glacial event that deposited the Kingston Peak Formation. A new sedimentologic investigation of this formation in the Silurian Hills demonstrates, for the first time, that some diamictites are ultimately of glacial origin. Abundant dropstone textures occur in interstratified heterolithic deposits, with clasts of identical composition (gneiss, schist, granite, metabasite, quartzite) to those of boulder-bearing diamictites suggesting a common source (the glacial conveyor belt). In stark contrast, megaclast-bearing diamictites, yielding clasts of carbonate and siliciclastic preglacial strata as much as 100 m across, are interpreted as olistostromes. The occurrence of syn-sedimentary faults within the succession allows glacial versus slope-derived material to be distinguished for the first time.

Late Ordovician glacial deposits are of great importance in North Africa and the Middle East as a result of their significance as reservoirs for hydrocarbons and groundwater. The sedimentary record of this glaciation in NW Saudi Arabia (the Sarah Formation) is generally preserved in meridionally oriented palaeovalleys cut beneath northward-flowing ice sheets. In the Tabuk region of NW Saudi Arabia, an apparently intersecting complex of north–south- and east–west-oriented palaeovalleys occurs in the Alwizam area. Field relationships show two generations of palaeovalley incision, suggesting that the north–south-oriented palaeovalley was cut subglacially, filled, subsequently deformed and then cross-cut by the east–west-oriented palaeovalley. Abundant facetted and striated quartzite clasts occur at the base of each palaeovalley, testifying to a subglacial origin. Detailed examination of the north–south-oriented palaeovalley shows it to be well-defined with symmetrical sides. Its fill is composed of nine lithofacies grouped into four facies associations. About 80% of the fill consists of three sandstone facies: a parallel-bedded massive sandstone, a stacked scoured sandstone and a massive sandstone. Centimetre-scale extensional faults developed in soft sediments are commonly found throughout the stratigraphy, along with a glacially striated surface seen mid-way through the succession. These features provide evidence for direct ice contact, synglacial fill, and consequent reworking, cannibalization and deformation by the fluctuating ice margin.

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.

Olistolith production and magmatism are processes commonly associated with extensional tectonic settings, such as rift basins. We present a cautionary exemplar from one such Precambrian basin, in which we reinterpret metabasite bodies, previously documented as sills, to be olistoliths. We nevertheless demonstrate that, on the basis of field observation alone, the previous but erroneous sill interpretation is parsimonious. Indeed, it is only by using isotopic age and compositional analysis that the true identities of these metabasite olistoliths are revealed. We present new data from metabasites and metasedimentary strata of the Kingston Peak Formation (Cryogenian) and Crystal Spring Formation (Mesoproterozoic) of Death Valley, USA. These include field observations, U–Pb apatite ages, U–Pb zircon ages (detrital and igneous) and whole-rock geochemistry. These data also provide a new maximum age for the base of the Pahrump Group and suggest that the Crystal Spring Diabase was more tholeiitic than previously thought. Similar sill/olistolith misinterpretations may have occurred elsewhere, potentially producing erroneous age and tectonic-setting interpretations of surrounding strata. This is particularly relevant in Precambrian rocks, where fossil age constraints are rare. This is illustrated herein using a potential example from the Neoproterozoic literature of the Lufilian belt, Africa. We caution others against Precambrian olistoliths masquerading as sills. Supplementary material: Details of a meta-igneous boulder from P12 of the Silurian Hills, LA-ICP-MS and whole-rock geochemistry methods and standards, and U–Pb apatite and zircon isotopic data, including standards and selected cathodoluminescence images, are available at https://doi.org/10.6084/m9.figshare.c.3990639

The Kingston Peak Formation of the Death Valley area, California, allows valuable insight into both regional Cordilleran stratigraphy and the number of glacial cycles preserved in the Cryogenian record. In the Kingston Range, the eponymous strata have been previously interpreted to record both Sturtian and Marinoan pan-glacial events. In the context of a search for a Global Boundary Stratotype Section and Point (GSSP) for the Cryogenian, we provide the first detailed description of the thickest diamictite-bearing interval in the western USA. Two clast-poor, muddy diamictite intervals within the succession-one at the base, and one near the top-have been used to support Sturtian and Marinoan events previously. However, new data from the southern part of the Kingston Range suggest that the upper diamictite interval is genetically related to underlying strata. The deposits are interpreted as glaciogenic debris flow deposits which probably represent the proximal tract of a subaqueous fan. Medial to distal portions of this fan are dominated by turbidites, which were transported down a consistent SE-oriented palaeoslope. Lowermost beds of the upper diamictite interval are intercalated with graded sandstones and sandy, matrix supported conglomerates. The graded beds (turbidites) and matrix-supported conglomerates (debrites) testify to a subaqueous setting, with the compositionally and texturally distinct diamictites indicating a glacial origin.