A tale of two rift shoulders, and two ice masses: the Cryogenian glaciated margin of Death Valley, California
Published:January 01, 2019
D. P. Le Heron, M. E. Busfield, D. O. Ali, T. Vandyk, S. Tofaif, 2019. "A tale of two rift shoulders, and two ice masses: the Cryogenian glaciated margin of Death Valley, California", Glaciated Margins: The Sedimentary and Geophysical Archive, D.P. Le Heron, K.A. Hogan, E.R. Phillips, M. Huuse, M.E. Busfield, A.G.C. Graham
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The Death Valley area of California, USA, exposes an outstanding record of a Neoproterozoic (Cryogenian) glaciated margin: the Kingston Peak Formation. Despite the quality of the exposure, however, the outcrops of glaciogenic strata are fragmentary, forming isolated, laterally offset outcrop belts at the western extremity of the Basin and Range province. Excellent evidence for glacially modulated sedimentation includes (1) ice-rafted dropstones in most ranges, (2) thick diamictites bearing a variety of exotic (extrabasinal) clasts, (3) striated clasts and (4) local occurrences of glacitectonic deformation structures at the basin margins. In tandem with this, there is a distinct signature of slope collapse processes in many ranges, including (1) up to kilometre-scale olistoliths, (2) extensional growth fault arrays, (3) dramatic proximal-distal thickness changes and (4) basalt occurrences. New sedimentological observations reinforce long-held views of rifting superimposed on glaciation (or vice versa), with both processes contributing to a complex record whereby rift and glacial processes vie for stratigraphic supremacy. We consider that a mechanism of diamictite accumulation in a series of rift-shoulder minibasins produced greatly contrasting successions across the Death Valley area, under the incontrovertible influence of hinterland ice sheets.
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Glaciated Margins: The Sedimentary and Geophysical Archive
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Understanding the sedimentary and geophysical archive of glaciated margins is a complex task that requires integration and analysis of disparate sedimentological and geophysical data. Their analysis is vital for understanding the dynamics of past ice sheets and how they interact with their neighbouring marine basins, on timescales that cannot be captured by observations of the cryosphere today. As resources, sediments deposited on the inner margins of glaciated shelves also exhibit resource potential where more sand-dominated systems occur, acting as reservoirs for both hydrocarbons and water. This book surveys the full gamut of glaciated margins, from deep time (Neoproterozoic, Ordovician and Carboniferous–Permian) to modern high-latitude margins in Canada and Antarctica. This collection of papers is the first attempt to deliberately do this, allowing not only the similarities and differences between modern and ancient glaciated margins to be explored, but also the wide spectrum of their mechanisms of investigation to be probed. Together, these papers offer a high-resolution, spatially and temporally diverse blueprint of the depositional processes, ice sheet dynamics, and basin architectures of the world’s former glaciated margins; a vital resource in advancing understanding of our present and future marine-terminating ice sheet margins.