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Quantifying Sediment Supply in Stratigraphy Using Cosmogenic Nuclides: Insights From the Pleasant Canyon Complex, Panamint Mountains, California


A quantitative measurement of sediment supply derived from stratigraphy is an elusive goal, but realization could provide the opportunity to elucidate dynamic interactions between sediment supply and other basin dynamics. To this end, we address the question of how changes in sediment supply influence stratigraphic patterns using cosmogenic nuclides to calculate paleo-denudation rates (a proxy for sediment supply) feeding a catchment-fan system. The Pleistocene Pleasant Canyon fan complex emanates from the west flank of the Panamint Mountains, Inyo County, California, and is exposed in a ~200 m-thick and 2 km-wide outcrop of mixed alluvial fan-lacustrine stratigraphy. Several cycles are preserved within the succession, defined by changes in dominant grain size, sedimentary structures, and a repeating motif of lacustrine marl-to-gravel transitions. Sedimentological interpretations indicate cycles represent catchment-fan system response to lacustrine fill-desiccation cycles, with marl deposits representing lake highstands. Synsedimentary normal faults are documented but likely account for minor changes in accommodation relative to abrupt lake level changes. Paleo-sediment flux estimates could disentangle sediment supply variability from base-level changes during glacial-interglacial cycles. A detailed stratigraphic framework and cosmogenic nuclide sample suite allows us to construct a depositional model incorporating age determinations derived from paired isotope measurements (26Al/10Be) yielding aggradation rates and ultimately paleo-sediment flux.