Holocene Depositional History Inferred From Single‐Grain Luminescence Ages in Southern California, North America

Abstract

The geologic history of sediment flux and deposition is influenced by changes in external environmental factors such as climate and tectonics and intrinsic factors such as lithology and the sedimentary system's internal dynamics (Romans et al., 2016;Toby et al., 2019). Due to the complexity of these various factors, it is challenging to identify the first-order control, whether external (allogenic) or internal (autogenic), on sediment generation, transport, and downstream deposition (Armitage et al., 2011(Armitage et al., , 2013. In addition, how these signals are recorded in stratigraphic archives and geomorphic landforms over various geologic timescales is still poorly understood (Caracciolo et al., 2020;Gray et al., 2019). This is particularly challenging since the studies often rely on spatially and/or temporally incomplete stratigraphic sequences (Jerolmack & Paola, 2010;Miall, 2015) or suffer from poor chronological constraints (Owen et al., 2014 and references therein). For example, researchers still debate whether the significant alluvial fan depositions in the American Southwest took place during relatively dry periods, especially during glacial to interglacial transitions with reduced soil moisture and vegetation cover (e.g.

The Transport History of Alluvial Fan Sediment Inferred From Multiple Geochronometers

“…If some grains were unbleached during the most recent depositional event, those grains could yield an age corresponding to a previous sunlight exposure event. In this way, a fluvial environment which fully bleaches only some grains during transport (Gray et al, 2018;McGuire & Rhodes, 2015) events may produce single-grain age populations which record multiple sunlight exposure events, assuming similar dose rate environments during burial (Gray et al, 2017;Saha et al, 2021). This approach assumes complete bleaching of some grains during each event.…”

“…Another advantage of luminescence dating is the ubiquity of datable material, either quartz or K-feldspar grains. Luminescence signals grow on timescales of 10 2 -10 5 yr and can therefore archive information about active tectonic deformation (Salisbury et al, 2018;Stockmeyer et al, 2017) or recent shifts in climate (Antinao et al, 2016;Brown et al, 2015;Saha et al, 2021).…”