New Sediment Record of Late Pleistocene-Holocene Wind Dynamics, Hydro-Sedimentary Processes and Climate Change in the al-Hajar Mountains (Oasis of Masafi, UAE)

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In arid environments, continental records of climate change are rare. In southeast Arabia, where most of the landscape is dominated by the ophiolithic al-Hajar mountains, palaeoclimatic data are mainly derived from sedimentary records on the piedmonts. In the mountains themselves, where human occupation could have prevailed during periods of climatic stress, sedimentary archives are weakly preserved. Recent studies have revealed the existence of thick but under-explored sedimentary archives in oases. In order to evaluate their potential as palaeoenvironmental records, we develop a geomorphic, sedimentological and mineralogical approach in the oasis of Masafi (UAE). Results allow us to identify sediment sources and deposition modes over the last 18 ka. Late Pleistocene deposits are comprised of quartz-rich aeolian sands from the Rub'al-Khali while Early to Mid-Holocene deposits (10-7.5 ka) are calcite-rich loess probably originating from the Persian Gulf, deposited on the slope upstream of the oasis and later remobilized during humid periods. Late Holocene records (after 2.7 ka) are more complex to interpret with the onset of anthropogenic activities. While sediment connectivity between the slope and the oasis still occurred up until the last 2 ka through the channelling of runoff water and gullying, we witness shifting soil management strategies and reduced sediment supply from the slopes after that date. As a conclusion, our results reveal complex morphoclimatic and anthropogenic processes in the oasis but its high potential as an archive of ancient climate change and alluvio-aeolian processes if studied with caution.Highlights : • Continental records of climate change are rare in arid mountainous environments • Stratigraphic sequences in oases provide an underexploited sedimentary archive • We develop a geomorphic, sedimentological and mineralogical study of oasian archives • Oasian sequences record regional climatic signals, local hydrogeological conditions and anthropogenic activities • Aeolian processes and hydric remobilization of windborne sediment are dominant sedimentation processes in the oasis • Sediment disconnectivity occurred during the last millennia as a result of reduced water resources