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A late Pleistocene linear dune dam record of aeolian-fluvial dynamics at the fringes of the northwestern Negev dunefield

Roskin, Joel, Bookman, Revital, Friesem, David E., Vardi, Jacob
Sedimentary geology 2017 v.353 pp. 76-95
camping, databases, drainage systems, energy, floodplains, floods, geometry, hinterland, microstructure, sand, sediment yield, stratigraphy, surface water, watersheds, wind power, wind speed, Israel
A late Pleistocene aeolian-fluvial record within a rare vegetated linear dune-like structure at the fringe of the northwestern Negev dunefield, Israel, provides direct evidence of dune-damming dynamics within the structure and its environs. Study methods included high resolution morphology and stratigraphy, micromorphology and sedimentological analyses. Chronology was based on eight archaeological sites from the structure and the INQUA Dune Atlas chronologic database. Low-energy fine-grained fluvial deposits underlying the structure and extending from its flanks indicate deposition by low energy hyper-concentrated flows in a floodplain environment and later in water bodies that formed by dune-damming of a mid-sized drainage basin. Interbedded sand with fine-grained deposits within the linear structure indicates interchanging dominances between aeolian sand incursion and seasonal floods. Sand deposition during dune elongation led to structure growth and dune-damming of its drainage system that in turn formed water bodies and upstream fine-grained deposition following seasonal floods. Calculations of current sediment yields indicate that fine-grained deposits accretion up to the structure's brim could possibly have rapidly occurred over a total time span of decades. However, artifacts dating to the Geometric Kebaran (~17.5–12.9calkyrBP) and Harifian (12.9–11.2calkyrBP) archaeological periods on the structure's surface indicates intermittent, repetitive, and short-term camping, utilizing adjacent water bodies over a time period of 4000–5000years. Fluctuating high winds and precipitation during a time window of increased fluvial availability of fine-grained sediment from the hinterland generated ample fine-grained deposition. After ~11calkyrBP, the abundance and recurrence of dammed water bodies decreased when reduced wind power constrained dune-dam maintenance. After sediment accommodation space dissipated, fluvial flow of the drainage basin led to dune-dam destruction and partial fluvial erosion of the fine-grained deposits that continues today.