Palaeoclimatic and geomorphic implications of late Quaternary aeolian-fluvial interactions in the northwestern Negev dunefield (Israel) - A review

Here, we review four decades of research on Aeolian-Fluvial (A-F) interactions, in particular, dune-damming impoundments that deposited expanses of playa-like fine-grained sediments in the Sinai-Negev erg. We focus mainly on the erg’s eastern edge, the arid northwestern Negev dunefield (Israel), where wadis flood 1-2 times a winter. The review relates to the mechanisms of formation, timing, morphology, sedimentology, landscape response, relations with prehistoric settlements, palaeoclimate, and methodological approaches.

Vegetated linear dune (VLD) incursion, mainly during the Heinrich 1 and Younger Dryas, indicated by spatially dense but well-spread OSL chronologies, initially dammed and impounded medium-sized (10¹-10² km²) fluvial systems, usually in a perpendicular angle. The impounded water bodies generated a dunefield margin landscape of widespread, playa-like flats comprised of sequences of A-F sediments. These sequences, usually <7 m thick, found to often lay over eroded dune sand, reveal distinct sedimentological structures such as massive loam and couplets that in some places overlap sand, and fluvial sand associated with adjacent VLD truncation. Couplets, indicative of single dune-dammed impoundment events are usually <dozen, per section, representing several flood seasons within a sequence spanning several thousands of years. This discrepancy may imply that impoundments were seasonally successive for only several years, recording high discharge floods transporting large amounts of fine-grained bedload. More likely, the sequences are incomplete, having gone through depo-erosional cycles.

Despite VLD stabilization at the end of the Younger Dryas, fluvial fine-grained sediments continued to accumulate until the early Holocene due to successions of dune-dammed impoundments, inland of the dunefield margins. This process demonstrates that the reopened fluvial systems gradually propagated downstream. Previously reported anomalic amounts of lithic-dominated concentrations and hearths, usually from the Epipalaeolithic period, appear near and within mapped A-F sediments. Recent OSL chronologies of the A-F deposits and radiocarbon dates of hearths and hearth-like remains, support these and newly found sites, some dating to the Neolithic period. The resultant landscape is a result of unique environmental transitions at a time-window of high up-basin loess availability, from open fluvial domination to aeolian domination (dune-damming) and finally, partial and gradual dune-dam breaching, reopening of the fluvial systems and incision within A-F sediments. The patchy landscape response during this transition is controlled by basin size and its accumulated sediment load, and dune-dam properties. Altogether, the studies reveal a dramatic geomorphic and direct fluvial landscape response to dune incursion during windy late Pleistocene periods where precipitation changes appear to constitute only a minor role.