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The Batsheva de Rothschild Seminar on Atmospheric Dust, Dust Deposits (Loess) and Soils in Deserts and Desert Fringe: The Sahara-Sinai-Negev as an Analogue for the Global Arid Regions; Jerusalem and the Negev Desert, 14–19 October 2015

[1] Most wind erosion studies that characterize dust emission potential measure particulate matter smaller than 10 mm (PM10) for air quality purposes or atmospheric modeling. Because the PM10 size fraction is only a portion of the total range of fine‐grained particles potentially emitted from desert landforms, we modified the miniature Portable In Situ Wind Erosion Lab (PI‐SWERL) by adding a new instrument to measure total suspended particulate matter (TSP). The modified PI‐SWERL is capable of measuring TSP with diameters

[1] Although high-latitude loess sequences have been studied extensively for reconstructing past climates, loess in desert margins has been mostly overlooked. Moreover, many low-latitude loess studies have focused on secondary, reworked sequences for which paleoclimatic inferences are complicated owing to postdepositional processes acting under local control. In this respect, the spatial distribution of the loess and its different types are crucial. In this study, we differentiate primary and secondary loess using remote sensing and field criteria. We present remote sensing and geographic information system procedures for mapping loess distribution, in general, and for identifying pristine hilltop loess sequences in particular. Then, we present the mineralogical and textural analyses combined with optically stimulated luminescence ages of one such primary, hilltop loess sequence in the Negev desert that show that the late Pleistocene Negev loess started accumulating at ∼95 ka, much earlier than previously proposed (∼70 ka). It was preceded by a previously unknown middle Pleistocene period of loess formation at ∼180–130 ka. The ages also suggest that the threshold of dust accretion rate needed for loess formation is ∼0.02 mm a−1 (∼30 g m−2 a−1), a factor of 2 or more lower than previously thought (0.04 to 1.0 mm a−1). Our results also provide insights into causes of late Pleistocene loess accretion and its close association with regional dune field activity. The methodology for mapping the loess distribution may potentially be generalized to help understanding loess formation in other, more remote desert areas.

[1] The Dead Sea (DS) pull-apart basin is one of the more seismically active segments of the DS Transform plate boundary. In the last decade, hundreds of collapse-sinkholes have been formed along the DS coastlines in Israel and Jordan, causing severe damage to the regional infrastructure. The formation of these sinkholes is attributed to the dissolution of a buried salt layer by fresh groundwater due to the drop of the DS and the associated groundwater levels. Here we show that the sinkhole distribution, combined with gradual land subsidence measured by radar interferometry (InSAR) track young fault systems suspected as active, concealed within the fill of the DS rift. This notion is supported by (1) sinkholes clustering along discrete lineaments with a striking trend similarity to that of the exposed rift-margin faults; (2) prominent discontinuities in seismic reflection profiles offsetting young sediments (several kyrs old) below sinkhole lines, and (3) straight boundaries of gradual subsidence features that coincide with or parallel sinkhole lines. Combined, the sinkhole lineaments and the InSAR measurements reveal a zigzag pattern of buried faults within the DS rift fill.