干旱区生态环境知识资源中心

The sources and routes of transport of fine detritus material (FDM) to the lakes filling the late Quaternary Dead Sea basin were studied by petrographic, mineralogical, grain size, chemical and Sr-Nd isotope analyses on sediments of the late Quaternary lacustrine formations, including river flood material, dust, and loess from the lake watershed. The lacustrine formations comprise two sedimentary facies: one that consists of alternating laminae of primary aragonite and silty-detritus material (aad facies), and another that consists mainly of laminated detritus particles and generally lacks aragonite (Id facies). The aad facies characterizes the glacial intervals (e.g. MIS2 and 4) when lake levels were high, while the Id facies characterizes interglacials (e.g. MIS1, 5) and warmer glacial intervals (e.g. MIS3), when lake levels were low. The detritus of both aad and Id facies show similar mineralogy: mainly quartz and calcite grains with minor feldspars and clays, but distinct grain-sizes (8-10 mu m and 50-60 mu m, respectively), and distinct Sr-87/Sr-86 and epsilon Nd (0.711-0.712 and similar to-7 to -8, versus 0.709-0.710 and similar to-5, respectively). The aad and Id FDM comprise desert dust of mixed granitic - basaltic composition that was blown from the Sahara desert and from the Nile delta to the northern Negev desert (e.g. the loess deposits) and the Judean Mountains bordering the Dead Sea basin, mainly during glacial intervals along with enhanced Mediterranean rain fronts. The aad FDM reflects an enhanced transport of Saharan granitic dust to the vicinity of the lake mainly during glacials. The Id FDM was recycled from the loess surface cover of the Negev desert mainly during interglacials and warm glacial intervals. (C) 2012 Elsevier Ltd. All rights reserved.