Evolution of Middle to Late Pleistocene sandy calcareous paleosols underlying the northwestern Negev Desert Dunefield (Israel)
Evolution of Middle to Late Pleistocene sandy calcareous paleosols underlying the northwestern Negev Desert Dunefield (Israel)
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DOI：
10.1016/j.palaeo.2013.07.018
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发表时间：
2013-10
期刊：
影响因子：
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通讯作者：
Joel Roskin;I. Katra;N. Porat;E. Zilberman
中科院分区：
文献类型：
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作者：
Joel Roskin;I. Katra;N. Porat;E. Zilberman
利用沉积学分析、光谱学和光学激发发光（OSL）测年技术，研究了西奈-内盖夫沙漠东端西北（NW）内盖夫沙丘地带的钙质古土壤与其下伏稳定沙丘和顺风黄土沉积物的关系。在中晚更新世期间，在第7期末期至第3期之间，经过几个砂片沉积、稳定、成土和侵蚀旋回，形成了内盖夫西北部砂质钙质古土壤的空间变化序列。在几千年到一万多年的稳定时期，以风成粉砂、粘土和盐的沉积后照射为特征，使得形成具有诊断性的、通常是硬化的、钙质的、Bk层（第I-III阶段），具有碳酸盐岩结核。古土壤的主要粒度模式（127 μm）介于上覆沙丘砂（MIS 2）和内盖夫北部沙丘砂（~ MIS 6 ~ MIS 2）的主要粒度模式之间。古土壤砂粒比沙丘砂粒略细，其空间沉积格局与后续沙丘入侵格局相关。这些结果表明：(1)Bk古土壤层抵抗（MIS 6-MIS 3）砂面风蚀，形成了年代分异的耐久面；(2)这些表面在很长一段时间内保持平衡，间歇性地被移动的砂饰面覆盖和保存；(3) MIS 2沙丘入侵事件遵循下垫古土壤砂基质的相同运输路线，但在Bk层面上产生有限的风成侵蚀；(4)古土壤与黄土具有相似的沉积学和年代学格局，具有部分成因联系。对于上覆沙丘而言，古土壤母质的风成沙供应最初受尼罗河三角洲沉积物有效性的控制，并可能与冰期-间冰期上升旋回以及冰期和寒期风活动有关。内盖夫西北部的砂沉积期与附近海岸砂质古土壤层序的年龄明显不同，说明在类似的古气候条件下，砂供应对古土壤层序发育的作用。
Calcareous paleosols in the northwestern (NW) Negev Desert dunefield, Israel, at the eastern end of the Sinai–Negev erg were studied in relation to their underlying stabilized dunes and downwind loess deposits, using sedimentological analyses, spectroscopy, and optically stimulated luminescence (OSL) dating. During the Middle to Late Pleistocene, between the end of MIS 7 and through MIS 3, several cycles of sand veneer (sheet) deposition, stabilization, pedogenesis, and erosion formed a spatially variable sequence of sandy calcareous paleosols in the NW Negev. Periods of stability on the order of several thousand years to over ten thousand years, characterized by post-depositional illuviation of aeolian silts, clays, and salts, enabled the formation of diagnostic, often-indurated, calcareous, Bk horizons (stages I–III), with orthic carbonate nodules. The primary particle-size mode of the paleosol (127 μm) is intermediate between the modes of the overlying (MIS 2) dune sand and the mode of primary northern Negev (~ MIS 6 through MIS 2) loess deposits in the dunefield periphery. The sand fraction of the paleosols is slightly finer than the dune sand, and its spatial sedimentation pattern correlates with the pattern of the subsequent dune incursions. These observations suggest that (1) Bk paleosol horizons were resistant to (MIS 6–MIS 3) sand veneer aeolian erosion and formed chronologically differentiated and durable surfaces; (2) these surfaces remained in equilibrium for extensive periods, being intermittently covered and preserved by shifting sand veneers; (3) the MIS 2 dune incursion episodes followed the same transport routes of the underlying paleosol sand substrate while producing a limited amount of aeolian erosion on the Bk horizons, and; (4) the similar sedimentological and chronological framework of the paleosols and loess deposits suggests a partial genetic connection. As for the overlying dunes, aeolian sand supply to the parent material of the paleosols was initially controlled by sediment availability originating in the Nile Delta and probably linked to glacial–interglacial eustatic cycles and glacial and cold-event windiness. The NW Negev sand deposition episodes that markedly differ from the ages of a nearby sandy paleosol sequence of coastal origin exemplify the role of sand supply on the development of paleosol sequences in a similar paleoclimate.