Granulometrical, mineralogical and geochemical characterization of loess deposits in the Tajo Basin
Granulometrical, mineralogical and geochemical characterization of loess deposits in the Tajo Basin
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DOI：
10.1016/j.quaint.2015.11.122
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发表时间：
2016-07
影响因子：
2.2
通讯作者：
F. Calvo;Jesús Sánchez;A. Acosta;D. Wolf;D. Faust
中科院分区：
文献类型：
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作者：
F. Calvo;Jesús Sánchez;A. Acosta;D. Wolf;D. Faust
黄土研究的优点是能够重建世界许多地方的更新世沉积动力学。然而，仍然有很少的信息发生在地中海地区的黄土沉积，即使这样的记录可能提供了一个独特的机会，调查景观演变的一段时间，在这一地区的陆地档案是非常罕见的。本文介绍了在西班牙中部塔霍河谷中部的黄土序列的调查的第一个结果。详细的粒度、矿物学、地球化学和颗粒形态分析的结果有助于对这些矿床的特征和组成进行初步概述。碳酸盐含量很高（约60%），石膏含量也很高，这两种物质都是原生的，表明含有泥灰岩和石灰岩的物质。此外，我们发现的证据可以更精确地推断可能的黄土出处。白云岩含量高达20%，表明伊比利亚山脉可能是黄土沉积物的重要源区。这些高地位于东部的事实似乎与冰川时期盛行西风的普遍假设相反。所研究的序列（帕拉伊索剖面）是西班牙中部上更新世景观动态重建计划的七个部分之一。在这种情况下，沉积物性质的详细描述是至关重要的讨论黄土物源和沉积环境。
Loess research has the merit of enabling reconstructions of Pleistocene sedimentation dynamics in many parts of the world. However, there is still very few information regarding the occurrence of loess deposits in the Mediterranean area, even though such records may provide a unique opportunity to investigate landscape evolution for a period for which terrestrial archives are very rare in this region. This paper presents the first results of investigations on a loess sequence in the middle Tajo Valley in central Spain. Findings from detailed granulometrical, mineralogical, geochemical, and grain morphological analyses help to give a first overview on character and composition of these deposits. Very high levels of carbonates (∼60%), but also of gypsum, both to large extents of primary origin, indicate the incorporation of material derived from marls and limestone. Furthermore, we found evidence that allows deduction of possible loess proveniences more precisely. Dolomite contents of up to 20% indicate that the Iberian Range might have been an important source area of loess sediments. The fact that these uplands are located to the east seems to be opposed to the common assumption of prevailing west winds for glacial periods. The studied sequence (Paraiso profile) is one of seven sections that have been investigated as part of a programme to reconstruct Upper Pleistocene landscape dynamics in central Spain. In this context, the detailed characterisation of sediment properties is crucial for discussing loess proveniences and sedimentary environments.