Holocene chemical precipitates in the continental sabkha of Tayma (NW Saudi Arabia) |
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| Institution: | 1. Institute of Geography, Goethe University Frankfurt a. M., Altenhöferallee 1, D-60438 Frankfurt, Germany;2. Institute of Geography, University of Cologne, Albertus-Magnus-Platz, D-50923 Cologne, Germany;1. Department of Pharmacognocy, College of Pharmacy, King Saud University, P. O. Box 2457, Riyadh, 11451, Saudi Arabia;2. UK National Crystallography Service, School of Chemistry, University of Southampton, University Road, Southampton, SO17 1BJ, UK;3. Department of Pharmaceutical Chemistry, College of Pharmacy, King Saud University, P. O. Box 2457, Riyadh, 11451, Saudi Arabia;1. Pulmonary and Critical Care, Internal Medicine, and Radiology, West Los Angeles VA Healthcare Center, Los Angeles, California;2. Department of Radiology, Stanford University School of Medicine, Stanford, California;3. Department of Diagnostic Radiology, University of Texas MD Anderson Cancer Center, Houston, Texas;1. Laboratory of Agronomy, Faculty of Crop Science, Agricultural University of Athens, 75, Iera Odos Str., Athens 11855, Greece;2. Laboratory of General Chemistry, Department of Food Science and Human Nutrition, Agricultural University of Athens, 75, Iera Odos Str., Athens 11855, Greece;3. Laboratory of Soil Science and Agricultural Chemistry, Department of Natural Resources Management and Agricultural Engineering, Agricultural University of Athens, 75, Iera Odos Str., Athens 11855, Greece |
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| Abstract: | Studies on playas (known locally as inland sabkhat) are rare and lack a focus on their role as geoarchives for Holocene climate and environmental change. We present characteristic sediments and processes that illustrate the change from relatively humid to hyperarid conditions within the sedimentary record of the playa of Tayma (Saudi Arabia). The shift from the Holocene humid period (10–8 ka BP) to the hyperarid conditions of today left traces in this geoarchive. During the humid period, a perennial lake had formed in the playa depression. The occurrence of biota, especially ostracod valves and foraminifer shells, adapted to salinity fluctuations and physiochemical reactions of ostracods and foraminifers testify environmental changes. Phases of lake contraction and high salinities were responsible for the formation of ‘open water’ evaporites, such as aragonite needles, and ooids. Dilution occurred during rain events and flooding of the playa; it is characterised in the sedimentary infill by clastic layers that were deposited in graded sequences. The smooth surface, the phenomenon of microsomia and sieve pore variations of the ostracod valves provide evidence for changing salinities, which are testimony to short lived changes. These processes and further aridisation resulted in the formation of ‘capillary’ evaporites, which are dominated by sulphate minerals. The precipitates undergo fractionation and re-dissolution, which results in a typical stratification of salts with different solubilities. |
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