Sedimentary facies, mineralogy, and geochemistry of the sulphate-bearing Miocene Dam Formation in Qatar

Dill, H. G., Botz, R., Berner, Z., Stuben, D., Nasir, S. and Al-Saad, H. (2005) Sedimentary facies, mineralogy, and geochemistry of the sulphate-bearing Miocene Dam Formation in Qatar Sedimentary Geology, 174 (1-2). pp. 63-96. DOI 10.1016/j.sedgeo.2004.11.004.

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The Miocene deposits of the Dam Formation were deposited in a narrow seaway stretching along the western edge of the Qatar Arch. During the initial stages of basin evolution the rising Zagros Nits. delivered debris in this fore deep basin. The paleocurrent and paleogeographic zonation are reflected by the heavy mineral assemblage, by the spatial distribution of phyllosilicates and the various types of sulphate. From NW towards the SE, the contents of smectite and palygorskite increase, whereas the illite and kaolinite contents decrease. Mega crystals of gypsum are found in the NW and massive fine-grained gypsum in the SE of the basin. During the waning stages of basin subsidence, the Arabian Shield became more and more important as a source for the Miocene sediments. In this study, the Dam Formation was subdivided into 7 members/lithofacies associations (lower, middle, upper Salwa, and Al Nakhsh Members, Abu Sarnrah Member). The Salwa Members at the base of the Dam Formation consists of heterolithic siliciclastic-calcareous sediments which were laid down under meso- to microtidal conditions. The Al Nakhsh Members formed under macrotidal conditions with sub- to supratidal depositional environments passing into continental ones. Celestite, gypsum, and microbial mats (stromatolites) are very widespread in these sabkha sediments. Crystals of gypsum and the thickness of stromatolites tremendously increase towards younger sediments indicating thereby a close genetic link between growth of microbial domes and gypsum precipitation. Throughout the Abu Samrah Member marine calcareous sediments were deposited in a microtidal wave-dominated environment. Dissolution of Eocene evaporites at depth governed the lithofacies differentiation in the Miocene Darn Formation. (C) 2004 Elsevier B.V. All rights reserved.

Document Type: Article
Keywords: evaporite siliciclastic-caleareous sabkha deposition miocene Qatar environmental significance isotopic composition oxygen isotopes marine foraminifera sulfur classification fractionation carbonate assemblages
Research affiliation: Kiel University
Refereed: No
DOI etc.: 10.1016/j.sedgeo.2004.11.004
ISSN: 0037-0738
Date Deposited: 18 Jan 2012 05:19
Last Modified: 08 Oct 2012 10:26

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