Contribution to the geology of Ataq area, Shabwah Province, southeastern central Yemen
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ORIGINAL PAPER
Contribution to the geology of Ataq area, Shabwah Province, southeastern central Yemen Khaled A. Al-Wosabi & Abdulwahab S. Alaug & Ali A. A. Khudeir
Received: 20 February 2013 / Accepted: 20 May 2013 # Saudi Society for Geosciences 2013
Abstract The Pan-African (Neoproterozoic) low-grade ophiolitic fragment occurring to the south of Ataq City, Shabwah Province, southeastern central part of Yemen is positioned tectonically between the underlying Pre-Pan-African syntectonic granite infrastructure and the overlying Mesozoic– Cenozoic sedimentary successions. It is incomplete and differentiated in the field into (a) NW plunging nappes, namely a lower metagabbro nappe, and (b) the upper metavolcanic nappe. The sedimentary successions separated from each other by eastward dipping normal faults. These successions can be subdivided into three main rock units: Amran, Tawilah, and Hadramawt groups. The Amran Group is represented in the study area by Shuqra and Madbi formations. The Shuqra Formation consists mainly of highly fossiliferous carbonate facies yielding several terebratulids and rhynchonellids. It belongs to the Toracian–Oxfordian (or probably extend to Early Kimmeridgian) age. The Madbi Formation consists of sand– marl intercalations of Kimmeridgian–Early Tithonian age. The Tawilah Group is mainly composed of variegated unfossiliferous continental sandstones with few siltstone intercalations, and on the basis of its stratigraphic position, it is dated as Cretaceous (probably Early Cretaceous). The Hadramawt Group in the study area is represented by Umm er Radhuma Formation, which is widely distributed in the Arabian Gulf countries. Keywords Ataq . Shabwah . Geology–Biostratigraphy . Amran . Tawilah and Hadramawt groups . Yemen K. A. Al-Wosabi : A. S. Alaug (*) Department of Geology, Faculty of Applied Sciences, Taiz University, 6803, Taiz, Yemen e-mail: [email protected] A. S. Alaug e-mail: [email protected] A. A. A. Khudeir Geology Department, Faculty of Science, Assiut University, Assiut 71516, Egypt
Introduction The study area is located to the south of Ataq City, Shabwah Province, southeastern central Republic of Yemen between longitudes 46° 47′–47° 00′ E and latitudes 14° 20′–14° 32′ N (Fig. 1). It lies to the north east of Al-Mahfid Terrane (Whitehouse et al. 1993; Windley et al. 1996) which covers the most part of Shabwah Province. The Al-Mahfid Terrane consists of belts of high-grade gneiss, amphibolites, gneissic granites, as well as low-grade ophilitic fragments comprising gabbros, basalts, marbles, and the thin conglomerate. The gneisses gave depleted mantel model age ranges of 2.73–3.03 Ga and are interpreted as remnants of Archean continental crust; Pan-African reworking of the highgrade rocks added juvenile components, resulting in mixed model ages (Windley et al. 1996). The part adjoining the Al-Mahfid Terrane from the east are covered by the Jurassic, Cretaceous, and Tertiary sedimentary sequences, composed of both clastic and carbonate facies deposited in a shallow marine
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