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Alegret, Ortiz & Kaminski (eds.), 2012. Ninth International Workshop on Agglutinated Foraminifera, Abstract Volume Rivas, V. & Cendrero, A. 1991. Use of natural and artificial accretion on the north coast of Spain: historical trends and assessment of some environmental and economic consequences. Journal of Coastal Research, 7, 491–507. UNSCEAR-United Nations Scientific Committee on the Effects of Atomic Radiation, 2000. Sources and Effects of Ionizing Radiation, 2000 Report, United Nations, New York. 31
Alegret, Ortiz & Kaminski (eds.), 2012. Ninth International Workshop on Agglutinated Foraminifera, Abstract Volume New agglutinated foraminifera, including multichambered taxa, from the Middle Ordovician Hanadir Shale of Northern Saudi Arabia Assad GHAZWANI 1 , Michael A. KAMINSKI 2 and Lamidi BABALOLA 3 1 Saudi Aramco, Exploration Resource Assessment Department, PO Box 1063, Dhahran, 31311, Saudi Arabia. 2 Earth Sciences Department, King Fahd University of Petroleum & Minerals, PO Box 301, Dhahran, 31261, Saudi Arabia. 3 Research Institute, King Fahd University of Petroleum & Minerals, PO Box 301, Dhahran, 31261, Saudi Arabia. e-mail: assad.gazwani@aramco.com The Hanadir Shale Member of the Qasim Formation is a black shale that represents a middle Ordovician maximum flooding event in the Arabian Peninsula. It is exposed in the Paleozoic outcrop belt in Central Saudi Arabia, however in the north of Saudi Arabia it occurs only in the subsurface. The age of the Hanadir Shale Member is constrained by graptolites and palynomorphs, indicating Didymograptus murchisoni zone. We examined samples from the Hanadir Shale collected from three wells drilled in the proximity of the Jauf Graben, north of the city of Al Jauf, Saudi Arabia. The foraminiferal fauna recovered from the Hanadir Shale Member contains a wellpreserved assemblage consisting entirely of agglutinated taxa. Currently, these are the oldest foraminifera reported from Saudi Arabia. As expected, the middle Ordovician assemblage contains numerous simple forms such as Rhizammina, Psammosphaera, Saccammina and Lagenammina, which are found in other Ordovician localities worldwide. In addition to the simple forms, we observe a diverse assemblage of lituolids and trochamminids, including the genera Ammobaculites, Bulbobaculites, Sculptobaculites, and diverse trochamminids. Our finding of coiled, multichambered agglutinated foraminifera in the Hanadir Shale of Saudi Arabia pushes back the known stratigraphic range of the suborder Lituolina to the middle Ordovician. The lituolids found in the Hanadir Shale assemblage are diverse, which implies the true first occurrence of this group of foraminifera is even older. Previous reports of these forms placed their origin in the early Devonian (Loeblich and Tappan, 1987). Our findings also give increased credibility to previously published reports of trochamminids from the upper Cambrian of Nova Scotia (Scott et al., 2003), which were regarded by some researchers as questionable owing to their poor preservation. Some of the trochamminids from the Hanadir Shale show radially elongated chambers, and likely belong in a new genus. The paleoenvironment of the Hanadir Shale Member in the north of Saudi Arabia is regarded as a deep, normal marine shelf with dysoxic, sometimes anoxic, bottom waters, open to the Paleotethys Sea. This environment fostered the development of the oldest fauna with abundant multichambered agglutinated foraminifera discovered so far. Our finding of agglutinated foraminifera will no doubt contribute to a better understanding of the depositional environment of the Hanadir member in NW Saudi Arabia. Reference: Scott, D.B., Medioli, F. & Braund, R. 2003. Foraminifera from the Cambrian of Nova Scotia: The oldest multichambered foraminifera. Micropaleontology, 49 (2), 109-126. 32
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