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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.
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