Similarities in the Paleozoic Successions of North Africa and Arabia and Implications for Petroleum Exploration

D. D. Clark-Lowes

From field studies in southwest Libya and northwest Saudi Arabia, the facies of the Paleozoic succession of the north African/Arabian stable cratonic margin of Gondwanaland are interpreted as fluvial, estuarine, deltaic, shallow marine, and glacial deposits. The facies of the Saq and Tabuk Formations of Saudi Arabia bear witness to a sedimentary history that is very similar to that of north Africa, the Saq Formation (Cambrian-Arenig) being equivalent to the Hassaouna Formation of Libya and the Tabuk Formation being subdivided and correlated using well-dated shale members to the following formations: Haouaz (Llanvirn-Llandeilo), Melez-Chograne (Caradoc), Memouniat (Ashgill), Tanezzuft/Acacus (Llandovery-Ludlow), and Tadrart (Gedinnian?-Emsian).

The Cambrian-Ordovician succession comprises Nubian-type fluvial and estuarine sandstones which pass up to regressive deltaic/shallow marine sequences overlain by Upper Ordovician glacial deposits that lie in deeply incised paleovalleys recorded from Saudi Arabia and north Africa. The Silurian succession comprises the deposits of a postglacial marine transgression of vast lateral extent and a subsequent regression, the sandstones of which are markedly diachronous. The Lower Devonian succession comprises fining-upward retrogradational deltaic (transgressive) sequences of Nubian-type sandstones (fluvial to shallow marine) which form widespread blanket sandstone bodies.

The prospectivity of these strata is well known from Algeria in the west to Jordan in the east, the Llandoverian oil-prone source rocks providing the key to Cambrian-Ordovician and Lower Devonian plays. The significance of underlying paleovalley-fill fluvioglacial sandstones as linear reservoir targets has yet to be fully appreciated.

AAPG Search and Discovery Article #91032©1988 Mediterranean Basins Conference and Exhibition, Nice, France, 25-28 September 1988.