Late Paleozoic (Late Carboniferous-Early Permian) glaciogenic sandstone reservoirs on the Arabian Peninsula

The Permo-Carboniferous (Latest Visean-Latest Sakmarian) Gondwana continental glaciation is known from the outcrops of Oman, Yemen and Southern Saudi Arabia and in the subsurface of Central Saudi Arabia. It has not yet been recorded in the Northern Saudi Arabia and Middle East Countries, suggesting that it shows less areal extension than the Late Ordovician glaciation. The glacial deposits (moraines and boulder beds) and glacially formed structures (grooves and striated pavements) have been recorded in deep and narrow paleovalleys in the Al Khlata Formation of Oman, Juwayl Formation of Southwestern Saudi Arabia and Kohlan Group of Yemen. Striated pavements and boulder beds occur in three successive horizons and interstratified with the cross-bedded glaciofluvial sandstones in the paleovalleys suggesting for multiple episodes of ice advance and retreat. The paleovalleys extended in south–north directions from Southern Arabian Peninsula and deposited hydrocarbon producing thick and well-sorted glaciofluvial and cold-climate eolian sandstones on the large sandur plain in Central Saudi Arabia, defined as the Haradh Formation of the Unayzah Reservoir. Large number of cores was studied to understand the stratigraphy, regional distribution and reservoir quality of these glaciogenic sandstones. The Jawb Formation conformably overlies the Haradh Formation and was deposited as organic-rich glaciomarine and glaciolacustrine sediments during the deglaciation stage. The limestones and dolomites of the Ruhaiya Formation in southeast Saudi Arabia represent the cap carbonate facies and correlates with the Haushi Limestone of Oman. Palynological studies indicated that the glaciation period extended between the Late Carboniferous (latest Visean, 330.9 Mabp) and Early Permian (Latest Sakmarian, 290.1 Mabp) time.