Abstract
Siliciclastics, carbonates and minor evaporites of fluvial, eolian, glacial, and shallow and deep marine environments representing all of the Paleozoic systems are well exposed and present in Saudi Arabia. The Paleozoic successions are exposed in a great curved belt along the northern, eastern, and southern margins of the Arabian Shield in three main basins: the Tabuk, Widyan, and Wajid basins, respectively. The basins are separated by the Hail Arch and the Central Arabian Arch. Two Paleozoic glacial episodes: The Late Ordovician glaciation (Saqiyah, Sarah, and Hawban formations in the Widyan and Tabuk basins and the Sanamah Formation in the Wajid Basin) and PermoCarboniferous glaciation (the Juwayl Formation in the Wajid Basin), are well defined and documented. Detailed regional lithologic, paleontologic, and structural field studies have resulted in dividing the succession into seven well marked mega tectono-depositional cycles: the Cambro-Ordovician (Tayma Group), Late Ordovician (Tabuk Group), Early Silurian (Qalibah Group), Late Silurian Sharawra (Group), Siluro-Devonian Huj (Group), Devono-Carboniferous Sakaka (Group), and PermoCarboniferous Buraydah (Group). These cycles or groups are separated by regional well- defined unconformities, probably caused by global time-equivalent movements: the Assyntic, Taconic, early and maximum Acadian, and early and maximum Hercynian movements. The Paleozoic rocks are becoming a primary exploration target and their tectono-stratigraphy has therefore attracted considerable attention. Porous and permeable siliciclastic and carbonate rocks host great quantities of oil, condensate, and natural gas in several oil and gas fields in Saudi Arabia.