Lower Cretaceous stratigraphy and depositional history of the Rub' Al Khali bsin

Abstract

The Lower Cretaceous Thamama Group in the Rub' al Khali basin, southern Arabia, disconformably overlies thick Upper Jurassic anhydrite of the Hith Formation. The Thamama is over 2900 feet (884m) thick, and consists, in stratigraphic sequence, of the Sulaiy Yamama, Buwaib/Biyadh (undiff.), and Shu'aiba Formations. Lower Cretaceous sediments were deposited during two major shallowing-upward cycles. The first cycle began with lime mudstone of the Sulaiy, and concluded with wackestone and packstone interbeds of the Yamama, followed by erosion in the southern part of the basin. The second cycle began with argillaceous lime mudstone of the basal Bwaib/Biyadh (undiff.) and concluded with thick skeletal packstone and grainstone of the Shu'aiba. Thick wedges of siliciclastics, the Biyadh Sandstone, prograded into the basin from the west, but the Bwaih/Biyadh contact cannot be correlated into the continuous carbonate rock interval in the subsurface. A widespread unconformity concludes the Lower Cretaceous.