Evolution of a terminal Neoproterozoic carbonate ramp system (Buah Formation, Sultanate of Oman): Effects of basement paleotopography

The Buah Formation is a carbonate unit of late Neoproterozoic age, exposed in the Jabal Akhdar of northern Oman and the Huqf region of central Oman. The Buah Formation is interpreted as a distally steepened storm-dominated ramp, containing inner ramp tidally influenced oolitic shoal and back-shoal lagoon facies and storm-dominated mid ramp facies. A slope break separates mid-ramp facies from outer ramp facies characterized by accumulation of redeposited carbonates on gently inclined slopes (1-2 degrees). Combined facies stacking patterns and outcrop correlation via delta(13)C profiles suggest that Buah carbonates formed as a highstand systems tract characterized by a general upward shallowing of facies and strong lateral progradation. On a regional scale, Buah facies distributions across Oman were controlled by the presence of basement highs defining areas of reduced subsidence, which promoted lateral progradation of the Buah carbonate ramp for tens of kilometers, while the faster-subsiding areas became sites of deep-water deposition.