Late Cretaceous chemical sediments related to a carbonate platform-foreland basin transition in the Oman Mountains

Abstract

In the Oman Mountains, ferruginous, phosphatic and minor siliceous chemical deposits accumulated in the Late Cretaceous (? upper Turonian-Campanian) related to the transition from a carbonate platform to a foreland basin. This process was synchronous with large-scale emplacement of nappes derived from the Mesozoic Tethys ocean. The platform edge was uplifted and later subsided, controlled by crustal flexure. Following initial drowning of the Arabian platform (? Turonian), flexural uplift produced a regional unconformity, the “Wasia-Aruma” break and the outer shelf area was deeply eroded. Further inboard, ferruginous oolites formed on shoals in shallow protected seas, and were later reworked with neritic bioclastic sediment. Following inferred passage of a flexural bulge, subsidence began and ferruginous crusts and nodules precipitated on hardgrounds located along the erosion surface. Impure lime-muds then were deposited on the floor of a subsiding shelf (10s–100 m) that was progressively tilted, with accumulation of phosphatic deposits in deeper water (100s–1000 m), on unstable slopes. Then the thrust-sheets docked with the Arabian continent and the platform edge was downflexed to form a foredeep in which deep-water clastic sediments accumulated, and this was followed by overthrusting of nappes from the Tethys ocean.