Maastrichtian tectono-sedimentary evolution of the western Fars area (Zagros, SW Iran): insights into a foreland basin deposits

Late Cretaceous time interval as a turning point in the Zagros history is characterised by the obduction of oceanic sedimentary cover of the Neotethys over the NE-tilted Arabian Platform. This event was associated with tectono-sedimentary loading and creating a foreland basin along the NE margin of the Arabian plate resulting in huge thickness and facies variations. For stepping the events and showing the foreland basin evolution during the Maastrichtian time, a SW-NE trending regional transect of several outcrop and well sections is constructed and interpreted in a high resolution sequence stratigraphic framework (six depositional sequences). In general, three phases of foreland basin evolution could be determined along the transect: tilting and backstepping of the platform, foredeep basin development and SW prograding of the subsiding platform during the Santonian, Campanian and Maastrichtian sequences respectively. The Tarbur Formation with shallow water carbonates is the main lithostratigraphic unit of the Maastrichtian, which laterally grades to the pelagic marls of the Gurpi Formation to the SW and onlaps onto the obducted radiolarite and ophiolitic complex to the NE Fars area. Temporal and spatial developments of platform carbonates of the Tarbur Formation and its equivalent basinal marls of the upper part of the Gurpi Formations is an indication to show how foreland basin migrated during this time interval. The Maastrichtian shallowing up cycles are composed of various shallow-water carbonate and pelagic facies and radiolarite and siliciclastic petrofacies deposited from tidal flat to basinal depositional environments. Initiation and re-activation of the basement faults are one of the most important controlling factors in accommodation spaces which overprinted locally by the holokinetic movements.