The Influence of Obduction on the Late Cretaceous Deposits in the Fars Province-Zagros, Iran

During the Late Cretaceous the northeastern margin of the Arabian plate (Zagros-Fars Area) is characterized by significant variations in sedimentary facies, sedimentation patterns, accommodation space and by shifting depocentres. A succession of events recording the evolution of the region from a passive to an active margin is documented by the study of eight outcrop sections and one well. This new study uses new age dating (benthic and planktonic foraminifera, nannoplankton and radiolarian biozonations and strontium isotope stratigraphy). Three tectono-sedimentary phases are recognised indicating the evolution from a passive to an active margin: Phase I (Late Albian to Cenomanian, before obduction) comprises three depositional 3rd order sequences comparable to the other parts of the Zagros and Arabian Plate. This interval is composed of shallow-water platform carbonates and intrashelf basins. Phase II (Turonian to Late Campanian, obduction phase) is characterized by major changes in depositional environments and sedimentary facies, due to obduction and foreland basin creation. Phase III (Late Campanian to Maastrichtian, after obduction) shows the development of rudist-dominated carbonates in the NE ,deep basinal facies in the centre of area. In the most-NE no sediments of this age have been recorded suggesting uplift at that time.