A transition from a passive to a tectonically active margin and foreland basin development in the Late Cretaceous of the Fars Area and offshore (Zagros)

The northeastern margin of the Arabian plate in the Fars Area was influenced by a series of tectonosedimentary events during the Late Cretaceous. These events are well documented by significant variations in sedimentary facies and sedimentation patterns and thickness. The presence of igneous dikes is another significant phenomenon at the top of Cenomanian platform. Nine regional transects parallel and perpendicular to the Zagros trend were prepared. These transects vertically contain three tectono-sedimentary phases: Phase I (Late Albian to Turonian), Phase II (Coniacian to Late Campanian) and Phase III (Late Campanian to Maastrichtian). Phase I is characterised by shallow-water carbonate platforms bordering intrashelf basins. Eustatic sealevel variations can be the main factor controlling the accommodation space in parts of the area, whereas to the southeast the role of the regional and salt tectonic are more dominant. Phase II is marked by major changes in the depositional environments and sedimentary facies, as a result of obduction and foreland basin creation. The pelagic marls host large volumes of carbonate and siliciclastic gravity flows and far-traveled radiolarites and ophiolites as well as thrust slices of older carbonates. Phase III is dominated by pelagic facies interfingering with shallow-water Omphalocyclus and Loftusiabearing facies.