Impact of salt layers interaction on the salt flow kinematics and diapirism in the Eastern Persian Gulf, Iran: Constraints from seismic interpretation, sequential restoration, and physical modelling.

Abstract

Interpretation of reflection seismic profiles, sequential restoration, and physical modelling are presented to understand the kinematics of salt flow and diapirism in the Eastern Persian Gulf, offshore Southern Iran. Salt tectonics in this area result from the overlapping Ediacaran-Early Cambrian Hormuz Salt, which is regionally present, and Oligocene-Early Miocene Fars Salt, which is locally developed. The Hormuz and Fars salts began flowing at Cambrian(?) and Early Miocene times, respectively. Diapirs fed by the Hormuz Salt rose passively during Palaeozoic and Mesozoic times and were rejuvenated by contractional deformation events in the Cenozoic. Fars-Salt structures exist either as salt walls and anticlines around those diapirs of Hormuz Salt that developed allochthonous salt bodies during a Palaeocene-Eocene contractional squeezing before deposition of the Fars Salt, or as gentle shallow salt pillows above deep pillows of Hormuz Salt, suggesting a kinematic linkage. Flow of Fars Salt was mainly triggered by differential sedimentary loading. It seems that its lateral flow kinematics was controlled by the behaviour of the underlying Hormuz-Salt sheets. More than ~10-km-long salt sheets were efficiently evacuated back towards the Hormuz-Salt diapir, and consequently, maintained the Fars-Salt evacuation and flow to the same direction, accompanied by welding of both salt layers. Conversely, smaller, less than ~3-km-long salt sheets allowed limited salt evacuation or rearrangement that was probably still sufficient to trigger Fars-Salt flow near the central (Hormuz-Salt) diapir. Fars-Salt evacuation was enhanced by differential sedimentary loading, resulting in incipient primary welds. Subsequently, the depocentres migrated towards the areas of available Fars Salt away from the central diapir. In both cases, layer-parallel shortening related to regional contraction probably played also a role in triggering the Fars-Salt flow at Early Miocene, but was more influential at later stages by squeezing the salt structures (Hormuz and Fars) since about Late Miocene onwards.