Salt Diapirism in the Iranian Sector of the Persian Gulf: Timing and Structural Evolution

Chiariotti, Luca ¹; Carruba, Stefano ²; Cattaneo, Luciano ²; Perotti, Cesare ¹; Bertozzi, Giuseppe ³; Bolis, Giorgio ²; Feltre, Luca ²; Rahimi, Mashallah ⁴
(1)Department of Earth Sciences and Environment, University of Pavia, Pavia, Italy. (2) Edison S.p.A., Milan, Italy. (3) Edison International - Iranian Branch, Teheran, Iran, Islamic Republic of. (4) NIOC (National Iranian Oil Company), Teheran, Iran, Islamic Republic of.

The sedimentary succession of the Persian Gulf basin is warped and pierced by numerous salt diapirs of the basal Late Proterozoic Hormuz Formation that deposited in intracratonic basins formed during Late Proterozoic transtensional events (Najd rifting), after the Precambrian basement accretion.

From Late Cambrian to Late Devonian, the Persian Gulf was a passive margin of the northeastern sector of Gondwana facing the Paleo-Tethys and characterized by continental clastic sedimentation. After a period of regional uplift due to the Hercynian Orogeny, a back-arch continental rifting (Middle Permian) led to the Neo-Tethys opening. A new carbonate passive margin formed that was stable until middle Cretaceous. In the Upper Cretaceous the area was affected by the first compressional events related to the Neo-Tethys closure (ophiolite obduction), which was followed in the Oligocene by the onset of the compressional deformation that created the Zagros Fold Belt, whose current active front borders the Persian Gulf foreland to the NE. In the study area a dense grid (2x2 km) of 2D seismic lines is available. Seismic interpretation was carried out on 12 horizons corresponding to formation tops or unconformities from Early Permian to Present and calibrated with well data. TWT structural maps of each interpreted horizons, TWT and isopach maps were produced and the sedimentation and average salt uplift rates calculated. Seismic lines restoration helped to reconstruct the structural evolution of diapirs, by analyzing the reflectors relationships indicative of tectonic and sedimentary events (e.g., onlaps, rim synclines, minibasins,..). The study of 20 not piercing diapirs reveals a good correlation in the evolution of the different structures. Salt uplift started during the Early Paleozoic and persisted with pulses of different intensity until present. The main phases occurred during the Paleozoic (when a continuous, synsedimentary growth took place), Upper Cretaceous and Upper Paleogene (with a post-depositional growth connected to the two principal regional unconformities), and early Neogene (synsedimentary uplift). Different periods of salt movements are characterized by different average rates of deformation, comprised between 1 and 25 m/Ma. A connection between periods of main salt activity and the geodynamic events that affected the Arabian Plate can be inferred.

AAPG Search and Discovery Article #90135©2011 AAPG International Conference and Exhibition, Milan, Italy, 23-26 October 2011.