Controls of Tectonic and Paleoclimate on the Middle-Late Triassic Dashtak Formation in the Zagros Domain, Iran: A Regional Seal and Subordinate Reservoir Rock (original) (raw)

The Middle-Late Triassic Dashtak Formation provides an effective, regional seal for the Permo-Triassic Dalan-Kangan (Khuff) reservoirs and also forms the subordinate reservoir in a number of gas fields in the Zagros domain. The evaporite-dominated formation is subdivided into six members. Lithofacies and isopack maps show strong controls of deep-seated faults, particularly Kazerun and Balarud during deposition of this formation. Comparison of isopack maps of the Dalan and Dashtak formations indicates that there is a shifting of depocenter from east- to westward of Kazerun Fault from Permian to Triassic. This shifting is interpreted to be the effect of the fault reactivation caused by the Neotethys opening. The Dashtak Formation consists of four large-scale carbonate-evaporite cycles, which was deposited in a carbonate/evaporite platform. Periodic development of carbonate and anhydrite intervals was controlled by relative sea-level fluctuations under a prevailing arid paleoclimatic conditions. The Dashtak Formation consists of four large-scale carbonate-evaporite cycles, which was deposited in a carbonate/evaporite platform. Periodic development of carbonate and anhydrite intervals was controlled by relative sea-level fluctuations under a prevailing arid paleoclimatic conditions. Strontium isotope ratios (87Sr/86Sr=0.7074-07085) record varies age from Early to Middle/Late Triassic for the studied formation.

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