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Hassan Mohseni, Bu-Ali Sina University (Islamic Republic of Iran)
Mehdi Khoshnoodkya , Bu Ali Sina University (Islamic Republic of Iran)
Mahmud Hajian, NIOC (Islamic Republic of Iran)
Behrouz Rafiee, Bu-Ali Sina University (Islamic Republic of Iran)
Hassan Mohseni, Bu-Ali Sina University (Islamic Republic of Iran)
Mehdi Khoshnodkya, Bu-Ali Sina University (Islamic Republic of Iran)
Mahmoud Hajian, NIOC (Islamic Republic of Iran)
Behroz Rafiee, Bu-Ali Sina University (Islamic Republic of Iran)
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Dashtak Formation is a significant seal for supergaint Dehram reservoir in the Zagros basin and mainly consists of evaporite and carbonates deposited in sabkha environment. This formation has been subdivided to Aghar shale member, A, B, C Evaporites, Sepidar dolomite and D Evaporite in ascending order. Dashtak formation were studied in (Aghar#1, West Aghar#1 and Naura #1 boreholes) for constrauction depositional environment and microfacies. petrographic examinations of five hundred thin sections prepard from well cutting, and gamma ray and sonic logs revealedthatthis formation consists eight facies including seventeen carbonate microfacies and four non-carbonate as follow: A (costal plain), B (supratidal), C (tidal flat), D (lagoon), E (shoal), F (restricted marine), G (open marine) and H (mid-ramp). Facies A is bounded by a sequence boundary with siliciclastics input to the basin. Facies B is microfacies anhydrite, chicken wire anhydrite, laminated evaporite-carbonate mudstone and silty mudstone. Facies C is stromatolite boundstone and dolomitize lime mudstone. Facies D interpreted as lagoon facies including bioclast muddstone, bioclast/ peloid wackestone and bioclast/ peliod packstone. Facies E mainly composed of interclast grianstone, peloid grianstone and ooid grianstone. Facies F is in a restricted marine with ostracod wackestone and sponge spicule mudstone. Facies G is bioclast wackestone with echnoid spine and facies H is intraclast grainstone, packstone and peloid packstone with storm events and grading. According to these facies association depositional environment of Dashtak formation is suggested a sabkha environment (inner? to middle ramp). Dashtak formation comprises four sequences of two bounded by boundaries type I surface sequence and three type III sequence boundares. Keywords: Dashtak Formation, Depositional environment, Microfacies, sabkha, sub costal Fars, Iran
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