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Mosaddegh Hossein, Damghan University of Basic Sciences (Islamic Republic of Iran)
Behrouz Rafiei, Bu-Ali Sina University (Islamic Republic of Iran)
Mehrdad Shahkaram , National Iranian Drilling Company (Islamic Republic of Iran)
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The lower Cretaceous Fahliyan Formation in the Zagros Basin consists of a thick sequence of shallow water carbonate that is conformably overlain by Gadvan Formation and underlain by the Hith and Surmeh formations in the subsurface and outcrop sections, respectively. A subsurface section in Garangan-2 well and an outcrop in Khami Anticline were studied. This study evaluates the depositional environments and the sequence stratigraphy of a carbonate system that developed in the southwest of Iran. Based on well cutting, thin sections and well log analysis, twenty four microfacies have been identified in these deposits representing four facies belt associations:
A) tidal flat facies belt consists of peloid/bioclast grainstone, bioclast/intraclast grainstone;
B) Back barrier lagoon facies belt is made of bioclast/peloid grainstone, algal wackstone and gastropod wackstone;
C) Barrier facies belt consists of coral bindstone, algal bindstone and peloid grainstone;
D) Open marine facies belt includes radiolarian wackstone, sponge spicule wackstone, echinoderm wackstone and fossiliferous lime mudstone. According to the mentioned facies, a shallow carbonate ramp with a gentle dip is suggested for the depositional environments of the Fahliyan Formation. Vertical succession of microfacies and relative depth changes of the Fahliyan Formation led to identification of one third-order depositional sequence.
The lower boundary of the sequence is a type 1 unconformity and the upper boundary is of type 2 unconformity.
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