Facies, depositional environment and sequence stratigraphy of Miocene deposits in the Haft cheshmeh section, Nourth of Nourabad, Sanandaj - sirjan Zone

The Miocene deposits are exposed in the Nourabad region of Sanandaj Sirjan Zone. In this study, one surface section (Haft cheshmeh) with a thickness of 125 m has been studied in order to determine the sedimentary environment and sequense stratigraphy. The lower boundary of Miocene deposits in the studied section is sharp with ophiolitic unit (E1v) and the upper boundary is erosional. The Miocene deposits in the studied area are mainly characterized by marl and thin to thick bedded limestone.Also based on the field observations, petrographic studies, textural and facial characteristics, as well as the abundance and distribution of foraminifera and other components,19 carbonate microfacies have been identified. These carbonate microfacies were deposited in 5 facies belts including lower slope, upper slope, margin, platform-margin sand shoals and lagoon facies.The existence of barrier reefs, intraclasts, oncoids, aggregate grains and the abrupt facies changes, also absence of widespread intertidal flat and the re-deposited carbonates (calciturbidites) represent that this sequence deposited on a rimmed carbonate platform. Sequence stratigraphy analysis led to identification of three 3rd order depositional sequences bounded by type I and type II sequence boundaries. The sequence 1 consists of TST and HST system tracts. This sequence is characterized by open marine, margin, sand shoals and lagoon facies. The lower boundary of this sequence is a sequence boundary type 1 (SB1)with ophiolitic unit (E1v)and the upper boundary is a sequence boundary type 2 (SB2) with sequence 2.The sequence 2 consists of TST and HST system tracts and is characterized by open marine, sand shoals and lagoon facies.The lower and upperboundaries of sequence 2 are sequence boundary type 2 (SB2).The sequence 3 consists of TST and HST system tracts and is characterized by open marine, sand shoals and lagoon facies. The lower and upper boundaries of sequence 3 are sequence boundaries type 2 andtype 1, respectively.