Himalayan Geology, Vol. 39 (1), 2018, pp. 133-143, Printed in India
Bio-sequence stratigraphy of Oligocene deposits in Interior Fars, Zagros Basin, Iran
MOHAMMADSADEGH DEHGHANIAN1*, BORZU ASGARI-PIRBALOUTI2
1Dept. of Geology, College of Science, Bandar Abbas Branch, Islamic Azad University, Bandar Abbas, Iran
2Dept of Geology, College of Science, Masjed-Soleiman Branch, Islamic Azad University, Masjed-Soleiman, Iran
*Email (Corresponding author): msadeghdehghanian@gmail.com
Abstract: The Asmari Formation is a thick sequence of carbonates of Oligocene to Early Miocene age that has been deposited in a foreland basin across the Zagros. Asmari Formation is the main petroleum reservoir rock in Zagros Basin. For the study of the lithostratigrahpy and bio-sequence stratigraphy in the Asmari Formation, the section was selected in the Northwestern Shiraz (Tang-e-jalab). The field studies show that the total thickness of the section is 214 m that contains eight lithostratigrahpic units. Through the study of microfacies, stacking pattern and identifying the bio-sequence stratigraphic surfaces which were obtain from the field and microscopic studies five bio-sequences (including one second-order and four third-order depositional bio-sequences) were identified in this section. The sea-level curve shows that this section partly corresponds to the global sea level curve which the rate of deposition and the depth of basin were in balance with the slowly uplifting of basin. Based on the facies study, six sedimentary environments such as bar shelf, open marine, bar, lagoon, back bar shelf and shoal were identified (lagoon to open marine). The above environments were part of the carbonate platform that was developed along an open shelf. Based on the study of the foraminifera dispersion pattern, the age of the Asmari Formation in Shiraz (Tang-e-jalab) section was determined as Oligocene (Rupelian-Chattian).
Key words: Bio-Sequence Stratigraphy, Oligocene deposits, Asmari Formation, Interior Fars, Zagros, Iran.
