Document Type : Original Research Paper
Authors
1 Ph.D. Student, Department of Geology, Faculty of Earth Science, Shahid Beheshti University of Tehran, Iran
2 Professor, Department of Geology, University College of Sciences, University of Tehran, Tehran, Iran
3 Professor, Department of Geology, Faculty of Sciences, University of Isfahan, Isfahan, Iran
Abstract
The Sarvak Formation in Well AZ 354 of Ahwaz Oil Field attains a thickness of 1712 meters and contains creamy to white and occasionally gray limestone. The recorded foraminifera indicate upper Albian to lower Turonian age for this formation. In order to study paleobathymetry and sea level changes during depositional course of the formation, three common methods were used: in the first method, the absolute number of benthic foraminifera and percentage of Hyaline, Agglutinate and Porcelaneous tests and their ratio were determined. In the second method, the ratio of Planktonic foraminifera to Epifaunal benthic foraminifera was determined via using Van der Zwaan equation, Depth= e (3.58718+(0.03534×%P), the obtained average depth was 130 meters for the most parts of the formation. In the third method, the morphotypes of planktonic foraminifera were used for determination of depth. Based on this method for the lower and middle parts, first and second morphotype groups (shallow areas indices) are abundant, showing a shallow sea. For the upper part the third morphotype groups (deeper areas indices) are abundant, indicating an open marine environment. The results showed that generally, the major parts of the Sarvak Formation has been deposited in a neritic environment and in the upper parts, depositional environment turned into a deeper one and reached the upper bathyal depths (340 m).
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