Authors
1
PhD student in Geology-Stratigraphy and Paleontology, Islamic Azad University, North Tehran Branch, Tehran, Iran
2
Department of Geology, North Tehran Branch, Islamic Azad University, Tehran, Ira
3
Department of Geology, Shiraz Branch, Islamic Azad University, Shiraz, Iran.
4
Department of Geology, Khorramabad Branch, Islamic Azad University, Khorramabad, Iran.
5
Department of Paleontology, Organization of Geology and Mineral Exploration of Iran, Tehran, Iran
Abstract
The purpose of this study is to investigate the microfacies, sedimentary environment, and paleo-depth fluctuations of the Gorpi Formation sedimentary basin, in Jam - Asalouye and Farashband stratigraphic sections in southwestern Iran located in Bushehr province. The dominant lithology of these sections is an interval of Chilean limestone and gray shales. In both stratigraphic sections, the Gorpi Formation is located with an erosional discontinuity between the Saruk and Pabde formations. Lithological and facies studies on the sedimentary thin sections of these sections led to the identification of three microfacies related to the deep parts of a ramp-type carbonate platform. The absence of sedimentary evidences such as calcareous turbidites, slip and fall sediments, reef facies, ancoid and pisoid facies characteristic of edged shelf, indicates the deposition of Gurpi formation in an external ramp type carbonate platform. Based on the percentage ratio of planktonic foraminifers to benthic foraminifers and the percentage of morphotype 3 and using the formula D = e (3.58718+ (0.03534 × 0.03534% P)) for the major parts of the Gorpi Formation in the studied sections, a depth between 450 and 602 meter was introduced. Examining the paleo-depth changes of the Gorpi Formation sedimentary basin, based on the morphotypes of planktonic foraminifers in the studied sections, indicates that the Gorpi Formation had a regressive succession, with the highest depth of the basin in the Late-Middle Campanian and Late Maestrichtian, and the lowest depth of the sedimentary basin based on the morphotype. Planktonic foraminifers belong to Santonian to late Campanian.
Keywords
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