Biostratigraphy of the Surgah formation in Kuh-e-Surgah and correlation with Tang-e-Gerab (West of Iran)
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ORIGINAL PAPER
Biostratigraphy of the Surgah formation in Kuh-e-Surgah and correlation with Tang-e-Gerab (West of Iran) Abdolvahab Kazemi & Abbas Sadeghi & Mohammad Hosein Adabi
Received: 17 June 2012 / Accepted: 16 October 2012 # Saudi Society for Geosciences 2012
Abstract In biostratigraphic studies of the Surgah formation in the Kuh-e-Surgah section, 145 samples were collected. The thickness of the Surgah formation is about 175 m, and it consists mainly of limestone and shale. The lower and upper boundaries of the Surgah formation are Sarvak and Ilam formations, respectively, and they are conformable with sharp lithology. Seventeen species which belong to six genera of planktonic foraminifera and four biozones have been identified in this study. Based on foraminifera assemblages and biozone determinations, the age of the Surgah formation is Late Turonian to Early Late Santonian. This section is correlated with the Tang-e-Gerab section.
(in 46°19′6″E and 33°35′9″N), is up to 175 m (James and Wynd 1965). Monjezi (2006) stated that the Surgah formation in the type section, located in the southeast of Ilam (in 46°46′32″E and 33°27′13″N), has a thickness of about 166 m. According to James and Wynd (1965) studies, the age of the formation is Turonian to Early Santonian (Motiee 1993). The lower and upper limits of the Surgah formation show some disconformity with respect to Sarvak and Ilam formations (Motiee 1993). The type section Surgah formation is compared with the Tange-Grab section which was introduced by James and Wynd (1965) due to lack of biostratigraphy studies. Moreover, detailed biostratigraphic studies in Kuh-e-Surgah have been presented in this study.
Keywords Surgah formation . Planktonic foraminifera . Biostratigraphy . Kuh-e-Surgah . Tang-e-Gerab Geographical location of the section Introduction The Sarvak and Ilam formations following Asmari formation are the most important carbonate reservoirs in many oil fields. The boundary between these two formations is sharp in the Lorestan Region in spite of the shale lithology of the Surgah formation in the region. The thickness of this formation in the type section, located in the southwest of Ilam
As James and Wynd (1965) slated the coordinates of the type section of the Surgah formation, the section is placed at 46°19′00″E and 33°35′16″N in Surgah Mountain and 8 km from the southwest of Ilam, on the main road from Ilam to Mehran which is shown in Figs. 1 and 2, respectively.
Method of study A. Kazemi (*) : A. Sadeghi : M. H. Adabi Department of Geology, Faculty of Earth Sciences, Shahid Beheshti University, Tehran, Iran e-mail: [email protected] A. Sadeghi e-mail: [email protected] M. H. Adabi e-mail: [email protected]
In a field work survey, we conducted a preparatory investigation and sampling. During the survey, 145 samples were taken in which there were 45 soft samples and 100 rocks. It was a systematic sampling perpendicular to the layers. Besides the sampling, all characteristics of rock properties, layer thicknesses, unit contacts
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