Abstract
Problem statement: The Upper Cretaceous Gurpi and lower Tertiary Pabdeh formations as units of folded Zagros Zone were studied in three different regions (Tang-e-Abolhiat, Tang-e-Zanjiran and Maharloo) in Fars Province, Iran. Approach: Gurpi formation consisted of thin to medium sized layers of gray marl and marlstone interbedded with thin layers of argillaceous limestone and shale. The dominant microfacies in this formation biomicrite; Index species of Globotruncana give the age of the Formation from lower companion to upper Maastrichtian. Pabdeh formation consisted of bluish gray, thin to medium sized layers of shale and marl and interlayers of argillaceous limestones with purple shales and thin cherty beds at lower part, dark gray shales and marls with interlayers of argillaceous limestones in the middle andalternative layers of thinly bedded argillaceous limestone, shale and marl at the upper part. The dominant microfacies are biomicrite. Index species of Globorotalia and Hantkenina give the age of formation from upper Paleocene to Eocene. Results: The sedimentary environment of both formations is a bathymetrical carbonate floored basin (deep shelf or basin margin) which had deposited its facies in transgressive stage. The contact between the two formations is of disconformity type. In Tang-e-Abolhiat it lies at the base of purple shale. In this region and also in Tang-e-Zanjiran and Maharloo, in addition to recognition of Globorotalia velascoensis, which was attributed to lower part of the Pabdeh formation, a glauconitic-phosphatic bed separates the two formations. Conclusion/Recommendations: The boundary between Gurpi and Pabdeh formations represented a non-depositional period from the late Maastrichtian to the end of early Paleocene.
Highlights
The main scope of this study is to study the lithoand bio-facies of Upper Cretaceous Gurpi and Paleocene-Eocene Pabdeh formations and identification of their sedimentary environments in three different regions in Fars Province in Iran (Fig. 1)
Globotruncana gansseri zone; associated microfossils are G. conica, G. falsostuarti, G. gagnebini and Hedbergella. This biozone is observed at Tang-e-Abolhiat and Fig. 5: A bed of layered and lenticular cherts at the Maharloo and the age is Middle to Upper base of Pabdeh formation
Deposition of Pabdeh marl and shale is an indication of redeepening of sea from upper Paleocene
Summary
The main scope of this study is to study the lithoand bio-facies of Upper Cretaceous Gurpi and Paleocene-Eocene Pabdeh formations and identification of their sedimentary environments in three different regions (north-east flank of Ghareh mountain in south of Maharloo lake; Tang-e-Zanjiran, about 35 km north of Firoozabad; Tang-e-Abolhiat, some 75 km west of Shiraz to Kazeroon) in Fars Province in Iran (Fig. 1). The three mentioned regions show remarkable outcrops of the two formations (Gurpi and Pabdeh; Fig. 2 and 3), which is due to structural impressions affected there and petrological nature of the formations. The effect of these two factors has formed special morphology which appears throughout the outcrops. Since the upper and lower parts of these formations are of hard carbonate rocks of Asmari-Jahrum and Sarvak formations[9,15], differential erosion has caused deep strike valleys due to the alternation of hard limestones and soft marls and dense branching drainage systems in the latter; the similar morphological elements are seen in all mentioned regions
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