Stratigraphy and Palaeontology
Ghamarnaz Darabi; iraj Maghfouri Moghaddam; Abbas Sadeghi; Bizhan Yusefi
Abstract
In this study, biostratigraphy and Paleobathymetry of the Gurpi Formation in section southwest of Kuhdasht were studied. The thickness of Gurpi Formation in this section is 160 meters and its main lithology includes Marl, Limy Marl, Limestone and Shale. In this section Lower boundary of Gurpi Formation ...
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In this study, biostratigraphy and Paleobathymetry of the Gurpi Formation in section southwest of Kuhdasht were studied. The thickness of Gurpi Formation in this section is 160 meters and its main lithology includes Marl, Limy Marl, Limestone and Shale. In this section Lower boundary of Gurpi Formation is transition with Ilam Formation, and its upper boundary with Amiran Formation is unconformably. Here, on the basis of foraminiferal studies,50 species belonging to 24 genera of planktic foraminifera and Benthic were identified. Based on the stratigraphic distribution of the well known foraminifers, six foraminiferal biozones were established in the Gurpi Formation including: Globotruncana ventricosa Interval Zone, Radotruncana calcarata Taxon Range Zone, Globotruncanella havanensis Partial Range Zone, Globotruncana aegyptiaca Interval Zone, Gansserina gansseri Interval Zone, Contusotruncana contusa Interval Zone.The age of Gurpi Formation in this examined is determined based on identified biozones of Middel Campanian to Late Maastrichtian. A depth of 450 - 600 m was assigned for most parts of the sediments Gurpi Formatan was assigned ccording to planktic/epibenthic ratio and Percentage Morphotype 3 and the regression equation Depth = e (3.58718 + (0.03534 × %P*))
Sedimentology
Mohadeseh Janbaz; Hassan Mohseni; Alireza Piryaei; Rudy Swennen; Bizhan Yousefi Yeganeh; Hassan Soradeghi Sufiani
Abstract
Middle-late Eocene Shahbazan Formation is exposed in the Lurestan area (Zagros region). The diagenetic features have been studied based on the data from five surface sections and four additional exploration wells. This investigation was carried out on the petrography of 700 thin sections, Cathodoluminescence ...
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Middle-late Eocene Shahbazan Formation is exposed in the Lurestan area (Zagros region). The diagenetic features have been studied based on the data from five surface sections and four additional exploration wells. This investigation was carried out on the petrography of 700 thin sections, Cathodoluminescence on 40 thin polished samples, Scanning Electron Microscope on six samples and Electron Probe Micro-Analysis on 11 thin polished sections. the most conspicuous diagenetic processes affected on the Shahbazan Formation are dolomitization, cementation, neomorphism, physical and chemical compaction, dissolution and dedolomitization, of which dolomitization is the most important. Dolomite distribution in studied sections suggest that fluid flow was probably toward SW of studied area, since the extend of dolomitization waning in this direction. Since the dolomites of the Shahbazan Formation are overlain by the Asmari Formation, the dolomitization predates deposition of the Asmari Formation and occurred in eogenesis. Majority of calcite cements deposited before dolomitization in eogenesis, excluding parts of the blocky and poikiotopic calcite which may form in telogenetic and mesogenetic realms respectively. Degrading neomorphism occurred in marine realm. Part of dissolution occurred in meteoric vadose of eogenesis. Compaction commenced in meogenesis with increasing over burden due to deposition of the Shahbazan Formation and culminated after deposition of the Asmari and Gachsaran Formations. Telogentic processes caused dissolution and dedolomitization of the Shahbazan Formation due to exhumation. by the exception of dedolomitization and neomorphism, other diagenetic features are occurred in all studied sections.
