Sedimentology
Seyedeh Zahra Pourheidar; Mohamad Hosein Adabi; Mir Reza Moussavi Tasooj; Abbas Sadeghi
Abstract
The Elika Formation forms the major part of the Triassic carbonate sediments in the Alborz basin. In this study, facies and sedimentary environments of this formation were studied in Shahmirzad section whith a thickness of 746 meters and in Zereshk-Darreh section whith a thickness of 756 meters in the ...
Read More
The Elika Formation forms the major part of the Triassic carbonate sediments in the Alborz basin. In this study, facies and sedimentary environments of this formation were studied in Shahmirzad section whith a thickness of 746 meters and in Zereshk-Darreh section whith a thickness of 756 meters in the southern part of central Alborz. Based on facies studies, four carbonate facies associations (tidal tlat, shoal, lagoon and open marine) have been identified, including twelve carbonate microfacies and have been deposited in a carbonate ramp. Deposition of sediments in this sequence can be divided into three stages. In the first stage, most of vermiculate limestone deposits are composed of bioturbated mudstone and clotted peloidal mudstone. The high frequency of facies such as laminated stromatolite, intraclastic packstone-grainstone and laminated mudstone are characteristic features of the second stage of sedimentation (middle dolomite) and indicate a decrease in the depth of sedimentary environment. In the third stage, the environment was suitable for the expansion of barriers and formation of packstone-grainstone facies.
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 ...
Read More
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
Majid Khazaee; Mahbobeh Hosseini-Barzi; Abbas Sadeghi; Hossein Mosaddegh
Abstract
The provenance of Jeirud Formation deposits (upper Devonian) in central Alborz has been investigated from study of siliciclastic sandstones (petrography, modal analysis and Heavy minerals assemblage) and mudstones (major and minor elements geochemistry). An integration of results suggest a mixture of ...
Read More
The provenance of Jeirud Formation deposits (upper Devonian) in central Alborz has been investigated from study of siliciclastic sandstones (petrography, modal analysis and Heavy minerals assemblage) and mudstones (major and minor elements geochemistry). An integration of results suggest a mixture of basic to acidic igneous rocks and recycling of older sedimentary rocks as the provenance that weathered under cold and arid to semi-arid climatic conditions. An integration of modal analysis and heavy minerals results into the geochemical studies including Roser and korsch diagram (Log K2O/Na2O versus SiO2) and Verma and Armstrong-Altrin Functional diagrams, indicate that, siliciclastic rocks of Jeirud, resulted from weathering of acidic-intermediate to basic rocks of collisional tectonic provenances (recycled orogens) and transporting on craton interior and have been deposited on a passive margin basin. Investigations and comparison with McLennan et al., studies, represent that geochemical results and proportions of study area are consistent with those of old upper continental crust (OUC) typical of collisional tectonic settings.
A Sadeghi; M Raziani
Abstract
In order to study of the Surgah Formation in Southwest of Ilam City, one section in the Shah Nakhjir anticline was selected. The thickness of the Surgah Formation is about 161 meters and consists mainly of green shales and olive green marly shales with intercalation of gray shaly limestones. The lower ...
Read More
In order to study of the Surgah Formation in Southwest of Ilam City, one section in the Shah Nakhjir anticline was selected. The thickness of the Surgah Formation is about 161 meters and consists mainly of green shales and olive green marly shales with intercalation of gray shaly limestones. The lower and upper boundaries of the Surgah Formation are the Sarvak and Ilam Formation, respectively and are conformable with sharp lithology and abundant iron nodules. In this study, 52 species belonging to 28 genuses of foraminifera and 3 biozones were identified. Based on the planktonic foraminifera and identified biozones, the Surgah Formation has an age of Late Turonian to early Late Santonian. Comparison of biozones identified in this section with those of the type section in Tang-e- Garab shows that these two sections are similar in biozones and age, and the only difference is in thickness of biozones.
