فهرست مقالات Triassic

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  1 - A study of the tectonic origin and the source of the clastic sediments of the Miankuhi formation in the Tarik Dareh region (Torbat Jam, NE Iran)
  Habib Allah Torshizian
  The study area is located in the northeast of Iran. Miankuhi Formation is 500m thick and comprises homogeneous shales, brown granular sandstone and siltstone. In this study, 45 samples were taken from Miankuhi shales and sandstones in order to determine their tectonic o چکیده کامل

  The study area is located in the northeast of Iran. Miankuhi Formation is 500m thick and comprises homogeneous shales, brown granular sandstone and siltstone. In this study, 45 samples were taken from Miankuhi shales and sandstones in order to determine their tectonic origin by using a polarizing microscope. Samples were analysed by X-Ray Fluorescence (XRF) method to determine their chemical compositions and tectonic origin. Twelve shale and siltstone samples were also analysed by the X-Ray Diffraction method with the aim of identifying their mineral composition. According to the investigations conducted, the type of sandstone is greywackes. Based on XRD results, quartz, albite, orthoclase, calcite, kaolinite, and illite have existed in shales and siltstones. Chemical analysis of the rocks indicated the source of these clastic rocks as oceanic arc areas and active peripheries of a landmass. The corrosive rocks of this formation are believed to originate from intermediate felsic igneous rocks and to a lesser extent from clastic quartz-containing rocks in the region.Keywords: Iran, Kopet-Dagh, Miankuhi Formation, Triassic پرونده مقاله
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  2 - Sedimentary structures and depositional environment of the Ashin Formation in Nakhlak area, Central Iran
  S. H. Vaziri
  Middle to Upper Triassic (Upper Ladinian to Lower Carnian) deep-sea sedimentary rocks crop out across a large area west of Nakhlak village, Central Iran and have been named Ashin Formation. The up to 304m thick, turbiditic, siliciclastic Ashin Formation consists of alte چکیده کامل

  Middle to Upper Triassic (Upper Ladinian to Lower Carnian) deep-sea sedimentary rocks crop out across a large area west of Nakhlak village, Central Iran and have been named Ashin Formation. The up to 304m thick, turbiditic, siliciclastic Ashin Formation consists of alternating turbiditic, thin- and medium-bedded calcareous sandstones, purple, fine-grained volcaniclastic sandstones, and mostly green and violet, very thin-bedded volcaniclastic shales that can be subdivided into three members. Ammonoids collected from members 1 and 3 of the Ashin Formation indicate a Late Ladinian to Early Carnian age for the formation. These alternations fine upwards and exhibit sedimentary structures such as graded bedding, parallel lamination (with parting lineation) convolute bedding, small-scale cross-bedding, load casts, groove casts, prod casts, flute casts, bounce casts, chevron casts, brush casts and chips and protraction traces indicating A to E parts of the Bouma cycle. Septarian nodules occur repeatedly. The lower surfaces of sandstones contain abundant trace fossils belong to the deep-sea Nereites ichnofacies. Numerous signs of strong current activity such as groove casts, flute casts and prod marks associated with trace fossils such as Paleodictyon, Protopaleodictyon, Megagrapton and Lorenzinia indicate that the Ashin Formation represents a deep marine environment. The field and petrographic studies show that the Ashin Formation was deposited in distal parts of submarine fans, on the abyssal plain. پرونده مقاله
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  3 - Biostratigraphic Correlation of Elikah Formation in Zal Section (Northwestern Iran) with Ruteh and Type Sections in Alborz Mountains Based on Conodonts
  Nazanin BadriKolalo Bahaeddin Hamidi Seyed Hamid Vaziri Seyed Ali Aghanabati
  Conodonts are the most important fossil remains from the largest Phanerozoic extinction as well as the mass extinction of the late Paleozoic and could be used for exact dating during this period. Triassic deposits located in the Elikah Formation contain exposures in mos چکیده کامل

  Conodonts are the most important fossil remains from the largest Phanerozoic extinction as well as the mass extinction of the late Paleozoic and could be used for exact dating during this period. Triassic deposits located in the Elikah Formation contain exposures in most of the Alborz sections as well as the Zal section in northwestern Iran. In this study, the Elikah Formation was investigated from a biostratigraphy point of view in the type section and Ruteh section of the Alborz Mountains and Zal section in the Jolfa region based on the existing conodonts. Biostratigraphy study of more than 300 samples taken from these three sections, resulted in the identification and introduction of the following conodont biozones: Taxone Range Zone Hindeodus parvus and Pachycladina symmetrica – Pachycladina Oblique Assemblage Zone in the type section, Hindeodus parvus Taxon Range Zone, Hadrodontina –Pachycladina Assemblage Zone and Parachirognathus – Furnishius Assemblage Zone in the Ruteh section and finally Hindeodus parvus Taxon Range Zone, Isracicella staeschei Taxon Range Zone and Arachirognathus – Furnishius Assemblage Zone in the Zal section. These biozones indicate that the Elikah Formation, in the three previously defined sections, is Early Triassic (Griesbachian). Additionally, comparison of the biozones in these sections illustrates a biostratigraphic correlation of Early Triassic deposits in the Zal, Ruteh and type sections. پرونده مقاله