Stratigraphy and Palaeontology
Hamta Ranjbar; Abbas Ghaderi; Hossein Gholamalian; Vachik Hairapetian
Abstract
Middle Devonian to Lower Carboniferous siliciclastic-carbonate successions in Eastern Alborz are characterized by Khoshyeilagh Formation. It is underlain by the Devonian red siliciclastic sequences and is overlain by the Carboniferous Mobarak Formation, can be divided into three different members; lower ...
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Middle Devonian to Lower Carboniferous siliciclastic-carbonate successions in Eastern Alborz are characterized by Khoshyeilagh Formation. It is underlain by the Devonian red siliciclastic sequences and is overlain by the Carboniferous Mobarak Formation, can be divided into three different members; lower carbonate, middle siliciclastic, and upper carbonate. The Khoshyeilagh Formation comprises various fossil groups of invertebrates, conodonts, palynomorphs and fish remains. In the present study, a collection of microscopic fish remains, obtained from the lower and upper carbonate members in Mighan, north of Shahrood, have been determined and described. This assemblage contains 14 different taxa of chondrichthyan fish including: Cladodoides cf. wildungensis, Ctenacanthiformis gen. et sp. indet, Dalmehodus turnerae, Deihim mansureae, Lissodus lusavorichi, Phoebodus aff. turnerae, Phoebodus fastigatus, Phoebodus gothicus gothicus, Phoebodus gothicus transistans, Roongodus phijani, Siberiodus mirabilis, Squatinactis glabrum, Stethacanthus resistens and Thrinacodus ferox. Some specimens of scales and teeth of actinopterygian and osteichthyan fishes are also present which all indicate a shallow environment of the continental shelf. The associated conodonts with this assemblage demonstrate the age of Frasnian (rhenana biozone) to early Tournaisian (duplicata biozone) for the whole succession.
Stratigraphy and Palaeontology
Parisa Mohammadi; Abbas Ghaderi; Ali Reza Ashouri
Abstract
The Julfa region in East Azerbaijan Province exhibits one of the best continuous marine sedimentary successions across the Permian to Triassic boundary. The present study is focused on the brachiopod contents of the Julfa beds in Qareh-Goz section (41.5 m thickness) in the south of Julfa. This study ...
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The Julfa region in East Azerbaijan Province exhibits one of the best continuous marine sedimentary successions across the Permian to Triassic boundary. The present study is focused on the brachiopod contents of the Julfa beds in Qareh-Goz section (41.5 m thickness) in the south of Julfa. This study is led to the determination of 11 genera and 21 species of the orders Athyridida, Orthotetida, Orthida, Productida, Spiriferida, and Terebratulida, all representing the Cathaysian bioprovince for this area in the Western Paleotethys. Accordingly, four Wuchiapingian biozones, including Araxilevis intermedius Zone, Araxilevis intermedius-Permophricodothyris ovata Interval zone, Permophricodothyris ovata Zone, and Transcaucasathyris araxensis Zone, have been detected. These biozones correlate well through the other stratigraphic sections of the Julfa area in the Ali Bashi and Zal Mountains, Dorasham section in the Transcaucasia, Hembast Formation in the Abadeh area, and Nesen Formation in the central Alborz, approving the potential of these brachiopods in biocorrelation at a regional scale in the Late Permian.
Stratigraphy and Palaeontology
Mir Amir Salahi; Abbas Ghaderi; Alireza Ashouri; Ali asghar siabghodsi
Abstract
To separate the different units of the Paleogene sequences of the Kopet-Dagh basin and their regional correlation with the adjacent areas in the Central Asia, the Oyster bivalves fossils are used in the current research. Also, the study of their paleobiogeography has been considered in this study. Based ...
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To separate the different units of the Paleogene sequences of the Kopet-Dagh basin and their regional correlation with the adjacent areas in the Central Asia, the Oyster bivalves fossils are used in the current research. Also, the study of their paleobiogeography has been considered in this study. Based on this fauna, Pycnodonte-Oestra community in the Chehelkaman Formation uppermost parts represents the late Paleocene age and the first occurrence of Flemingostrea hemiglobosa at the base of the Khangiran Formation confirms the beginning of Eocene epoch. Association of different species and subspecies of Turkostrea in the Khangiran Formation demonstrates the middle part of early Eocene and Sokolowia community near the top of the Khangiran Formation shows the Lotetian-Bartonin ages. These features are in full compliance with the bivalve communities recorded from the other parts of Central Asia such as Amu-Darya, Farghana, Afghan - Tajik and Trim basin of China. It illustrates the same geological history of the mentioned areas during Paleogene, indicates the occurrence of different types of molluscan taxa in the Kopet-Dagh basin is the same as parallel horizons and equivalent time units throughout the extensive Central Asian region.
Stratigraphy and Palaeontology
Abbas Ghaderi; Mahdi Badpa; Ali Reza Ashouri
Abstract
To study of Permian corals at the northwest of Iran, Ali-Bashi stratigraphic section was selected and sampled. After microscopic studies of several longitudinal, transverse, and serial sections were obtained from more than 180 coral fossils, 12 species belonging to 6 genera of rogues and tabula corals ...
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To study of Permian corals at the northwest of Iran, Ali-Bashi stratigraphic section was selected and sampled. After microscopic studies of several longitudinal, transverse, and serial sections were obtained from more than 180 coral fossils, 12 species belonging to 6 genera of rogues and tabula corals were determined. The Permian succession of the Julfa area is the dominion of two types of coral fauna. Waagenophyllidae fauna that is the territory of the colonial coral forms comprises typically Tethyan indicators such as Ipciphyllum and Waagenophyllum with the age of Middle?- Late Permian. Cyathaxonia fauna, Late Permian in age, include terminal phylogenetic representatives of the rugose corals, mostly composed of solitary one Pentaphyllum. This genus is persistent till the vicinity of the extinction horizon at the near end Permian in the Ali Bashi Formation topmost horizon. Also, the last standing tabula coral before the Late Permian extinction in the Julfa region is the genus Protomichelinia. The Permian coral fauna of the NW Iran finely corresponds to those of the Abadeh region in Central Iran and Transcaucasus. The Waagenophyllidae forms are the same as South China fauna, whereas the Cyathaxonia ones reveal a high endemism in the Late Permian of NW Iran.
A. Ghaderi; J. Taheri; A. Kerachian; A. Mousavinia
Abstract
Investigation of Silurian succession equivalent to the Niur Formation at the northwest of Robat-e-Qarebil (instantly south of Western Kopeh-Dagh), is led to introduction of lithostratigraphical units in details and identification of some Llandovery conodonts. The sampled interval in this stratigraphic ...
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Investigation of Silurian succession equivalent to the Niur Formation at the northwest of Robat-e-Qarebil (instantly south of Western Kopeh-Dagh), is led to introduction of lithostratigraphical units in details and identification of some Llandovery conodonts. The sampled interval in this stratigraphic section is composed of shale, fossiliferous limestone, sandstone, and dolomite with 295.5 meter thickness. With a marine volcanic rock unit at the base, this succession is conformably overlaid shales and sandstones attributed to the Ordovician system and overlain by quartzarenite and red shales of the Padeha Formation. Obtained conodonts from these sequences comprise different coniform, ramiform and pectiniform elements. Nineteen species of 10 genera belong to Aspelundia expansa Interval Zone which confirms uppermost Late Rhuddanian to Aeronian for the section. This age coincides with the ages which have already been given on the basis of brachiopods, cephalopods and palinomorphs for the same outcrops at the Western Kopeh-Dagh.
S. Hemati; M. Taherpour Khalil Abad; A. Ghaderi; A. R. Ashouri
Abstract
Micropaleontological study on the carbonate successions of the Tirgan Formation at the Taherabad village and Eshlir anticline stratigraphic sections is led to identification of various taxa of the calcareous algae belong to the families Dasycladaceae, Triploporellaceae, Udoteaceae, Solenoporaceae and ...
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Micropaleontological study on the carbonate successions of the Tirgan Formation at the Taherabad village and Eshlir anticline stratigraphic sections is led to identification of various taxa of the calcareous algae belong to the families Dasycladaceae, Triploporellaceae, Udoteaceae, Solenoporaceae and Gymnocodiaceae and also some specimens of small Gorgonacea. Based on the biometric measurements of morphological features, 16 genera and 20 species from the Taherabad section and 12 genera and 16 species from the Eshlir section have been recognized. Moreover, Permocalculus minutus and Permocalculus? halimedaformis have been found for the first time in the Tirgan Formation. Permocalculus? halimedaformis was introduced from the Minis Valley in Romania for the first time and its finding in this research is the second report around the world. According to this new finding, its geographic distribution is being extended more than 2800 km eastward on the northern margin of the Tethys ocean.
A. Ghaderi; A. Aghanabati; B. Hamdi; A. Saeedi
Abstract
To study the Shirgesht Formation biostratigraphy in Kalmard Horst in relation to its conodont content, the Miyugodar (Miangodar) stratigraphic section was selected which is located in southwest of Tabas city. The Shirgesht Formation in the mentioned section is mainly composed of siliciclastic rock units ...
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To study the Shirgesht Formation biostratigraphy in Kalmard Horst in relation to its conodont content, the Miyugodar (Miangodar) stratigraphic section was selected which is located in southwest of Tabas city. The Shirgesht Formation in the mentioned section is mainly composed of siliciclastic rock units and overlay unconformably on Kalmard Formation (attributed to Pre-Cambrian) and is overlain by Gachal Formation (Carboniferous). Thirty five rock samples were selected from appropriate rock units (Shirgesht and Gachal Formation). Samples were studied in laboratory for more details. According to the extracted conodont from Shirgesht Formation in Miyugodar section, the age of this formation can be regarded as Early Ordovician (Tremadocian – Arenigian). Three conodont assemblage zones were recognized in Early Ordovician units. They are: Cordylodus spp., Deltifer and Proteus Global Standard Conodont biozones. The recognized biozones are as followed:
1- Oneotodus - Drepanodus Assemblage Zone
2- Acodus deltatus - Protopanderodus Assemblage Zone
3- Acodus - Oistodus Assemblage Zone
A. Ghaderi; A. Aghanabati; B. Hamdi; J. F. Miller
Abstract
The Shirgesht Formation is one of the fossiliferous units of Central Iran which in the type section is defined (informally) in the terms of 3 members. This formation is mainly composed of limestone, marl, siltstone, shale and dolomite, conformably overlay on the upper part of the Derenjal Formation with ...
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The Shirgesht Formation is one of the fossiliferous units of Central Iran which in the type section is defined (informally) in the terms of 3 members. This formation is mainly composed of limestone, marl, siltstone, shale and dolomite, conformably overlay on the upper part of the Derenjal Formation with a gradual contact, composed of brachiopods limestone bearing (Billingsella limestone). The Shirgesht Formation is overlain by sandy limestone and volcanic rocks of the Niur Formation.
To do biostratigraphy studies on the first and second members of Shirgesht Formation in the type section, totally 99 rock samples were selected. The conodont fauna of lower part of its first member contain some species of Westergaardodina, Furnishina and prooneotodus which show an age of late Cambrian. Several species of Cordylodus, Oistodus, Drepanodus, Proconodontus and Paroistodus in distance of middle part of the lower member to the end of the second member represent an age of Tremadocian – Arenigian. According to conodont content of the first and second members of Shirgesht Formation, 7 conodont assemblage zones were determined in the type section which show an age of Late Cambrian – Early Ordovician. The recognized biozones are as follow:
1. Furnishina - Westergaardodina Assemblage Zone.
2. Proconodontus - Oneotodus Assemblage Zone.
3. Cordylodus proavus - Cordylodus oklahomensis Assemblage Zone.
4. Cordylodus lindstromi Assemblage Zone.
5. Cordylodus angulatus Assemblage Zone.
6. Drepanodus - Paltodus deltifer Assemblage Zone.
7.Paroistodus proteus Assemblage Zone.
The mentioned conodont assemblage zones are equivalent to Cordylodus spp., Deltiferand Proteus global standard conodont biozone. In contrast with the previous reports, the Cambrian – Ordovician boundary is located in the first member of the Shirgesht Formation. Thus, the Shirgesht Formation in type section is diachronous formation.
