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
Hamideh Noroozpour
Abstract
In this research the biostratigraphy and lithostratigraphy of the Talou section (northwest Damghan) have been studied based on brachiopods of Lower Carboniferous in Mobarak Formation. The 580 me thick Mobarak Formation in Talou section consists of dark gray limestone with intercalation of organic rich ...
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In this research the biostratigraphy and lithostratigraphy of the Talou section (northwest Damghan) have been studied based on brachiopods of Lower Carboniferous in Mobarak Formation. The 580 me thick Mobarak Formation in Talou section consists of dark gray limestone with intercalation of organic rich black shale. This formation in the studied area is conformably overlie on Jeirud Formation. Vermiculate limestone of Elika Formation overlies the Mobarak Formation with an erosional surface. In the studied interval 25 genera and 30 species of brachiopods were identified. 4 assemblage zones have been identified in the early Carboniferous.Biozone 1 (Early Tournaisian): this zone is characterized by the following indicator species community. Spinocarinifera nigra, Rugosochonetes cf. hardrensis (Phillips,1841), Rossirhynchus adamantinus, Shumardella sp., Cleiothyridina transversa., Rossirhynchusadamantinus, Shumardella sp.; Biozone 2 (Middle Tournaisian): Spirifermissouriensis, Spirifer attenuatus (Sowerby,1839), Spirifer cf. trigonalis (Martin, 1809), Athyrishibernica Syringothyriscospidata; Biozone 3 (Late Tournaisian): Tomiproductus elegantulus, Marginatia aff. burlingtonensis (Hall,1893), Leptagonia cf. regularis, Fusellatornacensis, Marginatiaburlingtonensis; Biozone of 4 (Early- Middle Visean): Buxtonia cf. praejuresanensis, Marginatia cf. kinghirica, Cleiothyridina cf. okensis (Grunt,1980). therefore, the age of Mobarak Formation in the Talou section, is Tournaisian to Middle Visean. The sedimentary environment of Brachiopods of the Mobarak Formation are lagoon, bar or reef and fore-reef.
Z Azimzadeh; A Jahangiri; E Saccani; Y Dilek
Abstract
The Misho gabbroic massif with an east- west trend, 30 Km length and 7 Km wıdth is penetrated in the Infra-Cambrian Kahar formation. The micro-gabbroic dykes have cut this intrusive massif. Gabbros have homogenous compositions and major phases are plagioclase and pyroxene and minor minerals are ...
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The Misho gabbroic massif with an east- west trend, 30 Km length and 7 Km wıdth is penetrated in the Infra-Cambrian Kahar formation. The micro-gabbroic dykes have cut this intrusive massif. Gabbros have homogenous compositions and major phases are plagioclase and pyroxene and minor minerals are olivine, amphibole, biotite, K-feldespar and opaque minerals. Their texture is granular. The results of EMP analysis of clinopyroxenes show that they have diopside to augite compositions. In different diagrams, gabbros mostly show tholiitic composition with MORB affinities in tectonic setting. Pyroxenes generally have high SiO2 (50.02-52.69 wt %), high Mg number [Mg/ (Mg+Fe2+)] (78.59-82.42wt %), variable Al2O3 (1.8–5.09 wt %), low TiO2 (0.53-1.33 wt %), low Na2O (0.21-0.47 wt %) contents and low Al [6]/Al [4] ratios (0-0.39), suggesting relatively low pressure crystallization conditions of the magma. The temperature calculated for the clinopyroxenes in gabbros is 1027-1306oC and pressure is less than 8 Kbars. The investigations of variation trends of clinopyroxene compositions don’t show any zoning in clinopyroxenes and clinopyroxenes are in chemical equilibrium with other minerals in the rocks. The obtained textural and mineral chemical data, suggest that the clinopyroxenes may have crystallized from a tholiitic magma derived from a depleted lithospheric mantle. This is confirmed by the whole-rock chemistry. The gabbroic massif intrusion in a tectonic setting of extensional rifting followed by the opening of Paleotethyan oceanic crust in early Carboniferous in NW Iran.
K Khaksar; F Rezvannia; M.R Kebriaei-Zadeh
Abstract
The rugose coral Marzanophyllum chalusense gen. and sp. nov. from late Visean (early Carboniferous) in the Vali-Abad section (Central Alborz, N Iran) is described in detail. This solitary coral has thick wall and thick septa with no dissepiment. The genus Zaphrentoides has similar structure, but it possesses ...
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The rugose coral Marzanophyllum chalusense gen. and sp. nov. from late Visean (early Carboniferous) in the Vali-Abad section (Central Alborz, N Iran) is described in detail. This solitary coral has thick wall and thick septa with no dissepiment. The genus Zaphrentoides has similar structure, but it possesses well developed cardinal septum. The new genus is placed in the Subfamily Zaphrentoidinae because of the fossula shape, structure of its septa and incompleted tabulae. This small and undissepimented solitary rugose coral belongs to Cyathaxonia family. They are found at oolitic limestone level. The corals of member C of the Mobarak Formation have endemic character and based on the accompanied fauna and stratigraphic position they are attributed to late Visean.
H. Gholamalian; M. R. Kebriaei zadeh; M. Ghorbani; S.M. Hosseini-Nezhad
Abstract
Investigation on brachiopods and conodonts of Mobarak Formation in Kalariz section confirms the age of Early Tournaisian to Middle Viséan. Some species as Bispathodus aculeatus aculeatus, Bi. stabilis, Spinocarinifera nigra and Shumardella sp.in the lowest part of section show the Early Tournaisisan ...
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Investigation on brachiopods and conodonts of Mobarak Formation in Kalariz section confirms the age of Early Tournaisian to Middle Viséan. Some species as Bispathodus aculeatus aculeatus, Bi. stabilis, Spinocarinifera nigra and Shumardella sp.in the lowest part of section show the Early Tournaisisan age, whereas the middle part is Middle to Late Tournaisian on the basis of the presence of Tomiproductus vaughani, Tomiopsis sp., Scabricosta sp., Polygnathus flabellus, P. rostratus, P. longiposticus, Clydagnathus cavusformis. Some faunas as Marginatia kinghirica and Buxtonia cf. praejuresanensis prove the Early to Middle Viséan for the upper part of section. Three domestic biozones are recognized on the basis of faunal distribution in the stratigraphic column. Biozone 1 (Early Tournaisian): this zone can be recognized by the association of these species: Spinocarinifera nigra, Rossirhynchus adamantinus, Shumardella sp., Cleiothyridina transversa, Bispathodus aculeatus aculeatus, Bi. stabilis, Polygnathus communis communis, P. inornatus. Biozone 2 (Middle to Late Tournaisian): Tomiproductus vaughani, Tomiproductus elegantulus, Tomiopsis sp., Scabricosta sp., Tylothyris planimedia, Syringothyris altaica, Leptagonia analoga, Leptagonia cf. regularis, Ripidomella michelini, Athyris hibernica, Spirifer missouriensis, Schelwienella sp., Leptagonia cf. regularis, Torynifer sp., Polygnathus flabellus, P. longiposticus, P. inornatus, P. aff. inornatus, P. rostratus, P. sp., P. communis communis, Bispathodus stabilis, Pseudopolygnathus primus, Clydagnathus cavusformis. Biozone 3 (Early to Middle Visean): this zone is identified by the presence of some index species as: Buxtonia cf. praejuresanensis, Megachonetes sp., Actinoconchus lamellosus, Orthotetes batesvillensis, Marginatia cf. kinghirica, Balakhoniasp. Mobarak Formation conformably overlies the Geirud Formation and disconformably underlies the Dorud Formation demonstrating Late Viséan to Gzelian hiatus as the result of Hercynian epeirogenesis.
