M. mohamadi; M. Yazdi
Abstract
There are many precious microremains of chondrichtyans (cartilage fishes) in calcareous beds of Geirud Formation. These micro remains consist of teeth, branchial denticles and sales species and genus of the family and subfamily: Phoebodontidae, Protacrodontoidea, HybodontoideaandCtenacanthoidea. Geirud ...
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There are many precious microremains of chondrichtyans (cartilage fishes) in calcareous beds of Geirud Formation. These micro remains consist of teeth, branchial denticles and sales species and genus of the family and subfamily: Phoebodontidae, Protacrodontoidea, HybodontoideaandCtenacanthoidea. Geirud Formation consists of alternating silisiclastics and calcareous beds with 1-2 basaltic units well distributed in Central Alborz. The upper Devonian/Lower carboniferous age assigned to Geirud Formation. The name of the Formation has been driven from type locality – Geirud village in north of Tehran. The upper Devonian/Lower carboniferous deposits have been studied along Alborz Mountain range and Central Iran. Faunal similarity between Famennian deposits of Central Iran and Eastern Alborz with Geirud Formation (Hairapetian & Klug 2002) confirm the basin relationship between these areas, also faunal relationship between these fauna and the fauna of Famennian in Morocco and Algeria confirm that these deposits belong to shelves of North Gondwanaland (Ginter & al., 2002). These fauna are associated with conodonts of expansa zone.
M. R. Kebria-ee
Abstract
Geirud Formation has a wide distribution in the Damghan region. The Formation Lithology is mostly composed of limestone, marly limestone, shale and quartizic sandstone and its thickness ranges from 10 - 200 meters. Brachiopoda of Geirud Formation in the southwest, north and northeast of Damghan region ...
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Geirud Formation has a wide distribution in the Damghan region. The Formation Lithology is mostly composed of limestone, marly limestone, shale and quartizic sandstone and its thickness ranges from 10 - 200 meters. Brachiopoda of Geirud Formation in the southwest, north and northeast of Damghan region (Darvar, Simeh- Kuh and Deh- Molla sections) were studied and resulted in recognizing some species that are as follows: Schellwienella sp., Mesoplica sp., Sentosia sp., Schizophoria impressa, Leptagonia sp., Aulacella interlineata, Zaigunrostrum iranicum, Leptocaryorhynchus jamensis, Araratella dichotomians assimulata, Araratella sp., Centrorhynchus charakensis, Megalopterorhynchus chanakchiensis, Paurogastroderhynchus nalivkini, Paurogastroderhynchus bikniensis, Cleiothyridina coloradensis, Cleiothyridina sp., Athyris tau, Composita cf. globosa,Lamellosathyris sp., Cyrtospirifer sergunkovae, Cyrtospirifer sp.,Cyrtiopsis graciosa chakhaensis, Cyrtiopsis lapparenti, Prospira struniana, Prospira lapparenti, Rigauxia cyrtinaeformis, Rigauxia crassiplicatus, Dichospirifer thylakistoides, Eobrachythyris sp.,Toryniferella echinulata, Cryptonella sp. Based on the above mentioned Brachiopoda an age of Early Famennian- Late Famennian can be considered for carbonate part of Geirud Formation in the these sections. Also, Geirud Formation in the sections is equivalent with middle and upper parts (with the exception of Rossirhynchusbiozone) of Geirud Formation in the type section (Central Alborz).
S. M. Hosseini-Nezhad; M. Yazdi; M. Ghobadi-Pour; H. Gholamalian
Abstract
Geirud formation deposits of Kalariz in the Eastern Alborz start with a relatively thick sequence of sandstone, shale, and red, white and brown colored siltstone changing into yellow dolomitic layers, fossiliferous limestone and shaly or marly limestone. This formation ...
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Geirud formation deposits of Kalariz in the Eastern Alborz start with a relatively thick sequence of sandstone, shale, and red, white and brown colored siltstone changing into yellow dolomitic layers, fossiliferous limestone and shaly or marly limestone. This formation lies over Mila formation with a disconformity and covered transitionally by limestones of Mobarak formation. In the above mentioned sequence, numerous and various conodonts and brachiopods were identified. Based on the distribution of brachiopoda, two assemblage zones and based on the conodonts, four assemblage zones were recognized with Famennian and Strunian age. The first brachiopoda biozone, equivalent to the first and second conodont biozones, belongs to early Famennian age (older than late crepida zone and romboidea to late trachytera zone) and the second Brachiopoda biozone which is equivalent to conodont biozone of number three and four has the late Famennian age (postera to late expansa zone and praesulcata zone). Paleontological and stratigraphical evidence indicates that Frasnian sediments are absent in the study area.
