H. Mosaddegh; A. Barari; H. Hamdi2
Abstract
During the Carboniferous time, Iran was a part of the northern margin of Gondwana. Carboniferous deposits of Iran are characterized by continental to shallow marine deposits. The studied section (Simeh- Kooh) is located in 5 Km Northwest of Damghan city in the east Alborz region. The lower Carboniferous ...
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During the Carboniferous time, Iran was a part of the northern margin of Gondwana. Carboniferous deposits of Iran are characterized by continental to shallow marine deposits. The studied section (Simeh- Kooh) is located in 5 Km Northwest of Damghan city in the east Alborz region. The lower Carboniferous Mobarak Formation consists of variable thickness of limestones interbeded with shale beds. The thickness of this section is about 115 m. The Mobarak Formation overlay the upper Devonian Jeirud Formation with a transitional contact and is unconformably underlain by lower Permian mixed siliciclastic-carbonate succession of Dorud Formation. This research is focused on the conodonts and facies. Conodont elements consist of 13 genus and 19 species. 5 Biozones is identified including, costatus zone (Latest Famennian), Sandbergi-L. crenulata zone, isostaticha-U. crenulata zone (Middle Tournaisian), typicus-anchoralis-latus zone (Late Tournaisian) and G. bilineatus zone (Middle-Late Visean) correspond to global zonation. The Tournaisian succession consist of alternation of organic matter rich shales and dark thin-bedded limestones is supposed to have deposited in a deep marine environment with a low oxygen condition. The paleontological and facies characteristics of Devonian-Carboniferous transition definitely show a rapid sea level rise and flooding event in this time in Eastern Alborz which corresponds with the Hangenberg Bioevent known in other parts of the world.
A. Fallah; B. Hamdi; H. Mosaddegh
Abstract
The studied section (Kiyasar)is situated in Central Alborz,75 Km. southeast of Sari. The thickness of Carboniferous sequences (Mobarak Formation) is 385 meter and consists of thin-bedded limestone at the base and various thickness of limestone (mostly with medium thickness) with intercalations of shales ...
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The studied section (Kiyasar)is situated in Central Alborz,75 Km. southeast of Sari. The thickness of Carboniferous sequences (Mobarak Formation) is 385 meter and consists of thin-bedded limestone at the base and various thickness of limestone (mostly with medium thickness) with intercalations of shales at the top. Because of lithological similarity and the lack of index microfossils in the uppermost of Devonian and lowermost of Carboniferous, deposits, determination of this boundary was impossible in the field and the approximate boundary has been identified after study of lab by conodont elements. Apparently, this boundary is conformable and continual that the rocks at the bottom of its attributed to Khoshyeilagh Formation. This boundary is located in the interval of samples 4.1(late Devonian) and 4.3(lower Carboniferous) which the distance between them is 4m.(thin to medium-bedded limestones).The limit of boundary is distinct with extinction of Genera and Species for example Icriodus costatus, Pelekysgnathus sp. and Polygnathus semicostatus in the late of Devonian(sample4.1)and appearance of species for example Polygnathus spicatus, Spa. crassidentathus, Po. thomasi and Cly. gilwernensis in early Carboniferous (sample4.3). in summery, limestone rocks in alternation with shale of upper Famenian is attributed to lower-middle costatus zone form lower part of Carboniferous rocks in the region. The top of Mobarak Formation is overlaid by alternations of sandstone, shales and limestone (in the middle part), belong of Dorud Formation (lower Permian) with a disconformity. Carboniferous conodonts (20 Genus, 36 Species, 7 Subspecies are reported from Mobarak Fm.,Kiyasar region, for the first time as well as the distinguished following 7 conodont zones: 1) sulcata zone 2) duplicata zone 3) sandbergi-L. crenulata zone 4) typicus zone 5) anchoralis-latus zone 6) texanus- A. scalenus zone 7) Gn. bilineatus zone. According to conodont data Carboniferous sequences in Kiyasar section were deposited from lower Tournaisian to upper Visean time interval.
H. Mosadegh; M. Lankarani
Abstract
The carbonate facies of Permian in Gaduk area (Central Alborz) are dominated by calcareous algae. Study of the facies resulted in recognition of several species of Cyanobacteria, Dasycladacean and Gymnocodiacean green algae and also Phylloid algae. In the studied succession, Phylloid algae are identified ...
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The carbonate facies of Permian in Gaduk area (Central Alborz) are dominated by calcareous algae. Study of the facies resulted in recognition of several species of Cyanobacteria, Dasycladacean and Gymnocodiacean green algae and also Phylloid algae. In the studied succession, Phylloid algae are identified in carbonate shoal facies. Cyanobacteria mostly occurred in tidal to lagoonal facies, as encrusters. Dasycladacean and Gymnocodiacean green algae mostly occurred in inner ramp facies. Gymnocodiaceans were found in deeper parts in comparison to Dasycladaceans. Occurrence of Cyanobacteria in depositional sequences coincides with type-one sequence boundaries. Phylloid algae are identified in the facies related to transgressive surfaces and maximum abundance of Dasycladaceans and Gymnocodiaceans was found around maximum flooding surfaces and in highstand systems tracts. Abundance of the calcareous algae shows an increasing trend from the base to the top of carbonate parasequences. Proliferation of the calcareous algae was found in close relationship to climate warming and ice-house to green-house transition in Permian of Alborz.