F. Shirezade Esfahani; A. Bayet-Goll; N. Kohansal Ghadimvand; A. Kangazian; A. Akbari Mohammadi; M. Sadri
Abstract
The carbonate successions (Tournaisian-Visean) exposed in the Tang-e-Darchaleh and Banarizeh sections from Sanandaj-Sirjan Zone (SSZ), Iran, have been used to generate a facies model. From the analysis of facies and their associations, four depositional zones are recognized on the Tournaisian-Visean ...
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The carbonate successions (Tournaisian-Visean) exposed in the Tang-e-Darchaleh and Banarizeh sections from Sanandaj-Sirjan Zone (SSZ), Iran, have been used to generate a facies model. From the analysis of facies and their associations, four depositional zones are recognized on the Tournaisian-Visean ramp: basinal environments, outer ramp (FA1 and FA2; deep subtidal associations), mid ramp (FA3, FA4 and FA6; shallow subtidal to lower intetidal associations), and inner ramp (FA5; shoal). The gradual transitions between facies and facies associations, as well as the depositional profile of the shelf transect indicate a low gradient ramp. The observed sedimentary features in the facies associations portray a transgressive, proximal-to-distal, wave-dominated combined flow marine ramp sequence, as recorded in stratigraphic changes in character of storm bed sequences and the spatial arrangement of types of storm bed along the depth related environmental gradients. This study suggests that during the Lower Carboniferous, a broad shelfal platform covered the southern margin of the Palaeotethys, which was characterized by dominantly shallow carbonate ramp.
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.
M. Khoshnoodkia; H. Mohseni; M. Hajian
Abstract
Carbonate – evaporates intervals of Dashtak formation is an important cap rocks in Zagros basin. Sequence stratigraphic analysis of Dashtak Formation in two wells (Aghar#1; West Aghar#1) was investigated in sequence stratigraphic framework. Data obtained from petrographic examinations of thin sections ...
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Carbonate – evaporates intervals of Dashtak formation is an important cap rocks in Zagros basin. Sequence stratigraphic analysis of Dashtak Formation in two wells (Aghar#1; West Aghar#1) was investigated in sequence stratigraphic framework. Data obtained from petrographic examinations of thin sections prepared from cuttings, in addition, a full suite of gamma ray and sonic logs were interpreted. Dashtak Formation comprises eight facies belts that are: (i) detrital clastics, (ii) supratidal, (iii) tidal flat, (iv) lagoon, (v) shoal, (vi) restricted marine, (vii) open marine, (viii) mid ramp. Dashtak Formation consists of four sequences with four transgressive, regressive and maximum flooding surfaces. Two sequence boundaries type I and three sequence boundaries type II were recognized in the Dashtak Formation. As far the depositional environment of the formation is interpreted as a homocline ramp with mild lateral changes in depositional environment, hence negligible lateral changes of stratigraphic sequences are expected in the study area.
S. A. Moallemi; M. H. Adabi; A. Sadeghi
Abstract
In order to determine the depositional environment and age of the carbonaceous Jahrum Formation, benthic foraminiferal assemblage of upper Eocene in the Jahrum Formation carbonates, located in GisakanMountain, 10 km east of the Borazjan city and adjacent fields, were studied. Based on the foraminiferal ...
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In order to determine the depositional environment and age of the carbonaceous Jahrum Formation, benthic foraminiferal assemblage of upper Eocene in the Jahrum Formation carbonates, located in GisakanMountain, 10 km east of the Borazjan city and adjacent fields, were studied. Based on the foraminiferal distribution and abundance, the paleoenvironment were reconstructed. Due to the presence of Nummulites fabianni and based on strontium isotopic analyses, the age between 33.7-35Ma (Priabonian) was determined. The mean sedimentation rate of ~ 2 m/10000 yr. was calculated. This study indicated Asmari Formation deposited after a hiatus, more than four million years (Rupelian stage). Gradual decreases of the sea level and hence the distribution of large benthic foraminifera resulted in the deposition of six sedimentary facies along the inner-middle to outer carbonate ramp system. These facies, from deep to shallow parts of the basin, include argillaceous carbonates containing planktonic foraminifera that were deposited in a hemipelagic to pelagic environment (which is the transition zone from the Pabdeh to Jahrum Formation), carbonate facies of operculina wackestone to packstone related to the outer carbonate ramp, discocyclina /nummulites wackestone to packstone facies deposited in the middle to outer ramp, nummulites wackestone facies occurred in the middle ramp, nummulites orbitolites wackestone to packstone belong to the middle to inner ramp, and finally the orbitolites/bioclast packstone deposited in the inner ramp.
