Sedimentology
Alireza Rostami; Mohammad Hossein Adabi; Abbas Sadeghi; Seyed Ali Moallemi
Abstract
The Dariyan Formation with the Aptian age is the youngest reservoir formation of the Upper Khami group which is important in terms of hydrocarbon reservoir potential. This formation is 135 meters thick in the Kuh-e-Mish surface section and consists of thin, thick and massive limestone, marl and shale. ...
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The Dariyan Formation with the Aptian age is the youngest reservoir formation of the Upper Khami group which is important in terms of hydrocarbon reservoir potential. This formation is 135 meters thick in the Kuh-e-Mish surface section and consists of thin, thick and massive limestone, marl and shale. Petrographic studies led to the identification of 13 microfacies. These have been deposited in four types of depositional environments, including inner ramp, mid ramp, outer ramp and basin, in a ramp type carbonate platform. Based on petrography, lateral and vertical facies changes, 3 third-order cycles distinguished. An integrated multidisciplinary approach including, petrography, surface gamma-ray spectrometry and trace element analysis have been used for recognition of original carbonate mineralogy and stratigraphic interpretations of this succession. Geochemistry of minor and major elements reveal original aragonitic mineralogy of the Dariyan Formation. Bivariate plot of Mn versus Sr/Ca values illustrated that the Aptian carbonates were affected by semi close diagenetic system with moderate water/rock interaction. Trace elements (Fe and Mn) contents are compared with distribution of sedimentary facies and depositional sequences to investigate and correlate stratigraphic boundaries, which are determined by sequence stratigraphy in shallow marine carbonate platform of the Dariyan Formation. The elemental peaks coinciding with the sequence boundaries and elemental peaks are correlated with maximum flooding surfaces.
N Etemad-Saeed; M. H Adabi; A. Sadeghi; M. Hosseini- Barzi
Abstract
This work is focused on tectonic provenance of the Late Neoproterozoic Kahar Formation in the northern Iran. KaharMountain (type locality) provides valuable information on tectonic events during this time. The Kahar Formation in this area is a well preserved sedimentary sequence and consists of about ...
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This work is focused on tectonic provenance of the Late Neoproterozoic Kahar Formation in the northern Iran. KaharMountain (type locality) provides valuable information on tectonic events during this time. The Kahar Formation in this area is a well preserved sedimentary sequence and consists of about 1000 meters of predominantly fine grained siliciclastic rocks and minor sandstones, conglomerates and dolomitized stromatolites. Kahar lithic arkose sandstones with low compositional and textural maturity, contain abundant feldspar (plagioclase and K feldspar), quartz, and volcanic lithic fragments and have an average composition of Q38F40L22, Qt39F40L21, Qm32F40Lt28,Qp27Lvm60Lsm13 and Qm44P33K23 suggesting a proximal source and a dissected arc setting. The type of lithic fragments in the sandstones show andesitic and felsic volcanic rock sources. Heavy mineral analysis (abundant metastable and unstable minerals such as biotite, and pyroxenes) indicate that Kahar sandstones were derived from unroofing of arc-type magmatic rocks. The low diversity of heavy mineral assemblages in the Kahar sandstones indicates that the source rocks were uniform and localized. Considering the two common tectonic views regarding the Late Neoproterozoic condition of Iran (rift-passive margin and magmatic arc-subduction zone), the results of this study which confirm the magmatic arc tectonic setting of Alborz-Iran at that time seems critical.
M. Motamedalshariati; A. Sadeghi; H. Vaziri Moghadam; R. Moussavi Harami
Abstract
A stratigraphic section in west of Maraveh Tappeh town has been selected and measured in order to study the Aitamir Formation in north west of Kopeh Dagh. The Aitamir Formation with 1070 m thickness, consists of sandstone in the lower part and shale and marl in the upper part. The lower and upper boundaries ...
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A stratigraphic section in west of Maraveh Tappeh town has been selected and measured in order to study the Aitamir Formation in north west of Kopeh Dagh. The Aitamir Formation with 1070 m thickness, consists of sandstone in the lower part and shale and marl in the upper part. The lower and upper boundaries of the Aitamir Formation with Sanganeh and Abdraz Formations are conformable. The biostratigraphic studies led to identification of 34 genera and 58 species of planktonic and benthonic foraminifera. Based on foraminifera assemblage three biozones are suggested as follows: Rotalipora appenninica zone, Rotalipora brotzeni zone, Whiteinella aumalensis –Dicarinella canaliculata zone. These biozones coincidence with global biozones. Based on foraminiferal fauna, a Late Albian to Late Cenomanian age is suggested for the upper shale member of Aitamir Formation.
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.
Z.K. Mossadegh; M.H. Adabi; A. Sadeghi
Abstract
We studied the geochemistry of the Asmari Formation in two outcrop sections: Tang-e-Sapou a 260 m section near Dehdasht City (Kohgiluyeh va Bouyer Ahmad Province) and Tang-e-Ban a 214 m section near Behbahan City (Khozestan Province). Sampling included the complete Asmari Formation and the top of the ...
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We studied the geochemistry of the Asmari Formation in two outcrop sections: Tang-e-Sapou a 260 m section near Dehdasht City (Kohgiluyeh va Bouyer Ahmad Province) and Tang-e-Ban a 214 m section near Behbahan City (Khozestan Province). Sampling included the complete Asmari Formation and the top of the Pabdeh Formation. The Late Oligocene to Early Miocene Asmari Formation lies above the Pabdeh Formation and is overlain by the Gachsaran Formation. Elemental geochemistry (Fe, Mg, Na, Sr, Mn, Ca), and Oxygen and Carbon isotope analyses indicate that meteoric diagenesis affected carbonates of the Asmari Formation. The δ18O/δ13C data plots in an inverted J-trend suggesting that meteoric diagensis occurred in a closed to semi-closed system. The geochemistry also suggests that the original mineralogy was Aragonite. The boundary between the Pabdeh and Asmari Formations can be recognized by changes in the δ 18O and δ 13C. In the Pabdeh Formation the δ 18O and δ 13C values are mostly negative, but in the Asmari Formation values range from positive to negative. Strontium is much higher in the Pabdeh Formation than in the Asmari Formation. Changes in isotope and elemental geochemistry clearly show the Chattian-Aquitanian and Aquitanian-Burgidalian boundaries.
M. H. Adabi; M. Khatibi Mehr; A. Moallemi; A. Sadeghi; M. A. Salehi
Abstract
The Ziyarat Formation is an Upper Paleocene to Middle Eocene carbonate sequences, located in North of Tochal Village (south-east of Tehran), near Emam Zadeh Abdollah. The Ziyarat Formation with the total thickness of 212.5 m conformably overlies the Fajan conglomerate and is overlain by greenish tufaceous ...
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The Ziyarat Formation is an Upper Paleocene to Middle Eocene carbonate sequences, located in North of Tochal Village (south-east of Tehran), near Emam Zadeh Abdollah. The Ziyarat Formation with the total thickness of 212.5 m conformably overlies the Fajan conglomerate and is overlain by greenish tufaceous siltstone of the Karj Formation. Petrographic studies led to the recognition of 11 microfacies. Different facies and evidences such as the absence of reefal facies, calciturbidite deposits, and widespread tidal flat deposits indicate that the Ziyarat Formation was deposited in a homoclinal carbonate ramp environment. Micritization, cementation, compaction, neomorphism, dissolution, dolomitization, fracturing and silicification are the major diagenetic processes in the Ziyarat Formation, occurring in meteoric and burial diagenetic environments. Major and minor elements and oxygen and carbon isotope values indicate that Ziyarat carbonates were deposited in a shallow warm water tropical environment and original carbonate mineralogy was aragonite. Bivariate plots of Mn versus Sr/Ca and δ18O illustrate that Ziyarat limestones were affected by open system diagenesis with high water/rock interaction. Early burial diagenetic temperature calculation based on heaviest oxygen isotope values of micrite and δw of Eocene seawater of 0.85 SMOW, shows that temperature was around 39˚C. Cathodluminescence studies of carbonate cements illustrated dull luminescence, because these carbonates afftected by both meteoric and burial diagenesis, and thus typical yellow to orange luminescence and zonations, evidence of meteoric diagenesis, are absent. This statement is confirmed by isotropic evidences.
R. Azimi; K. Seyed-Emami; A. Sadeghi
Abstract
The calpionellid biozonation within Shal and Kolur Formations in Shal region, SE Khalkhal are accomplished based on standard biozonation of Allemann et al. (1977). In this study, 5 biozones are introduced from Tithonian to Hauterivian:biozone. Biozone 1 belongs to Shal Formation ...
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The calpionellid biozonation within Shal and Kolur Formations in Shal region, SE Khalkhal are accomplished based on standard biozonation of Allemann et al. (1977). In this study, 5 biozones are introduced from Tithonian to Hauterivian:biozone. Biozone 1 belongs to Shal Formation and biozones 2 to 5 to Kolur Formation: 1- Crassicollaria intermedia Taxon Range Zone; Late Tithonian, 2- Calpionella alpina Acme Zone; Early Berriassian, 3- Calpionellopsis simplex - Calpionellites darderi Interval Zone; Late Berriassian to Early Valanginian, 4- Calpionellites darderi - Tintinopsella longa Interval Zone; Valanginian, 5- Tintinopsella longa - Tintinopsella carpathica Interval Zone; Late Valanginian- Hauterivian. Biozone 2 is also subdivided into the Calpionella alpina and Calpionella elliptica Subzones. Biozone 3 is subdivided into the Calpionellopsis simplex and Calpionellopsis oblonga Subzones. Based on this zonation, the Jurassic /Cretaceous boundary (Tithonian/ Berriassian) is defined at the Lower boundary of the Calpionella alpina zone which is equivalent to the Shal and Kolour Formations boundary.
M. Vahidinia; A. Sadeghi; A. Shemirani; A-A. Aryai; M-A. Adabi
Abstract
The Kopet Dagh basin was formed during and after the collision of Turan plate with Iran plate before late Carnian (about 225 m.y. ago). It is located in the northeast of Iran and has a WNW to ESE trend. Neyzar Formation is composed of siliciclastic sediments and sandy shale and sandy limestone. This ...
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The Kopet Dagh basin was formed during and after the collision of Turan plate with Iran plate before late Carnian (about 225 m.y. ago). It is located in the northeast of Iran and has a WNW to ESE trend. Neyzar Formation is composed of siliciclastic sediments and sandy shale and sandy limestone. This unit is widespread in the east and northeast parts of the basin. To determine the stratigraphy, microfossils, microfacies and depositional environment of Neyzar Formation, three stratigraphic sections were selected and measurement and detailed sampling carried out on each of them. These sections from east to west are as fallows :
1) Tang-e Neyzar (Neyzar gorge) section
2) Tang-e Chahchaheh section
3) Jalil abad section
In the previous studies, the base and top boundaries of Neyzar Formation with Abtalkh and Kalat Formations were reported conformable and transitional (Afshar Harb, 1373). However, according to present investigations in eastern regions, lower boundary of Neyzar Formation with Abtalkh Formation in sections 1 and 2 are disconformable (as a Paleosol). This boundary in the section 3 is conformable and transitional. The upper boundary of Neyzar Formation with Kalat Formation in 1, 2 and 3 sections are disconformable (as a paleosoil).
Two types of facies were identified based on micropaleontologic and petrographic studies: 1) Siliciclastic facies, 2) Carbonate facies. Based on microfacies studies it seems that the siliciclastic parts of Neyzar Formation was deposited in a lagoonal-barrier island environments and the carbonaceous parts in a shallow carbonate platform (ramp type).
In most of the published reports and articles Neyzar Formation was introduced as low fossil bearing unit with no index–fossil. The age of this formation was determined only by the basis of its stratigraphical situation, but in the present investigation, in addition, 41 genera and 30 species of microfossils have been identified for the first time from index fossils such as:
Orbitoides apiculata, Orbitoides tissoti, Lepidorbitoides sp., Siderolites calcitrapoides, Pseudosiderolites vidali, Abathomphalus mayaroensis.
These fossil assemblages suggest the Maastrichtian, especially Late Maastrichtian age for Neyzar Formation.
