P Gholami Zadeh; M.H Adabi; M Hosseini-Barzi; A Sadeghi; M.R Ghassemi
Abstract
The Miocene sediments in Neyriz region crop out in Zagros Crushed Zone, between Zagros Main Fault and Zagros Ophiolite Zone. For paleoenvironmental studies of these sediments, two stratigraphic sections (Kuh-e Asaki and Horgan sections) have been measured and sampled. The thicknesses of these two ...
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The Miocene sediments in Neyriz region crop out in Zagros Crushed Zone, between Zagros Main Fault and Zagros Ophiolite Zone. For paleoenvironmental studies of these sediments, two stratigraphic sections (Kuh-e Asaki and Horgan sections) have been measured and sampled. The thicknesses of these two sections are 424 and 440 m respectively and contain red and green sandstone, conglomerate and marl which are bounded unconformably between the Jahrum Formation and Bakhtiari conglomerate. Based on the field and petrographic studies, 14 sedimentary facies related to proximal, mid fan-delta; transition zone, delta slope and prodelta have been recognized for the Miocene succession. Due to the slope facies formed by the turbidity currents, grain fall and debris flows, the coarse grained clasts and poorly sorted texture, a fan-delta model is suggested for the succession. Also, the development of the slope facies indicates a paleo-slope and slope-type, deep-water fan-delta. The frequent intra-formational disconformities, irregular changes in grain size and present of gravity flows indicate an active tectonic sedimentary basin and reflux of coarse grained sediments (catastrophic events) to the proximal parts of Zagros Basin.
M Allameh; B Torabian
Abstract
Farrokhi Formation is a Cretaceous rock unit in Central Iran that lithologically contains lime, marl and marly lime accompanied by layers of fossiliferous limestones. This formation lays conformably over the Haft-Tuman Formation, while its upper boundary is disconformable with Chupanan Formation. In ...
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Farrokhi Formation is a Cretaceous rock unit in Central Iran that lithologically contains lime, marl and marly lime accompanied by layers of fossiliferous limestones. This formation lays conformably over the Haft-Tuman Formation, while its upper boundary is disconformable with Chupanan Formation. In this study, 23 rock samples from marl segment of the Farokhi Formation were prepared palynologically and their various palynological constituents were characterized and quantified by percent. Assessing the organic elements of formation demonstrated fair preservation of organic matters in marl segments and allowed determination of the sedimentation rate and oxygen content. Palynofacies investigation signifies that marl segment has been deposited in shallow to open marine environment with medium energy, and one palynofacies has been diagnosed for it. According to typical dinoflagellate cysts, a warm and rather shallow environment with medium energy and variable salinity is suggested for the period of sedimentation of the marl segment.
S.A Babazadeh; M Rahmati
Abstract
Carbonate sedimentary rocks equivalent to Asmari Formation containing thick and thin bedded and massive limestones with a thickness of 160m studied in Posht-Darband, Hamadan. The base of the sedimentary sequence begun with a transgressive conglomeratic horizon. This horizon is composed of rock ...
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Carbonate sedimentary rocks equivalent to Asmari Formation containing thick and thin bedded and massive limestones with a thickness of 160m studied in Posht-Darband, Hamadan. The base of the sedimentary sequence begun with a transgressive conglomeratic horizon. This horizon is composed of rock fragments such as cherts, schists and fossiliferouslimestones which are derived from adjacent old rock units. The lower contact of conglomerate horizon overlains the metamorphic rocks and the upper contact is covered by alluvium. Based on the study of thin sections from Asmari Formation, two main facies belts containing inner and middle ramps are recognized. The inner ramp composes restricted lagoon, rotalid shoal, protected lagoon and patch reef whiles the middle ramp contains proximal, middle and distal parts respectively. Based on microscopic studies, eight microfacies are presented which are consist of; 1-Large perforate foraminifera-bioclastwackestone, 2-Perforate foraminifera-red algal-bioclastpackstone/grainstone, 3-Coralgal-bioclast packstone/grainstone, 4-Coral-redalgal packstone/grainstone, 5-Imperforate foraminifera-pelloid-bioclastpackstone, 6-Rotalia grainstone, 7-Perforate-imperforate foraminifera packstone/grainstone and 8-Miliolid-bioclast-intraclast packstone. They are deposited in seven sedimentary environments. According to microfacies, this formation is distributed from tidal flat to middle ramp. The Chatian (Late Oligocene) age is attributed to these carbonate rocks based on benthic foraminifera recorded.
T Rabani; N Taghipour; R Aharipour
Abstract
Gheshlagh district contains coal deposits in a large syncline in Shemshak group sediments in East Alborz. To determine the palaeoenvironmental setting of the coal deposits based on organic and mineral components, eleven samples from coal seams from four active mines are collected. Minerals such as quartz, ...
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Gheshlagh district contains coal deposits in a large syncline in Shemshak group sediments in East Alborz. To determine the palaeoenvironmental setting of the coal deposits based on organic and mineral components, eleven samples from coal seams from four active mines are collected. Minerals such as quartz, kaolinite, pyrite, siderite, biotite, montmorillonite and dolomite are identified in Gheshlagh coal mines. The Ground Water Index (GWI) suggests ombrotrophic hydrological conditions for coal layers in Gheshlagh coal region. K13 and k11 layers have much higher GWI among others due to its higher mineral content than other layers. Vegetation index (VI) of the Gheshlagh coals is less than 3, which could indicative of the dominance of aquatic/herbaceous plants in the formation of coal seams. Petrographic data on organic and inorganic matter with facies diagram suggest evidences of anaerobic to low oxygen, alkaline conditions and variations in water level with relative proximity to the marine environment.
F Yousefi Moghadam; M Allameh; S.M Hosseininezhad; L Bakhshandeh
Abstract
Ab-deraz Formation is one of the Lithostratigraphic units of upper cretaceous the age of which is determined as touronian-santonian in Kopet-Dagh sedimentary basin located in northeast Iran. Its major lithology in Sanganeh section contains Marl, Marly limestone, and gray shales and light green shale ...
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Ab-deraz Formation is one of the Lithostratigraphic units of upper cretaceous the age of which is determined as touronian-santonian in Kopet-Dagh sedimentary basin located in northeast Iran. Its major lithology in Sanganeh section contains Marl, Marly limestone, and gray shales and light green shale along with three band of chalky limestones. This Formation thickness in Sanganeh section is measured as 530 meter out of which 41 samples were systematically taken. In order to interpret the Paleoenvironment and Sequence stratigraphy, this Formation in Sanganeh section was analyzed by using palynological facies and conformity of Osracodas and Dinoflagellates. Having examined the frequency ratio (abundance) of two groups of Ostracoda (Platycopids to Podocopids), it was observed that the most abundant oceanic dissolved oxygen is seen in Marly layers near Calcareous band of chalky limestones and the least abundant is seen in layers far from those bands. In addition, based on the abundance of Genus, such as Paracypris, Brachycthere, and Bairdia mostly seen near Calcareous band of chalky limestones and Ostracoda with ornamented Carapce and thicker layers such as Veenia, Pterygocythereis seen in Marly layers near chalky limestones, it can be stated that it is shallower near Calcareous band of chalky limestones and moving toward Marly and shale layers, it becomes deeper. Analyzing 82 Palynological slides resulted in identification of three Palynofaies of V, IV, II, in this Formation. The results obtained from statistical studies of palynological factors including AOM to Marine palynomorph ratio, abundance of Foraminifera test lining, and peridinioid/Gonyaulacoid ratio for determining the amount of oxygen in the environment indicate that often there were low levels of oxygen in this Formation, however, there were times when oxic condition was dominant. Also in order to Relative sea level changes by Palynological facies, two factors were used first one being dinocysts of specific inner neritic to outer neritic ratio and chorate/ proximate, proximochorate and cavate cysts (C/PPC) ratio. Studies in which Ostracoda were used confirm the results obtained from palynological studies and show that sediments of Ab-deraz Formation are deposited on each other in an open marine and change from Inner neritic to outer neritic in disoxic to suboxic environment.
N Hashemi; A.R Ashouri; M Aliabadian; M.H Mahmoudi Gharaie
Abstract
Paleozoology of Yafteh and Kani Mikaiel caves in center and northwest of Zagros Mountains led to the identification of small mammals' assemblage. Taxonomic determination revealed inclusion of four orders of small mammals including: order Rodentia with families of Muridea, Cricetidae, Calomyscidae, ...
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Paleozoology of Yafteh and Kani Mikaiel caves in center and northwest of Zagros Mountains led to the identification of small mammals' assemblage. Taxonomic determination revealed inclusion of four orders of small mammals including: order Rodentia with families of Muridea, Cricetidae, Calomyscidae, Dipodidae; order Lagomorpha with two families of Ochotonidae and Leporidae; order Soricomorpha with family Talpidae, and order Carnivores with family Mustelidae. These remains were recovered after systematic excavation in these caves. Radiocarbon analysis of these remains showed the oldest sample belonged to Yafteh cave with 35,000 BP. and Pleistocene period, whereas, Kani Mikaiel cave covered the periods from lat Pleistocene (19,000 BP.) to Holocene (17, 00 BP.). Geochronology analysis of Kani Mikaiel sediments showed that the lower layers of this cave belonged to the last glacial age in Pleistocene which gradually has been replaced by the warm weather in Holocene period. With continuing of this weathering varying, faunal spectrum of Pleistocene and Holocene periods has been migrated in cold and warm phases or more spread. The aim of this research, are the study of small mammal remains of Yafteh and Kani Mikaiel caves in center and northwest of Zagros mountains and the research about the study of paleobiodiversity, paleoenvironment conditions and the evolution of microvertebrate on the Iranian plateau.
M Allameh; Z Sardar
Abstract
Aitamir Formation is one of the formations in sedimentary basins of Koppeh-Dagh in the north east of Iran. This formation has been made of a sandstone part in the lower and a shale part in the upper. Both the part are Glauconitic and often seen in Olive-green color. This research is on a section of a ...
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Aitamir Formation is one of the formations in sedimentary basins of Koppeh-Dagh in the north east of Iran. This formation has been made of a sandstone part in the lower and a shale part in the upper. Both the part are Glauconitic and often seen in Olive-green color. This research is on a section of a Aitamir formation based on Palynomorphs which has been conducted on the route from Mashhad to Kalat-e-Naderi, isn the edge of Zavin village with the thickness of 506 meters and the coordinates 36°43̒45.42" north latitude, and 59°57̒5.56"east longitude. 40 samples of this section have been gathered and 120 Palynological slides have been prepared. The study of these slides has resulted in the identification of 28 genera and 47 species of Dinoflagellates. Regarding the identified Dinoflagellates, the age of Aitamir formation in the mentioned Albian-Cenomanian section was determined. The study of the factors involved in preservation of organic materials shows the low to moderate levels of oxygen conditions, with low deposition and an inner to the outer Neritic environment for an Aitamir formation in the mentioned section. Based on the studies that have been done, three Palynofacies were identified for the Aitamir formation in Zavin section.
J Rabbani; E Ghasemi-Nejad; A.R Ashouri; M Vahidinia
Abstract
The basal unit of the Pabdeh Formation at Bisheh-Deraz section composes of 47m purple to green to grey shale and marl. These beds gradually change to shale and argillaceous limestone in the top of the section. In order to study paleoecology and paleoenvironment of these beds, palynological evidences ...
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The basal unit of the Pabdeh Formation at Bisheh-Deraz section composes of 47m purple to green to grey shale and marl. These beds gradually change to shale and argillaceous limestone in the top of the section. In order to study paleoecology and paleoenvironment of these beds, palynological evidences including palynofacies, abundance and diversity of dinocysts and environmental index have been investigated. Four Palynofacies types including IV: shelf to basin transition, VII-VIII: distal dysoxic-anoxic shelf, IX: distal suboxic-anoxic basin) have been differentiated that propose a distal suboxic-anoxic basin as depositional setting. According to the microfacies of planktonic foraminiferal Wakestone/Packestone a deep environment is proposed as the depositional basin. Using such parameters as palynofacies evidences, C/PPC ratio, AOM/MP ratio, abundance and diversity of dinocysts and environmental index, three system tracts related to one sequence (3rdorder) with one sequence boundary type 2 and one maximum flooding surface have been determined. In general, the factors all together show a deepening upward trend through this rock unit.
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.
J. Daneshian; M. Shahrabi; M. Akhlaghi
Abstract
75 samples of the Qom Formation in Andabad, northeast Mahneshan, were investigated. The Qom Formation in the examined section with a thickness of 301m, mainly consists of limestone and marl, and disconformably overlies the Lower Red Formation and lies under the sediments of the Upper Red Formation. A ...
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75 samples of the Qom Formation in Andabad, northeast Mahneshan, were investigated. The Qom Formation in the examined section with a thickness of 301m, mainly consists of limestone and marl, and disconformably overlies the Lower Red Formation and lies under the sediments of the Upper Red Formation. A study of foraminifera was led to identifying 42 genera and 70 species of the benthonic and plankthonic foraminifera, which 37 genera and 57 species is reported from this area for the first time. Among them, benthonic foraminifera have more varieties and abundances, and used for biostratigraghy. Based on the identified foraminifera, the Andabad section is comparable to Assemblages Zone 1 and 2 introduced by Adams and Bourgeois. On the basis of occurrence of the index foraminiferal species and their stratigraphic distribution, the age of the Qom Formation in the studied section is Early Miocene (Late Aquitanian to Burdigalian).The assemblage, abundance, and species diversity of foraminifera in the examined samples shows noticeable changes in the paleoenvironmental conditions. The maximum diversity of foraminifera is sixteen species. Based on species diversity, the strata classified to nine assemblages A to I. The abundance of foraminifera in each assemblage indicates that the sediments of the Qom Formation belong to inner shelf environments.
