SEDIMENTARY FACIES
Year:2015 | Volume:8 | Issue:1|Papers Count:8

Introduction: Silisiclastic deposits of basal Quartzite of the Mila Group in Central Alborz, called Faham Formation in this research, were studied in Shahmirzad, Tueh-Darvar, Mila-Kuh and Deh-Molla sections in order to interpret depositional environments and reconstruct the sequence stratigraphic framework. Based on facies characteristics and stratal geometries, the size of bedforms, sedimentary structures and their complex arrangement, erosional base, predominantly sandy grain size, the height of the sand bodies together with evidences of the tidal action such as extensive cross-stratified sandstone, tidal bundles, reactivation surfaces and mud drapes, the siliciclastic successions of the Fasham Formation are interpreted to be deposited in a tide-dominated open-mouthed estuarine environment. During the initial inundation of the present-day Alborz region in the early Middle Cambrian time, siliciclastic deposits formed in open-mouthed estuarine. Basal sequence of the Middle Cambrian deposits is composed of a transgressive systems tract (TST) comprising the basal siliciclastic-dominated succession of the Fasham Formation and a carbonate-dominated highstand systems tract (HST) within the lower part of the Deh-Sufiyan Formation. It records the drowning of the terrigeneous sources and subsequent establishment of the carbonate system. Based on sequential infilling model for open estuaries during transgression and initial flooding, tidal flats were developed along the margin of the sea and sandy dunes formed along the central part of the estuary and their lower surface was interpreted as a subaerial unconformity formed due to lowstand erosion. The last stage of infilling involves the development of sand bars that gradually migrated towards the open sea until they completely occupied the mouth of the open estuary...

Introduction: Chehel-Kaman Formation is one of the carbonate successions of the Kopet-Dagh Basin which is exposed from east to west. This Formation (Paleogene) in the Kopet-Dagh basin is mainly composed of limestone, dolomite and interbeds of marl, shale and evaporite sediments. It conformably overlies the siliclastic sediments of Pestehligh and underlies the olive shale of Khangiran Formations. The type section of this formation is located at the Chehel-Kaman village in the eastern Kopet-Dagh basin. Based on litostratigraphic study of the Chehel-Kaman Formation at type locality, it is divided into 4 units. The most important features in the second and forth units is palaeosol horizon that shows exposures of platform at that time. During the field study, 82 samples were collected to determine associated larger benthic foraminifera in the carbonate rocks. Thin sections were stained by Alizarin red S to differentiate calcite from dolomite and studied using standard petrographic microscope techniques. Trace fossils have been identified in sandy limestone which include: Ophiomorpha irregulaire, Ophiomorpha nodosa, Ophiomorpha isp., Bergueria isp, and vertical trace...

Introduction: The Asmari Formation is one of the most prolific reservoirs in southwest Iran. It was deposited on a carbonate platform that was developed across the Zagros Basin. Biostratigraphic zonation of the Asmari Formation was first established by Wynd (1965). Recently, Laursenet al. (2009) and van Buchem et al. (2010), based on the foraminifera associations calibrated with strontium isotope stratigraphy, introduced a new biozonation for the Asmari Formation. Some recent published research on palaeoecology and biostratigraphy of the Asmari Formation are: Laursen et al. (2009), Vaziri-Moghaddam et al., (2010), van Buchem et al. (2010), Mossadegh et al. (2009), Rahmani et al. (2009) and Allahkarampour Dill et al. (2012)...

Introduction: Biostratigraphic analysis was carried out for the Pabdeh Formation based on calcareous nannofossil in the Qaleh Nar oil field, Zagros Basin located in southwest Iran. Type section of the Pabdeh Formation was introduced in the North of Lali oilfield by Wynd in1965. In this study, Pabdeh Formation in the north Dezful Embayment consists of marl, argillaceous limestone and shale, and conformity covered by Asmari Formation. The aim of the present study is to determine the exact age of the studied interval with regard to the calcareous nannofossils…

Introduction: Bauxite deposits can be classified into two main categories according to the bedrock lithology including karstic bauxites, overlying the carbonate rocks and lateritic bauxites overlying alumosilicate rocks (Bardossy, 1982). The Alborz structural zone in northern Iran is the host of a number of important karstic bauxite deposits. Tash and Astaneh bauxitic-lateritic deposits are two of them, located about 40 km north of Shahroud and 30 km northwest of Damghan, respectively. The Tash bauxite deposit has been developed as a strati form horizon along the contact zone of Ruteh limestone and Elika dolomitic limestone, whereas the Astaneh laterite deposit located along the contact zone of Triassic dolomitic limestones and Jurassic shale and sandstones. In this paper, the Tash and Astaneh bauxite deposits are examined in terms of field relations, lithologic associations, petrography, mineralogy and geochemistry. The objectives were to determine the deposit characteristics, the paleoenvironmental conditions in the region and the processes responsible for the mobilization, fractionation and deposition of Al, Fe, and Si...

Introduction: The Tarbur Formation is located in the interior of Fars region (east of Zagros Mountains) and is known as a carbonate unit with abundant larger benthic foraminifera, rudist and coral. This formation is exposed in the interior part of Fars and high Zagros zones and southwestward it laterally changes to thin limestone beds. The facies of this formation eventually changes into the Gurpi shale Formation. The purpose of this study is to assess the paleoecology and biostratigraphy of the Tarbur Formation based on present fauna (foraminifera) in Semirom area (SW of Isfahan). The study area with geographical coordinate of N: 31o 22' 48" and E: 51o 32' 01" is located at about 5kms southwest of Semirom area. The thickness of the Tarbur Formation in the study area is 462 meters. The formation mainly consists of carbonate and terrigenous rocks and has a gradual and conformable contact with underlying red shale unit (S2) while is overlaid by the Kashkan Formation which is marked by an erosional surface...

Introduction Bahram Formation (Middle-Late Devonian) is the second stratigraphic unit of the Ozbak-kuh Group in east of Central Iran. It generally consists of bluish-gray to gray limestones which gradually covers dolomites of the Sibzar Formation and is overlaid by Shishtu Formation or with an erosional contact in some regions (Aghanabati, 2010). Most of the previously published works, (e.g. Ahmadi & Ashuri, 1998; Bahariet al., 2006; and Ahmadzadeh Heravi et al., 2007), have had mainly focused on biostratigraphy and lithostratigraphy of Bahram Formation. But in recent years, some other studies about microfacies, sedimentary environment, sequence stratigraphy and paragenetic sequence of Bahram Formation have been carried out by Rostamnezhad et al. (2012), Hashemi et al. (2012) and Hoseinabadi et al. (2013). In this research, a stratigraphic section of carbonate rocks of Bahram Formation with 332 m thickness in the east of Ozbak-kuh village, north of Tabas city (Southern Khorasan Province), has been measured, sampled and studied. This sequence generally has been made of gray colored, thin to thick bedded limestones.

Introduction: The Kopeh-Dagh sedimentary basin formed after the middle Triassic orogeny in northeastern Iran. There is no evidence of major tectonic activity in this region; all formations are conformable, except for a few disconformities within the Cretaceous succession (Afshar-Harb, 1994). The lower contact of the Ab-Deraz Formation in Sanganeh section with the Aitamir Formation is paraconform, and the upper contact with the Ab-Talkh Formation is conform. This section of the Ab-Deraz Formation is about 300 meter thick. In this section, lithology is composed of light gray shale, olive green shale and three chalky limestone bands. Sequence stratigraphy can be used to interpret the sea level fluctuations during deposition of any stratigraphic succession. The new method of palynological factors, such as biological degradation of palynological particles, roundness and homogeneity of equidimensional phytoclasts, the relative abundance of opaque phytoclasts to transparent phytoclasts, the relative marine palynomorph to terrestrial particles ratio, relative abundance and diversity of dinoflagellate cysts and relative chorate to proximate, proximochorate and cavate (C/PPC) morphotype ratio can be use for interpretation of stratigraphic sequences (Schioler, 2002). In this study, these factors were used for differentiation of sequences.