SEDIMENTARY FACIES
Year:2011 | Volume:4 | Issue:1|Papers Count:8

Carboniferous corals of Sardar Formation, in Zeludu stratigraphic section (Ozbak Kuh Mountains) was collected and studied.After studies of 50 specimens of coral fossils, 9 species belong to 5 genera from rugosa and tabulata corals with Late Serpukhovian age were identified.These corals are included the following species: Heritschioides pseudosolitarius, Heritschioides vepres, Heritschioides cf. vepres, Paraheritschiodes antoni antoni, Paraheritschiodes sp.1., Paraheritschiodes sp.2., Multithecopora sp., Orygmophyllum sp.and Durhamina sp. In addition to review of the ages of Heritschioides vepres, H.pseudosolitarius, H. cf. vepres and Praheritschiodes antoni antoni species, two genera including Orygmophyllum and Durhamina are reported for the first time from Iran. These fauna can be compared with corals of Ural region. Based on ecological evidences, corallites arrangement and dissepiments thickness, it can be concluded that these deposits are formed in back parts of bar in a shallow carbonate platform of ramp type.

Microfacies and environmental interpretation of the Asmari and Jahrum Formations were studied in wells number 2, 10 and 11 in Gol-Khari oil field. Based on petrographic criteria, fauna assemblages, biofacies and sedimentary textures, 21 carbonate microfacies and 3 non- carbonate petrofacies were recognized. These microfacies were deposited in distinct depositional environments including tidal flat, lagoon, bar and open marine in a homocline carbonate ramp.

The Qom Formation in Ghohrud area has been investigated in order to determine its biostratigraphy and palaeoecology. The thickness of Qom Formation is about 325 meters at the study area and consists of thin, medium to thick bedded and massive limestones.They underline on Eocene volcanic with disconformity and it covers by alluvium deposits. Based on this study, 14 genera and 26 species of the benthic foraminifera were identified. The ssemblage of benthic foraminifera represents the Late Oligocene (Chattian) to Early Miocene (Aqitanian?) age. Large benthic foraminifera with thin hyaline wall such as large lepidocyclinidae and nummulitidae with symbiotic bearing algae are present. This is due to increase in water depth, low energy, normal salinity and prevailing of a deeper open marine environment. In shallower open marine environment, foraminifers wall (with hyaline wall) become thicker and smaller in size that represents decrease in water depth, and increase in light and energy. In this section, semi-restricted lagoon foraminifera with porcelaneous wall and foraminifera with hyaline wall are present together. In shallow water (restricted lagoon) foraminifera with porcelaneous wall such as Austrotirillina, Borellis, Miliolids and peneroplis are present, that reveals decrease of water depth and increase in light and salinity factors.

Kopet-Dagh basin is located in north and northeast of Iran. Khangiran Formation is one of the most important units of the Paleogene deposits. For study of Khangiran Formation bivalves, Chehel=Kaman Syncline section has been selected. This section is located west of Sarakhs city, east of Kopet-Dagh basin. Lithology of this Formation in the Sarakhs region is composed of marl, marly limestone and siltstone. In addition, a deposit with oyster shells consists of 50m thick olive green homogenous marl with large shells of oysters is present that are very well preserved. Based on this shells study, species of Sokolowia beldersaiensis and Sokolowia buhsii of Ostreidae family have been identified. These shells indicate sub-tidal to shallow marine environments and euhaline waters and represent the Middle Eocene age (Bartonian stage) for these sediments. Furthermore, paleobiogeography survey of this bivalves indicate that the Khangiran Formation belong to Tethyan realm, which is limited to central Asian region and located between Transylvanian basin of Romania, in the west and Tarim basin of China in the east. Retreats of this sea in the Middle Eocene cause these oyster shells to form during the Bartonian stage. These shells indicate dependency of Kopet-Dagh basin to Turan Sea therefore can support the theory of Urasian of Kopet-Dagh basin.

Sarcheshmeh Formation is one the Lower Cretaceous formations of the Kopet-Dagh Basin in NE Iran. An outcrop of this formation in the Daddanlou village section was studied, palynologically. The studied section has about 248 meters thickness and consists of gray marl and gray shale, with interbedded limestone. Based on study of 135 thin slides of 27 samples taken from this formation, most of the samples contain palynomorphs (dinoflagellates). Additionally, three forms of Chorate, Cavate, and Proximate have been observed. In this study, 37 species belong to 29 genera were indentified. According to identified dinoflagellate, Aptian age is determined for Sarcheshmeh Formation in Daddanlou section. The identified dinoflagellate in the studied section could be compare with part of Odontochitina operculata zone. Based on this study, three main groups of palynological elements (phytoclasts, marine palynomorph and amorphous organic matter) and results of statistical studies on protection factors of organic materials such as rate of transparent SOM to opaque SOM, rate of brown palynomaceral to opaque palynomaceral and rate of SOM to marine palynomorph indicates that rate of deposition and oxygen was different. Finally, based on index dinoflagellate, Sarcheshmeh Formation depositional environment varied from inner neritic to outer neritic.

Diagenetic processes in chalky-marl couplets of Ab-Deraz Formation are studied in Hamam-Qale and Padeha sections, which are located in east Kopet Dagh basin. Chalk units are composed of chalk-marl couplets with different diagenetic features. The common diagenetic processes in chalky and marly limestones are cementation, dissolution, compaction, aggrading neomorphism, pyritization, bioturbation and fracturing. The present of clay minerals and lack of grain framework in marly interbeds led to more dissolution and compaction, while the fewer amounts of clay minerals and abundance of grains in the chalky beds provide available condition for more cementation.Paragenetic sequence interpretation of Ab-Deraz Formation indicates that diagenetic processes have affected these sediments in marine, burial and uplift conditions.

The Upper Cretaceous thick bedded succession in Badamouyeh Mountain in Honooj area shows the Late Cenomanian-Santonian stages. Also, these deposits are well exposed in south-west of Bibihayat and south of Cheshmah Gaz village. In the studied section, Lower and Upper Honooj green marls (informal) with intercalation of Exogyroferous shaly limestone are overlain by thick bedded limestones and in turns disconformably cover the Jurassic shale and sandstones (probably Hojedk Formation). The presences of both platycopid and podocopid ostracods, high diverse assemblages of foraminifera and macrofossils in Honooj marls and also high diverse assemblages of benthonic foraminifera in upper limestone show a favorable condition during the deposition of the strata.

Calcareous nannofossils at the boundary of Tirgan and Sarcheshmeh Formations at Qalezo section have been studied. This section is located in western Kopet-Dagh Basin. In this study, 35 nannoplankton species of 17 genera were identified. According to the first occurrence of index species and fossil assemblages’ two calcareous nannofossil biozones (CC7-CC8) of Sissingh (1997) have been recognized. Based on these biozones, age of this boundary is Late Aptian - Early Albian.