جستجوی مقالات مرتبط با کلیدواژه "سازند آبدراز" در نشریات گروه "زمین شناسی"

In this study, Abderaz Formation at Qalezo section in the west of the Kopeh-Dagh sedimentary basin has been studied. It has consisted mainly of massive limestone, Marl and chalky limestone units at the mentioned section. Abderaz Formation at Qalezo section, the lower contact with Aitamir Formation is paraconform and the upper contact with Abtalkh Formation is conformed and continuous. The thickness of Abderaz Formation, 216 meters, has been measured. In this investigation have been identified 55 planktonic foraminifera species belong to 15 genera, in a frame of 4 biozones have been recognized. Finally, based on this research was distinguished from latest Early Turonian-Late Santonian ages for this section. In this study four planktonic foraminifera species, Dicarinella bouldinensis (Pessagno 1967), Dicarinella takayanagii Hasegawa 1999, Marginotruncana desioi (Gandolfi 1955), Marginotruncana caronae Peryt 1980 have been introduced for the first time in Iran. Also in this research planktonic foraminifera test geometric in Abderaz Formation at Qalezo section has been studied for sea-level changes. In Lower-Middle Turonian substages, the high frequency of the M1 group and low frequency of M3 group displayed fall seal level at this time. In Late Turonian frequencies of M3 group with accompany of %P was shown rise sea level. In the Coniacian and Santonian stages, the M1 group is dominant and the M3 group is low frequency and all of the mentioned evidence were demonstrates fall sea level. Also, the depth average of the studied section based on Depth = e (3.58718 + (0.03534 × %P)) has been calculating 146 meters which were shown these sediments deposited in Outer Neritic environment.

Apertural protective structures of the planktonic foraminifera in the Abderaz Formation have been studied in order to determine seal level changes in 4 stratigraphical sections including: Abderaz village, Muzduran pass, Padeha village and Shorb . Lithological study of the Abderaz Formation shown that Shorab section (east of the kopeh-Dagh basin) with 374 meters and Padeha village section with 602 meters represent minimum and maxiumum thickness, respectively. A total of 77 planktonic foraminifers species belonging to 19 genera, have been identified in studied sections. Eight Apertural protected plates have been recognized in the umbilical side of the distinguished planktonic foraminifera. Besides, 4 porticus structures (Simple lip, Tooth like-Porticus, Spiral Porticus, Imbricate Porticus) belonging to the morphotype 2 and 3, three Tegillum structures (Roll-type Tegillum, Strap-Shape Tegillum, Sheet like-Tegillum) belonging to the morphotype 3, and one Lip structure belonging to the morphotype 1, as well as their frequency have been recognized. Statistical analysis of protected structures of the umbilical area have been demonstrated that unlike to the imbricate porticus and sheet like Tegillum, the lip and simple lip structures show the highest frequency, indicating that the Abderaz Formation deposited in the relative shallow marine environment.

In this study the succession comprising Aitamir and Abderaz Formation boundary is investigated along Amir Abad section in eastern Koppeh-Dagh region. Based on Calcareous nannofossils and NC biozonation scheme, Late Albian to Late Turonian time of deposition is estimated for the measured succession. There is some evidence such as paleoecological changes and increase in organic carbon burial, enabling recognition of the Cenomanian – Turonian Oceanic Anoxic Event (OAE2) in this section. Anoxic events often occur as a result of high productivity leading to increased burial of organic matter. Paleoecological trends recorded including decrease in abundance of Broinsonia spp. and Biscutum spp. and increase in Watznaueria spp. at the beginning of the late Cenomanian interval suggest prevalence of oligotrophic condition during this interval of time. In the late Late Cenomanian and Cenomanian-Turonian boundary intervals, the increase in relative abundance of surface water high fertility markers such as Biscutum spp. and the increase of fertility index i.e. (Biscutum旫ꂮ᚛皋)/Watznaueria, point to amore eutrophic condition. The absence of Nannoconus spp., which are not seen in anoxic conditions, is another evidence of OAE2. The rising trend of total organic carbon content in the Late Cenomanian part of the sedimentary succession and the mentioned paleoecological evidences, suggest presence of Late Cenomanian Oceanic Anoxic Event in eastern Koppeh-Dagh. Although this global event is mostly reported from oceanic black shales, in some sections especially in the east of Tethys, it is sometimes recorded in shallow water sediments. Shale and marl succession in Koppeh-Dagh region can be considered as the continuation of their global trend in the eastern-most part of the Tethyan realm where the Late Cenomanian Oceanic Anoxic Event (OAE2) has occurred in a rather shallow environment of deposition.

Abderaz Formation is studied along Ghareh-Soo stratigraphic section, in eastern part of Kopet-dagh Sedimentary Basin which measures 958 meters in thickness. Nannofossil bioevents have been utilized to biostratigraphically classify the exposed sedimentary succession based on schemes of Sissingh (1977 modified by Perch-Nielsen, 1985), Roth (1978 modified by Bralower et al., 1995) and Burnett et al. (1998) and accordingly the rocks are attributed to Late Cenomanian to Early Campanian time interval. The results of palaeoecological studies along the succession show a decrease in high fertility marker taxa like Biscutum spp., and point to warm and oligotrophic surface water conditions in the late Cenomanian sediments i.e. upper parts of Aitamir Formation. A relative increase in high fertility taxa at the base of Abderaz Formation spanning the Cenomanian-Turonian boundary interval is also distinguishable. The Turonian part of Abderaz Formation is characterized by an increase in diversity and abundance of forms belonging to family Polycylolithaceae. Appearance of cool water taxa such as Gartnerago segmentatum, Ahmuellerella octoradiata and Kamptnerius magnificus in middle part of Abderaz Formation may probably be an indication of the Late Turonian to Campanian gradual and continuous cooling.

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 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 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 palynological studies and show that sediments of Ab-deraz Formation are deposited on each other in an open marine and change Inner neritic to outer neritic in disoxic to suboxic environment.

Ab- Deraz Formation is from the Lithostratigraphic units of the Kopet Dagh Basin in upper Cretaceous located in the North Eastern of Iran. According to the palynological studies by the use of Dinoflagellates, the age of Ab- Deraz in the section of West Sanganeh village Touronian to the middle Santonian was determined. The aim of this study is separation sequence units and determining water sea level changes by using palynological factors which is used for the first time on Ab- Deraz Formation. After reading the systematic of 41 samples of this Formation with the use of the palynological factors and agents three palynological facies identified and with the use of the triple a chart of Tyson was separated that includes three environment II: Marginal dysoxic-anoxic basin, V: Mud-dominated and oxic shelf, IV: Shelf to basin transition In order to separate sequence units based on three main changes of organic materials (Phytoclasts, palynomorphs and amorphs organic materials) and integration of these data with identified palynofacies, three sedimentary sequence kind of rank three with four sequence boundary ( three boundary of second kind and a type of first border) identified and determined.

In this research, we documented a paleontological study on the basis of planktic foraminifera, in five stratigraphic sections (Type, Padeha village, Shorab, Abderaz village and Qarehso) across the Santonian-Campanian transitional boundary in the eastern Kopeh-Dagh sedimentary basin. In all sections, no M. testudinarius Schlotheim (cosmopolitan species) was identified, which its last occurrence datum (LOD) is widely used to define the base of the Campanian stage. Several planktic foraminiferal biohorizons close to the Santonian/Campanian boundary were recorded, including the LOD’s of Ventilabrella austiniana Cushman, Dicarinella concavata (Brotzen) and Dicarinella asymetrica (Sigal), and the first occurrence datum (FOD) of Contusotruncana patelliformis (Gandolfi). The Santonian/Campanian boundary was placed in the upper part of the Dicarinella asymetrica Total Range Zone at the top of the Abderaz Formation in the type section and other sections in Shorab, Abderaz village, Padeha village, and at the base of the Abtalkh Formation in the Qarehso section. The acquired bio-models for the study sections are quite comparable with that of Gale et al, 2008 in WDS section, North Texas. On the basis of quantitative analysis of the planktic and benthic foraminiferal assemblages, the sparse presence of keeled planktic foraminifera and planktic foraminifera (%P) indicates that a shallow marine condition was prevailing just above the Santonian/Campanian boundary in the type section, Shorab, Abderaz and Padeha village sections. In addition, the abundance of such foraminifera (keeled planktic foraminifera and planktic foraminifera) reflects deeper water depths in the Qarehso section at the same time. Besides, estimation of the planktic to benthic ratio, which is based on the Van der Zwaan equilibrium, confirms that in the base of Campanian at one of the study sections (Qarehso section) the water depth was 160 m.

Abderaz Formation (Turonian-early Campanian in age) at its type section has a thickness of 300 m and contains light grey shale and marl. The study of the planktonic foraminifera in isolated form resulted in differentiating three morphotype groups. Also the planktonic to benthic (P/B) and infaunal to epifaunal ratios show that the water depth increased in the region at the end of Turonian and then decreased to less than 100meters in Coniacian. Increasing the water depth at the Coniacian-Santonian boundary and achieving has been observed as well as a deep diminishing trend to the end of the formation. Curves of morphotypes changes are in full agreement with the curves of the sea level changes and P/B. Frequency of epifauna to infauna morphotypes was used to reconstruct the oxygen level and food supply. At the base of section increase in the epifauna morphotypes indicate high oxygen condition and low food supply. In the middle part, decrease in epifauna to infauna ratio is indicative of low oxygen condition andhigh food supply. At top of the section, similar condition to that of the lower part is observed. Planktonic foraminiferas of Abderaz Formation are indicative of the Tethyan provinces.

The Stratigraphic analysis of the Abderaz Formation in Kopet-Dagh Basin, NE of Iran, at Taherabad Village has been studied. At this locating, the Abderaz Formation consists of gray to blue marl and white gray shale with 4 layers of chalky limestone.The thickness of Abderaz Formation is about 1955.5 m at this location. The boundary between Aitamir and Abderaz Formation is paraconformity and the boundry between Abderaz and Abtalkh, the top of this unit, is conformable. In this study, 70 species belonging to 35 genus of Foraminifera were recognized and 4 biozones in the Abderaz Formation have identified. Based on fossil assemblages, the age of the Abderaz Formation is Middel Turonian to Campanian. The age of upper most part the of Aitamir Formation is close to the end of Cenomanian. Therefore, at the end of Cenomanian and early parts of Middel Turonian a hiatus is present which is related to sub-Hercynian movment.