Stratigraphy and Palaeontology
Meysam Shafiee Ardestani; Mohammad Vahidinia
Abstract
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 ...
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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.
S. Sanjary; F. Hadavi; M. Notghi Moghaddam; M. Allameh
Abstract
In the present study the Abderaz Formation ostracods were investigated. The thickness of the formation in this section is 385m, and consists of shale and marl together with three horizons of chalky limestone. Paleontological studies led to identification of 16 genera and 51 species of ostracods ...
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In the present study the Abderaz Formation ostracods were investigated. The thickness of the formation in this section is 385m, and consists of shale and marl together with three horizons of chalky limestone. Paleontological studies led to identification of 16 genera and 51 species of ostracods and differentiation of four biozones in this section. According to the ostracods and correlation with calcareous nannofossils in this section, an age of late Santonian to early late Campanian is quoted to the formation at this section. Presence of warm water index species and absence of cool water forms suggest warm surface waters. Also changes in depth and oxygen were concluded during depositional course of the formation.
N Mousavi; A L.Kani; A Mosavinia
Abstract
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 ...
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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+Zeugrhabdotus)/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.
M Shafiee Ardestani; M Vahidinia; A Sadeghi
Abstract
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, ...
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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.
M. Shafiee Ardestani; E. Ghasemi-Nejad; H. Vaziri Moghaddam
Abstract
In order to study the fossil contents of the Abderaz Formation for biostratigraphical purposes the 300 meters thick section was sampled at type section. The sequence is mainly made up of grey shales and marls with two units of chalky limestone in upper part. The lower contact of the formation with Aitamir ...
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In order to study the fossil contents of the Abderaz Formation for biostratigraphical purposes the 300 meters thick section was sampled at type section. The sequence is mainly made up of grey shales and marls with two units of chalky limestone in upper part. The lower contact of the formation with Aitamir Formation is disconform while the upper contact with Abtalkh is continuous. Fifty six species belonging to 16 genera were identified and four biozones were differentiated. These are: Helvetoglobotruncana helvetica (Sigal)total range Zone, 2-Marginotruncana sigali - Dicarinella primitiva (Premoli Silva and Sliter) Partial range Zone, 3- Dicarinella concavata (Sigal)interval Zone and4-Dicarinella asymetrica (Postuma)total range Zone. Based on, these an age of Turonian-early Campanian is quoted to the formation. Also it was shown that Helvetoglobotruncana helvetica, the index species for middle Turonian exists at the base of the formation while, in the samples immediately below this belonging to Aitamir Formation Rotalipora appenninica, the index for middel cenomanian was recorded. Therefore, lack of index species for late Cenomanian- early Turonian shows a gap spanning this period between the Aitamir and Abderaz Formations. This could be a result of sub Hersinian orogeny.
L. Bakhshandeh; A. Aghanabati; F. Keshani; T. Mohtat
Abstract
To revise the Abderaz Formation in Koppeh-Dagh basin, its type section was studied considering stratigraphical properties. The main lithology of Abderaz Formation includes gray to blue shale with a thickness of 286.86 meters. This Formation has an attitude of N 45˚ W and 80˚ ...
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To revise the Abderaz Formation in Koppeh-Dagh basin, its type section was studied considering stratigraphical properties. The main lithology of Abderaz Formation includes gray to blue shale with a thickness of 286.86 meters. This Formation has an attitude of N 45˚ W and 80˚ SW. Its lower boundary with Aitamir Formation is unconformable and upper boundary with Abtalkh Formation conformable.
In this study, 58 planktonic species of 26 genuses were identified and presented. The age of Abderaz Formation, based on the identified planktonic foraminifera, was determined from Early Turonian to Early Campanian. Planktonic foraminifera fossils found in Abderaz Formation are more abundant than benthic foraminifera ones that show deep sea and continental slope environment.
Regarding the foraminifera content of the Abderaz Formation, 7 biozones were determined in the Mozduran section (Kopeh-Dagh) which shows Early Turonian – Early Campanian age for Abderaz Formation.
