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.
A Gholami fard; A Kani; A Mahanipour
Abstract
This study investigates the Lower Cretaceous sedimentary succession comprising Sarcheshmeh Formation and Sanganeh Formation in the Ghaleh zoo Section from the standpoint of Calcareous Nannofossils. The results reveals presence of 60 species from 33 genera of 15 families. Based on the index nannofossil ...
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This study investigates the Lower Cretaceous sedimentary succession comprising Sarcheshmeh Formation and Sanganeh Formation in the Ghaleh zoo Section from the standpoint of Calcareous Nannofossils. The results reveals presence of 60 species from 33 genera of 15 families. Based on the index nannofossil taxa, the upper part of NC6, NC7A, NC7(B&C) and NC8(A&B) nannofossil zones (equivalent to the upper part of of CC7a, CC7b and CC8 zones), are present in this section. The calcareous nannofossils found in this section point to an Early Aptian to Late Aptian age of deposition for the rocks of Sarcheshmeh Formation and Late Aptian to Early Albian for the rocks of Sanganeh Formation.
N Badri; A.L Kani
Abstract
The Gurpi Formation has a wide extent in the Zagros Sedimentary Basin.It has received considerable attention due to its unique stratigraphic position, chronostratigraphic importance, and floral and faunal diversity and abundance.In order to biostratigraphically classification and correlation of theGurpi ...
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The Gurpi Formation has a wide extent in the Zagros Sedimentary Basin.It has received considerable attention due to its unique stratigraphic position, chronostratigraphic importance, and floral and faunal diversity and abundance.In order to biostratigraphically classification and correlation of theGurpi Formation in Kuh-e-Gach andKuh-e Kurdeh sections (Lar region, Fars province), this study concentrated on the calcareous nannofloral content of sediments.From the prepared 300 microscopic slides, a total of 53 species from 30 genera belonging to 15 families were determined, described and photographed. The distribution of nannofloral assemblage of the Gurpi Formation in Kuh-e Kurdeh reveals presence of CC18 to CC24 zones indicating an Early Campanian to Early Maastrichtian age, while in Kuh-e Gach CC19 to CC24 zones with an age range of Early Campanian to Early Maastrichtian are present. Occurrence of various speciesof low latitude affinities points toward such positioning of depositional basin of the Gurpi Formation.
F Foroughi; A Lotfali Kani; S Gardin; M Vahidinia
Abstract
The Kopet-Dagh basin is located in the northeast of Iran, in the triangle border of Iran, Turkmenistan and Afghanistan and consists of the marine Jurassic to Neogene strata. The Abtalkh Formation is one of the thickest lithostratigraphic upper Cretaceous units in the eastern Kopet-Dagh basin and is composed ...
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The Kopet-Dagh basin is located in the northeast of Iran, in the triangle border of Iran, Turkmenistan and Afghanistan and consists of the marine Jurassic to Neogene strata. The Abtalkh Formation is one of the thickest lithostratigraphic upper Cretaceous units in the eastern Kopet-Dagh basin and is composed of light gray, green to bluish marl and silty marl. The Abtalkh Formation conformably overlies the Abderaz Formation, which contains marls and chalky limestones and is conformably overlain by the Nayzar Formation, which consists of sandstone, silty marl and limestone. The Abtalkh Formation contains very aboundant, rich and good to moderately preserved calcareous nannofossil assemblages of Tethyan realm. The total 220 samples in the jalilabad and 467 samples in the AbtalkhVillage stratigraphic sections, representing the oldest and youngest strata of upper Abderaz, Abtalkh and base of Nayzar successions, were collected. The thickness of Abtalkh Formation in the Jalilabad stratigraphic section is 1325.8m and for the AbtalkhVillage stratigraphic section is 1765m. One hundred sixteen nannoplanktonic species belonging to forty three genera and fifteen families were identified. The biostratigraphic study allowed the recognition of the calcareous nannofossil biozones of Sissingh (1977) emended by Perch-Nielsen (1985) and Burnett (1998). From bottom to top, part of CC19, CC20, CC21, CC22, part of CC23a biozones and UC14dTP, UC15bTP, UC15cTP, UC15dTP subzones and UC16 biozone were identified in the Jalilabad section. The Abtalkh Village section in the middle of eastern Kopet-Dagh basin is started with CC20 (UC15bTP) biozone and continued to CC23a (UC16) biozone. Nearly more than 30 calcareous nannofossil species were reported for the first time in Iran. The results of this study indicated that the age of Abtalkh Formation spans from early to uppermost Late Campanian for these two sections in the Kopet-Dagh basin.
M. A. Sina; A. Aghanabati; A. L. Kani; A. R. Bahadori
Abstract
Calcareous nannofossils are suitable for biostratigarphical studies since they are abundant, planktonic, rapidly evolving and largely cosmopolitan, especially in the late Cretaceous. In this regards, 131 microscopic slides from shale and marl sediments of Gurpi formation of Poldokhtar section with thickness ...
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Calcareous nannofossils are suitable for biostratigarphical studies since they are abundant, planktonic, rapidly evolving and largely cosmopolitan, especially in the late Cretaceous. In this regards, 131 microscopic slides from shale and marl sediments of Gurpi formation of Poldokhtar section with thickness of 320 meters were collected. Out of this, 22 genera and 35 species were determined and their range chart is plotted. The distribution of nannofossil species indicates that there are 9 biozones in the study Poldokhtar section that can be separated, based on first occurrence (FO) of index species. They can be placed in CC18-CC26 of Sissingh (1977) time zones. On this basis, the age of sedimentation of this formation can be suggested to be from lower Companion to late Masstrichtian. In addition, presence of index species of low latitude in Poldokhtar section of Gurpi formation shows that this sedimentary basin was located in low latitude at the time of sedimentation.
