Stratigraphy and Palaeontology
Somayeh Baharlouei Yancheshmeh; Ebrahim Ghasemi Nejad; Hossain Rahimpour-Bonab; Seyyed Ali Aghanabati
Abstract
Permo- Triassic subsurface section at Lavan 3 Well in Lavan Gas Field exhibits a 85 m-thick succession of limy dolostone and dolomitic limestone bearing anhydrite in the upper Dalan Formation, as well as a 154 m-thick succession of limy dolostone and dolostone with anhydrite ...
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Permo- Triassic subsurface section at Lavan 3 Well in Lavan Gas Field exhibits a 85 m-thick succession of limy dolostone and dolomitic limestone bearing anhydrite in the upper Dalan Formation, as well as a 154 m-thick succession of limy dolostone and dolostone with anhydrite intercalations in Kangan Formation. In the present study, 116 species belonging to 55 foraminifera genera were identified which were divided into two biozones, namely Charliella altineri- Paraglobivalvulina mira- Dagmarita chanackchiensis Assemblage zone (Dzhulfian in age) and Claraia aurita- Spirorbis phlyctaena Assemblage zone (Anisian in age). Nine primary microfacies were identified in the upper Dalan Formation, while, 13 microfacies were detected in Kangan Formation, together with different sub-environments (sabkha, tidal flat, lagoon, submarine ridge, and open marine) which were found to be deposited in a shallow marine carbonate platform in the form of a homoclinal ramp. Based on microfacies changes, aggradational, progradational and retrogradational stacking patterns of deposits and by conformation with the Gama-ray log, these strata could be divided into a couple of third-order sedimentary sequences for the upper Dalan Formation, as well as a couple of third-orders for the Kangan Formation, including two system tracts (TST and HST). On a global scale, the findings are comparable to the upper part of the Absaroka supersequence.
E. Zarei; E. Ghasemi-Nejad; A. Dehbozorgi
Abstract
The Gurpi Formation was studied from different aspects at two sections, Farhadabad and Kavar, in southwest and southeast of Ilam where it is composed of 205 m and 158 m of grey to blue marl and shale beds and occasionally thin beds of argillaceous limestones with two formal members of Seymareh (Lopha) ...
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The Gurpi Formation was studied from different aspects at two sections, Farhadabad and Kavar, in southwest and southeast of Ilam where it is composed of 205 m and 158 m of grey to blue marl and shale beds and occasionally thin beds of argillaceous limestones with two formal members of Seymareh (Lopha) and Emam-Hassan. In order to reconstruct paleoclimate during depositional course of the formation, paleontological and palynological data (ratio of specialist to generalist foraminifera (e.s/e.g) and warm-temperate waters dinocysts and spore and pollen grains) were used statistically. The results show that the Gurpi Formation is mainly deposited in a warm-humid climate with two sharp decreases happening in temperature in early Maastrichtian and Danian.
M.H Kazemzadeh; E Ghasemi-Nejad; H Vaziri-Moghaddam
Abstract
The Sarvak Formation in Well AZ 354 of Ahwaz Oil Field attains a thickness of 1712 meters and contains creamy to white and occasionally gray limestone. The recorded foraminifera indicate upper Albian to lower Turonian age for this formation. In order to study paleobathymetry and sea level changes during ...
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The Sarvak Formation in Well AZ 354 of Ahwaz Oil Field attains a thickness of 1712 meters and contains creamy to white and occasionally gray limestone. The recorded foraminifera indicate upper Albian to lower Turonian age for this formation. In order to study paleobathymetry and sea level changes during depositional course of the formation, three common methods were used: in the first method, the absolute number of benthic foraminifera and percentage of Hyaline, Agglutinate and Porcelaneous tests and their ratio were determined. In the second method, the ratio of Planktonic foraminifera to Epifaunal benthic foraminifera was determined via using Van der Zwaan equation, Depth= e (3.58718+(0.03534×%P), the obtained average depth was 130 meters for the most parts of the formation. In the third method, the morphotypes of planktonic foraminifera were used for determination of depth. Based on this method for the lower and middle parts, first and second morphotype groups (shallow areas indices) are abundant, showing a shallow sea. For the upper part the third morphotype groups (deeper areas indices) are abundant, indicating an open marine environment. The results showed that generally, the major parts of the Sarvak Formation has been deposited in a neritic environment and in the upper parts, depositional environment turned into a deeper one and reached the upper bathyal depths (340 m).
J Rabbani; E Ghasemi-Nejad; A.R Ashouri; M Vahidinia
Abstract
The basal unit of the Pabdeh Formation at Bisheh-Deraz section composes of 47m purple to green to grey shale and marl. These beds gradually change to shale and argillaceous limestone in the top of the section. In order to study paleoecology and paleoenvironment of these beds, palynological evidences ...
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The basal unit of the Pabdeh Formation at Bisheh-Deraz section composes of 47m purple to green to grey shale and marl. These beds gradually change to shale and argillaceous limestone in the top of the section. In order to study paleoecology and paleoenvironment of these beds, palynological evidences including palynofacies, abundance and diversity of dinocysts and environmental index have been investigated. Four Palynofacies types including IV: shelf to basin transition, VII-VIII: distal dysoxic-anoxic shelf, IX: distal suboxic-anoxic basin) have been differentiated that propose a distal suboxic-anoxic basin as depositional setting. According to the microfacies of planktonic foraminiferal Wakestone/Packestone a deep environment is proposed as the depositional basin. Using such parameters as palynofacies evidences, C/PPC ratio, AOM/MP ratio, abundance and diversity of dinocysts and environmental index, three system tracts related to one sequence (3rdorder) with one sequence boundary type 2 and one maximum flooding surface have been determined. In general, the factors all together show a deepening upward trend through this rock unit.
Z. Boroumand; E. Ghasemi- Nejad; M. R. Majidifard
Abstract
The Dalichai Formation at Talu section, 24 kilometers NE of Damghan is studied Palynologically. The Middle Jurassic sediments with a thickness of 168 meters in this section contain grey to green marl and grey marly limestone. A total of 35 samples were collected systematically and 200 palynological sildes ...
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The Dalichai Formation at Talu section, 24 kilometers NE of Damghan is studied Palynologically. The Middle Jurassic sediments with a thickness of 168 meters in this section contain grey to green marl and grey marly limestone. A total of 35 samples were collected systematically and 200 palynological sildes were prepared. Forty nine species of dinoflagellate cysts belonging to 30 genera were identified. A few fungal spores and foraminiferal test lining and spores and pollen grain were also recorded. Although, dinoflagellate species are abundant but all the species recorded were concentrated in lower parts of the section (0-110 meters). Two palynozones were identified; Cribroperidinium crispum Total Range Palynozone (Ccr), Dichadogonyaulax sellwoodii Interval palynozone (Dse). A local palynozoneof Ctenidodinium combazii/Ctenidodinium ornatum ornatum Acme Zone were also established in the succession. An age of Bajocian – Late Callovian was proposed for the succession studied.
E. Ghasemi-Nejad; M., Asadi; M. Shahmoradi; A. Aghanabati; T. Mohtat
Abstract
The Nayband Formation was sampled at Chal-Sefid and Zard mountains in central Iran, for palynology and palynostratigraphy in order to take the advantage of dinoflagellate cysts to locate the Triassic and so called Jurassic boundary. The Chal-Sefid section is located about 45 km southwest of Kashan city ...
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The Nayband Formation was sampled at Chal-Sefid and Zard mountains in central Iran, for palynology and palynostratigraphy in order to take the advantage of dinoflagellate cysts to locate the Triassic and so called Jurassic boundary. The Chal-Sefid section is located about 45 km southwest of Kashan city and Zard Mountain some 70 km northeast of Esfahan. The studied strata attain a thickness of 1750 meters in Chal-Sefid and 1820 meters in Zard Mountain. They consists sandstone and shale beds. Totally 75 samples from Chal-Sefid and 22 samples from Zard Mountain were collected and treated in the Palynology laboratory of the Geological Survey of Iran. The recorded dinoflagellate cyst species were differentiated in four palynozones in Chal-Sefid and two palynozones in Zard Mountain as follows: Chal-Sefid section: Palynozone 1: Rhaetogonyaulax wigginsii, encompasses 160 meters of the section, suggesting an early to middle Norian age. Palynozone 2: Suessia listeri with a thickness of 140 meters, suggesting a middle Norian age. Palynozone 3: Hebecysta balmei encompasses 550 meters of the section, suggesting middle to late Norian age. Palynozone 4: Rhaetogonyaulax rhaetica with a thickneses of 900 meters suggests an early to middle Rhaetian age. Zard Mountain section: Palynozone 1: Hebecysta balmei, encompasses 442 meters of the section, suggesting a middle to late Norian age. Palynozone 2: Raetogonyaulax rhaetica, encompasses 491 meters of the section, suggesting an early to middle Rhaetian age. It is revealed that all the rock units investigated here are of late Triassic age and no evidence of Jurassic ages was identified.
M. Asgharian Rostami; E. Ghasemi-Nejad; M. Shafiee Ardestani
Abstract
At this research are studied late cretaceous sediments at Ziarat-kola section, Central Alborz, in order to Palaeobathymetry and sea level change. These sediments are with about 200m thickness consist of monotonous Marl and limy marl. Based on Planktonic foraminifera gain Upper Maastrichtian stage (Abathomphalus ...
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At this research are studied late cretaceous sediments at Ziarat-kola section, Central Alborz, in order to Palaeobathymetry and sea level change. These sediments are with about 200m thickness consist of monotonous Marl and limy marl. Based on Planktonic foraminifera gain Upper Maastrichtian stage (Abathomphalus mayaroensis zone). In order toPalaeobathymetry and sea level change used to three methods common consisting of morphotype Planktonic foraminifera, ratio Planktonic foraminifera to benthic foraminifera and assigning genus and benthic foraminifera species. With morphotype analysis was indicated that third morphotype which are more deep index increase at the initial part and first morphotype that are shallow index increasing at middle section. In this manner, depth change was examinated to use two genus, Globotruncana (deep dweller) and Pseudoguembelina (Mixed layer dweller). In orther to assign paleodepth at this area used to Planktonic foraminifera to total foraminifera minus infaunal Benthic foraminifera and the regression equation [Depth = e (3. 58718 + (0. 03534 × %*p)].examination genus and Benthic foraminifera species depth index and such results gain at above method were indicating that this sediments in upper bathyal and middle bathyal. Thus, results indicate that beginning and end of are deeper from middle section.
M. Asgharian rostami; E. Ghasemi-Nejad; M. Shafiee ardestani; B. Balmaki
Abstract
In order to studying salinity and biostratigraphy in Central Alborz basin, two sections Jorband and Ziarat-kola are sampled and studied Planktonic foraminifera and Echinoids fossil. Studying of foraminifera In Ziarat-Kola section determining three biozone by planktonic foraminifera. 1: Racemiguembelina ...
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In order to studying salinity and biostratigraphy in Central Alborz basin, two sections Jorband and Ziarat-kola are sampled and studied Planktonic foraminifera and Echinoids fossil. Studying of foraminifera In Ziarat-Kola section determining three biozone by planktonic foraminifera. 1: Racemiguembelina fructicosa Interval zone 2:Pseudoguembelina hariaensis Interval zone 3: Pseudoguembelina palpebra Interval zone.that showing late maastrichtian. As well, at Jorband section assigning three biozone by Planktonic foraminifera 1: Contusotruncana contusa Interval zone, 2: Planoglobulina brazoensis Partial range zone, 3- Racemiguembelina fructicosa Interval zone. That showing maastrichtian. Likewise, in order to determining Paleosalinity select two sections at Jorband and Ziarat-Kola. Main object assigning Paleosalinity confirm sensitive Rugoglobigerina to changes of salinity. At former section used from excessive changes of Echinocorys and in later one used from ratio of kinds Foraminifera tests (Porcelaneous, Agglutinate and Hyaline). In middle parts of Ziarat-Kola section, percentage of porcelaneous tests was more than basal and upper ones. In middle parts of Jorband section salinity was less than basal and upper ones that examined by abundancy of the genus of Echinocorys. Physiological changes of body in this echinoderm also justify salinity changes throughout Jorband section. According to Whitenella is ancestor of Rugoglobigerina and also sensitive to salinity, it is possible that Rugoglobigerina show characteristic of its ancestor that justify by studying of salinity changes in two section of Central Alborz.
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.
E. Ghasemi-Nejad; & Z. Rezaei
Abstract
The Ab-Talkh Formation (Campanian- Maastrichtian) is one of the lithostratigraphic units of the Kopeh-Dagh sedimentary basin. So far no high resolution sequence stratigraphy has been done on this formation. In this study, we use the fossil evidences to analyse the formation in the sequence stratigraphy ...
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The Ab-Talkh Formation (Campanian- Maastrichtian) is one of the lithostratigraphic units of the Kopeh-Dagh sedimentary basin. So far no high resolution sequence stratigraphy has been done on this formation. In this study, we use the fossil evidences to analyse the formation in the sequence stratigraphy framework. For this purpose, after field studies 39 samples were collected and processed for palynology and palynofacies studies. Accordingly three palynofacies(V:Distal shelf , Ш:Proximal shelf , Π:Marginal shelf) determined. Based on changes in percentages of the three majour constituents of organic matter, the palynofacies and correlation of all data, three second-order sequences were differentiated. Abundance of warm water dinocysts, presence of fungal spores and the ratio of Peridinioids / Gonyaulacoids indicate dominance of warm climate during depositional course of the Ab-Talkh Formation.