Mohammad Parandavar; A Mahanipur; S. A Aghanabati; S. A. Hoseini
Abstract
In this study the upper part of Gurpi Formation and the lower part of Pabdeh Formation have been investigated with regard to the calcareous nannofossils. The thinkness of the studied section is about 127 meter and it consists of Marls, gray-green shales and purple shales. 50 genus and 101 species ...
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In this study the upper part of Gurpi Formation and the lower part of Pabdeh Formation have been investigated with regard to the calcareous nannofossils. The thinkness of the studied section is about 127 meter and it consists of Marls, gray-green shales and purple shales. 50 genus and 101 species of calcareous nannofossils have been recognised in the studied section. According to the index genus and species in the studied interval, calcareous nannofossil biozones CC25-CC26 have been recognized at the cretaceous sediments and NP1-NP5 and NTp1-NTp9 biozones have been determined at the Paleocene sediments that NP1-Np4 and NTp1-NTp7A biozones are reported for the first time from the upper part of Gurpi Formation at the studied section. With regard to these biozones, the age of the upper part of Gurpi Formation in the studied section is late Maastrichtian- late Danian (late early Paleocene) and the age of Pabdeh Formation is started from early late Paleocene. According to the nannofossil data, the K/Pg boundary is continuous and is located at the upper part of Gurpi Formation. The K/Pg boundary is marked by a decrease in abundance of Cretaceous species, increase in the abundance of Thoracosphaera operculata and the appearance of the new-Paleocene taxa. In the Danian sediments the Cretaceous species are present along with Paleocene species continuously and with a good preservation that can be considered as surviving species that may have passed the boundary and are present at the Danian sediments.
S. Senemari; Sh. Hasanpour
Abstract
Calcareous Nannofossils are good tool for biostratigraphy, especially in the Late Cretaceous. With respect to this and due to the lack of any precise paleontological study, the calcareous nannofossils of Ilam and Gurpi Formations were investigated in the Southwestern Sarvestan. These Formations consists ...
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Calcareous Nannofossils are good tool for biostratigraphy, especially in the Late Cretaceous. With respect to this and due to the lack of any precise paleontological study, the calcareous nannofossils of Ilam and Gurpi Formations were investigated in the Southwestern Sarvestan. These Formations consists of marl, clay limestone and shale. In this study, for the first time, 14 families, 22 genera and 39 species of nannofossils were identified. Based on the information obtained on nannofossils, the section is aged at Late Coniacian-Early Santonian to Early Maastrichtian corresponding to CC14-CC24 zones (Sissingh, 1977).
M. Azizi; S. Senemari
Abstract
Using calcareous nannofossils is a powerful way for biozonation in sub-stage level, especially in the Late Cretaceous and Cenozoic, because they are planktonic, cosmopolitan, abundant and have very short age. Considering lack of any precise paleontological studies about the Gurpi Formation in the NW ...
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Using calcareous nannofossils is a powerful way for biozonation in sub-stage level, especially in the Late Cretaceous and Cenozoic, because they are planktonic, cosmopolitan, abundant and have very short age. Considering lack of any precise paleontological studies about the Gurpi Formation in the NW of shiraz (Bavan), nannofossils chose to investigate. This Formation consists of shale, marl and limestone. In this study, 23 genera and 46 species of nannofossils were identified. According to the identified marker species, 14 biozones were diagnosed that classified as CC14-CC26 and NP1(Base of the Pabdeh Formation). According to these biozones, it has been suggested that this section is aged of the Gurpi Formation from Early Santonian to Danian. The existence of CC26-NP1 zonal marker species of the K/T boundary has been considered which indicates continuous sedimentation from the Late Cretaceous to Early Paleocene.
N. Ranjkesh; Bahaedin Hamdi Hamdi
Abstract
The Mobarak Formation with 347.5 m, thickness is well exposed in Valyabad section , at the Karaj - Chalus road . The lower contact with underlying Laloon Formation is disconformable ,whereas stratigraphic relation to the overlying Dozdeband formation is transitional. According to the lithological ...
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The Mobarak Formation with 347.5 m, thickness is well exposed in Valyabad section , at the Karaj - Chalus road . The lower contact with underlying Laloon Formation is disconformable ,whereas stratigraphic relation to the overlying Dozdeband formation is transitional. According to the lithological character, the studied section can be subdivided into rock units . The lower part of the fm. consist of dark- gray to black limestone as well as marly limestone, while upper part consist mainly of sandy limestone with interbeds of marlstone. According to the microfossil investigation 14 genius and species have been recognized which leads 2 conodont biozones . The both conodont biozones correspond to the international standard conodont biozonation which suggest an Early Tournisian to Middle Visean time interval . in addition , a Namurian age is suggested for deposites of informal Dozdeband formation , based on foraminifers . Received conodont bizones are as :
Neopriniodus peracutus - Polygnathus longiposticus Assemblage- Zone
Hibbardella roundya - Gnathodus girtyi Assemblage- Zone
More over , 5 Holotorian species as well as 6 genuse ,72 species Foraminifers in form of 5 biozone have been distinguished. These biozones are as :
Eotuberitina retligener - Endothyra spirilloformis Assemblage- Zone
Archaediscus permodiscus - Archaediscus(Paraarchaediscus)mixtus Assemblage- Zone
Endostaffella parva - Brunsina pulchera Assemblage- Zone
Tuberitina bulbacea - Kammaena sp. Barren Interval Zone
Lipinella notata - Archaediscus planoarchaediscus Assemblage- Zone
The studied foraminifers support the given age . Conodonts the Color Alteration Index(CAI) correspond 190 to 300 C◦ which indicate dry gas stage or empty of any hydrocarbon.
J. Daneshian; D, Baghbani; S.A. Aghanabati; N. Norouzi
Abstract
Oligocene-Lower Miocene sediments at Nareh section, situated in SW Jahrum consists of limestone, argillaceous limestone, marl and evaporatic sediments with a rich association of planktonic and benthonic foraminifera. In lower part of this succession, the Pabdeh sediments with a thickness of 115m is composed ...
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Oligocene-Lower Miocene sediments at Nareh section, situated in SW Jahrum consists of limestone, argillaceous limestone, marl and evaporatic sediments with a rich association of planktonic and benthonic foraminifera. In lower part of this succession, the Pabdeh sediments with a thickness of 115m is composed of shale, marl and intercalations of argillaceous limestone. The mentioned sediments continue through Late Eocene to Oligocene, which are overlain conformably by the Asmari Formation. The Asmari Formation consists of 250 m limestone and argillaceous limestone of which 210 m belongs to the lower Asmari and 40 m to middle Asmari. Argillaceous limestone and evaporatic-marly sediments of the Gachsaran Formation are overlain by the Asmari Formation. The Gachsaran Formation with a thickness of 510m is composed of three members of Chehel, Champeh and Moll. Pure and thick basal limestones of the Mishan Formation (Guri Member) with a thickness of 302 m, is situated above the Gachsaran Formation. Finally, Bakhtyari conglomerate lies uncomformably over the Mishan Formation. Variety of studied rock units in this section has caused different sedimentary environments, different facies and presence of abundant planktonic and benthonic foraminifera. By studying 203 samples including 193 hard and 10 washed samples, 34 genera and 47 species of benthonic foraminifera and 8 genera and 13 species of planktonic foraminifera, algae, briozoa and different macrofossils fragments were identified. Based on foraminiferal assemblages, the age of the lower part of the Pabdeh Formation is Late Eocene (Priabonian) and the upper part is Early Oligocene and the Asmari Formation is Oligocene (Late Rupelian-Chattian) to Early Miocene (Aquitanian). Also, the Gachsaran Formation belongs to Early Miocene (Aquitanian-Burdigalian) and the age of the Mishan Formation (Guri Member) is Late Miocene (Burdigalian) .On the basis of recognized foraminifera association, Nareh stratigraphical section can be correlated with first to fourth Biozones of biozonation of Adams and Bourgeois (1967) and 54,57,59,61,63 and 64 Biozones of Wynd (1965).
K. Seyed Emami; N. Behfar; M. R. Majidifard; A. Behfar
Abstract
Middle Jurassic strata are well developed northeast of Damghan (E Alborz). At the study section the Dalichai Formation has a maximum thickness of 156 m, consisting of an alternation of bluish-grey limestones and marls, being subdivided into 4 members. The lower boundary with the siliciclastics of the ...
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Middle Jurassic strata are well developed northeast of Damghan (E Alborz). At the study section the Dalichai Formation has a maximum thickness of 156 m, consisting of an alternation of bluish-grey limestones and marls, being subdivided into 4 members. The lower boundary with the siliciclastics of the underlying Shemshak Formation is unconformity, due to the Mid-Cimmerian tectonic event, whereas the upper boundary with the light and cliff-forming carbonates of the Lar Formation is gradational. The Dalichai Formation at the study section is very fossiliferous. Summing up 1750 fossil specimens were collected, among which the ammonoids with 1491 specimens clearly predominate. Altogether 27 genera, 33 species of ammonites, belonging to 6 biozones (Parkinsoni Zone, Zigzag-Aurigerus zones, Subcontractus Zone, Bullatus-Gracilis zones, Anceps-Coronatum zones, Athleta Zone) has been recognized. In addition 17 genera and 8 species of planktonic and benthic foraminifers are described.These can be divided into 2 biozones. The fossil-content is mainly concentrated within few meters of red and nodular limestone in the upper part of the section. Based on the ammonite fauna the age of the Dalichai Formation in the investigated area ranges from Upper Bajocian to Oxfordian. Paleobigeographically the fauna shows close relationship to western Europe and Sub-Mediterranean region. This indicates a paleogeographic position of the area at the northern Tethys during the Middle-Upper Jurassic.
Kh. Khosrotehrani; D. Baghbani; F. Keshani; M. Omrani
Abstract
In order to study Biostratigraphy of Cenomanian – Late Campanian deposits (upper part of Sarvak Fm.,Ilam Fm. and lower part of Gurpi Fm.), kuhe Assaluyeh stratigraphic section selected. Sediments of this interval consist of limestone, argillaceous limestone and marl with thickness of 162 m. In ...
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In order to study Biostratigraphy of Cenomanian – Late Campanian deposits (upper part of Sarvak Fm.,Ilam Fm. and lower part of Gurpi Fm.), kuhe Assaluyeh stratigraphic section selected. Sediments of this interval consist of limestone, argillaceous limestone and marl with thickness of 162 m. In this section Ilam Fm. in age of Santonian overlies Sarvak Fm. disconformably and is underlain by Gurpi Fm. conformably. By micropaleontological study on 55 thin sections, 5 genus and 9 species of planktonic and 16 genus and 13 species of benthic foraminifers were identified. Among distinguished foraminifers, Rotaliidae family forms were studied carefully and revised. It should be mentioned that, 5 genus and 6 species of benthic foraminifers (Rotaliid forms) were recognized in Iran for the first time (in Assaluyeh section) which consist of: Rotorbinella mesogeensis,Rotorbinella campaniola,Iberorotalia reicheli,Calcarinella schaubi, Pararotalia tuberculifera and Pyrenerotalia longifolia. Santonian age was determined for Ilam Fm. by identified foraminifers. In studied section, stratigraphy development of benthic foraminifers was compared by Martinez Biozones Martinez (2007). This biozones were presented on the base of Rotaliid forms for Pyrenees area in Spain. By this comparison, four biostratigraphy zones for upper part of Sarvak and Ilam Fm. are suggested.
R. Shabanian
Abstract
The Permian sequences of Aru and Bibishahrbanoo sections comprise the Dorud, Ruteh and Nesen formations respectively. A precise dating of the formations was provided based on the analysis of smaller foraminifers and fusulinid assemblages. The clastic Dorud Formation refered to Asselian and Sakmarian ...
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The Permian sequences of Aru and Bibishahrbanoo sections comprise the Dorud, Ruteh and Nesen formations respectively. A precise dating of the formations was provided based on the analysis of smaller foraminifers and fusulinid assemblages. The clastic Dorud Formation refered to Asselian and Sakmarian stages. The platform limestone of Ruteh Formation corresponds to Kubergandian – Murgabian stages. The Laterite and Bauxite horizon in the studied area attributed to Midian and finally, the uppermost beds of Permian in Bibisharbanoo corresponds to Early Dzhzulfian, based on the proposed of international subcommission on Permian stratigraphy concerning Tethyian stage bourdaries. Biolithic limestones of Ruteh Formation lying transgressively and disconformably on the underlying clastic and continental Dorud Formation with a great hiatus consists of Yachtashian and Bolorian stages. In both stratigraphical sections, thin vermiculate and oolithic limestone of Elika formation belonge to Early to Middle Triassic lying disconformably on the Permian sequence with hiatus. The hiatus between Permian and Triassic in Aru comprise Dzhulfian and Dorashamian stages and in Bibi Shahrbanoo stratigraphical section include Late Dzhulfian and Dorashamian stages. In this study 45 species belonging to 40 genus related to fusulinid families, smaller foraminifers and calcareous algae were recognized.
H. Gholamalian; S. M. Hosseini-Nezhad; Z. Khosravi; I. Turkzadeh Mahani
Abstract
Bahram Formation equivalent sequence in the Baghin area spans late Givetian to late Frasnian age. Thirty-two species and subspecies are identified. Ancyrodella alata, An. pristina, Polygnathus aspelundi, P. aequalis, P. subincompletus,P. politus, Icriodus alternatus alternatus, I. iowaensis iowaensis ...
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Bahram Formation equivalent sequence in the Baghin area spans late Givetian to late Frasnian age. Thirty-two species and subspecies are identified. Ancyrodella alata, An. pristina, Polygnathus aspelundi, P. aequalis, P. subincompletus,P. politus, Icriodus alternatus alternatus, I. iowaensis iowaensis are of important species. The presence of An. pristina and An. alata in the lower part of Bahram Formation in this section shows the late Givetian marine transgression. Five conodont biozones are recognized on the basis of stratigraphic ranges of species: Lower to Upper falsiovalis zones; transitans to punctata zones; Lower hassi to jamieae zones; Lower rhenana Zone; and Upper rhenana to ?linguiformis zones.
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.
J. Daneshian; D. Baghbani; Kh. Khosrow- Tehrani; L. Fazli
Abstract
In this study, foraminifera of the Ilam and Gurpi Formations, from Kuh-e- Assaluyeh section in east Kangan port in Boushehr province and Ivan well in Persian Gulf are investigated. Ilam Formation in Kuh-e-Assaluyeh section with 30 meter thickness and Ivan well with 68 meter thickness composed of limestone ...
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In this study, foraminifera of the Ilam and Gurpi Formations, from Kuh-e- Assaluyeh section in east Kangan port in Boushehr province and Ivan well in Persian Gulf are investigated. Ilam Formation in Kuh-e-Assaluyeh section with 30 meter thickness and Ivan well with 68 meter thickness composed of limestone and dolomitic limestone. The Ilam Formation in the study sections overlies unconformable the Sarvak Formation and underlies the Gurpi Formation. The Gurpi Formation in Kuh-e-Assaluyeh with 73 meter thickness and Ivan well with 56 meter thickness composed of argillaceous limestone, sandy limestone, shale and limestone. Also the Gurpi Formation in Kuh-e-Assaluyeh section and Ivan well overlies unconformable the Ilam Formation and underlies the Pabdeh Formation. The study of 70 samples from the examined section led to the identification of 13 genera and 19 species of planktonic foraminifera and 12 genera and 12 species of benthonic foraminifera. Planktonic foraminifera are as follow: Heterohelix globolusa, Macroglobigerinelloides ultramicrus, Globotruncanita elevata, Globotruncana bulloides, Globotruncana ventricosa, Muricohedbergella holmdelensis, Heterohelix striata, Macroglobigerinelloides prairiehillensis, Contusotruncana fornicata, spiropelecta sp., Rugoglobigerina rugosa Macroglobigerinelloides bollii, Muricohedbergella monmouthensis, Globotruncana falsostuarti, Gansserina gansseri, Archaeoglobigerina blowi, Globotruncana arca, Contusotruncana contusa, and benthonic foraminifera are as follow : Rotalia sp., Rotalia skourensis, Pseudedomia sp., Minouxia sp., Dicyclina schlumbergeri, Quinqueloculina sp., Marssonella sp., Gavelinela sp., Archaecyclus midorientalis, Ammobaculites sp. On the basis of stratigraphic distribution of index foraminifera, the Ilam Formation belongs to Santonian to Campanian, and the Gurpi Formation in Kuh-e-Assaluyeh section is Campanian to Maastrichtian and in Ivan well is Maastrichtian in age. The studies in Kuh-e-Assaluyeh section let to recognition four foraminifera zone from base to top: Globotruncanita elevata Zone, Globotruncana ventricosa Zone, Globotruncana falsostuarti Zone, Gansserina gansseri Zone. Lacking the main elements of Globotruncanella havanensis and Globotruncana aegyptiaca biozones caused that Globotruncana falsostuarti biozone is introduced on the basis of the first occurances of Globotruncana falsostuarti (at the base) and Gansserina gansseri (at the top). Also in Ivan well, Globotruncana falsostuarti Zone, Gansserina gansseri Zone, Contusotruncana contusa Zone were identified. Abathomphalus mayaroensis in absent at Ivan well and Kuh-e-Assaluyeh. Thus, Abathomphalus mayaroensis biozone is not recognizable, and instead of it Contusoutruncana contusa biozone is introduced. The boundaries of this biozone are identified by the first and last occurrences of Contusoutruncana contuse. Also comparison this study with Biozonation of Wynd, (1965), from base to top: 1-Rotalia sp. 22, Algae assemblage zone, 2- Archaecyclus midorientalis-Pseudedomia sp.assemblage zone, 3- Globotruncanita elevata zone, 4- Globotruncanita stuarti-Pseudotextularia variance assemblage zone. 5- Contusoutruncana contusa zone.
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.
M. Shams; K. Seyed-Emami
Abstract
The Dalichai Formation and its ammonite fauna is studied for the first time in the Parvar area, Central Alborz. At Parvar the Dalichai Formation, with a thickness of about 70 m, consist of an alternation of grayish silty marls, marlstones, marly limestone and limestone and is subdivided into 5 members. ...
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The Dalichai Formation and its ammonite fauna is studied for the first time in the Parvar area, Central Alborz. At Parvar the Dalichai Formation, with a thickness of about 70 m, consist of an alternation of grayish silty marls, marlstones, marly limestone and limestone and is subdivided into 5 members. A rich ammonite fauna (407 specimens) have been collected from the member 4 and 5, comprising the following families: Phylloceratidae, Lytoceratidae, Oppeliidae, Haploceratidae, Sphaeroceratidae, Parkinsoniidae, Morphoceratidae and Perisphinctidae. These indicate a Late Bajocian and Bathonian age. Member five consists of greenish to reddish, nodular and flaggy limestones and is a typical condensed horizon.
R. Shabanian; M. Parvanehne-Nezhad Shirazi; F. Javadinia
Abstract
The detailed stratigraphical and lithological analysis of the Permian sequence in north Marand, NW of Iran at Harzand village has been studied . At this locating the Permian sequence consist of Dorud (82 m..) Surmaq (258 m..) and Julfa (108 m.) formations respectively. The main lithology consist ...
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The detailed stratigraphical and lithological analysis of the Permian sequence in north Marand, NW of Iran at Harzand village has been studied . At this locating the Permian sequence consist of Dorud (82 m..) Surmaq (258 m..) and Julfa (108 m.) formations respectively. The main lithology consist of white to red sandstone, grey to dark, biogenetic limestone , marly limestone and thin bedded limestone. The lower boundary is non conformity, so that the Permian sequence is underlying a thick extrusive igneous rocks and at the top, a sequence of Miocene red clastic deposit covers the Permian sequence with disconformably. In this study 52 foraminiferal species belonging to 37 genus and 8 species of 9 Algal genus were recognized and 4 assemblages biozones in Surmaq and Julfa formations have identified. Based on fossils assemblages , the age of the Surmaq formations is Kubergandian - Murgabian (Middle Permian) and the age of Julfa formation is Middian - Early Dzhufian Stages(Late middle –Early late Permian).
A. Ghaderi; A. Aghanabati; B. Hamdi; A. Saeedi
Abstract
To study the Shirgesht Formation biostratigraphy in Kalmard Horst in relation to its conodont content, the Miyugodar (Miangodar) stratigraphic section was selected which is located in southwest of Tabas city. The Shirgesht Formation in the mentioned section is mainly composed of siliciclastic rock units ...
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To study the Shirgesht Formation biostratigraphy in Kalmard Horst in relation to its conodont content, the Miyugodar (Miangodar) stratigraphic section was selected which is located in southwest of Tabas city. The Shirgesht Formation in the mentioned section is mainly composed of siliciclastic rock units and overlay unconformably on Kalmard Formation (attributed to Pre-Cambrian) and is overlain by Gachal Formation (Carboniferous). Thirty five rock samples were selected from appropriate rock units (Shirgesht and Gachal Formation). Samples were studied in laboratory for more details. According to the extracted conodont from Shirgesht Formation in Miyugodar section, the age of this formation can be regarded as Early Ordovician (Tremadocian – Arenigian). Three conodont assemblage zones were recognized in Early Ordovician units. They are: Cordylodus spp., Deltifer and Proteus Global Standard Conodont biozones. The recognized biozones are as followed:
1- Oneotodus - Drepanodus Assemblage Zone
2- Acodus deltatus - Protopanderodus Assemblage Zone
3- Acodus - Oistodus Assemblage Zone
A. Ghaderi; A. Aghanabati; B. Hamdi; J. F. Miller
Abstract
The Shirgesht Formation is one of the fossiliferous units of Central Iran which in the type section is defined (informally) in the terms of 3 members. This formation is mainly composed of limestone, marl, siltstone, shale and dolomite, conformably overlay on the upper part of the Derenjal Formation with ...
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The Shirgesht Formation is one of the fossiliferous units of Central Iran which in the type section is defined (informally) in the terms of 3 members. This formation is mainly composed of limestone, marl, siltstone, shale and dolomite, conformably overlay on the upper part of the Derenjal Formation with a gradual contact, composed of brachiopods limestone bearing (Billingsella limestone). The Shirgesht Formation is overlain by sandy limestone and volcanic rocks of the Niur Formation.
To do biostratigraphy studies on the first and second members of Shirgesht Formation in the type section, totally 99 rock samples were selected. The conodont fauna of lower part of its first member contain some species of Westergaardodina, Furnishina and prooneotodus which show an age of late Cambrian. Several species of Cordylodus, Oistodus, Drepanodus, Proconodontus and Paroistodus in distance of middle part of the lower member to the end of the second member represent an age of Tremadocian – Arenigian. According to conodont content of the first and second members of Shirgesht Formation, 7 conodont assemblage zones were determined in the type section which show an age of Late Cambrian – Early Ordovician. The recognized biozones are as follow:
1. Furnishina - Westergaardodina Assemblage Zone.
2. Proconodontus - Oneotodus Assemblage Zone.
3. Cordylodus proavus - Cordylodus oklahomensis Assemblage Zone.
4. Cordylodus lindstromi Assemblage Zone.
5. Cordylodus angulatus Assemblage Zone.
6. Drepanodus - Paltodus deltifer Assemblage Zone.
7.Paroistodus proteus Assemblage Zone.
The mentioned conodont assemblage zones are equivalent to Cordylodus spp., Deltiferand Proteus global standard conodont biozone. In contrast with the previous reports, the Cambrian – Ordovician boundary is located in the first member of the Shirgesht Formation. Thus, the Shirgesht Formation in type section is diachronous formation.
L. Fazli; B. Hamdi
Abstract
The Mila formation from late Early Cambrain to Early Ordovician age is well exposed in the Shahmirzad section consists of 5 lithological members. Several biozones of conodonts have been identified in this section, several taxa of body and trace fossils have been collected ...
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The Mila formation from late Early Cambrain to Early Ordovician age is well exposed in the Shahmirzad section consists of 5 lithological members. Several biozones of conodonts have been identified in this section, several taxa of body and trace fossils have been collected from members 2 – 5 of this section.
Member 1, consisting of stromotolitic dolomite, indicates at least one paleosol in the middle part. The second lithological member which includes several beds of salt peseudomorphs does not indicate any condont, while trilobites as well as trace fossils such as Rusophycus sp. and Cruziana sp. have been found frequently. These trace fossils, characteristic of cruziana ichnofacies, occur only in shallow marine environments. Eocrinoids debris and epirelief of the root of this fossil strongly supports this fact. In addition, presence of storm beds and oriented deposition of Hyolithids indicate high degree of water agitation in environment of deposition. Biozones of Conodont have been identified from members 3-5.
F. Hadavi; K. Khosrow Tehrani; S. Senemari
Abstract
Nannofossils are good for biostratigraphy, since they are abundant, planktonic, rapidly evolving and largely cosmopolitan especially in the Late Cretaceous. With respect to this reality and due to the lack of any precise paleontological study, the nannofossils of Gourpi Formation were investigated in ...
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Nannofossils are good for biostratigraphy, since they are abundant, planktonic, rapidly evolving and largely cosmopolitan especially in the Late Cretaceous. With respect to this reality and due to the lack of any precise paleontological study, the nannofossils of Gourpi Formation were investigated in the north of Gachsaran. This formation consists of marl and clay limestone.
In this study, for the first time, 23 genera and 43 species of nannofossils were identified. Based on the obtained nannofossils, the study section is Late Santonian to Late Maastrichtian in age corresponding to CC16-CC26.
F. Hadavi; A. Pouresmaeil
Abstract
Nannofossils are suitable for biostratigraphical studied since they are aboundant, planktonic, rapidly evolving and largly cosmopolitan, especially in Late Cretaceous. ...
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Nannofossils are suitable for biostratigraphical studied since they are aboundant, planktonic, rapidly evolving and largly cosmopolitan, especially in Late Cretaceous.
According to this, due to the lack of any precise Paleontological study, the nannofossils of Neyzar Formation has been investigated in type locality. This formation consists of thick- bedded glauconitic sandstone,shale and a sandy limestone bed in the upper part. The Neyzar Formation conformably overlies the Abtalkh Formation and is itself conformably overlained by the Kalat formation. As a result of this study, for the first time, 22 genera and 42 species of nannofossils have been identified. Based on these obtained nannofossils, the section is Late Maasrichtian in age, corresponding to CC25- CC26 (Sissingh,1977) (equivalent to CC25c-CC26a-b, Perch- Nielsen,1985).