جستجوی مقالات مرتبط با کلیدواژه « کنودونت » در نشریات گروه « زمین شناسی »

The Ordovician marine sedimentary sequences of Iran are located in different structural blocks along the northern margin of Gondwana. In the north of the Kerman Basin, Ordovician sedimentary sequences named Katkoyeh Formation have been introduced, which consist of 70 to 300 meters of siliceous siliceous rocks, one or two thin carbonate horizons in the upper part, and pyroclastic deposits. Traditionally, the Cambrian-Ordovician boundary in the Kerman Basin has been determined between the Hatken Dolomite Member of the Kuhbanan Formation (Late Furongian) and the Lower Shale Member of the Katkuye Formation. However, determining the location of the previous Tremadocine boundary is uncertain because no fossils have been documented from this interval. For the purpose of biostratigraphy of the Katkuye formation in Kerman basin, Gezoye section with an approximate thickness of about 170 meters was selected. In this section, the Katkoyeh Formation is located on the Hatken Dolomite Member and under the Shabjareh Formation sandstones of Silurian age. In the Gezoiye section, due to the action of basalt dikes and intense tectonics in the region, the limestone layers containing fossils have been severely altered, and during three sampling stages, 320 conodonts were recovered from the carbonate horizon of the upper part of this formation, and 3 Genus and 7 species were identified and based on this, three conodont ranges were recorded: 1) Icriodella superba Range Zone (Katian - ? Hirnantian; Late Ordovician), 2) Amorphognathus ordovicicus Range Zone (Katian - Late Ordovician), 3) Amorphognathus superbus Range Zone (Katian - ? Hirnantian; Late Ordovician). Late Ordovician age in the Katkuye formation in the Gezoye section with at least three species of the conodont genus Icriodella (I. superba, I. deflecta, (I. cf. discrete and two species of A. superbus) Amorphognathus, A. ordovicicus) determined and led to the identification of the Katian-?Hirnantian rocks.

Kale-Sardar section, is located at the vicinity of Niaz village, 15 kilometers east of Tabas town. This section consists of 80 m thick and from Late Devonian deposits as known as Shishtu formation that upper part of this section has cut by a fault by Frasnian’s deposits. The entire studied thickness is subdivided into 12 lithostratigraphic units and in order to study of conodont elements, 27 species and subspecies belonging to 7 genera were recognized, that due to these revealed conodont elements, Shishtu formation’s age in the studied section spans from Eifelian to late Frasnian. The Frasnian-Famennian bio event in studied section is located between two intervals linguiformis Zone and Lower to Middle triangularis zones which is located at the top of the dark Frasnian shales and at the base of the thin limestones of the Famennian layer. The microfacies determined in studied section are subdivided into siliciclastic-carbonate and carbonate facies, which were deposited from the shore to the deep part of the marine environment. Gradual changes in facies within stratigraphical sequence, sedimentological hiatus due to sudden change in sedimentary environment’s slope, absence of reef facies (related to Wilson’s 5th facies zone) and presence of discontinuous bioclastic barrier (existence of semi-enclosed lagoon), convey that studied sediments were deposited in a homoclinal carbonate ramp.

Sorkh Shale Formation in Rabat-e-Shur stratigraphic section, west of the Tabas Depression, has been biostratigraphically investigated in this research. The Sorkh Shale Formation, with 48 meters thickness in this section, consists of shale, marl, and marly limestones, which are underlain by the Permian Jamal Formation and are overlain by the Triassic Shotori Formation dolomites. Nine conodont species belonging to four genera, Ellisonia, Hadrodontina, Parachirognathus, and Pachycladina were identified for the first time from this formation. The mentioned conodont assemblage is divided into three biozones: Hadrodontina aequabilis, Hadrodontina anceps, and Pachycladina obliqua. These taxa are in good agreement with the previously reported euryhaline assemblages from the near-shore and shallow water Western Tethyan realms in the south and east of Europe in the Early Triassic (Late Griesbachian-Middle Smithian). These conodont biozones are used for a better understanding of the distribution and affinities of the Early Triassic conodonts in West Asia, their paleobiogeographical rank, their significant role in the Early Triassic chronostratigraphy and their importance in bio-correlation of different section worldwide. Examination of the conodont alteration index of the obtained taxa from the Sorkh Shale Formation demonstrates CAI=5 during the late Griesbachian, CAI=4 in the Smithian, and CAI=6-8 in the Dienerian substages which is placed in the barren Zone for hydrocarbon production.

Devonian deposits of the Bahram Formation with a thickness of 458 m in the Bondar section 8 km east of Chatroud city in the structural zone of Central Iran were studied based on conodont fauna. According to 44 species and subspecies have been identified and based on their stratigraphic development, ten conodont biozones can be distinguished, which indicate the middle Givetian to upper Famennian age. The middle Givetian ansatus Zone and also the late Famennian Bispathodus aculeatus aculeatus Zone determine the oldest and newest reported age and determine the widest sequence of Bahram Formation in Kerman region. The first occurrence of Ancyrodella rotundiloba pristina marks the Givetian/Frasnian boundary in Sample B11.

Devonian-Carboniferous boundary is an exciting issue for researchers all over the world. In this boundary, significant events have occurred on marine organisms (specially conodonts elements) and terrestrial organisms, consisting of weather and sea-level changes, and relative coincidence with the Hangenberg bio-event (Mc. Ghee, 1998; Sandberg et al., 2002; Caplan & Bustin, 1999; Kaiser et al., 2006, 2011, Bahrami et al., 2011, 2019; Konigshof et al., 2021; Sattari et al., 2021). According to ICS, the Devonian-Carboniferous boundary, as defined by the first Appearance Datum (FAD) of the conodont species Siphonodella sulcata within the Siphonodella praesulcata- Siphonodella sulcata lineage and the GSSP is located in the La Serre Trench E’ section in France (Paproth et al. 1991). Khoshyeilagh Formation in Zoo section consists of shallow marine deposits attributed to the Late Devonian (Frasnian-Famennin) (Najjarzadeh, 1997). This study focuses on identifying and reviewing the Devonian-Carboniferous boundary in a part of the Eastern Alborz area and study the biostratigraphy of deposits near this boundary based on conodont fauna.

58 carbonate and 11 non-carbonate samples (3-4 kg/each) were collected and processed for conodonts. The samples were processed with the conventional acetic acid technique, but formic acid 10% with 10 hours was also used for some silty samples and compacted limestones. Then picked remaining deposits with the handpicking method. The following steps include pasting the conodont specimens on stab, photographing them under an SEM microscope, and naming conodonts elements based on available references (e.g., Branson & Mehl, 1934; …). Accordingly, the biozonation of the studied sequence using the global standard zonings of Ziegler & Sandberg (1990), Sommervile (2008), Poty et al. (2006), Spalletta et al. (2017).

Khoushyeilagh and Mobarak formations Late Devonian-Carboniferous conodonts fauna of Zoo section, (NE Jajarm), led to identifying 10 conodont genera, 23 species, and 8 subspecies. The conodont faunas which be obtained in this research indicate the presence of these biozones: Bispathodus ultimus Zone (Latest Famennian), From the base of Siphonodella duplicata to within Siphonodella crenulata interval (Tournaisian), and Pseudopolygnathos multistriatus Zone (Visean). According to this study, the Fm/T boundary is located at the end of Khoushyeilagh formation, 6m above the diabase layer. The conodonts, as mentioned above, are indicators for Polygnathid biofacies. These sequences are similar to other Famennian-Tournaisian deposits in the east Alborz, both in the litho-facies and bio-facies peculiarities. The conodont Color Alteration Index in the Carboniferous conodonts element increased compared to the Late Devonian elements.

Permian sequences of Zagros and Arabiab peninsula including Dalan Formation and its equivalent, Khuff Formation, are precisely investigated in order to hydrocarbon exploration. Type section of Dalan Formation is described by Szabo & Kheradpir (1978) and composed of three members; Lower and Upper Dalan and Nar evaporite Member between them. Studied succession in the present paper is located in Gahkum anticline, southeast of High Zagros Zone, SE Iran. We should pass 134 km northward from Bandar Abbas to attain Sarchahan village and then 7.7 km eastward in order to access the section. Coordinates of section are: 28° 5' 40.5"N, 55° 55' 18.19"E.

Numerous researches have been conducted on the Dalan and Khuff formations in the Middle-East. For example, Alsharhan & Narin (1995) studied the sedimentary environment and stratigraphy of Permian sequences in the Arabian Peninsula. Angiolini et al. (1998; 2003) and Henderson & Mei (2003) studied the paleogeography and paleoclimatology of North and southeast of Oman by using conodonts. Kolodka et al. (2011) studied the biostratigraphy and microfacies of Dalan Formation. Dalan Formation in the Gahkum section with 685m thickness conformably overlie the marine uppermost beds of Faraghan Formation and can be divided to Lower and Upper Dalan Members. No sign of Nar evaporate Member is seen between them. The absence of this member may be related to lateral facies changes of evaporite to carbonate. The Upper Dalan Member is disconfomably overlain by Middle to Late Triassic dolomites of Khaneh-Kat Formation (Fakhari, 1995, Sabzehei, 1993). On the basis of foraminifer stratigraphy, Kolodka et al. (2011) proposed the age of Wordian for the base of Lower Dalan Member, and the present conodont species; Sweetognathus iranicus, Hindeodus wordensis and Merrillina divergens prove this age. On the other hand, the base of Khuff Formation (equivalent of Dalan Fm.) in the southeast and interior Oman has the age of Wordian (Angiolini et al., 1998; 2003). Conodonts are associated with microvertebrate remains such as skeletal particles, scales and teeth of paleoniscoids, hybodontiforms and osteichthyan fishes.

Conodont studies in addition to the stratigraphic situation of the base of Dalan Formation in the Gahkum section show the age of Wordian. It seems that the base of Dalan Formation is diachronous and becomes younger from the northwest to the southeast of High Zagros. The absence of Nar evaporite Member between Lower and Upper Dalan carbonate members, may be related to the lateral facies changes. This is the first report of paleoniscoid, hybodontid and osteichthyan fish remains from the Permian strata of Zagros Mountains.Acknowledgment This paper is the result of project no. 95/200/168, so we appreciate Deputy of Research and Technology, University of Hormozgan for financial supports. Authors thank M.K. Kamali and F. Amin-Nezhad who helped us in field and laboratory works.

The Kuh-e-Bande-Abdol-Hossein section, which is located southeast of Anarak, was first mentioned by Reyer and Mohafez (1970) and later examined in more detail by Sharkovski et al. (1984) and Wendt et al. (2005). We re-examined this section because it is mainly composed of sedimentary rocks ranging from Ordovician to Permian age (Hairapetian et al. 2015; Lensch and Davoudzadeh 1982). Herein we focus on the Middle to Upper Devonian strata in order to establish the biostratigraphic framework of this section by means of conodonts. We also briefly discuss the conodont biofacies of the Kuh-e-Bande-Abdol-Hossein.

The measured profile is located approximately 32 km southeast of Anarak and 180 km northeast of Isfahan (E 53° 52′ 55″ and N 33° 10′ 90″ WGS coordinates). The entire section has a thickness of approximately 1200 m. In order to improve the biostratigraphy of the Kuh-e- Bande-Abdol-Hossein section, 78 conodont samples of roughly 2 to 3 kg each were taken from the 366m of carbonates and processed by conventional methods using 10% formic acid. Washed residues were sieved and separated into three fractions, and conodonts were handpicked utilizing a microscope. Depending on the depositional facies setting, the number of conodonts per sample is highly variable, e.g., in dolostones, no conodonts were found. In contrast, in shallow-water limestones, a good number of species occurred in separate beds. A total number of 1917 conodonts were obtained from the residues, which led to the identification of 41 species and subspecies within six genera.

Based on the revealed conodont data, six conodont zones were discriminated as follow: expansus zone, subterminus zone, Upper falsiovalis to transitans zones, transitans to lower rhenana zones,upper rhenana to linguiformis zones, triangularis to termini zones. Bahram Formation at the studied profile spans late Givetian (expansus zone) to Early Famennian (triangularis to termini zones. Biofacies interpretation and conodont frequency reveal the Icriodid-Polygnathis to Polygnathid-Icriodid biofacies due to the deepening of the depositional basin. CAI interpretation also shows the variation from CAI=1/5-2 to CAI=4-4/5. The studied interval is composed of an overall shallow-water, nearshore to open marine facies setting.

This study is undertaken at the Department of Geology, Faculty of Sciences, University of Isfahan. The financial supports by the Vice-Chancellor for Research and Technology, University of Isfahan, was highly appreciated.

In this study, the paleoecology, biostratigrapgy, and biofacies of the Khoshyeilagh Formation has been evaluated based on the found conodont species. The Khoshyeilagh Formation includes terrigenous-carbonate sequences which contains conodonts of shallow environments (Icriodus Polygnathu). The identification of 7 conodont species and sub-species led to the identification of 2 conodont biozones which are Upper rhenana-linguiformis, Lower triangularis-Lower crepida, respectively and also a biofacies named as Icriodus-Polygnathus. The identified biozones prove Late Devonian (Frasnian-Fammenian) age for the studied parts of the Khoshyeilagh Formation. The determined biofacies and the recognized conodonts in the studied sections represent shallow marine environment and warm tropical climate during the deposition time. Considering to the obtained fossil assemblages and comparing with the other sedimentary basins, the studied sections belong to the northern parts of Gondwana land. The analysis of biofacies and lithofacies show a decrease of depth at the end of Frasnian which is followed by an intense sea level drop similar to global examples. After a period of time and during Fammenian, the environment became deeper and open marine sub-environments (bioclast specule wakstone-packstone) were deposited.

Anarak section in northeast Isfahan, central Iran is evaluated regarding to sedimentary environment and sequence stratigraphy. Field studies and micro-facies analysis led to the identification of 12 micro-facies related to the open marine, the shoal, the lagoon and the tidal flat environments. Micro-facieses gradual change, lack of calciturbidite and lack of expanded barrier reef indicate the deposition of a sedimentary interval in a homoclinal ramp environment. Two type 3 sequences were identified by sequence stratigraphic study. Both of these sequences are separable TST and HST packages. The age of first sequence is Late Devonian (Bahram Formation) and its thickness is 42.3 meters and the second sequence with a thickness of 70.7 meters is Late Devonian-Early Carboniferous (Upper part of Bahram Formation and Shishtu2 Formation). The sequence boundary between first and second sequences is the second type boundary due to the lack of evidence for exposure.

Devonian deposits of the Bahram Formation with a thickness of 300 m were studied based on conodont fauna in Shahzadeh Mohammad section (33 km east of Zarand, 95 km north of Kerman city) in central Iran structural Zone. According to 31 identified species and subspecies and their stratigraphic development, nine conodont biozones belonging to the middle Givetian to the lower Famennian age were identified. The presence of Polygnathus ansatus  determines the ansatus Zone and Icriodus arkonensis arkonensis, determines the age of middle Givetian for the base of the Bahram Formation, which is the oldest age determined for the base of the Bahram Formation. Based on conodont distributions and conodont biofacies, polygnathid-icrodid biofacies are the most abundant biofacies in the section, indicating the middle shelf environment for the studied deposits.

The study area is located in the zone of Central Iran based on the structural divisions of Iran. Late Devonian deposits in central Iran are widespread. The Shishtu Formation is a two-stroke stratigraphic unit that is subdivided into two sub-formations called Shishtu 1 and Shishtu 2. Below the Shishtu 1 Formation is the Late Devonian (Frasnian-Famenian) and the Shishtu 2 Formation is early Carboniferous (Tournisian-Visean). The boundary between them is marked by a horizon of black charcoal shales called the Mouse horizon. The Paleozoic and Lower Triassic sediments in the Lut Zone are essentially similar to the Shotori Mountain Formations.

Howz-e-Dorah section is located 57 km from Tabas town and 5 km from Deyhok village. After conducting library studies and selecting the appropriate shear in terms of thickness and separation of layers, the tectonic status of the area and the intended purpose by measuring layer thickness, fossil record collection, photography and sampling, extraction was conducted to extract the conodont elements.

The Shishtu Formation 1 is exposed at a thickness of 152 m in the Howz-e-Dorah section. The lower boundary of this sequence with the Bahram Formation is in disconformity with Middle Devonian and its upper boundary is in conformity with the Shishtu 2 Formation. Lithology of the Shishtu Formation 1 alternates from medium to thick bedded brown sandstones, green shales and thin bedded dolomitic white limestones, thin to thick bedded gray limestones, and highly diverse masses. It is high in conodont microfossils and macrofossils such as brachiopods, bryzoas, corals and crinoids. Notable points in this section are the presence of coral limestones, especially brachiopods, which are of late Devonian age in central Iran. The uppermost and last rock unit of the studied section is a 28 m outcrop of cephalopod horizon, outcropped as intermediate red limestone, indicating a short period of no sedimentation. Based on conodonts element studies, the sequence of late Shishtu Formation 1 to Late Devonian (Early Frasnian - Late Feminine) introduces 4 genus, 13 species, 4 subspecies with 4 conodonts biozonesThe anterior part of Shishtu 2 Formation ages back to Late Tournisian - Late Visean. 6 genus, 13 species, 4 subspecies, 13 species and 2 subspecies were identified in Howz-e-Dorah section. According to the studied conodonts elements, the sedimentary environment of the studied section is shallow and close to shore, and the conodonts species in the Shishtu 2 Formation are formed in oxygen and continental slope environments.

The study of Shishtu Formation 1 and the basal part of Shishtu Formation 2 resulted in the identification of a high diversity of conodonts in the Howz-e-Dorah section. In addition to the high diversity of conodonts, the diversity of invertebrates, especially brachiopods, has been very high. Depending on the biofacies, depth and depositional environment of the Shishtu Formation 1, due to biofacies, the environment was offshore. Also, the presence of conodonts species is characteristic of tidal environments in Shishtu 1 Formation. The base part of Shishtu 2 is formed in low oxygen environments which are common in lower continental slopes.

In this research, Ordovician conodonts obtained from the sedimentary succession of the informal Katkoyeh formation is studied in a stratigraphic section at the south of Kuh-e-Bonorg, eastern flank of Kalmard Anticline in the west of Tabas (Central Iran). The formation which is partly equivalent to the succession of the Shirgesht Formation in Tabas Block is unconformably overlaid the Kalmard Formation (attributed to the Neoproterozoic) and disconformably overlain by the Carboniferous Gachal formation. The Katkoyeh formation with 214.8 meter thickness is divided into three lithostratigraphic members including the Lower Sandstone (mostly quartzarenite to litharenite), Middle Shale (red to green shales interbedded with some dolomitic and calcareous sandstones, in laminated wavy stromatolite structure at the base) and Upper Carbonate (limestones, dolostones and marls). The section was sampled bed by bed for conodont studies so that 80 samples have been selected, however only seven of them were productive. Within the selected samples, six genera and 14 species of coniform and ramiform conodont elements are determined, a few of them are reporting for the first time from Iran. The obtained conodonts demonstrate the faunal assemblages equal to the proteus, elegans-evae and diprion Zones which confirm the age of Early Ordovician (late Tremadocian–Floian) for the studied section. The whole conodont material display a faunal affinity with the Baltoscandic and Argentina paleobiogeographic provinces.

Investigation of Silurian succession equivalent to the Niur Formation at the northwest of Robat-e-Qarebil (instantly south of Western Kopeh-Dagh), is led to introduction of lithostratigraphical units in details and identification of some Llandovery conodonts. The sampled interval in this stratigraphic section is composed of shale, fossiliferous limestone, sandstone, and dolomite with 295.5 meter thickness. With a marine volcanic rock unit at the base, this succession is conformably overlaid shales and sandstones attributed to the Ordovician system and overlain by quartzarenite and red shales of the Padeha Formation. Obtained conodonts from these sequences comprise different coniform, ramiform and pectiniform elements. Nineteen species of 10 genera belong to Aspelundia expansa Interval Zone which confirms uppermost Late Rhuddanian to Aeronian for the section. This age coincides with the ages which have already been given on the basis of brachiopods, cephalopods and palinomorphs for the same outcrops at the Western Kopeh-Dagh.

The main Paleozoic sequences of Isfahan Province cropped out in the northern part of Isfahan e. g: Soh and Natanz (Najhaf, Neqeleh, Varcamar, North Tar and west Kesheh section) (Zahedi, 1973; Adhamian, 2003, Ghobadipour et al. , 2013; Bahrami et al. , 2015); Zefreh, Chahriseh and Dizlu areas (Brice et al. , 2006; Gholamalian, 2003; Habibi et al. , 2013). Kuh-e-Kaftar section (Chahriseh area) is one of the most complete sequence of Upper Devonian deposits in north Isfahan (central Iran), which have been devoted many papers by different researchers on the fossils content of these deposits (Ghavidel-syooki, 2001; Hamedani, 1996; Brice and Kebriae, 2000; Djafarian, 2000; Mistian and Gholamalian, 2000; Mistian et al. , 2000; Yazdi et al. , 2000; Turner et al. , 2002؛ Safari and kangazian, 2003; Gholamalian, 2003, 2007; Webster et al. , 2007 and Hairapetian et al. , 2000). This paper focused on the Famennian deposits of Kuh-e-Kaaftar section to establish precise age of the lower and upper boundary of sequence, as well as the lithostratigraphic characteristics. Forty-four samples (3-4 kg each) were collected from Kuh-e-Kaftar section, the samples were processed with conventional acetic/formic acid technique. All collected samples were prolific and yielded more than 1613 conodont elements which helped in erecting the stratigraphic framework of biozonation of the Shishtu I subformation. Although the abundance of conodont elements is scarce, but the acceptable diversity and presence of Zonal index taxa let to establish the age framework of the studied interval. The state of preservation of the conodonts is generally excellent, where many specimens are complete without contamination. The color of conodonts is dark black (C. A. I. 4. 5- 5) in total elements of sampled section. All the studied conodont specimens are coded under acronym of EUIC and redeposit in the Department of Geology, University of Isfahan, I. R. Iran The studied deposits of Kuh-e-Kaftar section, which is located in southwest of Chah-riseh village 55 km northeast of Isfahan, comprises Famennian deposits equivalent to the Shishtu Formation (Shishtu I subfromation). The thickness of the studied and measured profile is about 110 meters, including 4 lithostratigraphic units (limestone, sandy limestone, marly limestone, shale and sandstone levels) including: bivalve, bryozoan, crinoids stems, brachiopod, trilobite, goniatite, conodonts and vertebrate micro-fauna. Alternation of medium bedded limestone and shale can be seen at the basal levels of the section. Basal level overlies on Frasnian stage sediments and underlines with an eroded surface (red clays) can be dated to Permian system. In order to establish the biostratigraphical framework for the Shishtu I subfromation, 44 samples were collected systematically and the examined samples contain 1613 conodont elements. Twenty conodont species and subspecies belong to eight genera have been identified as follows: Bispathodus aculeatus aculeatus, Bispathodus aculeatus plumulus, Bispathodus costatus, Bispathodus stabilis, Branmehla bohlenana, Icriodus cornutus, Icriodus sp. , Mehlina strigosa, Pandorinellina insita, Pelekysgnathus inclinatus, Polygnathus delicatulus, Polygnathus deplanatus, Polygnathus nodocostatus, Polygnathus brevilaminus, Polygnathus semicostatus, Polygnathus sp. , Neopolygnathus communis group, and Scaphignatus velifer velifer. The abundance and distribution of conodont elements as well as the sedimentary record suggest marine conditions of an inner shelf environment. The conodonts are related to the following conodont biozones as: Upper marginifera, Uppermost marginifera to Upper trachytera, Middle expansa, and Upper expansa zones. In terms of biofacies, the conodonts can be assigned to the icriodid–polygnatid, polygnatid– bispathodid and bispatodid–polygnatid biofacies. This study undertaken at the Department of Geology, Faculty of Science, University of Isfahan. The financial supports by the Vice Chancellor for Research and Technology, University of Isfahan highly appreciated.

The Cambrian- Ordovician boundary strata in the Kalat section, western Koppeh-Dagh, comprise continuous succession of fine clastic sediments, mostly argillites with some shell beds, accumulated offshore. This interval contains analmost complete succession of conodont biozones, including the Cordylodus intermedius, Cordylodus lindstromi and Cordylodus angulatus biozones. The first appearance of the planktonic graptolite Rhabdinopora cf. Flabelliformis flabelliformis (Eichwald, 1840) in black argillite of the upper part of the Cordylodus lindstromi Biozone indicates relatively precise position of the Cambrian- Ordovician boundary in the section. Cambrian- Ordovician boundary beds in the eastern Alborz Region can be subdivided into three lithological units: Furongian bioclastic limestone mainly replaced by fine clastic sediments in the upper part, the terminal Cambrian Cruziana sandstone representing a shoal complex and the Tremadocian grey argillite accumulated offshore. In this area the position of Cambrian- Ordovician boundary is situated somewhat below the base of the Asaphellus inflatus- Dactylocephalus trilobite Biozone.

In this research, gray, green, red to cream limestone, shale and marly deposits of the Julfa, Alibashi and lower part of Elikah Formation at the Zal stratigraphic section, NW Iran, with 67.20 meter thickness have been studied based on conodonts. This investigation is led to identification of 27 species and 4 subspecies belong to 5 different genera of conodonts while a proposed new subspecies Clarkina leveni zalensis n. sub sp. belonging to the species Clarkina leveni have been described. Also, 18 conodont zones with the age of Wuchiapingian – Griesbachian have been determined. Amongst them, 5 biozones belong to Wuchiapingian, 10 to Changhsingian and 3 to Griesbachian whereas the Late Permian extinction horizon is located on the upper surface of the Paratirolites Limeston last bed like other sections in the Alibashi Mountains re gion. In addition, Wuchiapingian – Changhsingian boundary is located at the Julfa to Alibashi formations boundary and the Permian – Triassic boundary placed at the gray calcareous parts of the lower Elikah Formation, .90 m above the extinction horizon. Unlike some recent entries, the boundary between Alibashi and Elikah formations are continuous due to the presence of two conodont zones Clarkina meishanensis – Hindeodus praeparvus As. Zone and Merrillina ultima – Stepanovites ?mostleri As. Zone in the marine shaly Araxes member and lower carbonate part of the Elikah Formation, occurrence of small orthotetid brachiopods, bellerophontid gastropods and numerous Bairdiidae ostracods in this shaly member even several preceding geochemical and isotopic studies.

Introdaction
Upper Devonian-Lower Carboniferous rocks are widely exposed throughout Kerman Province (Central-East Iran Microplate). They are mainly represented by limestones, sandstones and interbedded shales, of the Bahram and Hutk Formations. The regional geology and stratigraphy of the Kerman area have been described by Huckriede et al. (1962) and Wendt et al. (2002). The Hutk section is located about 35 km north of Kerman in the Khajeh Mountain, where the Precambrian to Jurassic rocks are exposed. The study area is located in the southwestern part of the geological map of Zarand (Vahdati Daneshmand et al., 1995), and structurally belongs to the southwestern part of the Central-East Iran Microplate. This paper is the first study on stratigraphy and biostratigraphy of the Hutk Formation in the Hutk section, providing evidence of a Tournaisian age of the Formation. Nineteen samples (3-4 kg each) were collected from the Hutk Formation in Hutk section, and processed for conodonts. Of these, twelve samples yielded more than 101 conodont elements. In general, the preservation of the conodont elements is good, although a few specimens being broken or incomplete. The identified conodont fauna consists of thirteen species and subspecies of seven genera including: Gnathodus, Protognathodus, Polygnathus, Mehlina, Bispathodus, Clydagnathus, Siphonodella. In the present paper, we follow the standard conodont zonations of the Early Carboniferous, established by Sandberg et al. (1978). The conodont associations found in the 12 productive conodont samples from the Hutk section allows us to subdivide the deposits into three conodont biozones: the duplicata Zone, Upper part of Upper duplicata-Lower crenulata zones and anchoralis-latus Zone
duplicata Zone: Neopolygnathus communis, Polygnathus inornatus, Polygnathus sp. B, Polygnathus longiposticus, Mehlina sp., Clydagnathus cavusformis occur in this interval associated with the Bispathodus aculeatus aculeatus and Bispathodus stabilis. According to Molloy et al., (1997) Polygnathus longiposticus ranges from within the Lower duplicata Zone in to the Lower Crenulata Zone. Co-occurrence of this species with Clydagnathus cavusformis, which ranges from Middle expansa-Upper duplicata zones, defines the interval.
Upper part of Upper duplicata-Lower crenulata zones: An undifferentiated Upper part of Upper duplicata-Lower crenulata zones interval is discriminated from samples A12 to A16 by co-occurences of Neopolygnathus dentatus and Siphonodella obsoleta. Its lower limit is recognized by the first occurrence Siphonodella obsoleta, which ranges from the Upper part of Upper duplicata to the isostica-U. crenulata zones (Sandberg et al., 1978). The upper limit is identified by the last occurrence of Neopolygnathus dentatus, which ranges from the Latest marginifera to the Lower crenulata zones (Barskov et al., 1991; Ji & Ziegler, 1993).
Barren interval: There is a five-meter barren zone intervenes between the lowest sample attributable to anchoralis-latus Zone and the uppermost bed attributable to Upper part of Upper duplicata-Lower crenulata zones which do not yield any conodont specimen, so the age of this bed has been recognized on the basis of stratigraphic position as Upper crenulata-typicus zones.
anchoralis-latus Zone: The assosiation of Gnathodus pseudosemiglaber and Neopolygnathus communis can be seen here. Its lower boundary is defined by FAD of Gnathodus pseudosemiglaber that ranges from anchoralis–latus Zone to texana Zone (Lane et al., 1980). Co-occurences of this species with Neopolygnathus communis which extinct at anchoralis-latus Zone defines the interval.
Biofacies and Paleoecology: During the Early Carboniferous, the lateral distribution of conodonts across the shallow carbonate shelf to the open sea and basinal environments follows a similar pattern as during the Late Devonian time (Schonlaub & Kreutzer, 1993). The basic concept of conodont biofacies introduced by Sandberg (1976) and later completed by others (e.g. Sandberg & Ziegler 1979; Sandberg et al., 1988; Sandberg & Dreesen, 1984, 1987; Pohler and Barnes, 1990 and Savoy & Haris, 1993). The Paleoenvironment and paleoecology were interpreted from field observation and conodont assemblages. Shallow water conodont biofacies (icriodid-polygnathid) in Lower Famennian deposits of the studied section indicates an inner shelf to foreshore depositional environment for this part of section (Ahmadi et al., 2012). This is similar to most Iranian sequences of Central Iran such as Hojedk (Gholamalian & Kebriaei, 2008), Dalmeh (Hairapetian & Yazdi, 2003) and Chahriseh (Gholamalian, 2007). The middle-late Famennian deposits are characterized by clastic sediments which indicates a considerable sea level fall and marine regression at the Latest Devonian time. This situation is different from other sequences of Central Iran. Middle and late Famennian in some sections (eg. Ghale-Kalaghu and Howz-e-Dorah 1, 2) shows predominance an inner shelf environment (Bahrami et al., 2011) whereas in Kale-e-Sardar section (Eastern Tabas) deep marine sediment were deposited (Gholamalian et al., 2009). The duplicata Zone is characterized by 8 conodont taxa. Species of Polygnathus is most abundant followed by those of Clydagnathus and a low number of Bispathodus+Mehlina. The polygnathid biofacies and occurrences of Clydagnathus represent an inner shelf to mid-continental shelf environment. The upper beds (Upper part of Upper duplicata-Lower crenulata zones, anchoralis latus Zone) is characterized by the appearances of Gnathodus and Siphonodella. These genera have low abundance so the statical analysis is impossible but the presence of these genera represents a sea level rise and establishment of deeper environment during the late Tournaisian. From the Early Carboniferous sequences of Hutk section, north of Kerman, thirteen species and subspecies of conodonts were identified. The age of Hutk Formation has been determined as Tournaisian based on its fauna. Three biozones were recognized on the basis of vertical distribution of these taxa along the stratigraphic column. These strata lie unconformably over the Middle-Upper Famennian terrigenous sediments and covered disconformably by dolostones of Jamal Formation.

The Baghuk mountain section located in 50 km North- East of Abadeh, is studied regarding conodonts for the first time. The Abadeh locality is one of the most important area for analyzing the Permian-Triassic boundary in Iran. considering abundance of Conodonts in this section, Clarkina orientalis, has been identified for termination of Wuchiapingian or Dzhulfian and 7 Conodont biozones 1-Clarkina subcarinata 2-Clarkina changxingensis 3-Clarkina bachmnni 4-Clarkina nodosa 5-Clarkina abadehensis 6-Clarkina yeni 7-Clarkina hauschkei and 3 rock units lacking index fossil for Changhsinghian or Dorashamian and two conodont biozones including 1-Hindeodus parvus-Isarcicella staeschei 2-Isarcicella isarcica for base of Triassic, Griesbachian (Induan). Considering the age range, concluded studying Baghuk section, this region is comparable with some sections in the world such as South china, India, Alps, North Caucasus and regions in Iran such as north west of country, Amol, Shahreza (Shahzadeh Seyed Ali Akbar) and Hambast. Accomplished studies and type of fossils regarding bathymetry and existence of stromatolites structures, shows the shallow depths of the basin at the Permian- Triassic boundary.

Study of conodont fauna the Illanghareh Formation in Illanghareh, Illanlu and Pir-Eshag sections provide new data on the stratigraphy of this formation in the North West Iran. Illanghareh section is a terrigenous-carbonate rock sequence, consists mainly of quartzarenite sandstone, shale, and carbonate rocks. This sequence generally represents shallow-water Polygnathid-Icriodid biofacies and yielded five biozones: varcus, Older than rhenana, rhenana – linguiformis, Middle triangularis – Late trachytera, postera – expansa. Tectonic activities and erosion caused the Middle Devonian strata in the base of Illanghareh section to be omitted and the varcus Biozone is not recorded. Upper Devonian (Upper Famennian) rock units change into Carboniferous strata with a sedimentary gap though it is not recognizable in the field and no evidence of erosional surface is recognized. It is however, shown between Late Famennian and Late Turnaisian via conodonts recorded. The biozone bilineatus- bolandensis was also recorded in lower part of Carboniferous strata studied here.

The studied section is located in the southern flank of the Central Alborz, 5 kilometers north of Shahmirzad City in the Semnan province. This section is situated at 35° 48′ 40″ N latitude and 53° 16′ 59″ E longitude. The Mila Formation has 5 measurable members in Type Section (Mila Kuh, Damghan City) and only in this studied section. This formation overlies conformably the Early Cambrian Lalun Sandstone Formation and underlies disconformably the Early Devonian red conglomerates. Studied Conodonts of this formation are of Proconodontus type belonging to Coniform Groups. 14 species and 6 genera of these conodonts were acquired indicating an age of Mid-Late Cambrian and Early Ordovician. These Conodonts are listed as below: Proconodontus serratus, Proconodontus muelleri, Proconodontus rotundatus, Prooneotodus sp?, Prooneotudus tenuis, Furnishina furnishi, Furnishina asymmetrica, Furnishina sp., Furnishina obliqus-Hirsutodontus?, Westergardodina cf. mossbergensis, Westergardodina fossa, Cordylodus, Cordylodus intermedius, Cordylodus lindstromi, Cordylodus proavus, Oneotodus nakamurai & Problematoconites sp. A remarkable point is the discovery of species Prooneotodus tenuis in the second member of Mila Formation because no conodont has already been reported this member.
Other microfossils such as Trilobites, Brachiopoda, Hyolithes, Eocrinoidae, Rusophycus, Cruziana, Paleoscoleidae and Sponges were also obtained indicating the deposition of Mila Formation in a shallow marine environment. These fossils assemblage are comparable with those other parts of Iran and neighbor countries.