نشریه دیرینه شناسی
سال سوم شماره 1 (پیاپی 5، بهار و تابستان 1394)

The studied section, called Hassan-Abad section in this paper, is located near the village of Hasan-Abad about 13 km northwest of the city of Ferdows, northeast Iran. The studied section of Nayband Formation with altitude of 1300 meter is composed of a sequence of reefal carbonates and shales. The reefal carbonates contains rich macro-fauna, such as corals, sponges, gastropods, bivalves and micro-fauna including foraminifers, algae, and microproblematica. The thickness of Late Triassic Nayband Formation at the Hassan-Abad section is about 175 m. Considerable part of the section (about 100 m) consists of reef carbonates with micritic matrix that is gray in color. By approaching to the upper part, carbonate rocks decreases while intercalations of green shales are gradually appeared. Well-sorted red sandstones with iron oxides are present in the upper most parts of the measured section. The boundary of the Nayband Formation with Early Jurassic sandstones of Ab-Haji Formation is continuous.
Corals, hypercalcified sponges (including sphinctozoans, inozoans, chaetetids, spongiomorphs and stromatomorphs), and algae (Solenoporcea, dasycladaceans), are the most important reef organisms. Based on abundant occurrence of Heterastridium coglobatum Reuss, a possibly index fossil of Bidestan Member (Senowbari-Daryan, 1996), the studied section (Bidestan Member and Howz-e-Khan Member) is dated as being of Upper Norian and Rhaetian in age. Separation of the Howz-e-Khan Member, as the youngest part of the Nayband Formation, was not possible in this section therefore, this part of Nayband Formation doesn’t exactly same as one of the member of type locality, such as Bidstan or Howz-e-Khan, so that it has informal name which is Ferdows Member (Aghanabati, 2009). It can be indicative of different conditions for deposition of Upper Triassic reefs limestone in east of central Iran in Lute Block. Late Triassic reefs in the Tethys province and outside of the Tethys show the widest distribution during Norian- Rhaetian stages and are known from numerous localities in Mediterranean region including Alps, Caucasia, Southeast Asia and northwest America (Flügel, 1982). Although three different group of foraminifera are generally not abundant in the reefs of the Nayband Formation in this study, however comparison of foraminifera association of the Hassan Abad section with the associations known from Panthalassan and Tethys, according to Chablais et al. (2011), Iran can be considered in Provinces III (Eastern Laurasia).
The foraminifera divided to three Agglutinate, Hyaline and porcelaneouse groups. The porcelaneouse foraminifera including: Altinerina, Cucurbita, Decapoalina, Galeanella, Miliolechina, Miliolipora, Ophthalmidium, Orthotrinacria, Paraophthalmidium, Planiinvoluta, agglutinate forms: Agglutisolena, Endotebidae, Glomospira, Palaeolituonella, Tetrataxis, Trochammina and Hyaline taxa: Aulotortus, Austrocolomia, Duostomina, Coronipora, Trocholina.
In the Hassan Abad section, the porcelaneouse genera including Decapoalina, Galeanella, Miliolipora and Ophthalmidium are the most abundant the same as the Northern Calcareous Alps and south of Tethys. These genera are also abundant in all reefal facies of Upper Triassic deposits. Between Agglutinate foraminifera, Trochammina is abundant. Distribution of foraminifera in this area indicated that the Alp, SW Asia, Australia, Turkey and from other localities of Nayband Formation in Iran show most similarity to the Northern Calcareous Alps (Zaninetti, 1976; Schäfer and Senowbari-Daryan, 1981). Correlation of the Late Triassic reefs distribution indicates that northern margin of Lute Block, where Hassan Abad section (Ferdows member) deposited, had been situated in the lower latitudes and in the northern hemisphere during depositional time. In addition, similarities of the scleractinian corals of Hassan-Abad section (Amirhassankhani et al., 2010; Shepherd et al. 2012; Amirhassankhani & Ariayi, 2008) with scleractinian corals of the mentioned area proves a biogeographically connection and an appropriate condition for growing of Triassic corals. The aunal Association of the reefs in Hassan Abad supports their depositional environment in a tropical region. In this study, 28 species of foraminifera from families of Ammodiscidae, Ataxophragmidae, Cornuspiridae, Cuneolinidae, Duostominidae, Endothyridae, Hauerindae, Ichthyolariidae, Involutindae, Miliolechinidae, Milioliporidae, Nubecularidae, Ophthalmidiidae, Tetrataxadae, Trochammnindae and Verneuilnadae were identified and 11 species were introduced for first time from Iran. The abundance of porcelaneouse genera is more similar to the Northern Calcareous Alps and south of Tethys which indicate same condition during Late Triassic. The foraminifer’s assemblages prove Norian-Rhaetian age in carbonate deposits in Lute Block. The scleractinian corals and Comparison of foraminifers of the Hassan-Abad section with known taxa from Alps, SW Asia, Australia, Turkey, Oman and Iran as well as its precise correlation to trend of Late Triassic reefs distribution indicates that the Lute Block was situated in the low latitudes and in the northern hemisphere during the depositional time.

The Makran area is one of the largest accretionary wedges on Earth, located in SE Iran and South Pakistan. It extends about 1000 km between two, nearly N–S-running, transform fault systems (Dolati and Burg, 2013). Less biostratigraphic studies carried out in this area, therefore this research aims to investigate the Neogene strata of Coastal Makran Zone on the bases of calcareous nannofossil in the Jahati anticline. The calcareous nannofossils are among the best planktonic microfossils that used to determine relative ages of the Mesozoic and especially Cenozoic strata (Bown & Young, 1998). In this research, 81 samples were collected from intervals of mudstone, marl and marly limestone in the Jahati anticline (Gati-Jahati series) for calcareous nannofossil studies. To avoid small sized coccoliths, the samples were processed by simple smear slide and gravity methods as described by Bown and Young (1998). The slides were examined using aNikonE200 light microscope with cross-polarized light at a magnification of 1000X. For the systematic studies of calcareous nannofossil, Perch-Nielsen (1985) was used. The standard calcareous nannofossil zonations of Martini (1971), Okada & Bukry (1980) and Backman et al. (2012) were followed for the Neogene strata. In this research, many index nannofossils were identified, however, standard nannofossil biozonation was not performed, because the studied stratigraphic sections were thick and sometimes distance between coolected samples were wide. Therefore, the age determination was only based on index species, calcareous nannofossil assemblages and index bio-events.
The calcareous nannofossil study on the basal part of this section indicated co-occurrence of Sphenolithus heteromorphus and Helicosphaera ampliaperta species. According to the studies so far conducted (e.g. Perch-Nielsen, 1985; Fornaciari & Rio, 1996, Bown, 1998), presence of S. heteromorphus index species indicates the NN4-5 biozones and the LO of H. ampliaperta species was also considered as upper boundary of the NN4 zone (Perch-Nielsen, 1985; Bown, 1998). Then, at the middle part of the section, the nannofossil studies led to recognition of species Discoaster braarudii, Discoaster kugleri and Discoaster quinqueramus appearance, the FO of the rare Ceratolithus acutus, first appearance of Coccolithus pelagicus forms with bar, the FO of Discoaster asymmetricus, the FO of Pseudoemiliania lacunosa, and then the appearance of Gephyrocapsa spp. small from bottom to top of this part of the section, respectively.
At the upper part of the studied section, the frequency of Discoaster surculus, Discoaster pentaradiatus as well as the LO of Discoaster brouweri are low or sometimes rare, however some species of Discoaster genus was noted. Some evidences such as disappearance of various species of Discoaster genus, appearance of various and large species with high frequency of Gephyrocapsa genus such as Gephyrocapsa caribbeanica, Gephyrocapsa oceanica and Gephyrocapsa spp. (>4μm) are indicative of Pliocene to Pleistocene transition event at the upper part of the section. Finally, the FO of Emiliania huxleyi species at the uppermost parts of the section was recorded and continued to the top of the section. The present research is the first published study on the marine-clastic complete sequence of the Neogene of the Coastal Makran Zone of Iran. The calcareous nannofossil studies led to identification of 39 fair to well preserved species belonging to 11 genera. Based on index taxa, the basal part of the studied section was assigned to Helicosphaera ampliaperta zone (NN4) of Martini (1971) and the uppermost part to the Emiliania huxleyi zone (NN21), ranging in age from the late Early Miocene (late Burdigalin- early Langhian) to the Late Pleistocene. Also, the recognized biozones in this study are correlated to standard zonations of Backman et al. (2012) and Okada & Bukry (1980).

Khangiran Formation is one of the most important formations of Paleogene settings in the Kopet-Dagh basin that formed in the marine environment and has a little outcrop. Based on foraminifera fauna, this formations is Late Paleocene- Late Eocene and probably Early Oligocene in age (Afshar-Harb, 1969). Also the age of this formation based on study of nanofossils in the Chehelkaman syncline section Early Eocene to Late Oligocene was determined (Hadavi & Senemari, 2002). This study is considered the paleoecology of Early- Middle Eocene range within this formation based on small benthic foraminifera.
Type section of Khangiran Formation (E: 59° 08′ 31″ and N: 37° 32′ 15″) is located in the north west of Dargaz city, 8Km northwest of Yaghol village. For detail study of paleoecology of Early- Middle Eocene range within this formation, dense samples were collected at every 4 and 1 meter. Samples were crushed and soaked in water for 2 weeks and then washed through 297 μm, 125 μm and 63 μm sieves and dried. Small benthic foraminifera are common to abundant and very well preserved. The best outcrop of formations in the study area are at the Chehelkaman and Khangiran. Lithology of Khangiran Formation consists of green and yellow marl, sandstone and siltestone that is conformable overlies the Chehelkaman Formation and the upper bound of this formationis the Neogene red bed deposits. In this study, sampling collected from the base of Khangiran Formation up to the thickness of 505 m. The study of small benthic foraminifera fauna based on references, such as Alegret and Thomas (2001), Berrgrenand Aubert (1975), Molina et al (2006) and Ortiz and Thomas (2006), it is interpreted that the lower parts of the Khangiran Formation (Early-Middle Eocene range) were deposited in the neritic to middle bathyal paleodepth. Based on this study, we interpreted the paleodepth of 40 to 880m for this age range.
In the lower 230 m, epifaunal morphotype was observed and dominant. This indicates increase in oxygen content and decrease of nutrient-rich conditions. Toward the top of section, infaunal morphotype was dominant. This section demonstrate of abundant presence of infaunal genera such as Uvigerina, Bulimina and Globobulimina. Presence of this genera is related to increases of nutrient-rich conditions and decreases of oxygen content.

This region is located in south west of Khorasan Razavi Province, between Ferdows and Bajestan cities, which is coordinated between E 58 00׳ to 58 30׳ longitude and N 34 30׳ to 35 00׳ latitude. The Mazar and Bahabad sections have been selected in order to study of Rudist fauna in the Cretaceous deposits in the southwest of Bajestan city. Rudist fauna in the Late Cretaceous deposits in east of Iran have been considered mainly in the Eastern Iran Zone, but there is no significant publication about Lut Block in Central Iran so far, except the preliminary report of this study (Rezaie Soolgani et al., 2015). Some of the noticeable previous works in the other parts of eastern Iran have been done by Vredenburg (1909), Kuhn (1932), Vogel (1971) and Khazaei et al. (2009, 2014). In order to identify and analyze the collected specimens from both sections, detailed field works for measuring and recognition of rudist-bearing units have been done and the total number of 200 samples have been collected. Also, according to the field data, stratigraphic column of the studied sections have been drown. Based on the shape, size and position of internal structures, such as ligament, pillars, myophors and teeth, samples have been identified at the level of genus and species. Finally, 21 specimens from Mazar section and 4 specimens from Bahabad section belonging to 2 genera and 5 species of Hippuritidae family have been recognized. Mazar section, with 117.5 m thickness, is composed of 9 rock units, including alternating fossiliferous marl and limestone beds with bivalve and rudist shells, limestone and rudist-bearing limestone beds. Bahabad section, with 98 m thickness, consists of 4 main rock units which is composed of marl and limestone beds with bivalve, echinoderm and rudist bioclasts. This section starts with an erosional contact at the base of the succession.
Hippuritidae family derived from Caportinidae during the Turonian time and shows some features, such as the presence of pillars in right valve and perforates channels in left valve. This family along with Radiolitidae family have occurred during the Late Santonian to Middle-Late Campanian time, at the third stage of rudist's boom (Cestari & Sartorio, 1995).
One of the most important structural characteristics on the cross section of right valves is the angle between the structural elements (Moro & Cosovic, 2004) that were measured and mentioned in the biometric tables. These parameters consist of the angle between the ligamental ridge (L), first pillar (p1) and second pillar (p2). It is noteworthy that there is no possibility to measure the myocardinal axis, because of the poor preservation of teeth in most cases, the interior angles are measured based on the ligamental ridge.
According to the results of systematic identification of specimens and the biostratigraphic range proposed by many researchers, the Late Coniacian to Early Campanian age is suggested for the rudist-bearing units of these two sections.
The results of strontium stable isotope analyses which have been carried out on numerous indicator species in large areas of the Tethyan and Caribbean realms (Steuber, 2012) indicate calibrated numerical age that is different from the previously published works. The consequence of the present investigation on two species of genus Vaccinites, reveals the Late Turonian to Late Santonian age for these sequences. Hippurites family is one of the main Rudist families known in this region that includes five species as below: Hippurites canaliculatus, Vaccinates cornuvaccinum, Vaccinites galloprovincialis, Vaccinites chaperi and Vaccinites sulcatus. In addition, based on stratigraphical range of these species, Late Turonian–Santonian age is suggested for these successions.

The Paleogene deposits in the Zagros have formed during two sedimentary cycles. The Shahbazan and Asmari formations formed during the Jahrum (Paleocene to Eocene) and Asmari cycles (Paleocene to Early Miocene), respectively (Aghanabati, 2006; Motiei, 1993). The type section of the Shahbazan Formation is located in the Shahbazan village (near Andimeshk-Dourod railroad) and consists of white and brown-weathering, thick beds of porous, dolomite and dolomitic limestone (Aghanabati, 2006; Motiei, 1993). The type section of the Asmari Formation is located in south of Masjed Soleyman and Haftkel (Aghanabati, 2006). Anhydrite deposits (Kalhur Member) and lithic and limy sandstones (Ahwaz Member) also occur within the Asmari Formation (Motiei, 1993). The Qaleh Nar oil field with geographical coordinate of N: 32° 43' 54" and E: 48° 17' 44" is located about 4 km east Andimeshk-Bidrobeh (Seraj, 2005; Bakhtiari, 2013).The thickness of the Shahbazan Formation in the studied well is 228 meters. This formation consists mainly of limestone and dolomite. The lower boundary of the Shahbazan Formation with the Pabdeh Formation is conformable and its upper boundary with Asmari Formation is marked by an unconformity. The Asmari Formation with thickness of 157 meters consists mainly of limestone and dolomite. It is located between the Shahbazan Formation below and the Gachsaran Formation above. In order to study the biostratigraphy of the Asmari and Shahbazan formations in the studied well, 707 thin sections were prepared and examined, from which 564 thin sections belong to the Shahbazan Formation and 143 thin sections belong to the Asmari Formation. Paleontological studies documented a high diversity of shallow-water benthic foraminifera and rare planktonic foraminifera at this section. The distributions of foraminifera in the study area is used to determine the age of the Shahbazan and Asmari formations. Three assemblage Zones were recognized in the Shahbazan Formation. Turborotalia cf. Boweri (Lutetian) and Guembelitrioides (Globigerina) cf. lozanoi (early Yapresian to early Lutetain) are present in assemblage Zone 1, so that this assemblage Zone is indicative of early Lutetian age (BouDagher-Fadel, 2012). Turborotalia cf. Increbecens (late Bartonian to middle Ruplian) and Morozovella are identified in assemblage Zone 2. The last appearance of Morozovella was recorded in late Bartonian (BouDagher-Fadel, 2012; Berggern and Pearson, 2005). Therefore, this assemblage suggests the Bartonian age. Assemblage Zone 3 consists of Nummulites fabianiiand Chapmaninasp. This assemblage represents Priabonian age. This assemblage Zone is time equivalent to Chapmanina-Pellatispira-Baculogypsinoides assemblage Zone of Wynd (1965) and two assemblage Zones SBZ 19 and SBZ 20 of Serra-kiel et al. (1998). Two assemblage Zones have been recognized in the Asmari Formation. Assemblage Zone 1 consists of Archaias cf. kirkukensis and Archaias cf. hensoni (middle Ruplian to late Chattian). All species of Nummulites genus were extinct in Ruplian-Chattian boundary (Laursen et al., 2009; van Buchem et al., 2010) so that this assemblage indicates a Rupplian-Chattian age. This assemblage Zone is equivalent to Archaias asmaricus-Archaias hensoni-Miogypsinoides complanatus assemblage Zone of Laursen et al. (2009) and van Bouchem et al. (2010). Assemblage Zone 2 of the Asmari Formation due to lack of index fossils corresponds to Indeterminate Zone of Laursen et al. (2009) and van Bouchem et al,( 2010) and indicates an Aqitanianage. Finally the Shahbazan and Asmari formations in the studied well are considered Middle Eocene (early Lutetian) to Late Eocene (Priabonian) and Middle Ruplian to Aqitanian age respectively

In this research, in order to study ichnology of Paleocene-Eocene flysch deposits of the north Birjand, one section has been measure and smaples collected. The studied section is located about 40 km north of Birjand and 5 km east of Friznook village. Geographical coordinates are 32° 12′ and 33° 48′ north latitudes, and 58° 51′ and 59° 20′ east longitudes. Methods of research include sample collection, sample preparation and identification of ichnogenera and ichnospecies. At first, the based and top of the section identified, and then the section measured bed by bed. Forty-four specimens of ichnofossils have been identified and studied in field. Then, seventy specimens have been collected and studied in laboratory. In Birjand and Qayen areas, Paleocene and Eocene deposits are composed of different facies including flysch and carbonate as well as volcanic rocks and their distributions are related to structural zone of the area. The studied section (3662 m) includes alternations of siliciclastic sediments that formed during collision along with thin-bedded carbonate intercalations. There are foraminifera and other bioclasts such as algae and bryozoans in carbonates beds. The bioclasts are broken and formed fragments and seems to be re-deposited in the basin and formed allochthnous limestone. Based on fossil assemblages and stratigraphical position of sequence, two flysch units are separated and belong to Paleocene and Eocene age. In the studied sectione, twenty two ichnogenera and twenty six representative ichnospecies have been identifies as follow: Acanthorhaphe, Belcosmorhaphe, Cosmorhaphe, Fustiglyphus, Gordia, Granularia, Halopoa, Helminthoida, Helminthopsis, Helminthorhaphe, Laevicyclus, Megagrapton, Ophiomorpha, Palaeophycus, Paleodictyon, Phycodes, Planolites, Scolicia, Spirophycus, Spirorhaphe, Squamodictyon and Thalassinoides. Simce ichnogenera are formed in place, therefore they are clearly indicative of environmental conditions. Therefore they are important in interpretation of environmental conditions of sedimentary basins (Frey, 1978; Ekdal et al., 1984; Bromley, 1996).These biogenic structures are applicable for determination of depth, type of sediments and size of grains, oxygen contents and organic material (Bromley, 1996). Summary of lithological facies of the studied sequence as follows: 1- Carbonate facies with marly beds that probably deposited in a carbonate ramp.
2- Conglomerate facies that belong to submarine fan channels
3- Thick bedded sandstone facies with shale and marl intercalations that belong to middle part of the submarine fan.
4- Marl or shale facies with sandstone- thin-bedded siltstone intercalations that belong to distal part of submarine fan.
5- Marl or shale facies with thin-bedded siltstone interbedded that belong to deep environment of the basin.
Trace fossils, based on, sedimentation could be divided into two groups. 1- Trace fossils that form on muddy substrates before event sedimentation. These trace fossils are good characters for quite environments and often are created where the turbidity currents did not effect on the basin floor.2- Trace fossils that are formed after event sedimentation. The previous group are replaced by these trace fossils in unrest condition and intense erosion. The assemblage that are formed before sedimentation including Acanthorhaphe, Cosmorhaphe, Helminthoida, Helminthopsis, Helminthorhaphe, Laevicyclus, Megagrapton, Paleodictyon, Spirorhaphe, Spirophycus, Squamodictyon (Frey and Seilacher, 1980; Pemberton and Frey, 1992; Uchman and Wetzel, 2011; Uchman, 2007). According to ichnofacies classification (Pemberton and Frey, 1992) that include of sedimentary environment from terrestrial to deep marine environment, the studied and identified trace fossils belong to Nereites ichnofacies. The Nereites is divided into three subichnofacies including Ophiomorpha rudis, Paleodictyon and Nereites (Uchman and Wetzel 2011). Subichnofacies Ophiomorpha rudisare formed with thick-bedded sandstones that are deposited in channels and upper fan. Subichnofacies Paleodictyon could be assigned to sandy deposits of normal flysch and subichnofacies Nereites could interpret as outer parts of submarine fans with muddy sediments. Generally, Nereites ichnofacies contains fine grains sediments and typical pelgic sequence. According to above, graphoglyptid forms meander shape and before sedimentation assemblages, the studied assemblage could be assigned to Nereites ichnofacies and deep marine environment (Buatios et al., 2001; Leszczyński, 1992, 1993; Wetzel and Uchman, 1997; Uchman, 1995; Seilacher, 2007; Ekdale, 1985; Pickerill and Mitchell, 1999; Leszczyński and Seilacher, 1991). Ichnological and sedimentological analysis of the studied section indicate quite condition substrate for the basin. It is suggested environmental conditions such as amount of oxygen in substrate, organic material in the sediments, abundance of turbidity currents, texture of sediments, rate of sedimentation, abundance of fauna assemblage and style of their distribution led to abundance and variety of ichnogenera.

Cretaceous Heteromorph Ammonites are known as index fossils with widely distribution and narrow range in times which play an important role in Cretaceous biostratigraphy (Seyed-Emami & Aryai, 1981; Seyed-Emami et al., 1984; Immel et al., 1997; Mosavinia et al., 2014). Most of these specimens have short age with order of a sub-stage or a zone. More than ten stratigraphic sections from Kopeh-Dagh sedimentary basin were investigated in order to find the Heteromorph forms in the area, but Heteromorph Ammonites were observed in only three of them. Three stratigraphic sections have been measured and logged in the Koppeh Dagh Mountains north, northeast and east of Mashhad at the following localities: 1- Ghorghoreh, locatedabout 70 km E of Mashhad (coordinates: N 36° 13′ 34″, E 60° 24′ 18″)
2- Taherabad, located about 50 km NE of Mashhad (coordinates: N 36° 37′ 05″, E 60° 04′ 03″)
3- Sheikh, located about 20 km NE of Bojnourd (co-ordinates: N 37° 33′ 51″, E 67° 32′ 46″).
62 Specimen of Heteromorh Ammonites are collected from these sections and described which are systematically arranged in genus, species and subspecies as below:4 specimen of Pseudhelicoceras robertianum (Orbignyi, 1842) from Sheikh Section with the age of Early Late Albian, 3 specimen of Mariella (Mariella) cf. bergeri (Brongniart, 1822) from Taherabad and Ghorghoreh sections occur in Late Albian, 2 specimen of Mariella (Mariella) cf. bicarinata (Kner, 1852) from Ghorghoreh section which occur in Early Cenomanian, 8 specimens of Marialla (Mariella) lewesiensis (Spath, 1926) from Ghorghoreh section show the age of Early Cenomanian, 19 specimens of Mariella (Mariella) cenomanensis (Schluter, 1876) from Ghorghoreh section occur in Early Cenomanian, 11 specimens of Turrilitess cheuchzerianus (Bosc, 1801) from Ghorghoreh and Taherabad sections identifying the age of Late Early to Early Middle Cenomanian, 2 specimens of Turrilites costatus Lamark, (Bosc, 1801) from Taherabad section with the age of Middle Cenomanian, 8 specimens of Hypoturrilites cf. tuberculatus (Bosc, 1801) from Ghorghoreh section occur in Early Cenomanian and 5 specimens of Hypoturrilites wiedmanni (Collignon, 1964) from Ghorghoreh section occur in Early Cenomanian. Well preserved Heteromorph Ammonites have been recorded in this studyarea, consequently 9 taxa are described. The oldest one is Mariella (Mariella) bergeri of Stoliczkaia dispar zone, indicates the Late Albian age of the strata related to 100 ma. The youngest species which has been obtained is Turrilites costatus of Acanthoceras rhotomagense zone and Turrilites costatus subzone of the Middle Cenomanian estimates an age of 95.5 Ma.
The specimens belong to Mantelliceras mantelli zone, are relatively more abundant which are comprised of Mariella (Mariella) cenomanensis, Hypoturrilites cf. tuberculatus, Hypoturrilites wiedmanni, Mariella (Mariella) cf. bicarinata and Marialla (Mariella) lewesiensis. This Zone indicates the base of Early Cenomanian.

Plankton organisms are particular importance due to the high-speed evolution, vast geographical distribution and abundance in deep marine sediments. These criteria caused to found these organisms great importance in biostratigraphy (Bolli & Krasheninnikov, 1977). The main aim of this study was to evaluate content of Planktonic Foraminifera and present biozonation model. The studied section is located along the main road from Ghoochan to Dargaz about 40 kilometers to Dargarz. After travelling for three kilometers on a sidetrack, we arrive at the section site located in the north-western mountains of Bahadorkhan village. The place is known as Hussein Kadkhoda. The Geographical coordinates of the studied section are 58ᵒ 35′ 01 east latitude and 37ᵒ 41′ 25″ north latitude. Abtalkh Formation is 407/5 meters thick at Bahadorkhan section. Bahadorkhan section consists of calcareous shale, lime marl, marl and a few dispersed chalky limestone beds. Unlike the type section, the upper and lower boundaries of Abtalkh Formation are conformable with Abderaz and Neyzar formations. This section is composed of 7 lithostratigraphy portions.
micropaleontological studies of the Bahadorkhan section led to identification of 40 species belong to17 genera of planktonic foraminifera. According to vertical dispersion range of index forms and biozone maker, this stratigraphy section is divided into 4 biozones: 1. Globotruncanita elevata Partial range Zone: this biozone was introduced by Postuma (1971), from extinction of Dicarinella asymetrica which was not recorded in the studied section, to the first occurrence of Globotruncana ventricosa. The mentioned interval is composed of grey marl and brown calcareous marl.
2. Globotruncana ventricosa Interval zone: this biozone was introduced by Dalbiez (1955), interval from the FO of Globotruncana ventricosa to the FO of Rodotruncana calcarata. Mentioned part is composed of calcareous shale and calcareous marl.
3. Rodotruncana calcarata Total range Zone: this biozone the first was introduced by Herm (1926). Mentioned part is composed of calcareous shale and calcareous marl. Interval from the FO of Rodotruncana calcarata to the LO of Radotruncana calcarata.
4. Globotruncanella havanensis Partial range Zone: this biozone the first was introduced by Lapparent (1918). From extinction of Rodotruncana calcarata to the first occurrence of Globotruncana aegyptica. The mentioned part is of composed marl. According to extinction of both species of Marginotruncana: Marginotruncana marginata and Marginotruncana coronata and also first occurrence of Globotruncanita stuartiformis this boundary can be found in sample. No 30.
Lithostratigraphic comparison of Abtalkh Formation at Bahadorkhan section with Mozduran and Hamam-Ghale sections respectively in east Kopet-Dagh and east of central Kopet-Dagh and Aitamir section in west Kopet-Dagh showed that the thickness decreases in the central and western Kopet-Dagh basin, so that the least thickness belongs to Bahadorkhan section in central Kopet-Dagh. Also biostratigraphy correlation of Abtalkh Formation at type locality and Hamam-ghale section in east and central basin show Campanian- Maastrichtian and Early Campanian to Middle Masstrichtian age whereas the Abtalkh Formation in the Bahadorkhan area deposited during the late Late Santonian to Late Campanian. Microstratigraphy study conducted on 100 shaly and marly samples that collected from Abtalkh Formation successions led to identification of 40 species belong to 17 genera of planktonic foraminifera.