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

The biostratigraphy of the marly-limestone Pabdeh Formation has been studied in a section located in the Interior Fars (folded Zagros). Five assemblage biozones of plankton foraminifera with Early Eocene to Late Eocene age were identified in the studied section. Biozone 1 with a thickness of two meters has been identified at the base of the studied succession and includes Morozovellavela scoensis and Morozovella conicotruncata species defining the Early Eocene age. Biozone 2 with a thickness of 59 meters is the Early Eocene in age and is associated with the first occurrence of Morozovella aragonensis at the base and the last occurrence of Chiloguembelina wilcoxensis at the top. Biozone 3 with a thickness of 66 meters is defined by the first occurrence of Globigerinatheka kugleri at the base and the occurrence of Guembelitrioides nuttalli at the top and represents the beginning of the part of the Middle Eocene. The presence of Orbulinoides beckmanni indicates the Middle Eocene for biozone 4 with a thickness 88 meters. Biozone 5 with a thickness of 163 meters indicates the Middle–Late Eocene for the top of studied succession according to the first and last occurrence of Hantkenina alabamensis.

In order to paleobathymetry of the Farokhi Formation at type section, have been studied based on planktonic foraminifera. The thickness of this formation is 251 meters and was composed of limestone, marl, and limey marl with fossils limestone. The lower and upper contacts of studied formation with Haftoman and Choopanan formations are respectively conformed and disconform. Based on this research were realized 28 planktonic foraminifera species belonging to 9 genera. Comparing planktonic assemblages recovered from the formation with those biogeographical provinces indicate a close similarity with those of Tethyan provinces. Also, based on a statistical analysis of foraminifera assemblages, it has been proposed that Farokhi Formation was deposited at Middle-Outer Neritic open marine environment. In the Early Campanian Sea level is low and at the Middle-Late Campanian is high. At Campanian-Maastrichtian transition sea level is low and at the Maastrichtian stage is high. Finally based on a statistical analysis of %P, M3 and Van der Zwaan et al. (1990) depth equation was display Farokhi Formation was deposited at 75-meter depth.

In the present study, In order to study of the planktonic foraminiferal biostratigraphy of Qom Formation in north of Khoy city, West Azarbayjan province (Sanandaj-Sirjan fore-arc basin), stratigraphic section of Sagatlu was selected and sampled. Thickness of Sagatlu section 216 meters was measured. Lithology of this section contain shale, siltstone, conglomerate and sandstone. The lower boundary of these deposits is alluvium, and its upper boundary is hard limestone deposits of Qom Formation. Study of the planktonic foraminifera communities found in the mentioned section to identify 16 genera and 37 species of planktonic foraminifers. In this research, 4 biozone are included, Subbotina linaperta assemblage Zone, Paragloborotalia opima Highest-occurrence Zone, Ciperoella ciperoensis Partial-Range Zone, Globigerinoides italicus assemblage Zone were identified as being age equivalent to Priabonian-Burdigalian and comparable to world standard biozones..

In this study the Upper Cretaceous sediments in the Zagrous Basins Fars  province,the Pyrgheib Section,for the purpose of Biostratighraphy and sea level change studies were investigated. These sediments with about 206 m thickness consist of Limestone, Shale, Marl and limy marl. The investigated foraminifera led to identification of  70 species of planktonic foraminifera that belong to 16genera. Based on planktonic foraminifera the Upper Cretaceous deposits were divided into 6 biozone which are cosmopolitan and respectively are:biozone1 - Dicarinella concavata Interval Zone,Biozone2-  Dicarinella asymetrica Total Range Zone,Biozone3- Globotruncanita elevata Partial range zone Biozone4- Globotruncana ventricosa Interval Zone,Biozone5- Radotruncana calcarata Interval zone. Biozone6- Globotruncanella havanensis Partial range zone ,Biozone7- Globotruncana aegyptiaca Interval zone. Biozone8- Gansserina gansseri Interval zone, Biozone9- Contusotruncana contusa Interval Zone. The Upper Cretaceous sediments in the study area on the basis of Planktonic Foraminifera are of the Late middle Coniacian  to theLate Maastrichtian ages. According to the Morphotype groups of planktonic foraminifera deeping the basin from the Coniacian to the Middle Santonian is seen .However, in the late Santonian shallowing the basin and again in the Early Campanian deeping the  basin, in the Late Campanian and close to the Campanian-Maastrichtian boundary shallowing the basin and a sea regression is observed.

In this study, Abderaz Formation at Qalezo section in the west of the Kopeh-Dagh sedimentary basin has been studied. It has consisted mainly of massive limestone, Marl and chalky limestone units at the mentioned section. Abderaz Formation at Qalezo section, the lower contact with Aitamir Formation is paraconform and the upper contact with Abtalkh Formation is conformed and continuous. The thickness of Abderaz Formation, 216 meters, has been measured. In this investigation have been identified 55 planktonic foraminifera species belong to 15 genera, in a frame of 4 biozones have been recognized. Finally, based on this research was distinguished from latest Early Turonian-Late Santonian ages for this section. In this study four planktonic foraminifera species, Dicarinella bouldinensis (Pessagno 1967), Dicarinella takayanagii Hasegawa 1999, Marginotruncana desioi (Gandolfi 1955), Marginotruncana caronae Peryt 1980 have been introduced for the first time in Iran. Also in this research planktonic foraminifera test geometric in Abderaz Formation at Qalezo section has been studied for sea-level changes. In Lower-Middle Turonian substages, the high frequency of the M1 group and low frequency of M3 group displayed fall seal level at this time. In Late Turonian frequencies of M3 group with accompany of %P was shown rise sea level. In the Coniacian and Santonian stages, the M1 group is dominant and the M3 group is low frequency and all of the mentioned evidence were demonstrates fall sea level. Also, the depth average of the studied section based on Depth = e (3.58718 + (0.03534 × %P)) has been calculating 146 meters which were shown these sediments deposited in Outer Neritic environment.

In this research, the biostratigraphy of Oligocene deposits of the Pabdeh Formation in Bandar Abbas region is considered. For this purpose, the planktonic foraminifera was studied and identified. Based on the index forms of these microfossils, biozones were recognized and compared to global biozonation. Investigation of the stratigraphic distribution of these microfossils in the four studied surface and subsurface sections (Champeh, Safid, Band-e Lengeh, and Taftan) led us to the identification of the Eocene/Oligocene boundary and four biozones of planktonic foraminifera (Zone E16, Hantkenina alabamensis Highest-occurrence Zone, Zone O1, Pseudohastigerina naguewichiensis Highest-occurrence Zone, Zone O2, Turborotalia ampliapertura Highest-occurrence Zone, Zone O3, Dentoglobigerina sellii Partial-range Zone) in this region. Based on the foraminiferal assemblages and their biozonation, the age of Oligocene deposits of the Pabdeh Formation is Rupelian. Also, the lateral extension of Oligocene deposits of the Pabdeh Formation in the studied area has been considered.

The Gurpi Formation, the hydrocarbon source rock in the southwest Iran, is extended in Folded Zagros in Provinces Khuzestan, Lurestan, and Fars (James & Wynd, 1965). James & and Wynd (1965) measured the Gurpi Formation at the type section (49°13΄47˝ E, 32°26΄50˝N). The formation at the type section includes grey to blue marl and shale beds and occasionally thin beds of argillaceous limestone (Aghanabati, 2006). The Formation overlies the Ilam Formation and is disconformably overlain by the Pabdeh Formation at the type section. The marl and carbonate rocks of the Gurpi Formation were formed in a deep marine environment. Microfauna of the Gurpi Formation was studied by Kalantary (1976), Vaziri Moghaddam (2002), Darvishzadeh et al. (2007) and Fereydoonpour et al. (2104). The main objective of this paper is to identify depositional sequences by the study of planktonic foraminifera, planktonic to benthic ratio (P/B), percentage of morphotype groups of planktonic foraminifera and the carbonate content.

The Gurpi Formation in the study area is located at 14 km North of Lendeh city (50°28′ 94˝ E, 31° 01 ′11˝ N). The thickness of the Gurpi Formation at the Lendeh area (NW of Dehdasht) is 221m. In the study area, the formation overlies the Ilam Formation and is disconformably overlain by the Pabdeh Formation. Two hundred and eighteen of soft and hard samples were collected for this study. One hundred and eighty-eight of thin sections were prepared to analyze the planktonic foraminifera in hard samples. About 100 g of each soft sample was processed. The samples were dried, soaked in hydrogen peroxide (10%). The disaggregated samples were washed through a 63 μm, 125 μm, and 250 μm sieves. About 300 individuals were picked up for each sample in two size fractions (125–250 μm). The species and genera of planktonic foraminifera were identified based on Sliter (1989), Robozynki & Caron (1995), and Premoli Silva & and Verga (2004). The parameters such as the planktonic morphogroups, CaCO3 content, and P/B ratio were used for palaeodepth and sea-level changes of the Gurpi Formation (Mabrouk et al., 2007; Hart & and Baily, 1979; Mancini & and Tew, 1996; Mancini et al., 1996).

The study of planktonic foraminifera of the Gurpi Formation in North of Lendeh area led to the recognition of nine planktonic foraminifera biozones, that included: Dicarinella concavata Zone, Dicarinella asymetrica Zone, Globotruncanita elevata Zone, Globotruncana ventricosa Zone, Radotruncana calcarata Zone, Globotruncanella havanensis Zone, Globotruncana aegyptiaca Zone, Gansserina gansseri Zone, and Contusotruncana contusa Racemiguembelina fructicosa Zone. These biozones indicate that the Gurpi Formation deposited during the Santonian to Middle Maastrichtian. Based on the distribution of morphotype groups of planktonic foraminifera, planktonic to benthic ratio (P/B), and content of carbonate, nine third-order depositional sequences have been recognized. The sequences are comparable to those recognized in other parts of the Zagros Basin.

Sediments of Turonian to Santonian age are located in Surgah formation and characterized by Shale and marly Shale. Surgah formation as one of the formations of Bangestan group against other formations this group has limited expansion so that it only outcrops in Lurestan subbasin. During the Cretaceous time, two warming cycles occurred, the first cycle is observed in the Lower cretaceous (Albian) and second cycle is observed in the Upper Cretaceous (Turonian-Santonian). (Lowenstam & Epstein, 1954; Bowen, 1961). Therefore, in this study has been attempted to investigate the influencing factors on the planktonic foraminifera ecology during the seconded cycle Turonian-Santonian.

In this study, 168 samples were systematically collected during a Surgah formation. The samples include Shales and marly Shales. About 1 kg of each sample wase processed. The samples were dried, soaked in hydrogen peroxide (%10) for 12 hours. The mixture was washed over three sieves of 70, 100 and 120µm mesh to remove the clay fraction. This procedure was repeated several times when necessary. The residue was dried at 40˚ C. then, Foraminifera were identified and counted. At least 300 foraminifera were counted in each sample. The general taxonomy followes Robaszynski and Caron (1979), Caron (1985), Premoli Silva & Sliter (1999), Robaszynski et al. (2000), Premoli Silva & Verga (2007). Paleoecological indicators were obtained using the results of the counting process.

A type section of Surgah Formation in Ilam Kabir-Kuh anticiline in order to Paleoecology of Turonian -Santonian was selected, sampled and precisely studied for stratigraphy and paleontology. This sequence with a thickness of 168 m is composed of shale and marlyshales with interla of marlylimestone. Lower and upper boundaries of the Surgah Formation with Sarvak and Ilam limestone Formations are conformable with sharp lithological boundary respectively. Three biostratigraphic zones are proposed for the Turoniane - Coniacian interval in Surgah formation:1- Marginotruncana sigali - Dicarinella primitiva partial range Zone (latest middle (?) - late Turonian). Because the usual index species for this interval, Helvetoglobotruncana helvetica, has not been found at Surgah formation, therefore the base of this zone is not exposed in the this formation, then age of this zone is latest Middle (?) - late Turonian.2- Dicarinella concavata Interval Zone (latest Turonian - earliest Santonian).3- Dicarinella asymetrica Total Range Zone (Early Santonian - Campanian).Because Dicarinell asymetrica has been found all over Surgah formation, the top of this zone is not exposed in the Surgah Formation, then age of this zone is latest Early Santonian. On this basis, generally the age of the Surgah formation latest Middle Turonian - latest Early Santonian is determined. The ratio between planktonic and benthonic foraminifera (P/B) is one of the most reliable proxies to estimate palaeo-water depths.It has been known for a long time that the percentage of planktonic foraminifera in modern sediments increases with water depth (e.g., Boltovskoy & Wright, 1976; van der Zwaan et al., 1999). Van der Zwaan et al. (1990) described the regression curves with a mathematical formula, which can be used to estimate the water depth. Planktonic foraminifera are divided into five groups according to morphology and lifestyle (Hart & Bailey (1979); Coccioni & Luciani (2005); Reolid et al. (2015):1- Strongly keeled trocospiral: these forms are k- strategic and develop in conditions of reduced nutrients (oligotrophic - mesotrophic), increased oxygen and deep waters. Like geniuses: Dicarinella and Marginotruncana. 2- Weakly keeled trocospiral: these forms are k/r strategic and develop in conditions of oligotrophic - mesotrophic and increased oxygen. Like genus: Archaeoglobigerina.3- Unkeeled trocospiral: these forms are r- strategic and develop in conditions of increased nutrients (mesotrophic - euotrophic), reduced oxygen and surface waters. Like geniuses: Whiteinella and Hedbergella.4- Planispiral: these forms are r-strategic (opportunist) and develop in conditions of eutrophic, increased oxygen and surface to medium waters. Like genus: Macroglobigerinelloides.5- Biserial: these forms are r-strategic (opportunist) and develop in conditions of rincreased nutrients (eutrophic), poorly oxygenated and surface to intermediate waters. Like genus: Heterohelix.

Sediments of Turonian-Santonian age are located in Surgah formation and characterized by Shale and marly Shale with 168 m thickness. Lower and upper boundaries of the Surgah Formation with Sarvak and Ilam limestone Formations are conformable with sharp lithological boundary respectively. Generally for the Turonian to Santonian in the Surgah Formation deep open marine (upper bathyal) with an average depth of 662 m was determined. At the base of the Surgah Formation, Late Turonian, the frequency of deep forms (H3) and percentage of planktonic foraminifera (%P) increased therfore suggests sea-level rise, also killed-forms and K-strategies increasment suggests a lack of nutrients and Oligotrophic condition, whereas decrease of non-killed forms indicates increasment of water salinity in this biozone. In the middle of the Surgah Formation. late Turonian-Coniacian to earliest Santonian, the percentage decrease of planktonic foraminifera (%P) and shallow forms (H1) increasment is indicated sea level gradually falling also none-keeling forms and r-strategies increasment offers abundance of nutrients , Euotrophic conditions, and relative decrease of water salinity. On top of the Surgah Formation, Early Santonian fluctuations in environmental conditions are observed.

This research has aimed to study the biostrtigraphy and lithostratigraphy of late cretaceous deposits  in south of Maracan village , with 320 m thickness.This sequence overlaid the lower cretaceous deposits and have been covered  by Quaternary sedimentary and magmatic rocks. Based on field study and lithological diversity 8 lithic zone have been investigated.  102 samples have been picked up systematically from this sequence. This study lead to determining 41 species from 15 genera of planktonic foraminifera.The  systematic and classification of fauna are based on The (Postuma 1971) , (Caron1985) , (Loeblich and Tappan 1988) and (Permoli Silva And Verga 2004).  .Based on their range chart the bio zonation model for this deposit with 9 Bio Zones as bellow  have been suggested  and have compared with cretaceous global standard bio zones (Robazynsky and Caron 1985) and (Permoli Silva and Verga, 2004) Dicarinella concavata  Interval  Zone (Robazynsky and Caron, 1995) Dicarinella asymetrica Total  range  Zone(Robazynsky and Caron, 1995)  Globotruncanita elevata IntervalrangeZone(Robazynsky and Caron, 1995)   Globotruncana ventricosa IntervalZone  (Robazynsky and Caron, 1995) Rodotruncana  calcarata Total  range  Zone(Robazynsky and Caron, 1995)   Globotruncanella  havnensis  Partial Range Zone (Robaszynski  and Caron, 1985) Globotruncana aegyptiaca Interval  Zone (Robazynsky and Caron, 1995) Gansserina gansseri   Interval  Zone (Robazynsky and Caron, 1995) Abathamphalus mayaroensis  Total  range  Zone(Robazynsky and Caron, 1995)  The suggested age for th.is sequence based on planktonic foraminifera is upper coniantian to upper Maestrichtian  and belong to deep shelf area . Based on the morphology of planktonic foraminifera and their keei we suggest deep sea environment for these  deposits.

In this research, paleoecology and depositional environment of Surgah Formation at the Maleh Kuh section have been investigated. The thickness of Surgah Formation is 82 meters and consists of argillaceous limestone, calcareous shales with intercalated limestones. Based on the planktonic foraminifera, the age of Surgah Formation at the study area is late middle Turonian to Early Santonian. Statistical studies of the morphotype groups of Epicantinental Sea Forms (ESF), Shallow Water Forms (SWF) and Deep Water Forms (DWF) show that these foraminifera are related to DWF, which indicate specific condition of oligotrophic. Also high planktonic/benthic foraminifera ratio confirms the semi deep to deep marine condition of sedimentary environment. The salinity as an ecological parameter in the section was changed to very low amount at the Late Turonian-Early Santonian based on abundance of Muricohedbergella and Whiteinella. Finally, four mirofacies have been identified based on stratigraphic and biostratigraphy position of planktonic foraminifera which formed in the semi deep to deep open marine. This microfacies belongs to the outer ramp of a carbonate platform.

Due to the source nature and placement of the Gurpi Formation between the Asmari and Bangestan reservoirs, it has a special importance. The name of this formation has been derived from Gurpi Mountain in the northwest of Masjid-Soleyman County. At the type section, this formation includes 320 meters of marl and bluish gray shales together with subordinate thin layers of clayey (argillaceous) limestone which overlies the limestones of the Ilam Formation, along an erosional unconformity. The Gurpi Formation has an open marine and deep sea sedimentation environment, which is why it is a good talent for biostratigraphy studies using planktonic fauna. Studies conducted by some researchers on the Gurpi Formation represent a Late Santonian – Tanetian age in different parts of the Zagros area, based on different planktonic assemblages (e.g., Kameli Azan et al., 2004; Darvishzadeh et al., 2007; Abrari et al., 2010; Senemari & Sohrabi Molla Usefi, 2012; Senemari & Azizi, 2012; Beiranvand et al., 2013; Najafpour et al., 2014; Fereydoonpoor et al., 2014; Razmjooei et al., 2014.). This study is based on macroscopic field description of 252 meters of Upper Cretaceous sequences (Gurpi Formation) in the Gandab section located on southern flank of Kabir Kuh anticline in Lurestan Province of Zagros, southwest Iran. In total, 192 hand specimens were taken from rock samples and sediments from these sections for paleontological study. After washing, samples were dried on sieves and put in special cellules. Released fossils were studied by binocular firstly, and then by Scanning Electronic Microscope (SEM). Determination and naming genera and species was based on Robaszynski et al. (1984), Caron (1985), Loeblich and Tappan (1988), and Premoli Silva and Verga (2004). In this study, 57 species related to 20 genera and 7 biozones of planktonic foraminifers are recognized in Gandab section.
- Globotruncana ventricosa Interval Zone
This biozone is defined between Globotruncana ventricosa appearance at the bottom and Radotruncana calcarata appearance at the top. It is correlated with Globotruncana ventricosa biozone aged Middle to Late Campanian (Premoli Silva and Verga , 2004).
- Radotruncana calcarata Total range Zone
This biozone which its top and bottom is consistent with the appearance and extinction of Radotruncana calcarata respectively, It is correlated with Radotruncana calcarata biozone aged Late Campanian (Premoli Silva and Verga , 2004).
- Globotruncana aegyptiaca Interval Zone
This zone is defined according the appearance of Globotruncana aegyptiaca at the base and the appearance of Gansserina gansseri at the top and is parallel to Globotruncana aegyptiaca biozone aged the End of Late Campanian (Premoli Silva and Verga , 2004).
- Gansserina gansseri Interval Zone
It places between the appearance of Gansserina gansseriat the base andContusotruncana contuosaat the top. This biozone is parallel with Gansserina gansseri biozone aged the most final part of Campanian-Maastrichtian (Premoli Silva and Verga , 2004).
- Contusotruncana contuosa Interval Zone
This biozone is defined between the appearance ofContusotruncana contuosa at the base and Abathomphalus mayaroensis at the top and is equivalent of Contusatruncana contusa and Racemiguembelina fructicosa biozones and aged Early to Late Maastrichtian (Premoli Silva and Verga, 2004).
- Abathomphalus mayaroensis Interval Zone
It is defined between the appearance of Abathomphalus mayaroensis species at the base and its extinction at the top. This biozone equals Abathomphalus mayaroensisbiozone agedLate Maastrichtian(Premoli Silva and Verga, 2004).
Cretaceous – Paleocene (K-P) boundary
K-P boundary is located on top of the Gurpi Formation in Gandab section. It is characterized by the end of Abathomphalus mayaroensis zone and extinction of all planktonic foraminifers. In this research, because of the missing of Guembelitria cretacea Zone P0 as a result of far sampling distance, biozone of Abathomphalus mayaroensis related to Gurpi Formation, is located below Parvularugoglobigerina eugubina Zone (Pα) of the Pabdeh Formation (i.e. Danian).
Correlation
Biozones of the Gurpi Formation in Gandab section are compared with biozones of this formation at the in Kuh - e Siah anticline. In the Kuh - e Siah anticline studied by Fereydoonpoor et al, 2014, 8 biozones were introduced from the Gurpi Formation. These biozones give Early Santonian – Early Maastrichtianage for the Gurpi Formation in this section. The Gurpi Formation at the Gandab section with a thickness of 252m composing of limestone and argillaceous limestone. The lower boundary with the Ilam Formation is conformable with sharp lithology and upper boundary is gradational with the Pabdeh Formation in two sections. Through this study, 57 species related to 20 genera and 7 biozones of planktonic foraminifers in Gandab section were distinguished. According to these biozones and fossil content, the age of Gurpi was determined Middle Campanian to Late Maastrichtian.Transition from Maastrichtian to Paleocene was continuous and the K-P boundary located at the top of Gurpi Formation.

Micropalaeontological study based on planktonic foraminifera in the Cenomanian - Turonian succession of the Holul section, located in the Lurestan geological province (west of the Kermanshah City), resulted in distinction of Rotalipora cushmani, Whiteinella archaeocretacea and Helvetoglobotruncana helvetica biozones. Whiteinella archaeocretacea biozone globally defines the Cenomanian - Turonian transition. Detection of this biozone in the Holul section could be a clue for continuous sedimentation of the Cenomanian - Turonian transition in the studied stratigraphic section. Elongated chambers planktonic foraminifera such as Muricohedbergella simplex are relatively common during time span of Whiteinella archaeocretacea biozone in the Holul stratigraphic section. Results of the isotopical analysis in the studied section indicates an increasing - decreasing trend from the top of Rotalipora cushmani to the base of Helvetoglobotruncana helvetica biozones including two positive shifts before and after Whiteinella archaeocretacea biozone that can be correlated with carbon isotope peaks of OAE2 in the Neotethys Basin.

In order to determine the accurate microbiostratigraphy and bathymetery conditions of the Gurpi Formation, one stratigraphic section was studied at the Zangol anticline (SW of Khorramabad). On the basis of the recognized foraminifera, the age of the Gurpi Formation in the studied section is assigned to the Late Santonian to Middle – Late Maastrichtian In this study 35 species belonging to 15 genera of Planktonic foraminifera were idientified that result in determination of 8 biozone were reported as follows: Dicarinella asymetrica Zone, Globotruncanita elevata Zone, Globotruncana ventricosa Zone, Radotruncana calcarata Zone, Globotruncanella havanensis Zone, Globotruncana aegyptica Zone, Gansserina gansseri Zone, Contusotruncana contusa Zone. Study of the morphotype groups of Planktonic foraminifera represents an increase in depth marine condition for deposition of the Gurpi Formation less than 50 meters to more than 100 meters at the study area.

In this research, biostratigraphy of the Gurpi Formation in Jahangirabad section, SW Iran, has been studied .The thickness of the Gurpi Formation in this section is 263 and consists mainly of argillaceous limestone and limestone. The lower boundary with the Ilam Formation is comformable with sharp lithology and upper boundary with the Pabdeh Formation is gradational. In this study, 76 species belong to 17 genera and 8 biozones of planktonic foraminifera were recognized. The biozones consist of Globotruncana ventricosa Zone, Radotruncana calcarata Zone, Globotruncanella havanensis Zone, Globotruncana aegyptica Zone, Gansserina gansseri Zone, Contusotruncana contuosa Zone, Abathomphalus mayaroensis Zone and Pseudoguembelina hariaensis. The age of the Gurpi Formation in this section based on these biozones is Middle Campanian to Late Maastrichtian in this section.

The aim of this study to detect the Cretaceous-Paleogene (K/Pg) boundary in Coastal Fars based on lithological and micropaleontological characteristics and also gamma-ray logs in outcrop exposure and borehole wireline. This study has been done on one surface stratigraphic section in north flank of Gavbast anticline and one exploratory well in the same region and correlation between them.
A presumable interval from the top of the Gurpi and base of the Pabdeh formations with thickness of 50 m was measured where 195 samples were collected. Surface gamma-ray survey was performed a cross section by using a hand-held gamma-ray spectrometer in 30 cm intervals. To distinguish the K/Pg boundary in detail, the sampling and gamma-ray measuring interval was focused on 15 cm steps near the presumable K/Pg boundary. The sampling interval of cuttings in wildcat well at the drilling time was 2 m. The U (ppm), Th (ppm), K (%) and dose rate (nGy/h) were measured in every sampling site. The data was processed by Geolog software. Field gamma-ray was correlated with the wireline gamma-ray log from borehole by the CycloLog software. The results shows gamma radiation has wide range values (17.02 nGy/h - 81.94 nGy/h). The increasing of gamma-ray is not coincident to K/Pg boundary and this is due to high frequency of glauconite and phosphate near to K/Pg boundary. The minimum value of U is 1.36 ppm and maximum value is 13.24 ppm.
The planktonic foraminifera studied and photographed under thin section and also as washed samples. 25 genera and 50 species of planktonic foraminifera have been determined. The recognized biozones are Gansserina gansseri Zone, and Contusotruncana contusa Zone indicate latest Campanian to middle Maastrichtian age for upper part of the Gurpi Formation and Eoglobigerina edita Partial-range Zone (P1), Praemurica uncinata Lowest-occurrence Zone (P2) and Morozovella angulata Lowest-occurrence Zone (P3) assign Danian age for lower part of the Pabdeh Formation. Due to lack of Abathomphalus mayeroensis Zone, Pseudoguembelina hariaensis Zone, Pseudotextularia elegans Zone, Plummerita hatkeninoides Zone, Guembeliteria cretacea (P0) Zone and Parvularugoglobigerina eugubina (Pα)Total-range Zone, a paraconformity between the Gurpi and Pabdeh formations in the studied area was recognized, which encompasses since late Maastrichtian till earliest Danian. Presence of glauconite and phosphate near to top of the Gurpi Formation deposits reveals a hardground.
From lithostratigraphic point of view, due to lack of purple shale informal member at the base of Pabdeh Formation in Coastal Fars, the Gurpi and Pabdeh formations boundary was inferred at the low weathered marlstones beds at the base of Pabdeh Formation which comprises reworked Cretaceous planktonic foraminifera.

In this study, biostratigraphy and palaebathymetry Gurpi Formation in section Anticlin Sultan were studied. The thickness of Gurpi Formation in this section is 270 meters and its main lithology includes Marl, Limy Marl, Limestone and Shale. In this section Lower boundary of Gurpi Formation is transition with Ilam Formation , and its upper boundary with Amiran Formation is unconformably. Here, on the basis of foraminiferal studies,45 species belonging to 20 genera of planktonic foraminifera and Benthic were identified. Based on the stratigraphic distribution of the well known foraminifers, seven foraminiferal biozones were established in the Gurpi Formation including Globotruncana elevata zone, Globotruncana ventricosa Zone, Radotruncana calcarata Zone , Globotruncanella havanensis Zone , Globotruncana aegyptiaca Zone , Gansserina gansseri Zone , Contusotruncana contusa Zone . The age of Gurpi Formation in this examined is determined based on identified biozones of Early Campanian to Late Maastrichtian. A depth of 500- 650 m was assigned for most parts of the sediments Gurpi Formatan was assigned ccording to planktonic/epibenthic ratio and Percentage Morphotype 3 and the regression equation D = e (3.58718 (0.03534 × %P)).

The Moghan area (N38º 30’ to 39º 42’ and E46º 39’ to 48º 10’), as a part of the Kura sedimentary-structural Basin, is located in the NW Iran. The geological and structural history of this area is related directly to its location in northern part of the Talysh-Lesser Caucasus folded and thrusted belt. It is positioned at the collisional zone between the Eurasia and Africa-Arabian continental plates. The convergence is active today, at an estimated rate of 20-30 mm per year.

The area is included in the world’s largest continental collision zone, the Alpine-Himalayan belt, and is marked by intense compression and faulting. The Moghan sedimentary Basin is part of the Para-Tethys Basin that formed in a back-arc and volcanic belt developed from southern France, in the Mediterranean to western China. Tectonic deformations during the Neogene favored the subdivision of Para-Tethys in three major subdomains namely the western, central and eastern Para-Tethys.

This study focuses on the Upper Cretaceous carbonate sequences of the Moghan area, considered as one of the most important intervals in view of their potential as reservoir rocks. Here, facies analysis and paleo-environmental reconstruction of these sequences are presented for the first time in eight surface sections across the study area. This study is based on the stratigraphic and petrographic analysis of Upper Cretaceous sedimentary sequences in Nasir Kandi surface section in the Moghan area, NW Iran. A total of 498 meters of sedimentary thickness were studied and logged. Macroscopic field-features descriptions combined with the results of microscopic studies have been used for facies analysis, paleoenvironmental reconstruction and biozonation. In total, 161 hand specimens were collected for subsequent studies. Sampling intervals were generally between 1 to 3 meters. Upper Cretaceous paleogeographic maps from the eastern part of the Para-Tethys Basin indicate that the Moghan area was located at 30-35º paleolatitude in northern hemisphere. During this time, sea-level was at one of its higher levels in geological history and carbonate platforms developed on continental margins all around the Tethyan realm (Miller et al., 2004). Shallow- to deep marine carbonates were deposited in such platforms in a tectonically active back-arc basin simultaneously to volcanic activity and siliciclastic influx. Based on it paleolatitude location, a temperate to cool subtropical paleoclimatic condition could be considered for this area. This interpretation is also supported by our observations, especially regarding the grain association (skeletal and non-skeletal) of the studied sequences.

Faunal and floral association of this formation (including rudists, other bivalves, echinoderms, benthic and planktonic foraminifera, red algae and bryozoan) represents a foraminiferal-mollusk (foramol) or bryozoan-mollusk (bryomol) association (Coffey and Read, 2007; Einsele, 2013). These communities live in temperate and cold waters and also at deeper settings in comparison to the tropical chlorozoan association (Lees, 1975; Flügel, 2013).

In Nasir Kandi section in westernmost part of the Moghan area, deep-marine pelagic facies are the dominant. Therefore, it seems that the shallow inner parts of the Upper Cretaceous platform were located in the central parts of Moghan area. This shallow platform turns into deep marine settings with a steep slope and without any remarkable marginal barrier, to the southeast and southwest.  Accordingly, biostratigraphic analysis of these facies, based on planktonic foraminifera resulted in recognition of four biozones: Globotruncana ventricosa Zone (middle to late Campanian), Globotruncanella havanensis Zone (late Campanian), Globotruncana aegyptiaca Zone (latest Campanian) and Gansserina gansseri Zone (latest Campanian to early Maastrichtian). We are grateful to the National Iranian Oil Company- Exploration Directorate for financial support and data preparation. The University of Isfahan and the Pars Petro Zagros (PPZ) Company are thanked for the provision of facilities for this research. Journal editor and anonymous reviewers are acknowledged for their kind helps.