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

In order to study the biostratigraphy of the Gurpi Formation in the Fars area, a stratigraphic section is selected and sampled in the Sarbalesh anticline. The thickness of the Gurpi Formation in this section is 346.3 meters and its main lithology includes argillaceous limestone and shale. The lower boundary with the Sarvak Formation indicates a disconformity with dissolution holes and iron oxide bearing fragments, and its upper boundary with the Pabdeh Formation indicates a disconformity with a 30 cm thick key horizon containing phosphate nodules and manganese oxide traces. In this study, by identifying 66 species belonging to 22 genera of planktonic foraminifera, 9 biozones were identified and introduced based on the Tethys standard biozonation of Premoli Silva and Verga (2004). The age of the Gurpi Formation based on identified biozones is determined from the early Santonian to the late Maastrichtian. The K/Pg boundary is located at the end of the key horizon containing phosphate nodules and correlates with the lithostratigraphic boundary of the Gurpi and Pabdeh formations.

In order to biostratigraphic studies of Gurpi Formation, a section was selected in the north-east of Noorabad city in Fars. Structurally, this section is located in the folded-thrust zone of Zagros and geographically in the Fars zone (coastal Fars). The Gurpi Formation is extended of 229 meters in thickness, contains limestone, shale, marly limestone and argillaceous limestone. Its lower boundary with Sarvak Formation and its upper contact with Pabdeh Formation are discontinuous. The study conducted on foraminiferal biostratigraphy in this section led to the identification of 20 species belonging to 7 genera of planktonic foraminifera. Based on the stratigraphic distribution of the planktonic foraminifera, five biozones are determined which correspond with global biozonation. Described biozones are comprised of: 1-Globotruncanita elevata Partial range zone; 2-Globotruncana ventricosa Interval zone; 3-Radotruncana calcarata Total range zone; 4-Gansserina gansseri Interval zone; 5-Contusotruncana contusa, Contusotruncana walfischensis, Globotruncanita conica Assemblage zone. Based on these biozones, the age of Gurpi Formation is assigned to early Campanian to late Maastrichtian. The absence of the Marginotruncana and Dicarinella  asymetrica in the lower part of the Gurpi Formation indicates of the Santonian-Campanian boundary and the determination of the early Early Campanian age for the base of this Formation.

Biostratigraphy, microfacies and depositional environments of the Upper Cretaceous deposits (Gurpi and Amiran formations) were carried out in the Gerdbisheh section. The Gurpi Formation predominantly consists of shales interbedded with some argillaceous limestone layers. This formation disconformably overlies the Sarvak Formation and gradually underlies the Amiran Formation. The Amiran Formation is represented by grey to greenish shales, siltstones and sandstone intercalations which underlay the informal siliciclastic-carbonate unit 1. Planktonic foraminiferal assemblages have led to the recognition of six zones that reveal the late Coniacian?–early Maastrichtian age for the Gurpi Formation. Radiolaria and scattered planktonic foraminifera are the two main fossil groups present in the Amiran Formation. Therefore, based on the precence of the index planktonic foraminfera and the stratigraphic position the early-middle? Maastrichtian age is proposed for the Amiran Formation. We determined two microfacies in the interval of the Gurpi Formation and three petrofacies in the Amiran Formation. According to the obtained data the Gurpi Formation was deposited in the basinal setting, whereas the Amiran Formation is deposited as submarine fans on the slope part of a carbonate shelf under the control of turbidity currents.

In this research, biostratigraphic studies of the Gurpi Formation were carried out at the Chenareh section (Lorestan Zone). The thickness of Gurpi Formation at the studied section is 140 m and consists of limestobe, marly limestone and marl. The Gurpi Formation conformablely (with significant lithological changes) underlies the white limestones of the Ilam Formation and is covered by the sandstone of the Amiran Formation. On the basis of the recognized planktonic foraminifera, 7 biozone were reported as follows: Globotruncanita elevata Partial range Zone (Early Campanian), Globotruncana ventricosa Interval Zone (Middle to Late Campanian), Radotruncana calcarata Total Range Zone (Late Campanian), Globotruncanella havanensis Partial Range Zone (Late Campanian), Globotruncana aegyptiaca Interval Zone (Late Campanian), Gansserina gansseri Interval Zone (Late Campanian-Early Masstrichtian), Contusotruncana contusa  Interval Zone (Late Masstrichtian). In the studied section, the Seymareh and Imam Hassan sections are not observed, unlike other sections in the Lorestan basin. The thickness of this formation in Chenareh anticline is much less than other sections in the adjacent areas.

In the present study, calcareous nannofossil of the Gurpi Formation have been studied from well No. 123 of Marun oil field in the Zagros sedimentary basin. In this study, thirty-eight nannoplankton species belonging to eighteen genera were introduced from the Gurpi Formation deposits. Based on index calcareous nannofossil species, the Gurpi Formaation deposit was subdivided into nine calcareous nannofossil biozones, including CC17- CC25 zones (Sissingh, 1977) and UC12-UC20 (Burnett, 1998). The identified biozones are assigned to the Late Santonian-Late Maastrichtian ages for the studied interval. In order to paleoecology and Paleoenvironment studies, the diversity, abundance, size and extent of preservation of nannofossil taxa were also investigated. The distribution and abundance of some species such as Micula decussata, Micula murus and Watznaueria barnesiae indicate that the temperature and environmental stress have increased towards the end of the Formation. Also, the sedimentary environment of Gurpi Formation during the Late Cretaceous was mainly in low to mid-latitudes based on calcareous nannofossil assemblages.

Unlike similar sedimentary conditions in the Lower Cretaceous, the Upper Cretaceous sediments of Iran do not have the same facies features. Therefore, in this study, we try to study the sedimentary environment and microfacies. By using data and geochemical methods of Upper Cretaceous sediments, valuable information about the environment and conditions of formation and primary mineralogy of Upper Cretaceous sediments of Dombak-kuh are achieved.

In Dombak-kuh section, sampling has been done based on lithological and facies changes in the perpendicular direction towards the layers and at distances of less than 0.5 m to more than 2.5 m. These sections were stained with red alizarin solution and potassium ferrocyanide to distinguish calcite mineralogy from dolomite as well as iron content and the amount of iron in it by Dickson method (Dickson, 1965). The classification and naming of rocks is based on Dunham's method (Dunham, 1962). In sample naming, an attempt has been made to include all major allocations in sample naming in order of frequency. The percentage of abundance was obtained by comparing with Baccelle and Bosellini (1965) comparison tables. The known facies have been compared with the Flugel (2010) facies belt. In presenting the sedimentary model, the terms used in Burchett and Wright (1992) have been used.

Petrographic studies of this sections revealed 11 microfacies, with 2 microfacies from tidal flat, 1 microfacies from lagoon, 1 microfacies from shoal and 7 microfacies from open marine. All of them belonged to carbonate ramp and are mentioned hereforth: 1. Dolomicrites – Dolomicrosparaite 2. Intraclast Grainstone3.Bioclact Wackestone4. Bioclast Pelloidal Grainston 5. Oligosteginids Packstone6.Nezzazatinella, Dictyoconella Wackestone-Packston 7. Lenticulina/Marginotruncana/ Oligosteginids Wackestone-Packstone 8. Heterohelix /Globotruncana/Macroglobigerielloides Wackestone 9. Oligosteginids/ Macroglobigerielloides / Heterohelix Packstone 10. Heterohelix /Globotruncana/Marginotruncana packstone 11. Globotruncana/ Heterohelix  /Macroglobigerielloides Wackestone-packstone.
 The characteristics of these deposits indicate that the sedimentary environment was a ramp (hemocline). The absence of calcite turbidite deposits, fall structures, and large reef and oncoid and piezoidal dams confirm the carbonate ramp environment. The results of elemental analysis and plotting of these values against each other indicate that the Upper Cretaceous sediment limestones had primary aragonite mineralogy. The plotting of Mn values against Sr / Ca indicates a semi-closed to open diagenetic environment with a high water/rock ratio.

According to the studies carried out in the Dombak-kuh region, the Upper Cretaceous sediments (Cenomanian-Campanian) have a thickness of 327.7 m, the lower boundary of which is the Tizkuh Formation and is of a steep type, and its upper boundary is a fault which cuts through. Cenomanian sediments, which are 54.26 m thick, start with a progressive conglomerate, and then thoronine sediments, which are 22.85 m thick, first with thick-layered limestone and then with chert limestone, and then with Oligosthenic limestones change the facies and settle on it. Kenyasin sediments with a thickness of 19.85 m with a combination of oligoesterated limestones followed by Santonin sediments with a thickness of 182.80 m and then Campanian sediments with a thickness of 48.5 m form the Upper Cretaceous stratigraphic sequence. . In these sediments, 11 micro-facies were identified, which include tidal zone with 2 micro-losses, lagoon with 1 micro-loss, a dam with 1 micro-loss and open sea with 7 micro-losses. The characteristics of these deposits indicate that the sedimentary environment was a ramp (hemocline). The absence of calcite turbidite deposits, fall structures, and large reef and oncoid and piezoidal dams confirm the carbonate ramp environment. The results of elemental analysis and mapping of these values together indicate that the Upper Cretaceous sediments in this section have an aragonite primary compound, which is placed in a semi-closed to semi-open diagenetic region with a high proportion of water to rock (W/R).

To analyze the sedimentary palaeoenvironment of the Gurpi Formation in Bisheh–Deraz section in south of Ilam, various factors including diversity and abundance of dinocysts, a ratio of Peridinioid to Gonyaulacoid (P/G) dinoflagellate cysts, palynofacies parameters and "selective preservation of organic matter" have been used. In lower parts of the Gurpi Formation of Campanian age is very argillaceous and then shallows up in the upper part of Lopha Limestone that contains the small size of bivalve shell debris. This is followed by a stagnant condition due to sea-level rise that favored the preservation of organic matter in early Maastrichtian. The Emam-Hassan Limestone with high percentages of non-fluorescent amorphous organic matter represents a basin environment. The Latter member is overlain by the marls of Late Maastrichtian. Microbiostratigraphy, sedimentology, and palynofacies observation indicate sea-level fall and a 3.5 Ma hiatus at the K/P boundary. This is followed by deepening and the deposition of the basal purple shale of the Pabdeh Formation. The relative sea-level changes curve drawn based on palynomorphs in this study is well in accord with the existing eustasy curves that indicate the great effect of eustasy factor relative to other factors.

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.

The Gurpi formation in Bishe-deraz Section, south of Ilam, consists of 201m marl with intercalations of limy marl with two formal members of Seymareh (Lopha) and Emam-Hasan. The formation overlies the Ilam Formation and is gradationally overlain by the purple shales of the basal part of the Pabdeh Formation. The Gurpi Formation was divided to 9 biozone on the basis of planktonic foraminifera which almost are cosmopolitan and consist of: 1- Radotruncana calcarata Taxon-Range Zone. 2- Globotruncanita stuartiformis Partial-Range Zone. 3- Globotruncana aegyptiaca Interval Zone.  4-Gansserina gansseri Interval Zone. 5- Contusotruncana contusa Interval Zone. 6- Abathomphalus mayaroensis Interval Zone. 7- Praemurica uncinata Interval Zone. 8- Morozovella angulata Interval Zone.  9- Globanomalina pseudomenardii Interval Zone. The formation was deposited from upper Campanian through late Paleocene (Selandian-Thanetian?) according to the planktonic foraminifera recorded. A distinct hiatus was confirmed at the Cretaceous-Paleogene boundary according to microbiostratigraphic and sedimentologic studies and also field work observation.

In this study, biostratigraphy and Paleobathymetry of the Gurpi Formation in section southwest of Kuhdasht were studied. The thickness of Gurpi Formation in this section is 160 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,50 species belonging to 24 genera of planktic foraminifera and Benthic were identified. Based on the stratigraphic distribution of the well known foraminifers, six foraminiferal biozones were established in the Gurpi Formation including: Globotruncana ventricosa Interval Zone, Radotruncana calcarata Taxon Range Zone, Globotruncanella havanensis Partial Range Zone, Globotruncana aegyptiaca Interval Zone, Gansserina gansseri Interval Zone, Contusotruncana contusa Interval Zone.The age of Gurpi Formation in this examined is determined based on identified biozones of Middel Campanian to Late Maastrichtian. A depth of 450 - 600 m was assigned for most parts of the sediments Gurpi Formatan was assigned ccording to planktic/epibenthic ratio and Percentage Morphotype 3 and the regression equation Depth = e (3.58718 + (0.03534 × %P*))

In the present study, calcareous nannofossil biostratigraphy was investigated at the Paleocene ‒ middle Eocene interval at northeast Kazerun (Shahneshin anticline). A thickness of 50 m from the upper part of Gurpi ‒ lower part of Pabdeh formations is investigated and mainly consists of marly limestone, marly shale and marl. 180 species from 31 geneus of calcareous nannofossils are identified. According to the index calcareous nannofossils and based on Agnini et al. zonation, zone CNP3 to CNP11 and zone CNE1 to CNE8 are identified at the Paleocene and Eocene interval, respectively. These biozones corresponds with zone NP3 to NP9 (in Paleocene) and NP10 to NP14 (in Eocene), based on Martini zonation. Regarding calcareous nannofossil assemblages and biozones, the Paleocene ‒ Eocene boundary is located between CNP11/NP9 and CNE1/NP10 zones, where the top of Fasciculithus richardii group is recorded. The extinction of Fasciculithus is recorded at 23 m by the last occurrence of Fasciculithus tympaniformis, which is considered as an index for early Eocene. The appearance of some species, such as Rhomboaster spp., Tribrachiatus bramlettei and assymetrical species of Discoaster araneus is recorded at the Paleocene ‒ Eocene boundary similar to other parts of the world.

In this study the Paleocene sediments have been investigated at the upper part of Gurpi Formation and the lower part of Pabdeh Formation at Arkavaz section in southeast of Ilam. The upper part of the Gurpi Formation is mainly consists of grey shale and the lower part of the Pabdeh Formation consists of purple shale. As a result of this study, 22 species belong to 17 genera of calcareous nannofossils were detected. Nine bioevents were recorded and based on these bioevents, the Ellipsolithus macellus Zone (NP4/CNP6–CNP7) and Fasciculithus tympaniformis Zone (NP5/CNP7–CNP8) are recognized at the uppermost part of the Gurpi Formation. Subsequently, Heliolithus kleinpellii Zone (NP6/CNP8) and Discoaster mohleri Zone (NP7) / Heliolithus riedelii Zone (NP8) (NP7/8 combined Zone–CNP9/10), are identified at the base of the Pabdeh Formation, respectively. As a result of this study and based on the identified calcareous nannofossil biozones, the age of the uppermost part of the Gurpi Formation is Late Danian–Selandian and the lower part of the Pabdeh Formation is Selandian–Thanetian, and based on CNP8 the boundary between these two formations is continuous. The identified biozones in this study were compared with other parts of the Zagros Basin.     

One of the most extensive Cretaceous and Palaeogene deposits in Zagros is the marine sediments of the Gurpi and Pabdeh formations, which were first identified in the Zagros Basin on the basis of stratigraphy and paleontology. Type section of the Gurpi Formation is studied in Lali oilfield located in the NE of Masjed soleiman. Also, the term Pabdeh Formation has been introduced for the argillaceous limestone, marly limestone and shale succession exposed at the Tang-e Pabdeh, from the southeastern part of Pabdeh Mountain, located in north of the Lali oilfield. The most important thing to do in these formations is to determine the exact boundary by calcareous nannofossils. At the Arkavaz section, the upper part of Gurpi Formation (with 41.5 m thick) and the lower part of Pabdeh Formation (with 64.9 m thick) consists of 106.4 m thick was selected which mainly consists of gray shale and purple shale, respectively.  

n this study 47 samples from the Gurpi and Pabdeh formations have been studied. Samples were prepared following a standard smear slide method (Bown and Young 1998). All slides were studied under polarized light microscope at ×1000 magnification. Calcareous nannofossil nomenclature follows the taxonomic schemes of Perch-Nielsen (1985). 

Calcareous nannofossils recorded in the Mesozoic and Cenozoic strata are believed to be an appropriate means for biostratigraphic studies. As a result of this study, 17 genera and 23 species of calcareous nannofossils have been identified. Abbreviations used in this study are the NP (Nannofossil Paleogene) and CNP (Calcareous Nannofossil Paleocene). The nannofossil zonation used in the present study is based on the Nannoplankton zonation of Martini (1971) and Agnini et al. (2014), respectively. As a result of this study, 23 species belong to 17 genera of calcareous nannofossils were detected. Nine bio events were recorded and based on these bio events, the Ellipsolithus macellus Zone (NP4/CNP6–CNP7) and Fasciculithus tympaniformis Zone (NP5/CNP7–CNP8) are recognized at the uppermost part of the Gurpi Formation. Subsequently, Heliolithus kleinpellii Zone (NP6/CNP8) and Discoaster mohleri Zone (NP7)/Heliolithus riedelii Zone (NP8) (NP7/8 combined Zone–CNP9/10), are identified at the base of the Pabdeh Formation, respectively. Two biozones of the zonation of Martini (1971) are recognized at the upper part of Gurpi Formation as follows: (1) Ellipsolithus macellus Zone (NP4/CNP6–CNP7): The first nannofossil unit recorded in this study is the NP4 zone. This biozone is recorded from the FO Ellipsolithus macellus to the FO of Fasciculithus tympaniformis. The age of this zone is late Late Danian–Early Selandian. (2) Fasciculithus tympaniformis Zone (equivalent to NP5/ CNP7–CNP8): The second nannofossil unit recorded at the upper part of Gurpi Formation is the NP5 zone. This bio zone is recorded from the FO Fasciculithus tympaniformis to the FO of Heliolithus kleinpellii. The age of this zone is Selandian. Also, two biozones of the zonation of Martini (1971) are recognized at the lower part of Pabdeh Formation as follows: (1) Heliolithus kleinpellii Zone (equivalent to NP6/CNP8): The next nannofossil unit recorded in this study is the CC19 zone. This bio zone is recorded from the FO of Heliolithus kleinpellii to the FO of Discoaster mohleri. The age of this zone is Late Selandian–Early Thanetian. (2) Discoaster mohleri Zone (NP7) / Heliolithus riedelii Zone (NP8) or (NP7/8 combined Zone–CNP9/10): The last nannofossil unit recorded at the lower part of Pabdeh Formation is the NP7/8 combined zone. This biozone is recorded from the FO of Discoaster mohleri to the FO of Heliolithus riedelii. The age of this zone is Thanetian. In this study the Paleocene sediments have been investigated at the upper part of Gurpi Formation and the lower part of Pabdeh Formation at Arkavaz section in southeast of Ilam. The upper part of the Gurpi Formation is mainly consists of grey shale and the lower part of the Pabdeh Formation consists of purple shale. The detail study based on calcareous nannofossils, enables the subdivision of the studied deposits into four bio zones. As a result of this study and based on the identified calcareous nannofossil bio zones, the age of the uppermost part of the Gurpi Formation is Late Danian–Selandian and the lower part of the Pabdeh Formation is Selandian–Thanetian, and CNP8 Zone is located in the boundary between two formations. The biozones identified in this study were compared with sections from other regions of Zagros Basin.

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.

The Gurpi Formation at Anaran Anticline in SE of Lurestan province.consists of 269.5 meters of marl with intercalation of limy marl; two formal members of Seymareh limestone and Emam-Hasan argillaceous limestone are also exposed. Studies reveal presence of 70 species belonging to 38 genera of calcareous nannofossils based on which 8 global biozones were differentiated. Consequently, the Gurpi Formation was attributed to middle Campanian through Paleocene. There is a distinct hiatus in Cretaceous-Paleogene boundary based on paleontological evidence, as deduced from the absence of nannofossil biozones NP1-NP4. It seems that the reactivation of Anaran linement as paleohigh caused facies changes and hiatus in Gurpi Formation in SE of Lurestan province.

The Zagros mountain belt extends over 1800 km from Kurdistan in N Iraq to the Strait of Hormuz in Iran (Lacombe and Mouthereau 2006). Zagros Mountain belt is one of the richest oil provinces in the world (Emmami 2008) and is important to paleontological, sedimentological, structural and geological studies. The Cretaceous sediments in the Zagros Mountain Belt (SW Iran), is characterized by a large diversity of rocks and facies. The Gurpi Formation is one of the source rock for petroleum in Zagros basin and outcrops extensively to southwest Iran (James and Wynd 1965). The type section of this Formation (49° 13´ 47″ E, 32° 26´ 50″ N) is measured at Tang-e Pabdeh, north of the Lali oilfield in Khuzestan (James and Wynd 1965). This section is composed of 320 meters of dark bluish gray, thin-bedded marl and shale beds and occasionally thin beds of marly limestone (Motiei, 1995). The following publications have appeared for this formation (e. g. Kalantari, 1976; Vaziri Moghaddam, 2002; Ghasemi-Nejad et al. 2006; Darvishzad et al. 2007; Bahrami 2009; Rabbani et al. 2009; Bahrami and Parvaneh-Nejad Shirazi 2010; Bieranvand and Ghasemi-Nejad 2013; Parvaneh-Nejad Shirazi et al. 2013; Beiranvand et al. 2013, 2014 and Fereydoonpour et al. 2014). Late Cretaceous calcareous nannofossils study is still scarce in Zagros basin and is a strong motivation for investigating calcareous nannofossils in southwest Iran. Late Cretaceous calcareous nannofossils in Gurpi Formation were studied by (Senemari and Azizi 2012; Badri and Kani 2014; Razmjooei et al. 2014; Najafpour et al. 2015; Senemari 2015 and Hadavi et al. 2016).
The aim of the present study was to establish the biostratigraphic zonation for the Gurpi Formation and determine age range of this formation in Izeh sub- zone by means of calcareous nannofossils. A 215-m-thick, well-exposed section was chosen for this purpose. The Kuh-e Siah section is located about 15 Km to the north of Deh-Dasht area. This section was measured in detail at 30°54'31. 86 N and 50°36 38. 80 E. Lithologically, it consists of shale, shaly limestone, and shales with thin bedded limestone. It conformably overlies the Ilam Formation and is overlain unconformably by the pabdeh Formation. Material and Methods: In this study a 215-m thick of Cretaceous sediments including the upper part of Illam Formation, Gurpi Formation and the lower part of Pbdeh Formation were recognized. A total of 122 samples with ~ 1 ‒ 2 m sampling interval were collected. Calcareous nannofossils were processed by smear slides technique described by Bown and Young (1998). The slides were studied with a polarized microscope Olympous (BH2) with 1000×magnification. The zonal scheme proposed in this study is based on the ranges of the most important stratigraphically nannofossil taxa. Calcareous nannofossil taxonomy follows Perch-Neilsen (1985) and Bown, (1998). In this study the stratigraphic zonation developed by Sissingh, (1977) modified by Perch-Nielsen (1985) was applied and is compared with, Burnett, (1998) biozones. Discussion of Result and Conclusion: According to the first and last occurrences of the index species of calcareous nannofossils, Late Coniacian to Early Maastrichtian age were recognized for the sediments of Gurpi formation in this area. The standard zones identified are listed below from the oldest to the youngest:Reinhardtites anthophorus biozone (CC15) (Equivalent of Subzone UC11a and UC11b), late Coniacian.
Lucianorhabdus cayeuxii biozone (CC16) (Equivalent of Subzone UC11c and UC12), late Coniacian- middle Santonian.
Calculites obscurus biozone (CC17) (Equivalent of Subzone UC12 and UC13), middle Santonian- Santonian Campanian boundary.
Aspidolithus parcus biozone (CC18) (Equivalent of Subzone UC14 a, b, cTP), early Campanian.
Calculites ovalis biozone (CC19) (Equivalent of Subzone UC14dTP and UC15aTP), late early Campanian.
Ceratolithoides aculeus biozone (CC20) (Equivalent of Subzone UC15bTP), late early Campanian.
Quadrum sissinghii biozone (CC21) (Equivalent of Subzone UC15cTP), early late Campanian.
Quadrum trifidum biozone (CC22) (Equivalent of Subzone UC15dTP andUC15eTP), middle late Campanian.
Tranolithus phacelosus biozone (CC23) (Equivalent of Subzone UC16 and UC17), middle late Campanian- early Maastrichtian.
Reinhardtites levis biozone (CC24) (Equivalent of Subzone UC18), middle early Maastrichtian.
Arkhangelskiella cymbiformis biozone (CC25) (Equivalent of Subzone UC19), late early Maastrichtian.
Using of these results and their comparison to other global nanno events, which were reported on upper Cretaceous stage boundaries, can be used to better identify of these boundaries in this section. In this study the Coniacin- Santonian, Sntonian- Campanian and Campanian- Maastrichtian boundaries were identified as follows:Coniacin/ Santonian boundary: This boundary has been reported as the interval from the FO of M. staurophora to the FO of R. anthophorus by Perch-Nielsen (1985). Bralower et al. (1995) have been shown this boundary between the FO of the M. staurophora to the FO of L. cayeuxii. Burentt (1998), Melinte and Lamolda (2002) and Melinte and Lamolda (2007) have been considered the FOs of R. anthophorus, L. grillii, Micula concav, Lucianorhabdus inflatus and L. cayeuxii in the late Coniacin and the LO of L. septenarius in the Early Santonian. The Coniacin- Santonian boundary (CSB) has been placed between the FO of L. cayeuxii and the LO of L. septenarius, within the CC16 Zone of Sissingh (1977), and in the UC11c sub-zone of Burnett (1998). Also the presence of C. obscures after the FO of L. cayeuxii and higher abundance of M. concava, has been reported the CSB (Lamolda et al. 2014). The first sample of the Kuh-e Siah section contains R. anthophorus, L. grillii, Q. gartneri and M. staurophora. The FO of L. cayeuxii and the LO of L. septenarius has been recorded at 5m and 15 m, respectively. Based on these data, the lowermost part of the Kuh-e Siah section is late Coniacian and the CSB was considered in the Kuh-e Siah section in the UC11c/ CC16/ NC17 zones, between the FO of L. cayeuxii and the LO of L. septenarius.
Santonian/ Campanian boundary:At informal sections of GSSP (Hancock and Gale, 1996; Hampton et al. 2007). , this boundary is marked by the FO of A. parcus parcus. Two main suggested markers, i. e. the FO of A. parcus parcus and the LO of Dicarinella asymetrica occur closely to the base of Chron 33r which may be suggested as the main events for the base of the Campanian (Wagreich et al. 2015). The Santonian- Campanian boundary is described within the intetrval from the FO of A. cymbiformis (UC13a) to the FO of A. parcus parcus (UC14) (Gale et al. , 2008), while Melinte and Bojar, (2010) placed this boundary within the CC17/ UC13 and the LO of A. cymbiformis is located before the boundary. The Santonian- Campanian boundary is located at the base of CC18/UC14 zone, marked by the FO of Broinsonia parca parca, (Wagreich et al. , 2010; Cetean et al. , 2011; Russo, 2013; Dubicka et al. , 2017). In the Kuh-e Siah section, the Santonian- campanin boundary was marked by the FO of A. parcus parcus at the base of the CC18/ UC14/ NC18 at 45 m.
Campanian‒ Maastrichtian bondary: The Campanian ‒ Maastrichtian boundary (CMB) at GSSP is defined below the LO of Q. trifidum and Q. gothicus. The LO of B. parcus constricta is also recorded about 1. 8 Ma above the CMB (Gardin et al. 2001) and considered as an indicator of the CMB which is observed above the LO of Q. trifidum and Q. gothicus (Odin and Lamaurelle, 2001). At Gubbio area (Gardin et al. 2012), similar to Tercis-Les-Bains (Gardin et al. 2001), the LOs of Q. gothicus and Q. trifidum are followed by the LOs of A. parcus constrictus and Q. trifidum and differs with the proposed CC and UC zonations. It must be mentioned that the LOs of T. orionatus (Gardin et al. 2012) and A. parcus constrictus (Gardin et al. 2012; do Monte Guerra et al. 2016) are diachronous between different latitudes. Thibault also used the LO of Quadrum trifidum as marker for the CMB at low latitude site. In the Kuh-e Siah section, the Campanian- Maastrichtian boundary is identified by the LO of the Quadrum trifidum.
1- The presented data suggest that the age of sediments of Gurpi Formation in Kuh-e Siah section are late Coniacian to late early Maastrichtian. In kuhe Siah section
2- According to the continuous presence of L. grillii، M. concava و M. staurophora in samples of Illam and Gurpi Formations and the presence of Q. gartneri and R. anthophorus in the first sample of the Gurpi Formation, the Illam and Gurpi formations boundary is conformably.
3- The LO of B. hayi bio- evente has a reverse order in this study relative to biozones was described by Sissingh (1977). Although the LO of B. hayi was recorded in zone CC19 (Sissingh 1977), the LO of this species has been recorded up to the middle part of the CC20. In this section, the LO of Bukryaster hayi was recorded in the CC20. Razmjooei et al. , (2014) in the northeast of Kazeroon in Iran (Fars area) and Melinte and Bojar (2010) in southern Romania have also recorded the LO of B. hayi in zone CC20. Based on Melinte and Bojar, (2010), the LO of B. hayi in CC20 is attributed to diachronism or reworking.
4- Due to the presence of Biantholithus sparseus, Fasciculithus tympaniformis and Markalius inversus in the first sample of the Pabdeh Formation and the non-identification of the end zone of the CC25/ UC19 zones in this section, the Gurpi and Pabdeh Formations boundary is unconformably.

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.

The present study is an attempt to biostratigraphically classify the rocks of Gurpi Formation at Samand Anticline with the help of calcareous nannofossils. The succession measures 197 meters in thickness and consists of shale, marl and marly limestone. A total of 96 species belonging to 45 genera of calcareous nannofossils have been identified whose distribution points to delineation of 11 international biozones. Consequently, the rocks of Gurpi Formation are attributed to middle Campanian through late Paleocene (Selandian) time and the K/Pg boundary interval is found to be continuous. Taking into account the absence of nannofossil biozones NP2-NP4 as well as the sedimentological evidence observed, the non-deposition event at the boundary interval has occurred later than the previously thought time identified on the basis of planktic foraminifera.
Consequently, the rocks of Gurpi Formation are attributed to middle Campanian through late Paleocene (Selandian) time and the K/Pg boundary interval is found to be continuous. Taking into account the absence of nannofossil biozones NP2-NP4 as well as the sedimentological evidence observed, the non-deposition event at the boundary interval has occurred later than the previously thought time identified on the basis of planktic foraminifera.

The Gurpi Formation was studied from different aspects at two sections, Farhadabad and Kavar, in southwest and southeast of Ilam where it is composed of 205 m and 158 m of grey to blue marl and shale beds and occasionally thin beds of argillaceous limestones with two formal members of Seymareh (Lopha) and Emam-Hassan. In order to reconstruct paleoclimate during depositional course of the formation, paleontological and palynological data (ratio of specialist to generalist foraminifera (e.s/e.g) and warm-temperate waters dinocysts and spore and pollen grains) were used statistically. The results show that the Gurpi Formation is mainly deposited in a warm-humid climate with two sharp decreases happening in temperature in early Maastrichtian and Danian.

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)).