نشریه دیرینه شناسی
سال چهارم شماره 2 (پیاپی 8، پاییز و زمستان 1395)

This study is the first report of the terrestrial mammalian vertebrate fossils from the south of Ardabil. Terrestrial vertebrate fossil beds have great importance in paleontology studies. The role of these types of fossil groups is crucial in understanding paleoenvironments. In this study, extraction and identification of terrestrial vertebrate fossils families such as Bovidae, Equidae, Giraffidae, and Elephantidae are discussed.

Study area in Northwest of Iran, South of Ardebil and is in Kiwi city. The fossil layer studied in a railway trench at a height of 9 meters from the axial plane. After constructing a drilling platform at the trench and reticulation of platform fossil part extraction operations were done. Then, complete removal of parts from sediments and repair of damaged specimens and measurement of the required parameters was done. Systematic studies were also done based on information from fossil samples. The displacement of pieces of fossil specimens was completely evident before being fossilized by paleo fractures and also by separation from the main part. It should be noted that unfortunately before the fossil layer was found, some fossil parts were destroyed by road construction machinery. Components and identifiable parts included: premolar, Radial bone, Ulna, the top of the metatarsals of Family Giraffidae, Maxillary first molar to third (M1-M3) of Family Bovidae, metatarsals and incisors tooth of Family Equidae, Part of the femoral head Family Elephantidae.

Fossil parts of this study have the ability to reflect the characteristics of their paleoenvironment. Discussing these features from dental samples is more comprehensible and defensible. The exact study of dental Feature of different species of mammalian fossils with a vegetarian diet in Maragheh fauna and the study area was limited to the domain of fodder diets (family of Bovidae and Equidae) and leaf diets (family of Giraffidae), There is also the presence of various species of fossils such as Giraffidae, Bovidae, Equidae and even Elephantidae that exhibit these diets, which confirmed this type of nutrition at the time of its existence (Late Miocene). Therefore, using the study of the hypsodont tooth in the family of Bovidae and species of Equidae, as well as the presence of brachyodont type teeth in Giraffidae species, It can be said that the paleoenvironment of the studied area and Maragheh should be rich in grassland cover (hypsodont type), and in terms of tree cover to the extent that the leaf (brachyodont type) is used to feed it. Therefore, it is possible to compare the paleoenvironment of the studied area and Maraghe with some of the Savannah environments of today's Africa. As a result, the paleoenvironment Northwest of Iran (with a stronger probability of the southern provinces of Ardebil and Tabriz) in the Late Miocene could have been in the form of a vegetation plain with grasses, among which there were low shrubs. The study area is comparable to that of Maragheh fauna in terms of conditions the paleoenvironment and paleogeography and placing in the upper Miocene migration belt (Fortelius et al., 2003).

Different groups in the fossil layer including the family of Bovidae, Equidae, Giraffidae, and Elephantidae were extracted and identified. Initial field and laboratory studies indicate the transport of fossil parts before fossilization. Evidence of these displacements is the pre-fossil fractures, as well as the discovery of teeth from the jawbone. Fossil parts are oriented which specifies the direction of the paleo-currents. The sedimentary sequence of the fossiliferous layer contained sandy and clay layers. Regarding the importance of systematically studying these types of fossil groups, the finding of these fossils contributes greatly to recognizing the paleoenvironment for understanding the type of environment, biodiversity, and so on. This fauna can be compared to the co-eval fauna of the Maragheh representing a similar paleoenvironmental and paleogeographical character. The relative age of fauna can be assigned the late upper Miocene to earliest Pliocene.

The tectonic, morphology, geodynamic, stratigraphic architecture, and paleontological characteristics of the Zagros structural zone have studied by many researchers. However, we aimed to focus on the lithostratigraphy and microbiostratigraphy of the Neogene deposits, exposed in the Northeast of the Bandar Abbas. The studied area positioned at the south domain of the Kurgu Anticline, 65 Km north of the Bandarabbas. The Khurgu Anticline is the last outcropped anticline in the southeast of the Folded Zagros subzone. The studied area has never been studied before for microbiostratigraphical and lithostratigraphical characteristics. The studied successions include Mishan and Aghajari formations, which are outcropped in a syncline-anticline system.

The measured section of 2465 m thick consists of hard limestone, sandstone strata and loose marl, marly limestone, siltstone, non-solidified sandstone, and mudstone deposits. A systematic sampling process resulted in the collection of 324 loose and 54 hard samples. The loose and hard samples have processed for micropaleontological studies. The loose samples soaked in Sodium Sulfate solution and frizzed to disaggregating and washed over 2, 4 and 0.063 mm sieves. The faunal content of dried samples is handpicked and photographed by a Phenom Pro-X Desktop Scanning Electron Microscope connected to a 5MP camera. Several thin sections have prepared from hard samples and studied by a binocular microscope.

The lithostratigraphy of the section comprises limestone (Guri Member) and marly limestone at the base, marl and siltstone with marly limestone in the lower part, mudstone and marl in the middle parts and an alternation of sandstone and siltstone layers in the upper part. The sedimentary environment of the studied succession is marine in the basal and middle parts but in the upper part seems to be a marginal marine environment, influenced by coastal activities. The micropaleontology investigations resulted in the identification of 28 species of benthic, mainly deep benthic taxa, and 19 species of planktonic foraminifera. Based on the distribution of the identified taxa and the planktonic foraminifer’s biozonations (Bou Dagher-Fadel, 2013; Wade et al. 2011; Postuma, 1971; Blow, 1969; Bolli, 1966) and the ranges of the benthic foraminifera (Kender et al., 2008) the studied strata have deposited continually from the Early Miocene to the Pleistocene. The boundary between Mishan and Aghajari formations appears as gradual. The basal part of the Aghajari Formation is deposited in a marine environment.

The studied succession includes the deposits of the Mishan and Aghajari formations and comprises limestone, marly limestone, siltstone, sandstone, and mudstone strata. The basal and the middle parts of the section were deposited in a marine environment and the upper part was deposited in coastal and continental environments. The micropaleontological studies, based on the planktonic foraminifera, resulted in the identification of seven biozones and indicates that this succession deposited from the Lower Miocene to Pleistocene continuously. The sedimentary environment changes are gentle and no sedimentation disruptions had occurred.

Zagros sedimentary basin is one of the most important geological areas based on hydrocarbon potential in the world (Alavi, 2004) located between central Iran and the Arabian plate (Talebian & Jackson, 2004). Purple shale is one of the informal members at the base of the Pabdeh Formation in the Zagros basin (James & Wynd, 1965). This member in the Arabian plate was correlated to Rus and upper parts of Umm er Radhuma Formations (Ziegler 2001). We aimed to study the paleoenvironment and sequence stratigraphy of a section in the SouthEast of Malek-Shahi city, Ilam Province (West of Iran).

Purple shale member in this section is composed of three lithological parts (lower purple shale, middle gray shale, and upper purple shale). One hundred and eleven palynological slides related to the 37 rock samples have been prepared and studied. In sample preparation, we used HCl, HF, and ZnCl2 to extract palynological particles from carbonate and silicate minerals. All palynological slides were studied using a transmitted microscope. Three hundred and fifty palynological particles (including palynomorphs, structureless organic matter and phytoclasts) per one slide have been counted and relative abundance graph lines and charts including a palynological chart (Tyson 1993) have been plotted.

Palynofacies analysis and triangle chart can be used in paleoenvironmental reconstruction (Tyson, 1993). Plotting data on Tyson chart show four palynofacies areas including VI, VII, VIII, and IX. Most data show a high abundance of SOM (Palynofacies type IX). Based on this fact we can propose a distal suboxic-anoxic basin as the dominant paleoenvironmental conditions for this strata. Pridinioid/Gonialacoid ration in dinocyst assemblages can be used in productivity rate and upwelling current (Pross et al. 2006; Radi et al. 2006). Also, we used paleoecological index taxa for the reconstruction of paleoenvironment conditions including temperature, light, and energy current. We used cool water/warm water taxa ratio considering cool water taxa (Achomosphaera, Glaphyrocysta, Spiniferites) and warm water taxa (Areoligera, Exochosphaeridium) and other factors in this study based on Helenes and Tellez-Duarte 2002; Pross et al. 2006; Tyson 1993; Oboh & and Villiers 2003; Pross & and Schmiedl 2002; Stover 1996; Travers 2007; Gasemi-Nejad 2001). Palynological data and index dinocyst taxa can be used also in sequence stratigraphy studies (Carvalho, 2006; Robertson, 1993; Habib et al. 1992). One stratigraphic sequence has been identified based on palynological data in this study. 

Palynological investigations have been carried out for the reconstruction of the paleoenvironment and sequence stratigraphic of purple shale in the Zagros Basin. Based on this study, distal suboxic-anoxic basin, oligotrophic, low productivity and cool conditions have been proposed as the main paleoenvironmental conditions for this strata. Moreover, one stratigraphic sequence has been identified based on palynological data in these strata that shows a deepening upward trend in this section.

The Qom Formation consisting of limestones, marine marls, gypsum and siliciclastics (Reuter et al., 2009) was deposited at the last sea transgression in the Oligo-Miocene age (Khaksar & Maghfouri–Moghadam, 2007; Mohammadi et al., 2011, 2015; Mohammadi & Ameri, 2015) with northwest-southeast trending in three basins of Sanandaj-Sirjan fore-arc, Urumieh-Dokhtar intra-arc and Central Iran back-arc (Mohammadi et al., 2011; 2015; 2018; Mohammadi & Ameri, 2015). Due to the hydrocarbon resources and communicative role between Eastern and Western Tethys, the region the study of Qom Formation has been considered by many researchers (Mohammadi et al., 2018; Mohammadi & Ameri, 2015). This Formation was deposited at the north-eastern coast of the Tethyan Seaway (Reuter et al., 2009; Mohammadi et al., 2015). The Transgression of the Tethyan Seaway in the Iranian Plate started from the southeast and continued northwestward gradually (Mohammadi et al., 2013). Concerning the opening and closure times of the Tethyan Seaway on Iranian Plate, different views have been presented ranging from Early Oligocene (Rupelian) to Middle Miocene (Langhian) by Bozorgnia (1966), Schuster & Wielandt (1999), Berning et al. (2009),  Reuter et al. (2009), Harzhauser et al. (2007),  Bassi et al. (2009), and Khaksar & and Maghfouri Moghadam (2007). Due to the study of more than 100 stratigraphic sections of the Qom Formation and more than 30 geological maps of different parts of Iran (more than 1700 km of the north-eastern seashore of the Tethyan Seaway), Mohammadi et al. (2013) believed the opening time of the Tethyan Seaway on Iranian Plate began at 34°2´ latitude with the age of Rupelian, 35° latitude to the Chattian age and latitude greater than 35° to the Miocene.

In this research, seven marl, and thirty two calcareous samples were collected from Gonjan section, east of Rabor.

Qom Formation in the study area has 100 meters in thickness and consists of five limestone and marl informal members that these informal members are lower limestone, lower marl, middle limestone, upper marl, and upper limestone. Qom Formation in the study area lay on top of the Eocene volcanic rocks and the upper boundary is covered by recent alluvium. The following 41 species and 30 genera of foraminifera from the Gonjan stratigraphical section are identified: Triloculina trigonula, Discorbis sp., Chilostomella sp.,  Planorbulina sp., Pyrgo sp., Operculina sp., Haplophragmium slingeri, Valvulina sp., Sphaerogypsina sp., Amphistegina sp., Miliolids., Operculina camplanata, Elphidium sp., Textularia sp., Heterostegina sp., Eulepidina sp,. Nephrolepidina tournoueri, Nephrolepidina sp., Cibicides sp., Eulepidina cf. dilatata, Meandropsina iranica, Rupertina sp., Heterostegina cf. costata, Eulepidina cf. elephantina, Asterigerina rotula, Sphaerogypsina globulus, Rotalia viennotti, Uvigerina mioza, Uvigerina costata, Uvigerina sp., Amphistegina lobifera, Ammonia sp., Amphistegina hauerina, Rotalia sp., Quinqueloculina sp., Gyroidina sp., Lenticulina mamailligera, Nonion tuberculatum, Bolivina cf. churchi, Heronallenia kempii, Melonis simplex, Anomalinoides globulosa.Based on the diversity of the identified foraminifera in this section and also absence Nummulites fichteli, Nummulites intermedius and Nummulites vascus (index of Rupelian), Miogypsina (index of late Chattian-Aquitanian), Borelis melo curdica (index of the lower boundary of Burdigalian) and Abundance of lepidocyclinids, that suggested the age of Qom Formation deposits in Gonjan section is Rupelian?-Chattian. The presence and abundance of larger benthic foraminifera (such as Lepidocyclinids, Operculina, Heterostegina, Amphistegina), Coralline red algae and Coral fragments indicate the oligophotic to mesophotic and oligotrophic to mesotrophic conditions in the tropical to subtropical environments with normal salinity and low to high energy during the deposition of the Qom Formation.

Structural- facies region is divided into three subareas or structural zones of north Alborz, central Alborz, and south Alborz. Coaly sediments of Alborz according to structural specification, coal mining, and geographical divisions have been divided into three areas west Alborz, central Alborz, and east Alborz (Moin-o Sadat & Zade-Kabir, 1991). Range of study related to north Alborz subarea and from the viewpoint of coal mines classification is related west Alborz area. Between three formations of Ekrassar, Laleband and Kalariz with the age of Late Triassic (Late Carnian- Rhaetian) that before had depended on three members of Tazare formation, except Ekrassar formation, two formations of Laleband and Kalariz have coal veins that coal veins in Kalariz formation are very more and workable and economic so that in north Alborz, Kalariz formation is main beds of Shemshak Group coal mines. There are little exposures over in the area of north Alborz and SW Chaboksar (the eastern edge of Gilan province) coal local mines as more or less scattered related to sedimentary beds of Kalariz formation in near Kenar-Rud village as a small audit that not so long ago, people of the region used from these mines aim of limited extraction of coal. According to collapsing audits of the mines, a few plant remains have been found as loos specimens.

The localities studied are located in near of Kenar-Rud village in SW of Chaboksar, between 50° 29' and 50° 30' E and 36° 51' and 36° 53' N. Access path is Chalus, Ramsar, Javaher-Deh and Kenar-Rud road. Studied locality according to because of the Javaher-Deh formation located in north Alborz subarea. According to the last of divided of Shemshak group (Fürsich et al., 2009) in north Alborz subarea consists of four formations as Ekrasar formation (Late Carnian- Norian), Lale-band formation (Late Norian-Rhaetian), Kalariz formation (Rhaetian) and Javaher-Deh (Hettangian- Early Bajocian). Eastern bound of west Alborz is Chalus River. West Alborz is divided into five coaly regions of Sangrud, Aghusbon, Ramsar, Ghazwin, and Azarbayjan coal area, and the Ramsar coal region is divided into two sub-regions of Neydasht and Ekrassar, so that studied mines in this study located coal region of Ramsar and sub-region of Neydasht. The coal region of Ramsar is located in the northeast of the coal basin west Alborz in between Chaboksar to Tonekabon and Neydasht subarea is located in the northwest end of the coaly region of Ramsar. Studied beds related to the upper part of Kalariz formation near of Javaher-Deh formation beds.

In total, eight species are found from Kenar-Rud coal mines that include:Dictyophyllum nathorstii Zeiller 1903 (Age: Late Norian- Late Rhaetian), Nilssonia pseudobrevis (Barnard 1967b) Corsin & Stampfli 1977 (Age: Norian-Rhaetian), Pterophyllum aequale (Brongniart 1824) Nathorst 1878 (Age: Late Rhaetian), Pterophyllum sp., Dictyozamites asseretoi Barnard 1965 (Age: Rhaetian), Dictyozamites sp., cf. Nilssoniopteris musafolia Barnard 1965 (Age: Rhaetian), Anthrophyopsis crassinervis Nathorst 1878 (Age: Late Rhaetian).
Kalariz formation in north Alborz structural- facies zone; Kalariz and Alasht formations in central Alborz structural- facies zone and Kalariz, Alasht & Dansirit formations in south Alborz structural- facies zone consist of economic coal. Alasht formation in central Alborz structural- facies zone and Kalariz formation in the north and south Alborz has maximum coal in a total of west Alborz. Kanar-Rud coal mines in SW of Chaboksar located in the west Alborz coal area, Ramsar coal region, and Neydasht coal sub-region.

Coal mines around of Kenar-Rud village in SW of Chaboksar (East of Gilan province) consist of Rhaetian plant macrofossils from Kalariz formation that according to species of Dictyophyllum nathorstii, Anthrophyopsis crassinervis, Nilssonia pseudobrevis, Pterophyllum aequale & Dictyozamites asseretoi age of studied beds are Rhaetian and particularly two species of Anthrophyopsis crassinervis and Pterophyllum aequale the age of beds are Late Rhaetian (upper Kalariz). Dictyozamites and two species of Nilssonia pseudobrevis and Dictyozamites assretoi from western Alborz basin, Pterophyllum aequale from Ramsar region and Anthrophyopsis crassinervis Neydasht sub-region have been reported for the first time. Three divisions of Cycadophyta (especially order of Bennettitales), Filicophyta (true ferns) and Pteridospermophyta (seed ferns) in a total of genus trance is 78% and in species, trance is 81% from the total of plant macrofossils collection of western Alborz basin and remains of genus and species related to three divisions of Coniferophyta, Sphenophyta, and Ginkgophyta. The vegetation of Rhaetian time in two regions of Ghazwin and Sangrud-Aghuzbon is somewhat similar of each other (with Sorensenʼs similarity index 47%) and on the other hand vegetation of Ramsar region has different with two regions of Ghazwin (with Sorensenʼs similarity index 17%) and Sangrud- Aghuzbon (with Sorensenʼs similarity index 23%). Plant macrofossils collection in the western Alborz coal basin confirms the subtropical wet weather up to the tropical weather for the Rhaetian time (Kalariz formation).

One of the most extensive Cretaceous deposits in Zagros, the marine sediments of the Ilam and Gurpi Formations, the first in the Zagros based on stratigraphy and paleontology was identified (James & Wynd, 1965). The type section of the Gurpi Formation is studied in the Lali oil field, located in the NE of Masjed Suleiman. The type section of the Ilam Formation is situated in the Kabirkuh area, located in Lurestan. The most important things that can be done given of these formations in Zagros, determining the exact boundary of by calcareous nanofossil. At the oil field Bahr-e-Gansar, the upper part of the Ilam Formation and the lower part of the Gurpi Formation consists of 17 m thick was selected which mainly consists of marl, marly limestone, shale, and limestone.

In this study, twenty-seven samples from Ilam and Gurpi Formations have been studied. Samples were prepared following a standard smear slide method (Bown & and Young 1998). Calcareous nannofossil nomenclature follows the taxonomic schemes of Perch-Nielsen (1985). As a result of this study, twenty-two genera and thirty-five species of calcareous nannofossils have been identified.

Calcareous nannofossils recorded in the Cretaceous strata are appropriate and index taxa for biostratigraphic studies. Abbreviations used in this study are the CC (Cretaceous Coccoliths), UC (Upper Cretaceous), and the NC (Nannofossil Cretaceous). The nannofossil zonation used in the present study is based on the Nannoplankton Cretaceous zonation of Sissingh (1977), Burnett (1998), and Roth (1978). According to our biostratigraphic data, CC15 to CC20 biozones are introduced for the Ilam-Gurpi formations boundary. Four biozones of the zonation of Sissingh (1977) are recognized at the upper part of Ilam Formation as follows:Reinhardtites anthophorus zone (equivalent to UC11/ NC16): The first nannofossil unit recorded in this study is the CC15 zone. This biozone is recorded from the FO Reinhardtites anthophorus to the FO of Lucianorhabdus cayeuxii. The age of this zone is late Early Santonian.Lucianorhabdus cayeuxii zone (equivalent to UC12/ NC16): The second nannofossil unit recorded at the upper part of the Ilam Formation is the CC16 zone. This biozone is recorded from the FO Lucianorhabdus cayeuxii to the FO of Calculites obscurus. The age of this zone is early Late Santonian.Calculites obscurus zone (equivalent to UC13 / NC17): This zone spans the interval from the FO of Calculites obscures to the FO of Aspidolithus parcus parcus. The age of this zone is Late Santonian-Early Campanian.Aspidolithus parcus zone (equivalent to UC14/ NC18): The last nannofossil unit recorded in the uppermost part of the Ilam Formation is CC18 zone. This zone spans the interval from the FO of Aspidolithus parcus parcus to the LO of Marthasterites furcatus. The age of this zone is Early Campanian.Two biozones of Sissingh’s zonation (1977), recognized at the lower part of Gurpi Formation are as follows:Calculites ovalis zone (equivalent to UCl5aTP / NC18): The next nannofossil unit recorded in this study is the CC19 zone. This biozone is recorded from the LO of Marthasterites furcatus to the FO of Ceratolithoides aculeus. The age of this zone is late Early Campanian. Ceratolithoides aculeus zone (equivalent to UCl5bTP/ NC19): The last nannofossil biozone recorded at the lower part of the Gurpi Formation is the CC20 zone. This biozone is recorded from the FO Ceratolithoides aculeus to the FO of Quadrum sissinghii. The age of this zone is Late Early Campanian.

The detailed study based on calcareous nannofossils enables the subdivision of the studied deposits (upper part of the Ilam and lower part of Gurpi Formations) into six biozones and thus the boundary between the two formations appears to be transitional suggesting an age of the late Early Santonian to Late Early Campanian.

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.