نشریه دیرینه شناسی
سال چهارم شماره 1 (پیاپی 7، بهار و تابستان 1395)

Belemnites are one of the most important groups of invertebrate fossils for biostratigraphical and paleoecological studies, particularly in the Jurassic system. The Badamu Formation is named after the village of Badamu and Kuh -e- Badamu (Badamu Mt) 24 km west of Kerman. This formation has been well known for many years because of its rich fauna, and its use in mapping the coal-bearing Jurassic deposits in the Kerman area (Seyed-Emami, 1967). The belemnites described in this paper have been collected from the Badamu Formation near the Cheshmeh Gaz village, about 60 km south of the Kerman. The Badamu Formation in Cheshmeh Gaz section has a thickness of approximately 52 meters and is predominantly composed of light-grey to cream limestones with shale intercalations in the middle part. Generally, a lower consisting of thin- to medium bedded marls with intercalations of limestones and an upper part of thick-bedded and cliff-forming limestone can be distinguished. The Badamu Formation is part of Shemshak group that was established in major parts of Central Iran ranges from the Late Triassic to Middle Jurassic (Aghanabati, 1977).

The present material was collected by the senior author during several field works.  From the Cheshmeh Gaz section, 68 specimens collected from marls and thin layers of yellow shaly limestone of this section. Well preserved specimens were cleaned, using a mild detergent and whenever necessary by using an ultrasonic vibrator and a preparation needle.

After closure of the Palaeotethys in the Late Triassic, the Iran Plate (Central and North Iran) occupied a position at the southern margin of Eurasia (Seyed-Emami et al 2008). According to palaeogeographic maps of the Early Jurassic (Seyed-Emami et al 2008) Central Iran occupied a fairly high latitudinal position at the northeastern margin of the Western Tethys. The faunal migration routes during the Early Jurassic and earliest Middle Jurassic followed most probably the epicontinental platforms at the southern margin of the Eurasian landmass (Seyed-Emami et al 2008). In this study 7 genera and 17 species belemnites are reported from the Badamu Formation, in Kerman area, for the first time. Based on identified belemnites, the age of corresponding strata is Toarcian-Middle Bajocian coinciding with Tenuicostatum- Humphriesianum ammonite zones. Belemnites study indicates an oceanic anoxic event at the beginning of Tenuicostatum biozone. The relative abundances at the genera level are: Acrocoelites (%35), Pachybelemnopsis (%6), Parapassaloteuthis (%12), Holcobelus (%12), Homaloteuthis (% 6), Eocylandroteuthis (%12) and Passaloteuthis (%17). In the Cheshmeh Gaz section the following belemnites genera are present: Acrocoelites levidensis, Acrocoelites longiconus, Acrocoelites subtenuis, Acrocoelites triscissus, Acrocoelites trisulculosus, Acrocoelites vulgaris, Eocylindroteuthis corneliaschmittae, Eocylindroteuthis trautscholdi, Holcobelus tetramerus, Holcobelus trauthi, Homaloteuthis spinata, Pachybelemnopsis baculiformis, Parapassaloteuthis robusta, Parapassaloteuthis sp., Passaloteuthis bisulcata, Passaloteuthis laevigata and Passaloteuthis milleri. Similarity between Thissection belemnites with north-West Europe belemnites (Weis & Marriotti, 2008; Mariotti et al 2007; Mariotti et al 2010; Mariotti et al 2012; Dolye & Kelly, 1988; Iba et al 2014), can be state relation between mentioned sections on Toarcian to Bajocian sedimentary basins. Belemnites study indicates an oceanic anoxic event at the beginning of Tenuicostatum biozone. Based on Palaeoecological interpretation, the Badamu Formation in Central Iran was deposited in an open, shallow and warm environment with normal salinity.

I am greatly indebted to Prof. Alsen Peter (Geological Survey of Denmark and Greenland), Prof.  Qiong Li (University of London) and Prof. Robert Weis (Museum national d'historie naturelle de Luxembourg) for their valuable comments on the identification of belemnites. I am deeply indebted to Prof. K. Seyed-Emami (University of Tehran) and Prof.  N. Raisossadat (University of Birjand, Iran) for their guidance and constructive discussions.

The first study on the Gachsaran Formation was first done by Pilgrim (1908), and others continued investigations from the 1920s (e.g., Richardson, 1924; Furon, 1941; Watson, 1960; James & Wynd, 1965; Setudehnia, 1972) Stratigraphic and sedimentologic studies of the Gachsaran Formation were carried out by Gill & Ala (1972), Kashfi (1980) and Motiei (1993). The studies were continued by Bahroudi & Koyi (2004), Moussavi Harami et al. (2010), Bahadori et al. (2011), Torabi et al. (2012), Gorjian et al. (2012), Aghdam et al. (2013) and Soleimani & Bahadori (2015). Most of these studies considered for geophysical properties, digenesis, and the geochemistry of deposits. There are a few biostratigraphic studies. Hence, the study of biostratigraphy and age determination of the Gachsaran Formation in this area improves understanding of this formation and provides useful and valuable information for exploration.The study area is located in the Zagros zone and the Coastal Fars as a sub-basin. Herein, we investigate the Gachsaran Formation for the identification of foraminiferal taxa, faunal assemblages, and biozones at a subsurface section in Bostaneh anticline located in the northwest of Bandar- e Lengeh.

In this research, 446 thin sections of well cutting were examined. Taxonomy of foraminifera was carried out in the micropaleontology laboratory of the Kharazmi University, using Loeblich and Tappan (1988), Henson (1950), Kennett & Sirinivasan (1983), Huang (1964), Adams & Bourgeois (1967), Papp & Schmid (1984), Bolli & Saunders (1985), Postuma (1971), Daneshian & Ramezani Dana (2007). Based on Gamma-ray logs and laboratory results, the lithostratigraphic boundaries were determined. The resulted biostratigraphy of foraminifers was followed and compared to those presented by Wynd (1965) and Adams & Bourgeois (1967).

The thickness of the Gachsaran Formation in Bostaneh anticline is 1288 m and consists of limestone, argillaceous limestone, anhydrite, salt deposits, marl, and thin layered shale. The studied sequence thickness is divided to Chehel, Champeh, and Mol members. In the investigated section, Gachsaran Formation underlies the Mishan Formation and overlies the Pabdeh Formation. Totally, 30 genera and 42 species of benthic foraminifera, and two genera and five species of planktic foraminifera were identified, from which the following zones have been identified.

Macro-borings are macroscopic traces on hard substrates produced by animals that penetrate hard substrates by drilling, grinding, dissolving, and scraping. They are considered as biogenic structures that are produced mechanically or biochemically by guest animals or parasites in hard substrates (Miller, 2007). The survey of such buildings was studied in the present study. Bioerosion is a general process in substrates and widely extended on non-living hard substrates such as rock and woods (Bromley, 1994). However, living substrates can also be used as temporary substrates by different organisms and play the role of inorganic hard substrates, in smaller dimensions. The process of bioerosion on living substrates has long been attracted the attention of many paleontologists, and extensive studies have been carried out to clarify the details of predation on bivalves and, interestingly, most of these studies on Cenozoic fossil communities have been studied (Martinell & Domènech, 1981; Bromley & Martinell, 1991; Kitchell et al., 1981). Many invertebrates can drill. Warme & McHuron (1978) have identified at least 12 species of invertebrates as having the capacity to hunt through the digging of other calcareous shells. According to Stanley (2008), the importance of the hunting process is to the extent that it affects an important part of the diversity of marine faunal specimens. Investigating the location of hunting remains and borings on the hunt can provide information on the behavior of the predator attack. The study of borings in recent decades has become an important topic in many paleontological studies due to the key role of these works in providing important information on the process of hunting, digging animals and even paleontological analyzes (Taylor, 1970; Kitchell et al, 1981; Bromley, 1981). Since borings are generally categorized as trace fossils, they provide valuable evidence of the constructive behavior of the trace that cannot be achieved through the study of body fossils. Besides, the study of these borings, as they are part of the bioerosion process, provides evidence of organisms (Miller, 2007).

Oyster bivalves are the most abundant biological debris present in marine sediments due to the high preservation potential of their shells. Accordingly, these organisms provide the hardest living substrates for different groups of organisms (El-Hedeny, 2005). For this reason, bioerosion is the most important taphonomic process that affects the oyster shells, and so identifying these patterns is important in the study of their taphonomy (El-Hedeny, 2005). On the other hand, most of the oysters, which are semi-infaunal, are in the tidal zone. This group attaches itself to the substrate by special methods to be resistant to the high energy of this region (Stenzel, 1971). Post-mortem oyster shells are also a good substrate for organisms (Farinati & Zavala, 2002). Some carnivorous species can make holes in the outer calcareous skeleton of invertebrates. Interesting observations of some of these activities were observed in the oyster shells of the Chehelkaman Formation in the Sheikh section. These borings extend extensively on the larger left valves of oysters and include vertical, cylindrical, and horizontal traces that developed on the shells. The distribution of encrusters on the gastropods indicates that they are concentrated near the mouth of these organisms. This distribution is apparently due to the high capability of these parts to use nutrients for their growth (Žítt et al., 2003). The vertical and oblique borings that examined in this study were divided into two groups in size. Larger varieties have a maximum depth of 5.15 mm and a maximum diameter of 5.08 mm. Smaller types that are more abundant have a maximum depth of 2.50 mm and a maximum diameter of less than 3 mm. The edges are clear and the walls are smooth. Interior is concave, flat, vertical, or concave-flat. The internal and external openings can also be centered or non-centered. The drilled axis is also at different angles to the surface of the shell, giving rise to different shapes. On this basis, as well as on the geometric structure five different groups A to E can be named. In the Sheikh section, the central part of the oyster shells exhibits the highest concentration of borings. Interestingly these parts are not the thinnest part of the shells. More precisely, it can be seen that these points are located in the muscles situation of the bivalves and these parts have been skillfully targeted by the predator, which assures the immediate opening of the valves (Kelley, 1988). Thin shells break down after drilling, and thus, types of thick shells are more likely to be affected by biological erosion. In older specimens with a thick shell, there is no evidence of attack or predation. Therefore, it is likely that these organisms will not be considered as prey by hunters.

In this study, the oyster fauna and gastropods of the Chehelkaman Formation at Sheikh section were studied for bioerosion and encrustation. Accordingly, five groups borings (A to E) were separated on the oyster shells. Most excavations were observed in Pycnodonte sp. In this study ichnogenus Oichnus (Bromley, 1981) belonged to the Naticid, and Entobia (Bronn, 1837) belonged to the sponges. Maeandropolydora (Voigt, 1965) and Talpina (Von Hagenov, 1840) were attributed to worms' activities. Most excavations in the specimens were concentrated in the central part of the bivalves and the excavations were more selective.

Due to difficult access to Makran Basin, a few geological investigations have been performed so far. The successions of Band-e-Chaker Unit in Tejek, Kermestann, and Irer sections were measured and studied. Bioerosion is frequently seen in the corals of the studied sections. Through this paper, we investigate on bioerosion and its related factors in carbonate coral-bearing parts of Band-e Chaker Unit in studied sections around Band-e Chaker Syncline with Burdigalian age. Tejek section is composed of pure limestone and Kermestan and Irer sections are mostly composed of marly limestone and clastic.

Based on the presence of corals, foraminifera, and previous studies (McCall et al., 1994), the studied sections are attributed to Burdigalian. According to diverse coral morphotypes, these sections indicate shallowing upward trends. In the studied sections, the effect of bivalves and polychaetes (serpula worms) in bioerosion is more obvious. Serpula worms are often the first organisms that colonize the coral surfaces (Hutchings & Peyrot-Clausade, 2002). Trypanites sp. and honeycomb borings are the most observed serpula traces on corals. In lower parts of sections that are concordant with deeper parts, serpula worm borings are thicker in diameter in comparison with upper and shallower parts. The other trace fossil that could be seen in the sections is Gastrochaenolites sp. which is created by bivalves; these are less frequent than serpula worms and mostly are present in shallower parts of the sections. Beside nutrient level, different environmental factors such as oxygen and salinity can affect in bioerosion process. Clastic and siliciclastic inputs decrease water transparency and increase nutrient level; increasing nutrient level is concordant with decreasing large benthic foraminifera and enhancement of filter-feeders and encrusters and finally bioerosion (Morsilli et al., 2012). Bioerosion, encrustation, and abundance of bryozoa are the result of an increase of nutrient availability. Based on the mentioned notes, a nutrient condition in the Tejek section is oligotrophic to slightly mesotrophic, and in Kermestan and Irer sections mesotrophic nutrient condition is identified. Size measurements of bioeroders show that increasing depth reduces the diameter and abundance of them. In this case, it seems that the dissolved oxygen in the water can play an important role in bioeroders’ diameter size.

We would like to thank Dr. A. Bahrami, Dr. E. Mohammadi, and Dr. C. Chaix who helped us in this investigation.

The Kopeh‍ Dagh sedimentary basin is located in the North and North East of Iran (Stöcklin & Setudehnia, 1991) and contains the most complete Cretaceous sediments (Darvishzadeh, 2010). Abtalkh Formation is has a maximum thickness in the East of Kopeh Dagh basin (Stöcklin & Setudehnia, 1991). The lithology of Abtalkh Formation mainly consists of light gray, blue to green shale, and siltstone. It conformably overlies the Abderaz Formation and the upper boundary is conformable with Neyzar Formation (Khosro-Tehrani, 2007). In this research, we aimed to present biostratigraphy of ostracods from Abtalkh Formation in the Babafaraji section.

The thickness of the Abtalkh Formation is 840 m in the Babafaraji section. In this study from Abtalkh Formation, 80 samples were collected every 10 meters. The samples were prepared to identify the Ostracods and Nannofossils. The samples were taken from a depth of approximately 50 cm and have been prepared as below.For sample preparation, we placed 500 grams of a sample in a beaker and soaked it with a solution of water and hydrogen peroxide for 24 hours then the remaining sediment washed and then dried by using the sieves (30 and 60 mesh) which respectively are stacked from coarse to fine. Then all ostracods removed from each sample by brush and put on a slide. All slides were studied under a Zeiss ZH55 reflective microscope and photographed with a scanning electron microscope. Samples examined for calcareous nannofossils content were prepared using traditional smear-slide techniques. Besides ostracods from the Babafaraji section, calcareous nannofossils were also investigated, and the biozonation of ostracods has been discussed alongside the stratigraphic distribution of calcareous nannofossils. The ostracods of Abtalkh Formation in the Babafaraji section have good preservation. In this research, 31 genera and 88 species of ostracods have been identified representing a well-diversified fauna. Generally, ostracods reached their maximum diversity and abundance in the lower part of the formation and are considerably reduced towards the upper part, especially near the boundary of Abtalkh and Neyzar formations. Ostracods often are living in lakes, deep seas and oceans and are strongly influenced by environmental parameters due to sensitivity to environmental conditions more than other species. (Riha, 1995). Therefore, ostracods are useful to palaeoecology studies, reconstruction of environmental conditions, and also in determining the biological horizons and age determination of marine and continental strata on local and regional scale.

According to the stratigraphic distribution of identified species, four interval biozones are as follow:Cytherelloidea sp.1 biozone with a thickness of 210 m is equivalent to Quadrum sissinghii Zone (CC21) and the age of this zone is early Late Campanian.Alatacythere sp.2 biozone with a thickness of 273 m is equivalent to Quadrum trifidum Zone (CC22) and indicating the uppermost of Late Campanian age.Limburgina sp. biozone with a thickness of 227.5 m is equivalent to Tranolithus phacelosus Zone (CC23) and is very end of Late Campanian to Early Maastrichtian in age.Cythereis sp.12 biozone with a thickness of 73.5 m is equivalent to Reinhardtites levis zone (CC24) and indicating Early Maastrichtian age.According to the studied ostracods and corresponding with nannofossil zones, the age of Abtalkh Formation in Babafaraji section was identified upper Late Campanian to Early Maastrichtian.

The Oligo/Miocene carbonate succession of the Asmari Formation from Zagros foreland Basin is cropped out in Dehdasht area (southeast of the Izeh zone). In compare to depositional area of the Asmari intra-shelf basin (more than 1500 kilometre2) and available data, the study area is nearly untouched and need more investigation. This study mostly focused on biostratigraphy of the Asmari Formation though four naturally well-exposed outcrops (Ganaveh, Siang, Arand and Dehdasht). A precise biostratigraphic interpretation of the Asmari Formation was compiled on the basis of the larger benthic foraminifera biozones allowing subdivision of the successions into four well-dated assemblages. Assemblage 1 only is present in the Ganaveh and Siang sections, indicating the Rupelian-Chattian? age. This assemblage toward the NW of the study area (Arand and Dehdasht) replaced by pelagic marl of the Pabdeh Formation. Assemblage 2 is restricted to the Chattian due to the first occurrence of Spiroclypeus blanckenhorni and also flourishing of the Archaias species. The low diversity of biotic contents and existence of Miogypsina and Favreina asmarica mark Assemblage 3 referring to the Aquitanian. Appearance of the Borelis melo group as a main characteristic of Assemblage 4 indicates Burdigalian. This investigation proves that the carbonates of the Asmari Formation in the studied area started to deposit in a proximal domain of a carbonate platform from Rupelian, whereas it was started in distal position from Chattian.

Up to now, the global community maturation cycle of Eocene deposits on the basis of Alveolina species was hitherto unknown from Iran. In this research, three evolutionary lines were identified based on phylogenetic and environmental parameters, represented by Alveolina ellipsoidalis (Schwager), Alveolina subpyrenaica (Leymerie), Alveolina moussoulensis (Hottinger), Alveolina laxa (Hottinger), Alveolina ilerdensis (Hottinger), Alveolina canavari (Checchia-Rispoli).  The phylogenetic and environmental parameters of Alveolina species, are revealed in a part of the fourth phase of the global community maturation (GCM) cycle within the five shallow benthic zones (SBZ7-SBZ11) in the western Alborz zone (Soltanieh Mountains).        

The material was collected from two sedimentary successions in Gheynarjeh and Baghdareh localities. The Gheynarjeh section of 52 m thick, in close proximity of Gheynarjeh village is exposed at 19 km southeast of Zanjan. The Baghdareh section of 85 m thick is measured approximately 1.5 km of the southwest of Baghdareh village and ca. 30 km west of Khoram Dareh. The section is situated about 90 km southeast of the town of Zanjan. This study is based on the samples collected of tow continuously outcropping stratigraphic sections (Baghdareh and Gheynarjeh) with special emphasis on alveolinids. The Alveolina assemblages were studied on about 80 oriented random thin-sections since the indurate carbonate rocks do not allow specimens to be freed from their encasing sediment. Systematic determinations of Alveolina species were adopted using Hottinger (1960), Drobne (1977), and Sirel & Acar (2008).

The global community maturation (GCM) cycle of Eocene deposits based on species of Alveolina from the Ilerdian-Cuisian shallow marine successions in the western Alborz (Soltanieh Mountains) are represented by 3 evolutionary lines into three groups:1- Ellipsoidalis group with evolutionary trend of Alveolina ellipsoidalis and Alveolina moussoulensis, associated with species of Alveolina aragonensis, Alveolina cf. dedolia, Alveolina pisiformis, Alveolina subpyrenaica and Alveolina tumida. 2- Subpyrenaica group consists of Alveolina ilerdensis and Alveolina subpyrenaica evolutionary line that is together with ovoidal species such as Alveolina sakaryensis and Alveolina decipensis. 3- Canavarii group is represented by Alveolina canavarii - Alveolina laxa evolutionary lineage with the first occurrence of Alveolina bayburtensis species. Therefore, the lower part of the fourth phase of the global community maturation (GCM) cycle (Hottinger 2001) is distinguished by the dominance of A-forms of Alveolina species with life strategy (r-mode) in the three evolutionary lineages, as explained above.