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Permian fusulinid assemblages and stratigraphy of the transcaucasia

Authors:
Ernst Leven at Geological Institute of RAS, Moscow, Russia
Ernst Leven
  • Geological Institute of RAS, Moscow, Russia
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Abstract

The Permian sequence of the Transcaucasia, which comprises the Davaly, Asni, Gnishik, Arpa, Khachik, and Akhura Formations, is described. A precise dating of the formations based on the analysis of fusulinid assemblages is also provided. The Davaly Formation corresponds to the Bolorian Stage of the Lower Permian (Cisuralian); the Asni Formation corresponds to the Kubergandian Stage, and to the lower half of the Murgabian Stage of the Middle Permian (Guadalupian); the Gnishik Formation corresponds approximately to the upper half of the Murgabian Stage; and the Arpa and Khachik Formations represent the entire Midian Stage of the Middle Permian. Only the uppermost Chanakhchy Beds of the Khachik Formation are referred to the upper series of the Permian (Lopingian), based on the latest proposal of the International Subcommission on Permian Stratigraphy concerning series boundaries. The Akhura Formation encompasses the Dzhulfian and Dorashamian Stages of the Upper Permian. Refined correlations between the Permian sequence of the Transcaucasia and the most complete Permian sequences of the Tethyan region (Central Iran, southestern Pamirs, South China, Japan) are presented. The transgressive overlapping of the Permian deposits is recorded in these areas, similar to the Transcaucasia. Although the transgression began during the Bolorian, it reached the widest extent in the Kubergandian and therefore, in most sections the transgressive series begins with deposits of Kubergandian age. The Middle and Upper Permian deposits of the Transcaucasia, Iran, and southern Turkey belonged to a single carbonate platform. Similar extensive carbonate platforms are recorded in the southern parts of Afghanistan and China. A change in the sedimentary regime was recorded in all these platforms at the boundary between the Guadalupian and Lopingian epochs. The Guadalupian time was marked by the intensive accumulation of biolitithic and detrital limestones produced by benthic organisms, mainly algae and foraminifers, whereas in the Lopingian time, carbonate and clayey micritic deposition dominated, and the role of nectonic-planctonic and nectonic organisms, such as cephalopods and conodonts, increased. The sedimentation change was abrupt and caused probably by the short-term post-Midian regression. The change resulted in a significant biotic crisis when larger fusulinids, goniatitids and agoniatitids, tabulate corals, most rugose corals and other organisms became extinct. These events marked the onset of the Late Permian 'Great Extinction', which ended at the Permian/Triassic boundary. Nine paleontological plates show the main fusulinid assemblages. Nine new species are described: Codonofusiella (?) vediensis, Chalaroschwagerina davalensis, Pseudofusulina arpaensis, P. araxensis, P. pjatakovae, Rugosochusenella davalensis, Misellina (Misellina) caucasica, Cancellina armenica, and Sumatrina vediensis.
Leven 1996 Transcaucas
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Leven 1996 Transcaucas
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... Since the Permian stages and events are marked by conodont biozones described in stratotype sections and points (GSSP; e.g., Jin et al., 2006aJin et al., , 2006b, the correlation of successions where conodonts or ammonites are absent or rarely recovered, is challenging. Co-recovery of foraminifera with conodonts yielded adequate correlation between the ammonite-based Permian stratigraphy of the Western Tethys and the conodont-based division of the Eastern Tethys (e.g., Pronina, 1988;Leven, 1998Leven, , 2003Leven, , 2009Sahakyan et al., 2017). The species of the Order Fusulinida are the basis for attribution to Permian stages in shallow warm water carbonate and mixed sediments. ...
... In David 1 this species co-occurs with Pseudodunbarula minima (Sheng et Chang, 1958) and Geinitzina ichnousa (Sellier de Civrieux et Dessauvagie, 1965), and in Pleshet 1, also with Codonofusiella erki Rauzer-Chernousova, 1965 (Fig. 2, marks 7, 27, 28). These species are attributed to the basal part of the Wuchiapingian or to the GLT, widely in the Tethys region (Chanahchi beds, Khachik Fm., Afghanistan; Armenia and in NE Iran respectively; sensu Arefifard and Davydov, 2015;Kotlyar et al., 1983;Leven, 1998;Rahman et al., 2022;Sahakyan et al., 2017). Their association with Pseudodunbarula arpaensis Chedija, 1984 ( Pronina, 1988Pronina, , 1997Kotlyar et al., 1999;Turhan et al., 2004;Zhang et al., 2015, Rahman et al., 2022. ...
... hainanica Sheng, 1965 was recovered from the middle of the high carbonate content interval in the Arqov Formation in Gevim-1 borehole, W. Israel (Orlov-Labkovsky, 2004), 8 km west to Pleshet-1 borehole (Fig. 5), without any other representatives from the Middle Permian. Since the Yangchienia species considered absent from the Late Permian successions of the Tethys, as reported from Tibet, Turkey, Transcaucasus, Zagros, Iran, and China (e.g., Leven, 1998;Kolodka et al., 2012;and others), the finding of this species in Gevim 1 borehole in the upper part of Arqov Fm (4293-99 m depth), and despite being the only indicative relevant finding for the Middle Permian, the interval in Gevim-1 borehole attributed the formation to the Midian (Middle Permian; Orlov-Labkovsky, 2004, Plate 3/18 there). However, the absence of Yangchienia, Yabeina and Lepidolina species in the equivalent interval in Pleshet-1 challenges the age determination for the Arqov Formation. ...
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... The Chhidru Formation contains relatively few fossils in the upper part and is topped with the White Sandstone Unit containing numerous gastropods. Although no age indicative fossils have been found, the White Sandstone Unit represents deposits during the worldwide end-Permian regression, and similar deposits have been documented at the base of the Waagenites Unit at the Selong Xishan section in Tibet (Shen et al., 2006) Gaetani et al. (1995), Angiolini (1995), Angiolini et al. (2005); Southeast Pamir: Grunt and Dmitriev (1973), Grunt and Novikov (1994), Kozur (1994), Leven (1998), Angiolini et al. (2015), Chernykh et al. (2020); Eastern Myanmar, Southern and western Thailand: Brönnimann et al. (1978), Waterhouse (1981), Waterhouse (1982), Unit (Pakistan-Japanese Working Group, 1985;Schneebeli-Hermann et al., 2012 Figure 7). ...
... The base of this formation contains fusulines and foraminifers such as Colaniella parva and Palaeofusulina aff. fusiformis (Leven, 1998). Kozur (1994) reported the conodont Clarkina subcarinata in the upper part of this formation, suggesting that the Takhtabulak Formation may belong to the Changhsingian Stage or the undifferentiated Lopingian Series (Figure 7). ...
Integrative Permian stratigraphy, biotas, paleogeographical and paleoclimatic evolutions of the Qinghai-Tibetan Plateau and its surrounding areas
Article
  • Sep 2023
The Permian Period was a critical time interval during which various blocks of the Qinghai-Tibetan Plateau have experienced profound and complex paleogeographical changes. The supercontinent Pangea was formed to its maximum during this interval, hampering a global east-to-west trending equatorial warm ocean current. Meanwhile, a semi-closed Tethys Ocean warm pool formed an eastward-opening oceanic embayment of Pangea, and became an engine fostering the evolutions of organisms and environmental changes during the Paleozoic-Mesozoic transition. Stratigraphy and preserved fossil groups have proved extremely useful in understanding such changes and the evolutionary histories of the Qinghai-Tibetan Plateau. Widely distributed Permian deposits and fossils from various blocks of the Qinghai-Tibetan Plateau exhibited varied characteristics, reflecting these blocks’ different paleolatitude settings and drifting histories. The Himalaya Tethys Zone south to the Yarlung Zangbo suture zone, located in the northern Gondwanan margin, yields fossil assemblages characterized by cold-water organisms throughout the Permian, and was affliated to those of the Gondwanaland. Most of the exotic limestone blocks within the Yarlung Zangbo suture zone are Guadalupian (Middle Permian) to Early Triassic in age. These exotic limestone blocks bear fossil assemblages that have transitional affinities between the warm Tethys and cold Gondwanan regions, suggesting that they most probably represent seamount deposits in the Neo-Tethys Ocean. During the Asselian to Sakmarian (Cisuralian, also Early Permian), the Cimmerian microcontinents in the northern part of Gondwana preserved glacio-marine deposits of Asselian to Sakmarian, and contained typical Gondwana-type cold-water faunas. By the middle Cisuralian (∼290–280 Ma), the Cimmerian microcontinents rifted off from the Gondwanaland, and drifted northward allometrically due to the active magmatism of the Panjal Traps in the northern margin of the Indian Plate. Two slices of microcontinents are discerned as a result of such allometic drifting. The northern Cimmerian microcontinent slice, consisting of South Qiangtang, Baoshan, and Sibuma blocks, drifted relatively quickly, and preserved widespread carbonate deposits and warm-water faunas since Artinskian. By contrast, the southern Cimmerian microcontinent slice, consisting of Lhasa, Tengchong, and Irrawaddy blocks, drifted relatively slowly, and were characterized by widespread carbonate deposits containing warm-water faunas of late Kungurian to Lopingian (Late Permian). As such, these blocks rifted off from the northern Gondwanan margin since at least the Kungurian. Thus, it can be inferred that these blocks were incorperated into the low latitude, warm-water regions later than the northern Cimmerian slice. Such discrepancies in depositional sequences and paleobiogeography imply that the rifting of Cimmerian microcontinents resulted in the formation of both Meso-Tethys and Neo-Tethys oceans during the Cisuralian. By contrast, the North Qiangtang block, because of its further northern paleogeographical position, contains warm-water faunas throughout the whole Permian Period that are affiliated well with the faunas from the South China, Simao, and Indochina blocks. Together, these blocks belonged to the members of the northern Paleo-Tethys Ocean. Thus, an archipelagic paleogeographical framework divided by Paleo-, Meso-, and Neo-Tethys oceans was formed, fostering a global biodiversity centre within the Tethys warm pool. Since most of the allochthonous blocks assembling the Qinghai-Tibetan Plateau were situated in the middle to high latitude regions during the Permian, they preserved most sensitive paleoclimate records of the Late Paleozoic Ice Age (LPIA), the Artinskian global warming event, and the rapid warming event at the end-Permian. Therefore, sedimentological and paleontological records of these blocks are the unique window through which we can understand global evolutions of tectonic movement and paleoclimate, and their impacts on spatiotemporal distributions of comtemporaneous biotas.
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... Biogeography. This family was cosmopolitan and distributed in the tropics and subtropical environments (Rauser − Chernousova et al., 1951;Skinner and Wilde, 1966;Leven, 1998). ...
... Ivanova, 1973;2008;PostoJalko, 1975;Einor, 1979;Chuvashov et al., 1986;Kulagina, 1988;Kulagina et al., 1992;2014a;Kulagina and Gibshman, 2002;Pazukhin et al., 2010), and Central Asia (e.g. Chuvashov et al., 1986;Leven, 1998;Leven and Davydov, 2001;Orlova-Labkovsky and Bensh, 2015). ...
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... Biogeography. This family was cosmopolitan and distributed in the tropics and subtropical environments (Rauser − Chernousova et al., 1951;Skinner and Wilde, 1966;Leven, 1998). ...
... Ivanova, 1973;2008;PostoJalko, 1975;Einor, 1979;Chuvashov et al., 1986;Kulagina, 1988;Kulagina et al., 1992;2014a;Kulagina and Gibshman, 2002;Pazukhin et al., 2010), and Central Asia (e.g. Chuvashov et al., 1986;Leven, 1998;Leven and Davydov, 2001;Orlova-Labkovsky and Bensh, 2015). ...
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... However, during the late Guadalupian, the Permian Chert Event saw chert accumulation greatly expand at the expense of carbonate deposition (Murchey and Jones, 1992;Beauchamp and Baud, 2002). Thus, platform carbonates are overlain by cherts in the Guadalupian Series of western North America (Murchey and Jones, 1992;Beauchamp and Baud, 2002;Matheson and Frank, 2020a), Far East Russia (Ueno et al., 2005) and Transcaucasia (Leven, 1998). The main contributors to Permian carbonate platform formation were foraminifers, calcareous algae, along with microbes and reefbuilders (Kiessling et al., 2003). ...
... In the Arabian isolated platform and southern Primorye in Far East Russia (Fig. 1A, locations 5 and 9), the retreat of carbonate platform margins is evidenced by a facies shift from bioclastic limestone to mudstone or cherts in the upper part of the Guadalupian succession (Weidlich and Bernecker, 2007;Kani et al., 2018). Similar changes occur in Transcaucasia, the Abadeh area and the Pha Nok Khao platform (Fig. 1A, locations 6-8), where light grey, thick-bedded limestone becomes increasingly blackish and thinner, and contains a higher chert proportion upwards both in the middle and upper parts of the Capitanian succession, reflecting platform contraction during the T2 and T3 transgressions, respectively (Leven, 1998;Hada et al., 2015, Fig. 4;Arefifard and Payne, 2020, Fig. 10b). ...
Stratigraphy of the Guadalupian (Permian) siliceous deposits from central Guizhou of South China: Regional correlations with implications for carbonate productivity during the Middle Permian biocrisis
Article
Full-text available
  • Mar 2022
  • EARTH-SCI REV
In comparison with the amount of study undertaken on the end-Permian mass extinction, the preceding Guadalupian mass extinction has received little investigation, even though it marks a significant biotic turnover associated with global environmental changes. During the earlier event, reef carbonate production shut down and was replaced by siliceous, mud-rich deposits (SRDs) in South China. However, changes in carbonate platform productivity during this epoch remain to be clarified. This paper presents sedimentological and conodont biostratigraphic investigations on the Guadalupian SRDs developed on the Yangtze Carbonate Platform (YCP) in central Guizhou. The findings are viewed in the context of Guadalupian sequence correlation of South China successions, which shows that the integrity of the YCP failed to match the platform tectonic evolution. The platform evolution saw the onset of major intra-platform depressions and the gradual onlap by SRDs along the platform margin. Stratigraphic correlation reveals that the platform experienced three phases of onlap by SRDs during the early Roadian, the late Wordian and the late Capitanian upwards. Platform carbonates re-expanded their extent following the first two phases, but not during the final phase. An evolutionary model is proposed for the Guadalupian carbonate platform, which follows the contemporaneous eustatic sea-level fluctuations. The partial drowning observed within the platform interior and increasing retreat along the platform margin could suggest an insufficient carbonate sediment supply shedding from the platform top during the Guadalupian. The variation in carbonate productivity raises our attention to the change in shallow-water carbonate factories, which is closely related to the fortunes of carbonate-secreting biota and environmental factors impacting the carbonate platform producers during the Guadalupian.
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... For example, Pseudofusulina and Misellina from all the microfacies have been reported from Chiang Dao of the northern Thailand (Ueno et al., 2008), the Tarn To Formation of Yala in the southern Thailand, and the Kinta Valley area in the western Malaysia (Ueno et al., 2015). Chalaroschwagerina from the microfacies 1 has been reported worldwide, including Longlin of Guangxi (south China), northern Tibet, Indochina, southwest Japan, and middle Asia (e.g., Toriyama et al., 1974;Zhou, 1989;Ueno, 1996;Leven, 1998;Zhang et al., 2013). Microproblematicas, encrusted sponges, and calcimicrobes common in the samples appear to be younger than the Permian. ...
Lower Permian limestone associated with ocean floor rocks in the Inthanon Zone of northern Thailand: new evidence for mélange
Article
  • Jan 2024
Scattered outcrops of various lithologies such as limestone, chert, sandstone, mudstone or shale, and microgabbro have been recently exposed in the Hariphunchai Education Center of Chiang Mai University (HECCMU), the northern Lamphun area of the northern Thailand. The outcrops are located in the Inthanon Zone where Palaeo-Tethyan ocean plate stratigraphy is well known. Field and microfacies analysis of limestone blocks recognizes four microfacies interpreted as low-energy lagoon or platform interior and reef flank or shoal of fore-reef. Foraminiferas from the limestone are the Sakmarian (lower Cisuralian) to Kungurian (upper Cisuralian) of the early Permian in age. Field and petrographic analysis of co-occurring radiolarian chert, microgabbro, pelagic mudstone, and turbidites suggest that the limestone blocks were mid-oceanic carbonate build-ups on seamount which were chaotically mixed with oceanic rocks such as chert and gabbro and then embedded in shale matrix. It is concluded that the outcrops are part of mélange formed during the Palaeo-Tethys closure and are significant in representing the Cisuralian (lower Permian) carbonate remnant in the mélange of the Inthanon Zone.
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... Wardlaw和Mei (1999) (Kozur, 1994 fusiformis (Leven, 1998). Kozur(1994)在该组上部报道 有牙形类Clarkina subcarinata, 因此, Takhtabulak组可 能大部分属于长兴阶或者整个乐平统(图7). ...
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... The conodont-based (Kozur, 1980;Taraz et al., 1981;Sweet and Mei, 1999a, b;Gallet et al., 2000;Partoazar, 2002;Kozur, 2004Kozur, , 2005Kozur, , 2007Henderson et al., 2008;Richoz et al., 2010;Shen and Mei, 2010;Ghaderi et al., 2014a;Isaa et al., 2016;Gliwa et al., 2020), the brachiopod-based (Stepanov et al., 1969;Teichert et al., 1973;Taraz et al., 1981;Ghaderi et al., 2014b;Garbelli et al., 2014;Viaretti et al., 2021), the ammonoidbased (Stepanov et al., 1969;Teichert et al., 1973;Taraz et al., 1981;Ghaderi et al., 2014a;Korn et al., 2016) and the foraminifera based (Altiner et al., 1980;Okimura and Ishii, 1981;Kotlyar et al., 1984Kotlyar et al., , 1989Leven, 1975Leven, , 1998Vachard, 2003, 2005;Kobayashi and Ishii, 2003) biostratigraphic dating in Lopingian Julfa and Abadeh sections provided an opportunity to assemble complete and precise biozonations and follow the detailed faunal diversity changes throughout the Lopingian and after the Permian/Triassic boundary (PT-B). Moreover, the well-exposed Permian and Triassic sediments in Iran have been extensively studied in terms of carbon isotope changes with specific focus on the mass extinction (Baud et al., 1989;Korte et al., 2004Korte et al., , 2010Heydari et al., 2000Heydari et al., , 2003Richoz, 2006;Horacek et al., 2007;Richoz et al., 2010;Shen et al., 2013). ...
Depositional environment and sequence stratigraphy architecture of continuous Upper Permian and Lowermost Triassic deep marine deposits in NW and SW Iran
Article
  • Aug 2022
  • PALAEOGEOGR PALAEOCL
The end-Permian mass extinction, the greatest biotic crisis through the Phanerozoic, caused a severe loss of marine organisms in terms of abundance and diversity. Knowing sea level fluctuations, environmental conditions and the sequence stratigraphic architecture of the Upper Permian deposits will enable us to reconstruct events before the mass extinction and across the Permian/Triassic boundary in a regional and global context. The Upper Permian deposits are examined in well-known sections in Julfa, NW Iran and Abadeh in SW Iran using microfacies analyses, depositional environment interpretation and sequence stratigraphic framework. Detailed petrographic examination and microfacies analyses show third- and fourth-order cycles both in Wuchiapingian and Changhsingian deep-water distally deposited strata of Julfa and Abadeh sections. Considering Iranian tectonics during Permian through Triassic time, there was rifting accompanied by drift and subsequent subsidence. Tectonics was a main factor that influenced the depositional environment and sequence stratigraphic framework in the study areas. According to previous studies, since subsidence increased in a North to SW direction during Middle Permian through Triassic time, this effect is seen in lithologic characteristics of the Wuchiapingian with more mid-ramp settings in Julfa Beds in Julfa area, compared to the more outer-ramp settings of the Unit 6 of the Hambast Formation in Abadeh area. Tectonic subsidence influence was also responsible for creating the fourth-order cycles within third-order cycles despite the absence of common glacial events to create high-frequency cycles in Iran during the Lopingian. The Lopingian successive deepening in Iran caused the faunal changes which is evident in decreasing trend of body size and biodiversity in brachiopods and ammonoids and also marks the beginning of the transgressive system tracts during this time interval.
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... The Nankinella-Chusenella assemblage, among them, might not be ideal for paleogeographic analysis, since its occurrences most likely reflect the facies preference for nearshore setting with restricted water circulation (Zhou and Sheng, 1994;Huang et al., 2015). This assemblage also occurs in other Gondwana-derived blocks, e.g. the Bawei Section of the Baoshan Block (Huang et al., 2017), the upper part of the Arpa Formation in Transcaucasia (Leven, 1998), the Surmaq Formation in the M-K section, Central Iran (Kobayashi and Ishii, 2003). Even in eastern Tethys, Nankinella specimens could form the Nankinella acme zone in the Chihsia Formation in South China (Chen, 1964;Zhou and Zhang, 1984). ...
Distribution pattern of Middle Permian fusulinids in the Lhasa Block, Tibet and their paleogeographic implications
Article
Full-text available
  • Dec 2021
  • PALAEOGEOGR PALAEOCL
The paleobiogeographic affinity of fusulinids in the Lhasa Block remains contentious, despite its significance for deciphering the complex Paleozoic history of the Tibetan Plateau. Our new collection from the Lhunzhub area and literature data recently accumulated necessitate an up-to-date overview of the Middle Permian fusulinids in this block from both taxonomic and paleobiogeographic perspectives. Systematic identification reveals Lepidolina multiseptata multiseptata, Colania ozawai, Verbeekina cf. tenuispira, V. americana etc., indicative of a Midian age, in the new materials from the Luobadui Formation. Overall, the Middle Permian fusulinids of this block could be distinguished into two types: 1) characterized by verbeekinids and neoschwagerinids; 2) dominated by Nankinella and Chusenella. Furthermore, these fusulinids as a whole were compared, at the generic rank, with their counterparts from other Gondwana-derived blocks, as well as Cathaysian South China, both qualitatively and quantitatively (cluster analysis and principal ordination analysis). Results show that these fusulinids of the Lhasa Block, is closely affiliated with those of the South Qiangtang, both of which paleobiogeographically belong to the Cimmerian Province, especially based on the occurrence of Rugososchwagerina (Xiaoxinzhaiella) and smaller foraminifer Shanita. Meanwhile, the Lhasa Block also bears resemblance with Cathaysian South China by sharing some genera of verbeekinids and neoschwagerinids, including the Lepidolina which more commonly occurs in the eastern Tethys and Panthalassa. It is remarkable that the Lhasa Block accommodates more diversified Middle Permian fusulinids than the eastern Cimmerian blocks do, given its lacking Early Permian fusulinids. Such contrast between the Early and Middle Permian fusulinids reflects considerable climatic amelioration of the Lhasa Block, which is interpreted to mainly result from its rifting from Gondwana before the Guadalupian time and northward drifting afterwards. The Lhasa Block was possibly located near to the South Qiantang Block, and at lower paleolatitudes than the eastern Cimmerian blocks during the Middle Permian.
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... The semi-quantitative percentages of the carbonate and sandstone framework components were calculated using visual estimation charts of the Baccelle and Bosellini (1965). The age-diagnostic larger benthic foraminiferal species were identified and presented by consulting the published literature (e.g., Davydov & Arefifard, 2013;Gaillot & Vachard, 2007;Hayward et al., 2012;Jenny-Deshusses & Baud, 1989;Ke et al., 2018;Kobayashi, 2012aKobayashi, , 2012bLeven, 1998; Mertmann & Sarfraz, 2000;Nestell, Nestell, Wardlaw, & Sweatt, 2006;Scholle & Ulmer-Scholle, 2003;Tekin et al., 2019;Ueno, Miyahigashi, & Charoentitirat, 2010;Wang, Ueno, Zhang, & Cao, 2010). The diagenetic features of the sandstone and carbonates were identified using petrography, SEM, and EDS analyses. ...
The Late Permian clastic-dominated carbonate shelf, Northwestern Pakistan: Implications for palaeoenvironments, palaeoclimate, and reservoir modelling
Article
Full-text available
  • Aug 2021
  • GEOL J
The Indus Basin of Pakistan has archived thick and laterally extensive Permian carbon-ates. The current study focuses on constraining the palaeoenvironments, reservoir potential, and ambient climatic conditions during the deposition of Late Permian clastic-dominated carbonates of the Chhidru Formation, Indus Basin, Pakistan. At outcrop, the unit shows laterally variable thicknesses of dominantly thick-bedded, fossiliferous, channelized calcareous sandstone, and sandy limestone. The microscopic textural, compositional, and biotic attributes divulged four microfacies, arguing for the deposition in a range of diverse depositional environments including lagoonal to delta-dominated middle shelf. The deposition of clastic-rich carbonates of the Chhidru Formation on the underlying pure carbonates of the Wargal Formation hints strongly towards a sea-level fall on the northwestern margin of the Indian Plate. The regression tightly correlates with the stratigraphic record of the adjacent continents, including South China, the Persian Gulf, and northern Gondwana regions. The abundance of detrital material indicates terrestrial influx to the basin, inhibiting the benthic activity and consequently resulting in poor microfossil content. Nevertheless, 11 age-diagnostic foraminiferal taxa were identified, suggesting a Late Wuchiapingian to Changhsingian age. The X-ray diffraction analysis of argillaceous horizons revealed several climate-sensitive clay minerals. Based on the dominance of illite, palygorskite, sepiolite, and chlorite, an extremely arid and cold climate is suggested for the region during the time of deposition of the Chhidru Formation. Petrographic observations suggest reworking of sediments shed from the Indian Shield of the Aravalli system and Malani Range. The petrography, scanning electron microscopy, and energy-dispersive X-ray spectroscopy revealed multiple diagenetic phases including marine, meteoric, and burial that have shaped the unit into a poor to the moderate reservoir.
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Uppermost Permian and Permo-Triassic Transition Beds in Central Iran
Article
  • Jan 1971
  • AAPG BULL
A continuous marine carbonate sequence (more than 2650 m or 8692- ft thick), commencing with the Artinskian transgression and ending with the regression of probably early Middle Triassic age, was discovered by the writer in 1967 in Central Iran near the town of Abadeh and is described in detail. The writer proposes that this formation be recognized as representing the Abadehian Stage, between the Guadalupian and Dzhulfian Stages. The Abadeh Formation may help in the correlation of the scattered Upper Permian sections throughout the world.
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