Middle–Late Devonian boundary conodonts from Anarak and Sar-Ashk sections, central Iran

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The Middle/Late Devonian boundary is investigated based on twenty-four conodont species and subspecies from the Anarak and Sar-Ashk sections in the northwest and southeast of Central East Iran Microplate. The earliest Frasnian strata are defined by the first appearance of Ancyrodella rotundiloba pristina and can be correlated with the global stratotype in the Montagne Noir, South of France. The Late Givetian – Early Frasnian carbonates of the Bahram Formation in the Sar-Ashk section transgressively overlie the sandstones of the Padeha Formation, whereas the coeval interval in the Anarak section composes the middle part of the Bahram Formation.

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Nội dung Text: Middle–Late Devonian boundary conodonts from Anarak and Sar-Ashk sections, central Iran

Turkish Journal of Earth Sciences Turkish J Earth Sci (2022) 31: 71-84 http://journals.tubitak.gov.tr/earth/ © TÜBİTAK Research Article doi:10.3906/yer-2011-5 Middle–Late Devonian boundary conodonts from Anarak and Sar-Ashk sections, central Iran 1, 2 1 Hossein GHOLAMALIAN *, Vachik HAIRAPETIAN , Mohammad POOSTI  1 Department of Geology, Faculty of Sciences, University of Hormozgan, Bandar Abbas, Iran 2 Department of Geology, Esfahan (Khorasgan) Branch, Islamic Azad University, Esfahan, Iran Received: 06.11.2020 Accepted/Published Online: 22.11.2021 Final Version: 28.01.2022 Abstract: The Middle/Late Devonian boundary is investigated based on twenty-four conodont species and subspecies from the Anarak and Sar-Ashk sections in the northwest and southeast of Central East Iran Microplate. The earliest Frasnian strata are defined by the first appearance of Ancyrodella rotundiloba pristina and can be correlated with the global stratotype in the Montagne Noir, South of France. The Late Givetian – Early Frasnian carbonates of the Bahram Formation in the Sar-Ashk section transgressively overlie the sandstones of the Padeha Formation, whereas the coeval interval in the Anarak section composes the middle part of the Bahram Formation. Conodont biostratigraphy of Late Givetian – Early Frasnian strata in both sections revealed the presence of the Lower hermanni to Lower hassi zones. A new polygnathid species, Polygnathus anarakensis, is also proposed. Key words: Givetian, Frasnian, boundary, conodont, biostratigraphy, Iran 1. Introduction Ancyrodella rotundiloba early form (Feist and Klapper, Eifelian marine strata are rarely exposed in central 1985; Klapper, 1985; Klapper et al., 1987). Ancyrodella Iran (e.g. Zefreh area NE of Esfahan), which is studied rotundiloba pristina has recently been accepted as the by Brice et al. (2006). On the other hand, Givetian to synonym of An. rotundiloba early form (Klapper and Famennian sequences are extensively cropped out in the Kirchgasser, 2016); so, we follow this opinion and apply Central-East Iran Microplate (Wendt et al., 2002; 2005). it in the definition of the base of Frasnian. In addition to Many researchers have recently examined the Givetian to the stratotype, more recent studies are carried out on the Famennian strata of Iran by means of cephalopods and basis of conodonts and other faunas in some countries e.g., corals (Hairapetian and Korn, 2011, Korn et al., 2019, Morocco, Spain, and Belgian Ardenne (Aboussalam and Khaksar et al., 2006, Abbasi et al., 2014). Fish remains Becker, 2007, Liao and Valenzuela-Rìos, 2008; 2012; 2013; from these strata are studied by Hairapetian et al. (2006; 2016, Casier et al., 2013). 2008), Hairapetian and Ginter (2009), Hairapetian and Studies on the Givetian – Frasnian boundary in the Burrow (2016), and Hairapetian et al. (2016). Ghobadi southwestern Asia are restricted to the recent works, Pour et al. (2013; 2018) studied trilobites of these strata. such as the ones by Gholamalian et al. (2013) and minor Conodonts from the Givetian - Famennian time interval referrals of Ashouri (2004), Gholamalian and Kebriaei from central Iran have been described by Weddige (1984), (2008), Gholamalian et al. (2011), Königshof et al. (2017), Yazdi (1999), Ashouri (2004; 2006), Gholamalian (2003; Bahrami et al. (2019) and Wendt et al. (2002, 2005) in Iran 2007), Gholamalian and Kebriaei (2008), Gholamalian et and Özkan et al. (2019) who studied the Taurides of Turkey. al. (2009; 2011; 2013; 2014), Adhamian (2003), Hairapetian So, the absence of precise studies causes a lack of enough and Yazdi (2003), Bahrami et al. (2011; 2014; 2015; 2018), knowledge about the Middle/Late Devonian boundary and Königshof et al. (2017). in the north Gondwana/peri-Gondwana margin. On the The subcommission on Devonian Stratigraphy (SDS) other hand, many of mentioned researchers in Iran (e.g. has proposed the Middle – Late Devonian boundary Global Wendt et al., 2002; 2005), due to scarce sampling, did not Stratotype Section and Point at the base of bed 42á of Col attain Ancyrodella rotundiloba as the index species of G/F du Puech de la Suque, Montagne Noir, southern France. boundary and delineated the beginning of Frasnian stage This definition is based on the first appearance datum of based on other faunas or stratigraphic positions. * Correspondence: hossein_gholamalian@yahoo.com 71 This work is licensed under a Creative Commons Attribution 4.0 International License.
GHOLAMALIAN et al. / Turkish J Earth Sci Gholamalian et al. (2013) identified the position of Baghin, and Sardar sections in the north and west of G/F boundary in Hojedk, Baghin, and Sardar sections Kerman. Gholamalian (2006) and Bahrami et al. (2011) of Kerman area, southeast Central East Iran Microplate concluded the age of Middle Frasnian to Famennian and (Figure 1). In the present work, we examined the Sar- Late Frasnian to Early Famennian in the Hutk and Shams- Ashk (Kerman area) and Anarak sections in the southeast Abad sections of Kerman area, respectively. and northwest of Central East Iran Microplate in order to The Shishtu Formation (limestone, shale, and correlate G/F boundary interval. sandstone) is described by Ruttner et al. (1965) in Ozbak- The retrieved polygnathid conodonts have shown Kuh, north of Tabas. Its reference section is introduced in some hitherto unknown morphological and sculptural the Shotori Range, south of Tabas (Stöcklin et al., 1965). The characteristics, enabling us to make new species, boundary between the Bahram and Shishtu Formations is Polygnathus anarakensis. not known, so Wendt et al. (2002; 2005) would prefer to use the name of the Bahram Formation for all the Middle 2. Devonian lithostratigraphy of central Iran to Late Devonian limestone successions. Devonian strata of central Iran are divided into four lithostratigraphic units: the Padeha, Sibzar, Bahram, and 3. Studied sections Shishtu formations. The Padeha Formation is mostly The Anarak and Sar-Ashk sections in the northwest and composed of red shales and sandstones, but, because of southeast of Central-East Iran Microplate (CEIM) are the very scarce palaeontological data, its age of Early to selected for this work (Figure 1). The Anarak section is Middle Devonian is only known based on the stratigraphic located at the northeastern flank of Band-e-Abdolhossein position (Stöcklin and Setudehnia, 1991). Conodonts Those Mountain, 35 km southeast of the Anarak town and 235 are recovered from the Shabjereh section near Zarand km northeast of Esfahan (Figure 1). The Sar-Ashk section (Kerman Province) prove the age of Emsian – Givetian is located 71 km north of Kerman. This section is near the for the Padeha Formation (Nasehi, 1997; 2018). The Sibzar Sar-Ashk village on the eastern side of the Kerman – Ravar Formation dolostones transgressively overlie the Padeha road (Figure 1). Formation in many areas such as Ozbak-Kuh, Shirgesht, Coordinates of sections are as follows: N33˚10΄48.03˝, and Anarak (Stöcklin and Setudehnia, 1991; Wendt et al., E53˚52΄34.76˝ (Anarak) and N30˚49΄35.16˝, E57˚2΄2.71˝ 2005). This formation is unfossiliferous, so its age can (Sar-Ashk). only be estimated on the basis of its stratigraphic position. 3.1. Anarak section This formation is absent in most parts of the Kerman Anarak metamorphic complex (Neoproterozoic to area, such as Hojedk, Hutk, Hur, Baghin, Sardar, and Sar- Cambrian schists and marbles) is the oldest stratigraphic Ashk sections and laterally changes to the limestones of unit of this area (Sharkovski et al., 1984). Red to brown the lower part of the Bahram Formation (Ahmadi et al., clastic and carbonate beds of Ordovician and Silurian 2012, Gholamalian, 2006, Gholamalian et al., 2011; 2013; cover the metamorphic rocks (Popov et al., 2015). The 2014). The Bahram Formation limestones in these sections red sandstones of the ?Early to Middle Devonian Padeha of Kerman area directly cover red sandstones and shales of Formation conformably overlie the Silurian strata the Padeha Formation (Gholamalian and Kebriaei, 2008, and underlie the Middle Devonian Sibzar Formation. Bahrami et al., 2011; 2014). According to Wendt et al. (2005), the Bahram Formation The Bahram Formation is composed of fossiliferous with 341.2 m thickness conformably overlies the Middle gray limestones those conformably overlie the Sibzar Devonian Sibzar Formation dolomites and disconformably Formation in most parts of central Iran (except for Kerman underlies the Tournaisian – Namurian (Bashkirian) Sardar area). Formation (Figure 2). The base of the Bahram Formation Limestones of the Bahram Formation are widely in the present section is composed of 60.7m medium to exposed across central Iran and diachroneously overlie thin-bedded limestone and shales. It continues with 38.6m the Sibzar Formation (or the Padeha Formation in some biostrome and massive talus limestones (unit 5 of Wendt areas). The age of the Bahram Formation is Eifelian to et al., 2005) and 19.5m thin-bedded limestone and shale Frasnian in the Zefreh and Negheleh sections in the (including G/F boundary beds in the present paper). The north and northeast Esfahan (Kebriaei, 2003, Brice et rest of this section is composed of 42.5m massive limestone, al., 2006, Königshof et al., 2017, Gholamalian et al., in 60m thin-bedded limestone, and 85.9m alternation of press). Khaksar et al. (2006) stated the Early Givetian to thin-bedded limestone and shale. The uppermost part of Frasnian age for this formation in the Ozbak-Kuh section, the section is made of 14.7m deep marine marly limestone. eastern central Iran. Gholamalian and Kebriaei (2008) and Wendt et al. (2005) reported Early Famennian conodonts Gholamalian et al. (2013) revealed the Late Givetian to from this unit (Figure 2). The top of the section is covered Famennian age for the Bahram Formation in the Hojedk, by Tournaisian - Bashkirian beds (Wendt et al., 2005). 72
GHOLAMALIAN et al. / Turkish J Earth Sci Bahrami et al. (2019) examined the Anarak section (triangularis to ultimus zones) pelagic conodont fauna and attributed it to the Late Givetian to Early Famennian. from these beds. Sattari et al. (2021) investigated the upper part of the 3.2. Sar-Ashk section section and attributed it to the Famennian - Bashkirian This section is located at the northeastern flank of Zarand time interval. They extracted the Early to Late Famennian syncline in the north of Kerman, southeastern part of Figure 1. Structural maps of Iran showing Devonian outcrops (in red) including the discussed sections herein. Light grey area is Central East Iran Microplate (CEIM). Abbreviations: AZF – Abiz Fault; DRF – Doruneh Fault; KBF – Kuhbanan Fault; KMF – Kalmard Fault; MAF – Mehdi-Abad Fault; MZT – Main Zagros Thrust; NAF – Nostrat-Abad Fault; NBF – Nayband Fault; NHF – Nehbandan Fault; NNF – Nain Fault; OKF – Ozbak Kuh Fault; RVF – Rivash Fault; SBF – Shahr-e-Babak Fault; SHF – Siah Kuh Fault; TKF – Taknar Fault (modified after Hairapetian et al., 2017). 73
GHOLAMALIAN et al. / Turkish J Earth Sci Central-East Iran Microplate. The incidences of some sandstone that transitionally changes upward to the basal N-S trending faults (Naiband and Lakar-Kuh) with NW- 0.2m sandy limestone and thick-bedded limestones of the SE Kuhbanan fault are important structural elements in Bahram Formation (Figure 4). The sequence continues this region. Neoproterozoic to Late Cambrian strata (Rizu with 2.5m thick to medium-bedded shelly limestone, and Desu Series, Lalun and Mila formations) are present 1.6m laminar sandstone, and 16.1m medium-bedded overall. Because of an epeirogenesis phase (time-equivalent reddish shelly limestone. The Givetian/Frasnian boundary to the Caledonian Orogenesis), Ordovician and Silurian is identified within this part at 12.1m above the base of strata have been eroded (Sahandy and Haj Molla Ali, 1992). Bahram Formation (Figures 4 & 5). The section continues Middle to Late Cambrian dolomites of the Mila with 8.5m marly limestones, 40.2m massive limestones, Formation are thrusted on the red to white sandstones 13.8m sandstones and dolomites and 31.5m massive and red shales of the ?Early - Middle Devonian Padeha limestones containing two biostrome beds. Forty-eight Formation by a reverse fault (Figure 3). The siliciclastics meters of sandstone with 37.9m thin-bedded to massive of the Padeha Formation are fossil-barren, so their age can limestones make the upper part of Bahram Formation only be estimated on the basis of stratigraphic position that has the age of late Frasnian (rhenana – linguiformis and correlation to other areas. The upper part of the zones) (Bahrami et al., 2014). The Bahram Formation is Padeha Formation is composed of 7.5m white to light pink disconformably overlain by the Permian Jamal Formation Figure 2. Devonian and Carboniferous strata with the position of G/F boundary in the Anarak section. Ages are based on Wendt et al. (2005) and Bahrami et al. (2019). Figure 3. Cambrian and Devonian strata (Mila, Padeha and base of Bahram formations) in the Sar-Ashk section with the position of G/F boundary. 74
GHOLAMALIAN et al. / Turkish J Earth Sci Figure 4. A- Studied part of the Anarak section. B- Succession of sampled beds in the Anarak section. C- Medium to thin bedded mudstones of the base of sampled interval in the Anarak section. D – Close up view of transitional boundary between Padeha Formation siliciclastics and Bahram Formation limestones in the Sar-Ashk section. E- Close up view of the G/F boundary in the Sar-Ashk section. that shows a hiatus spanning the Famennian to Late of the samples are dissolved in buffered 25% acetic acid by Carboniferous. using the method of Jeppsson (2005). Studied conodont Bahrami et al. (2014) evaluated the Bahram Formation taxa were obtained from 25 of 49 samples collected in the Sar-Ashk section and entirely referred it to the Early from the Anarak and Sar-Ashk sections. Preservation of to Late Frasnian. elements is relatively good, and their color alteration index is almost 4. All of the conodont elements are stored in the 4. Material and Method Department of Geology, Faculty of Sciences, University of Forty-nine samples (3–4 kg each) are collected from Hormozgan under the repository codes of HUIC579 to limestone beds of the Anarak and Sar-Ashk sections. All HUIC643. 75
GHOLAMALIAN et al. / Turkish J Earth Sci Figure 5. Stratigraphic columns and conodont biozonation of studied successions. Productive samples are shown in bold. Biozonation is based on Klapper (1989), Klapper & Johnson (1990), Ziegler & Sandberg (1990) and Klapper & Kirchgasser (2016). 76
GHOLAMALIAN et al. / Turkish J Earth Sci 5. Biostratigraphy 5.1. Barren interval Twenty-four species and subspecies belonging to three Our samples from the base to G-F5 of the Sar-Ashk section genera (Polygnathus, Icriodus and Ancyrodella) enabled us were barren. According to the stratigraphic position, to use the global zonations of Klapper & Johnson (1990), the age of this interval is considered here as “older than Klapper (1989), and Klapper & Kirchgasser (2016) for the hermanni Zone” (Figure 5). Late Givetian and Frasnian biostratigraphy, respectively 5.2. Lower hermanni Zone - norrisi Zone (Figure 5, Tables 1 & 2). The first occurrence of An. The base of this interval in both Anarak and Sardar sections rotundiloba pristina as the index species for the beginning is defined by the first occurrence of P. dubius ranging from of the Late Devonian enabled us to designate the base of the Lower hermanni Zone to the upper part of the Lower Frasnian in the sections and correlate biozones to those hassi Zone (Narkiewicz and Bultynck, 2010, Figure 9). of the GSSP in the Col du Poech de la Suque section E of The top of the present interval is coincident with the first Montagne Noire, south of France (Klapper, 1985, Klapper appearance of Ancyrodella rotundiloba pristina at the base et al., 1987; Klapper, 1989). Moreover, as for the beds of the next interval. younger than Early Frasnian, the biozonation of Ziegler & The other associated fauna in the Anarak section are as Sandberg (1990) is used (Figure 5, Tables 1 & 2). follows: Polygnathus cf. dubius, P. aff. dubius, P. xylus xylus, Abbreviations used here are as follows: An. = P. aff. xylus, P. alatus, P. hojedki, P. aff. webbi, P. anarakensis Ancyrodella, I. = Icriodus, P. = Polygnathus. n. sp., P. sp. 1, P. sp. 2, Icriodus expansus and I. subterminus. Table 1. Distribution chart and biozones of conodonts in the Anarak section. Upper Zone 1 Biozones Lower hermanni to norrisi Lower Zone 1 ?Zone 3 to Lower hassi to Zone 2 GA GA GA GA GA GA GA GA GA GA GA GA GA GA GA GA GA GA Species Samples 2 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 20 21 An. rotundiloba pristina 1 2 5 3 3 An. binodosa 3 4 1 An.aff. binodosa 1 I. cedarensis 1 2 3 7 5 5 1 5 I. excavatus 5 2 7 5 12 20 6 I. expansus 7 3 3 1 4 7 10 6 14 3 10 5 11 17 7 1 I. subterminus 2 1 1 1 3 1 1 1 I. tafilaltensis 1 2 2 P. alatus 1 2 1 1 1 2 4 P. anarakensis n. sp. 2 15 P. dubius 2 4 7 1 29 8 7 6 10 8 6 2 5 4 1 P. cf. dubius 2 P. aff. dubius 1 1 4 1 P. hojedki 1 2 P. praepolitus 40 10 56 3 6 16 2 1 1 P. xylus xylus 6 10 66 23 24 25 95 50 1 13 9 5 5 7 5 2 P.aff. xylus 2 1 P. aff. pollocki 1 1 2 P. aff. webbi 1 2 1 1 1 P. sp. 1 1 1 1 P. sp. 2 1 1 P. sp.3 1 1 Unassigned elements 6 16 28 32 10 36 20 3 9 23 25 69 32 21 4 4 77
GHOLAMALIAN et al. / Turkish J Earth Sci Table 2. Distribution chart and conodont biozones in the Sar-Ashk section. Lower hermanni to Lower Biozones Upper Zone 1 – Zone 2 ?Zone 3 - Lower hassi norrisi Zone 1 Species Samples G-F6 G-F8 G-F13 G-F14 G-F15 X9 X10 An. rotundiloba pristina 5 3 4 1 An. binodosa 2 1 I. excavatus 25 8 2 I. expansus 2 1 35 28 1 I. lilliputensis 4 3 4 I. subterminus 2 2 P. alatus 2 P. dubius 6 1 16 4 1 P. praepolitus 10 4 3 P. xylus xylus 1 1 45 33 2 6 P. aff. webbi P. aff. subincompletus 1 Unassigned elements 7 33 34 8 7 Icriodus cedarensis ranging from the uppermost part of of this species was only based on a lower view of one the Upper hermanni Zone into the Lower rhenana Zone element, and the upper view is not presented. Moreover, (Narkiewicz and Bultynck, 2010) occurs in beds GA5, they erroneously delineated the base of Frasnian by the GA7, and GA8 (Table 1). Upper falsiovalis Zone that cannot be precisely correlated The associated fauna in the Sar-Ashk section are to the global zonation of Ziegler and Sandberg (1990). as follows: Polygnathus xylus xylus, P. alatus, Icriodus In the Sar-Ashk section, Bahrami et al. (2014) defined expansus, I. subterminus, I. lilliputensis. the lower limit of Frasnian just at the base of the Bahram 5.3. Lower Zone 1 Formation on the basis of the presence of one fragmentary The base of this zone in the Anarak and Sar-Ashk sections element of Ancyrodalla pristina in their single sample Z1. is designated by the first appearance of Ancyrodella The lower view of the element is not illustrated, which rotundiloba pristina that is the index for the beginning makes their identification problematic. On the other of Frasnian (Klapper, 1985; Klapper et al., 1987; Klapper, hand, they have incorrectly set the base of the Frasnian 1989; Klapper & Kirchgasser, 2016). The upper boundary with the Middle falsiovalis Zone that is not compatible is defined by the presence of An. binodosa in the next with the Late Devonian standard global zonations of interval (Figures 6.1 – 6.12). Ziegler and Sandberg (1990) and Klapper & Kirchgasser The associated species of the Anarak section are as (2016). In our opinion, the lower limit of this zone is 12.1 follows: Polygnathus dubius, P. cf. dubius, P. aff. dubius, m above the base of the section. P. xylus xylus and P. praepolitus. Icriodus tafilaltensis that 5.4. Upper Zone 1 – Zone 2 ranges from the base of the Lower hermanni Zone to The lower and upper boundaries of this interval in the upper boundary of transitans Zone (Narkiewicz and both sections are coincident with the total range of An. Bultynk, 2010) occurs in this interval (Figures 7.3, 7.4). binodosa. According to Narkiewicz and Bultynk (2010, The associated species of the Sar-Ashk section are Figure 9), this species ranges from the Upper Zone as follow: Polygnathus xylus xylus, P. dubius, P. alatus, P. MN1 to the base of Zone MN2. Other species in the praepolitus, Icriodus excavates, and I. expansus. Anarak section are as follows: Ancyrodella rotundiloba, The lower limit of this zone in the Anarak section Polygnathus dubius, P. xylus xylus, P. praepolitus, P. sp. is located at 121.4 m above the base of the Bahram 2, Icriodus expansus, I. cedarensis I. excavatus and I. Formation, but Bahrami et al. (2019, Figure 3) designated subterminus. Polygnathus pollocki ranging from the base the G/F boundary 19.6m above our level based on two of the Upper disparilis Zone to the upper boundary of the poorly preserved specimens of “Ancyrodella cf. pristina”, jamieae Zone also occurs here (Narkiewicz and Bultynk, obtained from a single sample (S105). Identification 2010, Figure 9) (Table 1). 78
GHOLAMALIAN et al. / Turkish J Earth Sci Figure 6. 1-2. Ancyrodella rotundiloba pristina Khalymbadzha & Chernysheva, 1970, upper and lower views of HUIC579, sample GA12, Anarak section. 3-4. Ancyrodella rotundiloba (pristina Khalymbadzha & Chernysheva, 1970, upper and lower views of HUIC580, sample GA12, Anarak section. 5. Ancyrodella rotundiloba pristina Khalymbadzha & Chernysheva, 1970, lower view of HUIC581, sample GA14, Anarak section. 6. Ancyrodella rotundiloba pristina Khalymbadzha & Chernysheva, 1970, upper view of HUIC582, sample GA14, Anarak section. 7. Ancyrodella binodosa Uyeno, 1967, upper view of HUIC583, sample GA13, Anarak section. 8. Ancyrodella binodosa Uyeno, 1967, upper view of HUIC584, sample GA13, Anarak section. 9. Ancyrodella aff. binodosa Uyeno, 1967, upper view of HUIC585, sample GA13, Anarak section. 10. Ancyrodella rotundiloba pristina Khalymbadzha & Chernysheva, 1970, upper view of HUIC586, sample G-F13, Sar-Ashk section. 11. Ancyrodella binodosa Uyeno, 1967, upper view of HUIC587, sample G-F14, Sar-Ashk section. 12. Ancyrodella binodosa Uyeno, 1967, upper view of HUIC588, sample G-F14, Sar-Ashk section. 13. Icriodus expansus Branson and Mehl, 1934, upper view of HUIC589, sample GA8, Anarak section. 14. Icriodus expansus Branson and Mehl, 1934, upper view of HUIC590, sample GA12, Anarak section. 15. Icriodus cedarensis Narkiewicz and Bultynck, 2010, upper view of HUIC591, sample GA8, Anarak section. 16. Icriodus cedarensis Narkiewicz and Bultynck, 2010, upper view of HUIC592, sample GA12, Anarak section. 17. Icriodus cedarensis Narkiewicz and Bultynck, 2010, upper view of HUIC593, sample GA13, Anarak section. 18. Icriodus cedarensis Narkiewicz and Bultynck, 2010, upper view of HUIC594, sample GA7, Anarak section. 19. Icriodus expansus Branson and Mehl, 1934, upper view of HUIC595, sample GA10, Anarak section. 20. Icriodus subterminus Youngquist, 1947, upper view of HUIC596, sample GA7, Anarak section. 21. Icriodus subterminus Youngquist, 1947, upper view of HUIC597, sample GA2, Anarak section. 22. Icriodus subterminus Youngquist, 1947, upper view of HUIC598, sample GA16, Anarak section. All scale bars are 0.2 mm. 79
GHOLAMALIAN et al. / Turkish J Earth Sci Figure 7. 1. Icriodus subterminus Youngquist, 1947, upper view of HUIC599, sample GA14, Anarak section. 2. Icriodus subterminus Youngquist, 1947, upper view of HUIC600, sample GA16, Anarak section. 3-4. Icriodus tafilaltensis Narkiewicz and Bultynck, 2010, upper and lateral views of HUIC601, sample GA12, Anarak section. 5. Icriodus excavatus Weddige, 1984, upper view of HUIC602, sample GA16, Anarak section. 6. Icriodus excavatus Weddige, 1984, upper view of HUIC603, sample GA15, Anarak section. 7. Icriodus excavatus Weddige, 1984, upper view of HUIC604, sample G-F13, Sar-Ashk section. 8. Icriodus excavatus Weddige, 1984, upper view of HUIC605, sample G-F13, Sar-Ashk section. 9. Icriodus excavatus Weddige, 1984, upper view of HUIC606, sample G-F13, Sar-Ashk section. 10. Icriodus subterminus Youngquist, 1947, upper view of HUIC607, sample G-F6, Sar-Ashk section. 11. Icriodus lilliputensis Bultynck, 1987, upper view of HUIC608, sample G-F8, Sar-Ashk section. 12. Icriodus expnsus Branson and Mehl, 19 34, upper view of HUIC609, sample G-F13, Sar-Ashk section. 13. Polygnathus xylus xylus Stauffer, 1940, upper view of HUIC610, sample GA8, Anarak section. 14. Polygnathus xylus xylus Stauffer, 1940, upper view of HUIC611, sample GA8, Anarak section. 15. Polygnathus xylus xylus Stauffer, 1940, upper view of HUIC612, sample GA6, Anarak section. 16. Polygnathus xylus xylus Stauffer, 1940, upper view of HUIC613, sample GA2, Anarak section. 17. Polygnathus aff. xylus Stauffer, 1940, upper view of HUIC614, sample GA6, Anarak section. 18. Polygnathus xylus xylus Stauffer, 1940, upper view of HUIC615, sample GA10, Anarak section. 19. Polygnathus xylus xylus Stauffer, 1940, upper view of HUIC616, sample G-F6, Sar-Ashk section. 20. Polygnathus xylus xylus Stauffer, 1940, upper view of HUIC617, sample G-F6, Sar-Ashk section. 21. Polygnathus alatus Huddle, 1934, upper view of HUIC618, sample GA21, Anarak section. 22. Polygnathus alatus Huddle, 1934, upper view of HUIC619, sample GA21, Anarak section. 23. Polygnathus sp. 1, upper view of HUIC620, sample GA7, Anarak section. 24. Polygnathus sp. 2, upper view of HUIC621, sample GA13, Anarak section. 25. Polygnathus sp. 3, upper view of HUIC622, sample GA8, Anarak section. All scale bars are 0.2 mm. 80
GHOLAMALIAN et al. / Turkish J Earth Sci Figure 8. 1. Polygnathus aff. webbi Stauffer, 1938, upper view of HUIC623, sample GA6, Anarak section. 2. Polygnathus dubius Hinde, 1879, upper view of HUIC624, sample GA12, Anarak section. 3. Polygnathus dubius Hinde, 1879, upper view of HUIC625, sample GA6, Anarak section. 4. Polygnathus dubius Hinde, 1879, upper view of HUIC626, sample GA13, Anarak section. 5. Polygnathus dubius Hinde, 1879, upper view of HUIC627, sample GA7, Anarak section. 6. Polygnathus dubius Hinde, 1879, upper view of HUIC628, sample G-F6, Sar-Ashk section. 7. Polygnathus dubius Hinde, 1879, upper view of HUIC629, sample G-F6, Sar-Ashk section. 8. Polygnathus aff. dubius Hinde, 1879, upper view of HUIC630, sample GA5, Anarak section. 9. Polygnathus aff. dubius Hinde, 1879, upper view of HUIC631, sample GA5, Anarak section. 10. Polygnathus cf. dubius Hinde, 1879, upper view of HUIC632, sample GA5, Anarak section. 11. Polygnathus dubius Hinde, 1879, upper view of HUIC633, sample GA5, Anarak section. 12. Polygnathus praepolitus Kononova, Alekseev, Barskov and Reimers, 1996, upper view of HUIC634, sample G-F13, Sar-Ashk section. 13. Polygnathus praepolitus Kononova, Alekseev, Barskov and Reimers, 1996, upper view of HUIC635, sample G-F14, Sar-Ashk section. 14. Polygnathus praepolitus Kononova, Alekseev, Barskov and Reimers, 1996, upper view of HUIC636, sample G-F13, Sar-Ashk section. 15. Polygnathus aff. subincompletus Ovntanova and Kononova, 1996, upper view of HUIC637, sample G-F14, Sar-Ashk section. 16-17. Polygnathus hojedki Gholamalian, Hairapetian, Barfehei, Mangelian and Faridi, 2013, upper and lower views of HUIC638, sample GA7, Anarak section. 18-19. Polygnathus anarakensis n. sp., upper and lower views of HUIC639, sample GA7, Anarak section. 20. Polygnathus anarakensis n. sp., upper view of HUIC640, sample GA7, Anarak section. 21. Polygnathus anarakensis n. sp., upper view of HUIC641, sample GA7, Anarak section. 22-23. Polygnathus anarakensis n. sp., upper and lower views of HUIC642, sample GA7, Anarak section. 24. Polygnathus anarakensis n. sp., upper view of HUIC643, sample GA7, Anarak section. All scale bars are 0.2 mm. 81
GHOLAMALIAN et al. / Turkish J Earth Sci The associated taxa in the Sar-Ashk section are as follow: narrow in the anterior one-third and become very shallow Ancyrodella rotundiloba pristina, Polygnathus xylus xylus, in the rest two-third of the platform. The outer lobe is wide P. dubius, P. alatus, P. praepolitus, P. aff. subincompletus P. and extends to the posterior end but the inner one is small. aff. webbi, Icriodus lilliputensis, I. expansus and I. excavatus The platform surface is covered by longitudinal rows of (Table 2). coarse nodes. The anterior part of the platform is narrow. 5.5. ?Zone 3 to Lower hassi Zone The small basal pit can be seen beneath the anterior one- The assemblage of Polygnathus dubius, P. cf. dubius, P. fourth of the platform. The free blade is composed of eight alatus, P. xylus xylus, P. praepolitus, P. aff. webbi, Icriodus to ten medium-size isometric denticles and reached up to expansus, I. excavatus, and I. subterminus occurs in this one-third of element length. interval in the Anarak section. The assemblage of An. Remarks: This new species can be distinguished from rotundiloba pristina, P. dubius, and P. xylus xylus is present Polygnathus ovatinodosus by having coarse nodes on the in this interval in the Sarashk section. platform surface instead of transversal ridges and the The base of this interval is defined by the upper limit carina that is fused and high only in the anterior one-third of the previous zone. The upper limit of the present zone of platform. Polygnathus eiflius resembles the P. anarakensis is coincident with the last appearance datum of P. dubius. in general outline, but the former species has deeper adcarinal troughs and tiny nodes on the platform surface. 6. Systematic palaeontology Polygnathus pseudofoliatus differs from P. anarakensis Order Ozarkodinida Dzik, 1976 by having broader inner and outer lobes, deep adcarinal Family Polygnathidae Bassler, 1925 troughs, and transverse ridges on the platform surface. Genus Polygnathus Hinde, 1879 Stratigraphic Range: Late Givetian; Lower hermanni to Type species: Polygnathus dubius Hinde, 1879 norrisi zones. Polygnathus anarakensis Gholamalian and Hairapetian n. sp. 7. Conclusion Figures 8.18 to 8.24. The Givetian – Frasnian boundary is defined in the Anarak Holotype: HUIC639, sample GA7, Anarak section. and Sar-Ashk sections (north and southeast of Central Paratype: HUIC641, sample GA7, Anarak section. East Iran Microplate) on the basis of the first presence of Material: Two Pa elements are found in bed GA5 and Ancyrodella rotundiloba pristina as the index marker of the 15 in GA7, Anarak section, Central East Iran Microplate. base of Late Devonian. Lower hermanni – norrisi, Lower Etymology: The species is named after the Anarak Zone 1, Upper Zone 1 to Zone 2, and ?Zone 3 to Lower town near the type locality in the center of Iran. hassi Zone are recognized here. Polygnathus anarakensis, Diagnosis: Pa elements of this new species are n. sp. is described from the Late Givetian (the Lower recognized by an asymmetric tongue-shaped platform hermanni – norrisi zones) strata of the Anarak section. with coarse nodes those are scattered on the surface and form very short ridges in some cases. This broad shallow Acknowledgment platform has a restricted narrow and short neck. The outer This research was under the financial and official supports part of the platform is broad and forms a wide lobe, but the of the Deputy of Research and Technology, University of inner part has a small lobe. Hormozgan, project no. 96/200/170. We thank Mr. Tollabi Description: The widest part of the platform is in the (Faculty of Dentistry, Esfahan University of Medical mid-length and becomes narrow and sharp to the posterior Sciences) for SEM micrographs. We also appreciate our end. Carina is fused without any denticle on the anterior friends who assisted us in all stages of this project, Dr. M.J. one-third of the platform, but it continues as separated Hassani, M.K. Kamali, M. Gholami, F. Amin-Nezhad, A. nodes to the posterior end. Adcarinal troughs are deep and Shahvaladian, and H. Shafiei. References Abbasi MA, Khaksar K, Ashouri AR (2014). Description of some Adhamian A (2003). Middle Devonian (Givetian) conodont rugose corals from the Givetian and Lower Frasnian of the biostratigraphy in the Soh area, north of Esfahan, Iran. Courier Eastern Alborz Mountains, NE Iran. Geopersia 4 (2): 237-257. Forsch- Institut Senckenberg 245: 183-193. Abboussalam ZS, Becker RT (2007). New Upper Givetian to basal Ahmadi T, Dastanpour M, Vaziri MR (2012). Upper Frasnian Frasnian conodont faunas from the Tafilalt (Anti-Atlas, (Upper Devonian) Polygnathus and icriodus conodonts Southern Morocco). Geological Quarterly 51 (4): 345-374. from the Bahram Formation, Hur section, Kerman province, southeastern Iran. Revista Italiana di Paleontologia e Stratigrafia 118: 203-212. 82
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