1. Introduction
The Istanbul Terrane is located along the southwestern Black Sea coast and is characterized by a thick, Palaeozoic (Ordovician–Lower Carboniferous) sedimentary succession without any major lithostratigraphic break. The Palaeozoic succession lies on Cadomian basement and was deformed during Carboniferous–Permian times. It is unconformably overlain by a Triassic sedimentary succession (e.g. Haas, Reference Haas1968; Okay, Sengör & Görür, Reference Okay, Sengör and Görür1994; Görür et al. Reference Görür, Monod, Okay, Sengör, Tüysüz, Yiğitbaş, Sakinç and Akkök1997; Özgül, Reference Özgül2012; Bozkaya, Yalçin & Göncüoğlu, Reference Bozkaya, Yalçin and Göncüoğlu2012 b; Göncüoğlu, Reference Göncüoğlu, Göncüoğlu and Bozdogan2012).
The lithostratigraphic units in the Istanbul Palaeozoic succession have been studied since the 1930s (Paeckelmann, Reference Paeckelmann1938; Haas, Reference Haas1968; Kaya, Reference Kaya1973; Önalan, Reference Önalan1987/1988; Gedik et al. Reference Gedik, Pehlivan, Timur and Duru2005; Özgül, Reference Özgül2012). Recently, a paper summarizing the stratigraphy of the Istanbul Palaeozoic succession, used in this study, has been published by Özgül (Reference Özgül2012). Existing stratigraphical knowledge on the Devonian of Turkey has been summarized by Yalçin & Yilmaz (Reference Yalçin and Yilmaz2010).
The Devonian–Carboniferous successions of the Istanbul area are dominated by a transgressive deepening-upward succession from a shallow shelf into a basin with deposition of nodular limestones and shales with radiolarites (Görür et al. Reference Görür, Monod, Okay, Sengör, Tüysüz, Yiğitbaş, Sakinç and Akkök1997; Yalçin & Yilmaz, Reference Yalçin and Yilmaz2010; Göncüoğlu, Reference Göncüoğlu, Göncüoğlu and Bozdogan2012).
There are few modern studies on Devonian ostracods from NW Turkey. Dojen et al. (Reference Dojen, Özgül, Göncüoglu and Göncüoglu2004 b) documented 11 silicified ostracod taxa from limestone intercalations within the transition interval between the Pelitli and Pendik formations in the Yakacik area (southern part of the Istanbul area). In addition to this, Nazik, Çapkınoğlu & Şeker, (Reference Naz˙ik, Çapkinoğlu and Şeker2012) described Famennian ostracods from the southern part of the Istanbul area. Late Frasnian entomozoacean ostracod species have been reported by Nazik & Groos-Uffenorde (Reference Naz˙ik and Groos-Uffenorde2011).
The present paper identifies 41 ostracod species belonging to 33 genera from the Devonian (Emsian–lower Eifelian) of the Kozyatağı Member of the Pendik Formation. Together with conodonts, ostracods are important biostratigraphical indices for correlating the rock succession and may be useful for palaeogeographic reconstruction.
2. Geological setting
The Pontides consist of three terranes (the Strandja, Istanbul and Sakarya units) amalgamated during Cretaceous time (Okay & Tüysüz, Reference Okay, Tüysüz, Durand, Jolivet, Horváth and Seranne1999). The Istanbul Terrane is separated in the south from the Sakarya Zone by the Intra-Pontide suture, and in the west from the Strandja Massif by the right-lateral strike-slip West Black Sea Fault (Okay, Sengör & Görür, Reference Okay, Sengör and Görür1994; Özgül, Reference Özgül2012).
Most of the Pendik Formation consists of micaceous fine-grained clastic rocks. There are also limestone intercalations present at certain horizons, especially in the upper levels. The Pendik Formation has a thickness of about 600–800 m, and is subdivided into two members: the Kartal and Kozyatağı (Özgül, Reference Özgül2012). The age of the Pendik Formation was suggested as Emsian–Eifelian based on trilobites (Gandl, Reference Gandl1973); late Emsian – early Eifelian based on goniatites (Kullmann, Reference Kullmann1973); Emsian based on bivalves (Babin, Reference Babin1973); and as Pragian–Emsian based on corals (Kaya, Reference Kaya1973). The conodont evidence clearly indicates an Emsian–Eifelian (serotinus–partitus biozones) age (Gedik et al. Reference Gedik, Pehlivan, Timur and Duru2005; Boncheva et al. Reference Boncheva, Sachanski, Gedik, Özgül, Göncüoğlu, Okuyucu, Saydam, Lakova and Yanev2005; Saydam-Demiray & Çapkınoğlu, Reference Saydam-Demiray and Çapkinoğlu2012).
The Kozyatağı Member of the Pendik Formation comprises limestone and shaly limestone intercalations. Its thickness varies between 5 and 100 m, and shows lateral and vertical transitions to shales of the Kartal Member (Yalçin & Yilmaz, Reference Yalçin and Yilmaz2010; Özgül, Reference Özgül2012).
A late Emsian age was proposed for the upper part of the Kozyatağı Member using trilobites (Gandl, Reference Gandl1973). This biostratigraphic age was supported by Kullmann (Reference Kullmann1973), based on corals and goniatites.
The Büyükdere section of the Kozyatağı Member, studied herein, has a thickness of 12.25 m. It is situated about 1.5 km SW of the Ömerli Dam and 1.25 km east of the village of Kurtdoğmuş (Fig. 1), on the western end of the Çatalca Peninsula, Istanbul, NW Turkey (Saydam-Demiray & Çapkınoğlu, Reference Saydam-Demiray and Çapkinoğlu2012). The section starts with grey, greenish-grey, thin- to medium-bedded, limestone–shale alternations and is overlain by greenish-grey to grey, thin- to medium-bedded limestones with intermittently laminated limestone and shale intercalations (Fig. 2). A diverse fossil assemblage consisting of silicified ostracods, juvenile trilobites, conodonts and agglutinated foraminifers (common Ammodiscus and rare Hemisphaerammina) has been recovered from limestone interbeds in this section.
Location map of the study area in northwestern Turkey.
Stratigraphical section of the Pendik Formation in northwestern Turkey. Modified after Saydam-Demiray & Çapkınoğlu (Reference Saydam-Demiray and Çapkinoğlu2012) and Özgül (Reference Özgül2012).
The conodont fauna indicates an age extending from the late Emsian (samples BD-1 to BD-24) into the earliest Eifelian (samples BD-25 to BD-26) and defines an interval extending from the serotinus Biozone into the partitus Biozone (Saydam-Demiray & Çapkınoğlu, Reference Saydam-Demiray and Çapkinoğlu2012).
3. Material and methods
Eighteen of 26 limestone samples processed for conodonts by Saydam-Demiray & Çapkınoğlu (Reference Saydam-Demiray and Çapkinoğlu2012) produced silicified ostracods consisting mainly of single valves and rare carapaces. Samples were dissolved in formic and/or acetic acid. Subsequently, residues were washed, dried and picked under the stereoscopic microscope.
The ostracods were mounted on aluminium stubs, coated with platinum and imaged using a Philips XL 20 scanning electron microscope in the Institute of Paleobiology, Polish Academy of Sciences, Warsaw, Poland.
The studied ostracod material is deposited in the collections of the Department of Geological Engineering of Çukurova University (Adana, Turkey), under the inventory numbers BD (1–216).
4. Palaeontological notes on the ostracods
More than 4000 ostracod specimens were extracted from the limestone strata of the Büyükdere section. A total of 41 species were identified. Of these, 23 species belong to previously known taxa, and 15 have been described in open nomenclature. One genus and three species are newly described. The distribution of species is summarized in Figure 3.
Faunal log from the Büyükdere outcrop, showing distribution of ostracods. Abbreviations: Micro. – Microcheilinella; Praep. – Praepilatina; Cyther. – Cytherellina; Boh. – Bohemina; Acravi. – Acravicula.
Diversity ranges from 2 to 20 species in each horizon. It is most diverse (21 species) at the base of the section. Assemblages from the samples BD-14 to BD-16 show a decrease in species diversity.
The ostracod fauna of the Büyükdere section includes species belonging to the orders Palaeocopida, Podocopida and Myodocopida (Figs 4–7). The higher classification used in this study follows Whatley, Siveter & Boomer, (Reference Whatley, Siveter, Boomer and Benton1993) with small modifications. The Whatley, Siveter & Boomer, (Reference Whatley, Siveter, Boomer and Benton1993) scheme is a shell-based taxonomy for the Palaeozoic forms, and recent discoveries of Palaeozoic ostracods with soft anatomy may lead to a radical rethinking of these taxonomic schemes in due course.
4.a. Order Palaeocopida Henningsmoen, Reference Henningsmoen1953
Four species of Hollinoidea are recognized: Ctenoloculina latisulcata Adamczak, Reference Adamczak1968 (Fig. 4a, b); Semibolbina alcaldei Becker & Sánchez de Posada, Reference Becker and Sánchez De Posada1977 (Fig. 4c, d); Thuringobolbina sp. (Fig. 4e); Foeditatis? sp. (Fig. 4g); and indeterminate Hollinoidea species (Fig. 4f).
Devonian ostracods from the Pendik Formation. (a, b) BD-26/184, Ctenoloculina latisulcata Adamczak, Reference Adamczak1968, heteromorphic left valve in lateral and oblique ventral view. (c, d) BD-25/197, Semibolbina alcaldei Becker & Sánchez de Posada, Reference Becker and Sánchez De Posada1977, heteromorphic right valve in lateral and oblique ventral views. (e) BD-01/196, Thuringobolbina sp. juvenile right valve in lateral view. (f) BD-1/10, Hollinoidea indet., juvenile left valve in lateral view. (g) BD-26/192, Foeditatis? sp. right valve in lateral view. (h, i, j, k) Bodzentia cf. sulcata Adamczak, Reference Adamczak1968: (h, i) BD-17/71, left valve in lateral and oblique ventral views; (j, k) BD18/205, right valve in lateral and oblique ventral views. (l, m) ‘Selebratina’ sp.: (l) BD-1/13, right valve in lateral view; (m) BD-25/178, left valve in lateral view. (n, o) Clavofabellina? sp.: (n) BD-20/132, left valve in lateral view; (o) BD-25/183, left valve in lateral view. (p, q) BD18/107, Buregia? sp., right valve in lateral and oblique ventral view. (r, s) BD-1/6, ‘Aparchites’? sp., left valve in lateral and oblique ventral view. (t, u) Ulrichia (Ulrichia) ex gr. spinifera (Coryell & Malkin, Reference Coryell and Malkin1936): (t) BD-11/208, left valve in lateral view; (u) BD-20/129, carapace in left lateral view. Scale bar 200 μm.
C. latisulcata was found in the uppermost part of the Büyükdere section and indicates an early Eifelian age for this part of the succession. This species is previously reported from the lower Eifelian – lower Givetian Yeraїfia Formation in the southwestern Anti-Atlas (Becker, Lazreq & Weddige, Reference Becker, Lazreq and Weddige2004). It was also reported from the lower Eifelian of the Holy Cross Mountains (Adamczak, Reference Adamczak1968). S. alcaldei has been found only in the upper part of the Büyükdere section, in the transition beds of the Emsian–Eifelian boundary. This short-ranging species is also known from the upper Emsian strata of the Moniello Formation of Asturias, northern Spain (Becker & Sánchez de Posada, Reference Becker and Sánchez De Posada1977). It also occurs in the upper Emsian Santa Lucía Formation of northern León, Spain (Becker, Reference Becker2001), the upper Emsian Khebchia Formation of the southwestern Anti-Atlas, Morocco (Becker, Lazreq & Weddige, Reference Becker, Lazreq and Weddige2004), and the upper Emsian Tentaculite Shale of Thuringia, Germany (= Parabolbina n. sp. of Zagora, Reference Zagora1968). Thuringobolbina sp. is similar to Thuringobolbina thuringensis Zagora, I., Reference Zagora1967 from Pragian age strata of Thuringia (Zagora, I., Reference Zagora1967) but differs slightly from the latter in the presence of a spine on the anterodorsal part of the carapace. Foeditatis? sp. is similar in the location of spurs to juvenile specimens of Foeditatis spinosa Wang, Reference Wang1989 from the upper Emsian succession of Guangxi, China (Wang, Reference Wang1989), but differs in having a poorly developed adductorial sulcus.
Representatives of Primitiopsoidea are common in the Büyükdere section, represented by Bodzentia cf. sulcata Adamczak, Reference Adamczak1968 (Fig. 4h–k); ‘Selebratina’? sp. (Fig. 4l, m); Clavofabellina? sp. (Fig. 4n, o); and Buregia? sp. (Fig. 4p, q). All these species are poorly preserved, and features such as the marginal structures of valves are difficult to discern. Sexual dimorphism was not observed. B. cf. sulcata is conspecific with Bodzentia sp. 7 of Groos-Uffenorde (in Feist & Groos-Uffenorde, Reference Feist and Groos-Uffenorde1979) from lower Emsian strata of the Montagne Noire (southern France); it also occurs in the lower upper Emsian Aguión Formation of Asturias, northern Spain (Becker, Reference Becker2000).
Three taxa from the superfamily Drepanelloidea are recognized: Ulrichia (Ulrichia) ex gr. spinifera Coryell & Malkin, Reference Coryell and Malkin1936 (Fig. 4t, u); Ulrichia (Subulrichia) fragilis Warthin, Reference Warthin1934 (Fig. 5a–c); and Aechmina tenuispina, Zagora, K., Reference Zagora1967 (Fig. 5f, g).
Devonian ostracods from the Pendik Formation. (a, b, c) Ulrichia (Subulrichia) fragilis Warthin, Reference Warthin1934: (a) BD-17/74, left valve in lateral view; (b, c) BD-17/85, right valve in lateral and oblique ventral views. (d, e) BD-25/176, Berdanella igesohni Becker, 1989, right valve in lateral and oblique ventral views. (f, g) Aechmina tenuispina Zagora, K., 1967: (f) BD-20/123, left valve in lateral view; (g) BD-20/124, left valve in lateral view. (h, i) Cryptophyllus sp. A of Becker & Sánchez de Posada (Reference Becker and Sánchez De Posada1977): (h) BD-11/35, left valve in lateral view; (i) BD-23/151, right valve in lateral view. (j, k) Eridoconcha spinosa Zagora, Reference Zagora1966: (j) BD-26/185, left valve in lateral view; (k) BD-17/78, right valve in lateral view. (l, m) BD-5/29, Poloniella sp. A of Becker & Sánchez de Posada (Reference Becker and Sánchez De Posada1977), right valve in lateral and oblique ventral views. (n, o, p, q) Thlipsohealdia abadia Becker, 1989: (n, o) BD-23/143, left valve in lateral and oblique ventral views; (p) BD-23/140, left valve in lateral view; (q) BD-24/166, right valve in lateral view. (r) BD-5/31, Simplicithlipsa cortes Becker, Reference Becker1996, right valve in lateral view. (s) BD-20/204, Marginohealdia costata (Zagora, Reference Zagora1968), left valve in lateral view. (t) BD-1/210, Marginohealdia sp. 1, right valve in lateral view. (u) BD-23/146, Marginohealdia sp. 2, left valve in lateral view. Scale bar 200 μm.
U. (U.) ex gr. spinifera and U. (S.) fragilis are geographically widespread and long-ranging species, known from the Lower to Middle Devonian of Europe, North Africa and North America (Zagora, Reference Zagora1968; Kesling & Chilman, Reference Kesling and Chilman1978; Becker, Lazreq & Weddige, Reference Becker, Lazreq and Weddige2004; Dojen, Reference Dojen2004; Dojen et al. Reference Dojen, Gozalo, Carls and Valenzuela-Ríos2004 a; C. Dojen, unpub. Ph.D. thesis, Tech. Univ. Carlo-Wilhelmina, Braunschweig, 2005; Maillet et al. Reference Maillet, Tanjaoui-Arif, Milhau, Nicollin and Ouali Mehadji2013). A. tenuispina was reported from the Eifelian of Thuringia, Germany (Zagora, K., Reference Zagora1967). It might be conspecific with Aechmina sp. of Blumenstengel (Reference Blumenstengel1962) from the Pragian of Thuringia and with Aechmina sp. A of Becker & Sánchez de Posada (Reference Becker and Sánchez De Posada1977) from the upper Emsian Moniello Formation. It is also similar to Aechmina sp. of Becker (Reference Becker2001) from the upper Emsian Santa Lucía Formation (northern León, Spain).
Two species from the suborder Eridostracina are recognized: Cryptophyllus sp. A of Becker & Sánchez de Posada (Reference Becker and Sánchez De Posada1977) (Fig. 5h, i), and Eridoconcha spinosa Zagora, Reference Zagora1966 (Fig. 5j, k).
C. sp. A belongs to the group of morphologically very similar taxa reported from throughout the Devonian of Europe, North Africa and North America (for details see Kesling & Chilman, Reference Kesling and Chilman1978; Becker, Lazreq & Weddige, Reference Becker, Lazreq and Weddige2004). The occurrence of E. spinosa in each bed suggests age equivalence with the upper Emsian Tentaculite Shale of Thuringia (Zagora, Reference Zagora1966) and upper Emsian Moniello Formation strata of Asturias, northern Spain (Becker & Sánchez de Posada, Reference Becker and Sánchez De Posada1977).
Berdanella igesohni Becker, Reference Becker1989 (Fig. 5d, e), which has not been assigned to any known superfamily, has been reported from the Emsian Abadía Formation (Polentinos Member) and lowermost Eifelian Gustalapiedra Formation of the Palencia Basin, Cantabrian Mountains (Becker, Reference Becker1989). It seems to be conspecific with Berdanella sp. A of Becker, Lazreq & Weddige (Reference Becker, Lazreq and Weddige2004) from lower Eifelian strata (Yeraïfia Formation) of Morocco, and with Kirkbyella (Berdanella) sp. 57 of Groos-Uffenorde (in Feist & Groos-Uffenorde, Reference Feist and Groos-Uffenorde1979) from lower Emsian strata of the Montagne Noire, France.
Three species of unknown relationships are represented by the scrobiculid Roundyella pokornyi (Zagora, Reference Zagora1968) (Fig. 7s, t); R. goekchenae Olempska & Nazik sp. nov. (Fig. 7o–r); and Omerliella rectangulata Olempska & Nazik gen. et sp. nov. (Fig. 7u–w).
R. pokornyi is known from the upper Emsian Moniello Formation strata of Asturias, Spain (Becker & Sánchez de Posada, Reference Becker, Lazreq and Weddige1977); upper Emsian of the Santa Lucía Formation, Spain (Becker, Reference Becker2001); and the Emsian Tentaculite Shales of Thuringia (Zagora, Reference Zagora1968). R. goekchenae and O. rectangulata are described fully in Section 4.d below.
The family Aparchitidae is represented by specimens of the ‘bag’ genus ‘Aparchites’ (‘A’.? sp.; Fig. 4r, s). Specimens from the Büyükdere section are insufficiently preserved to determine if they belong to this genus.
4.b. Order Podocopida Müller, Reference Müller1894
The platycopine Kloedenelloidea is represented by two specimens of Poloniella sp. A (Fig. 5l, m) of Becker & Sánchez de Posada (Reference Becker and Sánchez De Posada1977), previously reported from the upper Emsian Moniello Formation of Asturias. It is similar to Poloniella spriesterbachi Zagora, Reference Zagora1968, known from the upper Emsian (tentaculite cancellata Biozone) Tentaculite Shale of Thuringia (Zagora, Reference Zagora1968), and to Poloniella sp. gr. P. cf. diversa from the Santa Lucía Formation of northern Spain (Becker, Reference Becker2001).
Five species from the metacopine family Thlipsuroidae are recognized: Thlipsohealdia abadia Becker, Reference Becker1989 (Fig. 5n–q); Simplicithlipsa cortes Becker, Reference Becker1996 (Fig. 5r); Marginohealdia costata (Zagora, Reference Zagora1968) (Fig. 5s); Marginohealdia sp. 1 (Fig. 5t); and Marginohealdia sp. 2 (Fig. 5u).
T. abadia, which has a delicately ribbed valve surface, was described from the upper Emsian Abadía Formation (Polentinos Member), Spain (Becker, Reference Becker1989). S. cortes is known from the upper lower Emsian to lower upper Emsian of the Abadía Formation; upper Pragian to upper lower Emsian La Vid Formation of the Cantabrian Mountains (northern León, Spain) (Becker, Reference Becker1996); and the upper Emsian Khebchia Formation of Morocco (Becker, Lazreq & Weddige, Reference Becker, Lazreq and Weddige2004). M. costata was reported from the upper Emsian ‘Richter’sches konglomerat’ (tentaculite cancellata Biozone) of Thuringia (Zagora, Reference Zagora1968), and from the upper Emsian Khebchia Formation in southwestern Morocco (Becker, Lazreq & Weddige, Reference Becker, Lazreq and Weddige2004).
The metacopine family Quasilitidae is represented by two species: Jenningsina planocostata Jordan, Reference Jordan1964 (Fig. 6a, b) and Absina ectina Gründel, Reference Gründel1962 (Fig. 6c).
Devonian ostracods from the Pendik Formation. (a, b) Jenningsina planocostata Jordan, 1964: (a) BD-1/5, left valve in lateral view; (b) BD-1/23, juvenile left valve in lateral view. (c) BD-1/211, Absina ectina (Gründel, Reference Gründel1962), left valve in lateral view. (d) BD-18/206, Healdia? sp., left valve in lateral view. (e, f) Microcheilinella ex gr. clava (Kegel, Reference Kegel1932): (e) BD-25/172, carapace in right lateral view; (f) BD-17/55, left valve in lateral internal view. (g, h) Microcheilinella istanbulensis Olempska & Nazik sp. nov.; (g) holotype BD-17/63, left valve in lateral view; (h) BD-17/104, right valve in internal view. (i, j) Praepilatina ex gr. praepilata (Polenova, Reference Polenova1960): (i) BD-5/28, right valve in lateral view; (j) BD-13/50, left valve in internal view. (k, l) Acravicula moniellana Becker & Sánchez de Posada, Reference Becker and Sánchez De Posada1977: (k); BD-17/61, left valve in lateral view; (l) BD-25/194, right valve in lateral view. (m) BD-23/159, Baschkirina sp., right valve in lateral view. (n, o, p) ‘Cytherellina’ inconstans Zagora, K., 1967: (n) BD-17/96, right valve in lateral view; (o) BD-23/160, right valve in internal view; (p) BD-17/97, left valve in lateral view. (q, r) BD-26/193, Orthocypris sp. A of Becker & Sánchez de Posada (Reference Becker and Sánchez De Posada1977), carapace in left lateral and ventral views. Scale bar 200 μm.
J. planocostata is a long-ranging species known from the Lower and Middle Devonian of Europe and North Africa (see details in Becker, Lazreq & Weddige, Reference Becker, Lazreq and Weddige2004; Dojen et al. Reference Dojen, Gozalo, Carls and Valenzuela-Ríos2004 a; C. Dojen, unpub. Ph.D. thesis, Tech. Univ. Carlo-Wilhelmina, Braunschweig, 2005; Maillet et al. Reference Maillet, Tanjaoui-Arif, Milhau, Nicollin and Ouali Mehadji2013) and has no biostratigraphic significance for the studied section. A. ectina is known from the Gattendorfia Stage of Thuringia (Gründel, Reference Gründel1962).
The Healdiidae are represented by poorly preserved specimens of Healdia? sp. (Fig. 6d).
The possible sigillioid Pachydomellidae is represented by Microcheilinella ex gr. clava (Kegel, Reference Kegel1932) (Fig. 6e, f) and Microcheilinella istanbulensis Olempska & Nazik sp. nov. (Fig. 6g, h).
M. ex gr. clava appears to be a ‘bag’ taxon, which needs revision, and closely related species are known from the Lower Devonian (Emsian) of Europe (Spain, Cantabrian Mountains; Germany, eastern Thuringia; Poland) and North Africa (Morocco, lower–upper Emsian) (see details in Becker, Lazreq & Weddige, Reference Becker, Lazreq and Weddige2004). It is very common throughout the Büyükdere section, but poorly preserved. M. istanbulensis is described fully in Section 4.d below.
Four species from the superfamily Bairdiocyprididae are recognized: Praepilatina ex gr. praepilata (Polenova, Reference Polenova1960) (Fig. 6i, j) sensu Becker, Lazreq & Weddige, (Reference Becker, Lazreq and Weddige2004); ‘Cytherellina’ inconstans Zagora, K., Reference Zagora1967 (Fig. 6n–p); Acravicula moniellana Becker & Sánchez de Posada, Reference Becker and Sánchez De Posada1977 (Fig. 6k, l); and Baschkirina sp. (Fig. 6m).
P. ex gr. P. praepilata is widespread and well known from the Emsian of NW Anatolia, Turkey (Dojen et al. Reference Dojen, Özgül, Göncüoglu and Göncüoglu2004 b) and the Lower Devonian of Russia, Central and Western Europe, North Africa and North America, Australia and probably South China (see Becker, Lazreq & Weddige, Reference Becker, Lazreq and Weddige2004). ‘C.’inconstans was reported from the upper part of the Pelitli Formation and the lower part of the Pendik Formation (lower to upper Emsian), NW Anatolia, Turkey (Dojen et al. Reference Dojen, Özgül, Göncüoglu and Göncüoglu2004 b); from the Eifelian of Thuringia (Zagora, K., Reference Zagora1967); and from Spain (upper Emsian to Eifelian) and Morocco (upper Emsian) (details in Becker, Lazreq & Weddige, Reference Becker, Lazreq and Weddige2004). A. moniellana was previously reported from the upper Emsian succession (Moniello Formation) (Becker & Sánchez de Posada, Reference Becker and Sánchez De Posada1977) and from lower Emsian strata of the Montagne Noire, France (Feist & Gross-Uffenorde, Reference Feist and Groos-Uffenorde1979). Baschkirina sp. is poorly preserved and does not allow a precise identification.
The bairdioidean species Orthocypris sp. A of Becker & Sánchez de Posada (Reference Becker and Sánchez De Posada1977) (Fig. 6q, r) is known from the lower Emsian to lower/upper Emsian transition beds of the La Vid Formation in the Cantabrian Mountains of Spain (Becker, Reference Becker1998); from the upper Emsian Moniello Formation (Becker & Sánchez de Posada, Reference Becker and Sánchez De Posada1977); and from the lower upper Emsian strata of the Aguión Formation, Asturias (Becker, Reference Becker2000).
The cytheroidean Tricorninidae are represented by Tricornina elegans Zagora, K., Reference Zagora1967 (Fig. 7a, b); Tricornina prantli Šnajdr, Reference Šnajdr1951 (Fig. 7c–e); Bohemina paragracilis Blumenstengel, Reference Blumenstengel1965 (Fig. 7i–k); Bohemina cf. longispina Blumenstengel, Reference Blumenstengel1962 (Fig. 7f–h); and the berounellid species Kirkbyellina spinosa Blumenstengel, Reference Blumenstengel1962 (= Berounella) (Fig. 7l–n).
Devonian ostracods from the Pendik Formation. (a, b) BD-1/2, Tricornina elegans Zagora, K., Reference Zagora1967, right valve in lateral and oblique ventral views. (c, d, e) BD-20/127, Tricornina prantli Šnajdr, 1951, left valve in lateral, oblique ventral and anterior views. (i, j, k) Bohemina paragracilis Blumenstengel, 1965: (i, j) BD-23/161, left valve in oblique ventral and lateral views; (k) BD-25/182, left valve in lateral views. (f, g, h) Bohemina cf. longispina Blumenstengel, Reference Blumenstengel1962: (f, g) BD-18/108, right valve in lateral and oblique ventral views; (h) BD-23/150, right valve in lateral view. (l, m, n) Kirkbyellina spinosa Blumenstengel, 1962: (l) BD-18/106, right valve in lateral view; (m, n) BD-25/199, left valve in lateral and oblique ventral views. (o, p, q, r) Roundyella goekchenae Olempska & Nazik sp. nov.: (o) BD-17/67, left valve in lateral view; (p, q) holotype BD-17/81, right valve in lateral and oblique ventral views; (r) BD-20/214, right valve in internal view. (s, t) Roundyella pokornyi (Zagora, Reference Zagora1968): (s) BD-17/83, left valve in lateral view; (t) BD-25/173, juvenile left valve in lateral view. (u, v, w) Omerliella rectangulata Olempska & Nazik gen. et sp. nov.: (u, v) holotype BD-26/189, right valve in lateral and oblique ventral views; (w) BD-19/115, right (?) valve in lateral view. (x, y) Quasipolycope sp.: (x) BD-17/57, valve in lateral view; (y) BD-17/64, valve in lateral view. Scale bar 200 μm.
T. elegans has been reported from the Eifelian of Thuringia (Zagora, K., Reference Zagora1967). T. prantli was reported from the Eifelian of Thuringia (Zagora, K., Reference Zagora1967) and the Eifelian of the Choteč limestone of Bohemia (Šnajdr, Reference Šnajdr1951). Specimens from the Büyükdere section are well preserved and show three rows of small tubercles along the anterodorsal margin, just below the long anterodorsal spine. B. paragracilis is a long-ranging species known from the Upper Devonian of Central and Western Europe (see Becker & Blumenstengel, Reference Becker and Blumenstengel1995). B. cf. longispina is a long-ranging species reported from the Pragian Tentaculite Limestone of Thuringia (Blumenstengel, Reference Blumenstengel1962) and Eifelian of Thuringia (Zagora, K., Reference Zagora1967). Kirkbyellina spinosa is rare at Büyükdere, previously being reported from the lower upper Emsian Aguión and upper Emsian Santa Lucia formations of the Cantabrian Mountains (Becker, Reference Becker2000); the upper Emsian Moniello Formation (Becker & Sánchez de Posada, Reference Becker and Sánchez De Posada1977); lower Emsian of the Montagne Noire (Feist & Grooos-Uffenorde, Reference Feist and Groos-Uffenorde1979); the Pragian of Thuringia (Blumenstengel, Reference Blumenstengel1962); and the Emsian Receptaculites Limestone, Australia (Reynolds, Reference Reynolds1978).
4.c. Order Myodocopida Sars, Reference Sars1866
Quasipolycope sp. (Fig. 7x, y) is the only representative of the Myodocopida in the Büyükdere section.
4.d. Description of new species (Ewa Olempska & Atike Nazik)
Order PALAEOCOPIDA?
Superfamily Uncertain
Family Scrobiculidae Posner, Reference Posner1951
Genus Roundyella Bradfield, Reference Bradfield1935
Type species. Amphissites simplicissimus Knight, Reference Knight1928.
Roundyella goekchenae Olempska & Nazik sp. nov.
Figure 7o, p, q, r
Holotype. Right valve (BD-17/81), Figure 7p, q.
Derivation of name. Dedicated to Professor Nuran Sönmez-Gökçen (retired from Dokuz Eylül Üniversity, Turkey).
Type locality and horizon. Büyükdere section, 1.5 km SW of the Ömerli Dam and 1.25 km east of the village of Kurtdoğmuş, Çatalca Peninsula, upper Emsian – lower Eifelian (patulus–partitus biozones).
Material. Thirty-four valves.
Diagnosis. Roundyella with elongate rectangular shape in lateral view; surface reticulate with densely spaced spines, sulcus absent; marginal structure a row of very small tubercles.
Description. The carapace is elongate, rectangular shape in lateral view; dorsal margin is long and straight, ventral almost straight, anterior and posterior margins almost symmetrically rounded. Surface gently reticulate with strong spines; marginal structure poorly developed as row of small tubercles.
Discussion. Roundyella goekchenae is similar to Roundyella sp. 37 of Groos-Uffenorde (in Feist & Groos-Uffenorde, Reference Feist and Groos-Uffenorde1979) in having densely spaced spines on the surface, but differs in having a poorly developed marginal structure. It differs from Roundyella pokornyi (Zagora, Reference Zagora1968) in the presence of spines on the surface.
Genus Omerliella Olempska & Nazik gen. nov.
Type species. Omerliella rectangulata Olempska & Nazik gen. et sp. nov.
Derivation of name. The name is derived from Ömerli lake.
Diagnosis. A palaeocopide(?) genus with rectangular shape in lateral view; dorsal margin straight and long; nearly symmetrical lateral outline of valves; surface covered with narrow, thin vertical ribs; on anterior and posterior part of valve the ribs are almost parallel to margins, almost straight in central part of the valve; narrow marginal ridge present, extending along free margin.
Remarks. The Scrobiculidae are a poorly known group of ostracods with characters transitional between palaeocopid kirkbyoideans and podocopid metacopines. They have been described either as ‘Palaeocopida?’ (e.g. Whatley, Siveter & Boomer, Reference Whatley, Siveter, Boomer and Benton1993) or as ostracods with unknown taxonomic position (e.g. Becker, Reference Becker1997). The genus described here does not show an obvious similarity with any other known Palaeozoic ostracods. It is similar in ornamentation to some species of Jenningsina (Costatia), and some Amphicostella species, but differs in having a rectangular lateral shape to the valves. The symmetrical anterior and posterior parts of the carapace and laterally flattened carapace suggest possible Scrobiculidae affinities. The amplete almost rectangular shape, laterally flattened carapace, long and straight dorsal margin, and narrow admarginal rim are reminiscent of Roundyella. It differs from Roundyella in its ornamentation of narrow ribs that are sub-parallel to the anterior and posterior margins. The ornamentation of the vertical ridges is also reminiscent of Svantovites Pokorný, Reference Pokorný1951.
Omerliella rectangulata Olempska & Nazik sp. nov.
Figure 7u, v, w
Holotype. Right valve (BD-26/189), Figure 7u, v.
Derivation of name. From the rectangular lateral shape.
Type locality and horizon. Büyükdere section, 1.5 km SW of the Ömerli lake and 1.25 km east of the village of Kurtdoğmuş, Çatalca Peninsula, upper Emsian – lower Eifelian (patulus–partitus biozones).
Material. Four valves.
Diagnosis. As for the genus, which is monotypic.
Description. The lateral shape of the valve is rectangular. The anterior and posterior outlines of the valve are nearly symmetrical, and gently rounded. The dorsal margin is straight and long, ventral margin almost straight. The surface is covered by 18–20 vertically oriented delicate ribs. The marginal ridge is thin and present along the entire free margin. The small adductor muscle field is visible in the centre of the valve.
Remarks. The specimens described are similar in ornamentation to Jenningsina (Costatia) infrequens Přibyl, Reference Přibyl1990 from the Lochkovian of Bohemia but differ in their rectangular lateral shape. It seems likely that one of Přibyl's specimens (Přibyl, Reference Přibyl1990, pl. 2: 7) may be conspecific with O. rectangulata.
Suborder BAIRDIOCYPRIDOIDEA Shaver, Reference Shaver and Moore1961
Family Pachydomellidae Berdan & Sohn, Reference Berdan, Sohn and Moore1961
Genus Microcheilinella Geis, Reference Geis1933
Microcheilinella istanbulensis Olempska & Nazik sp. nov.
Figure 6g, h
Holotype. Left valve (BD-17/63), Figure 6g.
Derivation of name. From İstanbul, the magnificent city that straddles the Bosphorus.
Type locality and horizon. Büyükdere section, 1.5 km SW of the Ömerli Dam and 1.25 km east of the village of Kurtdoğmuş, Çatalca Peninsula, upper Emsian (patulus Biozone).
Material. Thirty valves.
Diagnosis. Microcheilinella with strongly reticulate valve surface, and a row of small spines developed along the posterior margin of both valves.
Description. Carapace small, not extending in length greater than 0.52 mm. Lateral shape elongate, suboval; dorsal margin long and straight, ventral margin straight to gently convex. Left valve overlaps the right along free margin; a row of small spines is developed along the posterior margin of both valves. Surface strongly reticulate.
Discussion. This species is very similar to Microcheilinella sp. AG of Becker (Reference Becker2001), from the Santa Lucía Formation, upper Emsian of Spain but differs in having a row of spines at the posterior margin. It is also similar to Microcheilinella shiloi Bless, Reference Becker, Bless, Whatley and Maybury1984 (in Shilo et al. Reference Shilo, Bouckaert, Afanasjeva, Bless, Conil, Erlanger, Gagiev, Lazarev, Onoprienko, Poty, Razina, Simakov, Smirnova, Streel and Swennen1984) from the upper Famennian and middle Tournaisian of the Omolon region, Russia from which it differs in the presence of spines along the posterior margin of both valves.
5. Ostracod palaeoecology
Three main Devonian ostracod eco-types have been recognized: (a) benthic ostracods in high-energy shallow-water environments denoting the Eifelian Mega-Assemblage; (b) benthic and nektobenthic ostracods in low-energy basinal environments denoting the Thuringian Mega-Assemblage; and (c) pelagic ostracods denoting the Entomozoacean Mega-Assemblage (e.g. Bandel & Becker, Reference Bandel and Becker1975; Becker & Bless, Reference Becker, Bless, Whatley and Maybury1990; Olempska, Reference Olempska1992, Reference Olempska1997; Becker & Blumenstengel, Reference Becker and Blumenstengel1995; Becker, Reference Becker1999; Groos-Uffenorde, Lethiers & Blumenstengel, Reference Groos-Uffenorde, Lethiers and Blumenstengel2000; Casier Reference Casier2004; Becker, Lazreq & Weddige, Reference Becker, Lazreq and Weddige2004). ‘Mixed fauna’ of these main types have also often been recognized.
5.a. Sedimentological aspect of ostracod palaeoecology
The clastic sediments and carbonates of the Pendik Formation were deposited in a clastic relatively deep-shelf environment, suggested by laminated sedimentary structures and fossil content (Yalçin & Yilmaz, Reference Yalçin and Yilmaz2010). However, part of the shelf was probably affected by currents and storm waves, and micaceous material (sericite), abundant in silty and sandy intervals, indicates a nearby erosional land area within a short transportation distance (Yalçin & Yilmaz, Reference Yalçin and Yilmaz2010). The limestone intercalations in the upper part of the Pendik Formation indicate a reduction in the clastic input from the land (Özgül, Reference Özgül2012). The Devonian succession of the Istanbul area displays a progressively deepening marine environment from a shallow shelf at the beginning of the Devonian to basin conditions in the early Carboniferous (Görür et al. Reference Görür, Monod, Okay, Sengör, Tüysüz, Yiğitbaş, Sakinç and Akkök1997; Yalçin & Yilmaz, Reference Yalçin and Yilmaz2010; Göncüoğlu, Reference Göncüoğlu, Göncüoğlu and Bozdogan2012). The Famennian ostracod fauna from the Istanbul area represents a Thuringian Mega-Assemblage (Nazik, Çapkınoğlu & Şeker, Reference Naz˙ik, Çapkinoğlu and Şeker2012), and suggests a much deeper marine shelf setting than those of the Pendik Formation.
5.b. Ostracod assemblage palaeoecology
The ostracod assemblages from the Büyükdere section belong to a ‘mixed fauna’, composed of thick-shelled epineritic ostracods and thin-shelled, often delicately to strongly spinose, ostracods. This ‘mixed fauna’ indicates an offshore position in deeper, and less agitated water below the normal wave base (Becker, Reference Becker1999).
The presence of a full range of well-preserved juveniles and adults suggests that the ostracods were not transported and may represent biocoenoses.
The Büyükdere ostracod assemblage is characterized by the common occurrence of nektobenthic thin-shelled strongly spinose forms such as Tricornina, Bohemina and Kirkbyellina, which occur in a lithofacies representing deeper shelf settings. Metacopine thlipsuroids common in open marine environments (Thlipsohealdia, Marginohealdia) and quasillitidids (Absina) with small spines also occur. Species of Aechmina with their long dorsal spine commonly occur throughout the succession.
The spinose palaeocopid Semibolbina alcaldei also occurs in lithofacies representing open marine shelf settings (Becker & Sánchez de Posada, Reference Becker and Sánchez De Posada1977; Becker Reference Becker2001; Becker, Lazreq & Weddige, Reference Becker, Lazreq and Weddige2004). The primitiopside taxa with delicately spinose valves (e.g. ‘Selebratina’, Bodzentia) are common in samples.
However, elements of shallower marine assemblages such as thick-shelled Microcheilinella ex gr. clava are numerically dominant. Genera like Ulrichia, Jenningsina and Praepilatina occur in shallow and deeper shelf settings.
The Büyükdere ostracod fauna differs from contemporaneous Iberian assemblages in the absence of the podocopine Bairdia and some metacopine ostracods e.g. Polyzygia, which otherwise occur all over Europe, and Zeuschnerina, which usually occurs in equivalent age rocks of the Moniello Formation, Spain (Becker & Sánchez de Posada, Reference Becker and Sánchez De Posada1977), Santa Lucía Formation, Spain (Becker, Reference Becker2001), Abadía Formation, Spain (Becker, Reference Becker1989) and Moroccan Khebchia Formation (Becker, Lazreq & Weddige, Reference Becker, Lazreq and Weddige2004).
The Büyükdere ostracod fauna also differs from those from N Africa, Iberia and Thuringia in the presence of the myodocope Quasipolycope sp., which is present in many Late Devonian, Carboniferous and Permian age assemblages. The majority of living Polycopidae are benthic/nektobenthic and some are interstitial forms (Horne, Reference Horne, Park and Smith2003); therefore, species occurring in Thuringian assemblages probably were nektobenthic forms.
6. Palaeobiogeographical relationships
During Early Devonian time, Gondwana extended from the South Pole to the Equator and beyond. The new Palaeothethys Ocean had probably started opening in latest Silurian time, separating most of Southern Europe (the Armorican Terrane Assemblage, Adria, the Pontides of Turkey and the Hellenic Terrane) from Gondwana. As the Palaeozoic progressed, these peri-Gondwanan terranes drifted from Gondwana northward across the Rheic Ocean (e.g. see Cocks & Torsvik, Reference Cocks, Torsvik, Gee and Stephenson2006). The peri-Gondwanan marginal terranes were described as the Hun superterrane (Stampfli, von Raumer & Borel, Reference Stampfli, von Raumer, Borel, Martínez Catalán, Hatcher, Arenas and Díaz García2002; Stampfli & Borel, Reference Stampfli and Borel2002).
6.a. Ostracod biogeographical significance
Ostracods from the Pendik Formation support the notion that the Istanbul Terrane, the peri-Gondwanan Armorican terrane-collage and the northern margin of Gondwana were in palaeogeographical proximity in Early Devonian times (Fig. 9). Ostracods show close similarities at the species level to the faunas of similar sedimentary facies of both the northern African part of Gondwana, especially the Khebchia Formation (Fig. 8) of the southern Anti-Atlas (Becker, Lazreq & Weddige, Reference Becker, Lazreq and Weddige2004), and the Armorican terrane-collage (Cantabrian Mountains, Spain; Montagne Noire, France; Thuringia, Germany). Particularly close relationships exist between the Emsian–Eifelian faunas from the Cantabrian Mountains, Spain with altogether 18 common species, and Thuringia, Germany with 17 common species (Figs 8, 9). However, the presence of compatible marine facies may also have played a role in ostracod migrations between these areas.
Distribution of ostracod species present in the Büyükdere section compared with approximately contemporaneous (Pragian–Eifelian) ostracod faunas of North Africa, Western and Central Europe and North America. Morocco – upper Emsian, Khebchia Fm, southwestern Anti-Atlas (Becker et al. Reference Becker, Lazreq and Weddige2004); Spain – upper Emsian, Moniello Fm, Asturias (Becker & Sánchez de Posada, Reference Becker and Sánchez De Posada1977); upper Emsian Santa Lucía Fm, Asturias and northern León (Becker, Reference Becker2001); upper Emsian Aguión Fm, Asturias (Becker, Reference Becker2000); lower Emsian – lower upper Emsian La Vid Fm (Becker, Reference Becker1998); lower Emsian – lower Eifelian Abadía Fm (Becker, Reference Becker1989, Reference Becker1996). Montagne Noire – lower Emsian (Feist & Groos-Uffenorde, Reference Feist and Groos-Uffenorde1979). Thuringia – Pargian–upper Eifelian (Blumenstengel, Reference Blumenstengel1962; Zagora, I., Reference Zagora1967; Zagora, K., Reference Zagora1967; Zagora, Reference Zagora1968). Laurentia – Emsian–Eifelian (Adamczak, Reference Adamczak1968; Kesling & Chilman, Reference Kesling and Chilman1978). Abbreviations: Go. – Gondwana, Mor. – Morocco.
Palaeogeography of the Southern Hemisphere in Early mid-Devonian time (Emsian, 400 Ma). Modified from Cocks & Torsvik (Reference Cocks, Torsvik, Gee and Stephenson2006).
Exchange of biostratigraphically short-ranging species such as Semibolbina alcaldei, Simplicithlipsa cortes, Marginohealdia costata, Thlipsohealdia abadia and Acravicula moniellana between Gondwana and peri-Gondwanan areas (Morocco, Spain, southern France, Thuringia and the Istanbul Terrane) took place in late Emsian time (e.g. see Becker, Lazreq & Weddige, Reference Becker, Lazreq and Weddige2004).
Nektobenthic spinose ostracods may have migrated between the Gondwana margin and peri-Gondwanan terranes probably without restriction. Strongly spinose species that occur in the Pendik Formation (Aechmina tenuispina, Tricornina elegans, T. prantli and Bohemina cf. longispina) have Thuringian affinity (Zagora, Reference Zagora1968). At this time, the Saxo-Thuringia microplate is considered to be a part of the Armorican terrane-collage (e.g. Linnemann & Buschmann, Reference Linnemann and Buschmann1995; Tait et al. Reference Tait, Bachtadse, Franke and Soffel1997; Linnemann et al. Reference Linnemann, Gehmlich, Tichomirowa, Buscjmann, Nasdala, Jonas, Lützner, Bombach, Franke, Haak, Oncken and Tanner2000) and thus lay in geographical proximity to the Istanbul Terrane. Additional faunal links with peri-Gondwanan terranes are indicated by the occurrence of the strongly spinose Kirkbyellina spinosa (= Berounella) in the upper lower Emsian ‘Calcaires a polypiers siliceux’ strata of the Montagne Noire, southern France (Feist & Groos-Uffenorde, Reference Feist and Groos-Uffenorde1979) and in a ‘mixed fauna’ of the lower upper Emsian Aguión Formation of Asturias, Cantabrian Mountains (Becker, Reference Becker2000).
More widespread is the large dimorphic palaeocope Ctenoloculina latisulcata, which first occurred in the upper Emsian (Grzegorzowice Beds) of Baltica (Adamczak, Reference Adamczak1968) and later appeared in the upper Emsian of the Pontides and in the lower Eifelian Yeraïtia Formation of Morocco (Becker, Lazreq & Weddige, Reference Becker, Lazreq and Weddige2004). Bodzentia cf. sulcata is the only other biogeographical link with Baltica (Figs 8, 9).
Less palaeogeographically decisive are the widespread Gondwanan, peri-Gondwanan and Laurussian long-ranging taxa such as Ulrichia ex gr. spinifera, Praepilatina ex gr. praepilata and Microcheilinella ex gr. clava, noted from different environments, and considered as ‘bag’ taxa that need systematic revision before their biogeographical significance can be determined. The widespread Jenningsina planocostata (= Jenningsina (Costatia) decorocostata), also present in the Pendik Formation, probably first appeared in the Lochkovian of Bohemia (Přibyl, Reference Přibyl1990) and may have migrated during the Pragian, Emsian and Eifelian to Morocco and areas of Spain, the Montagne Noire, the Rheinish Slate Mountains and the Istanbul Terrane (e.g. Feist & Groos-Uffenorde, Reference Feist and Groos-Uffenorde1979; Becker, Reference Becker1989, Reference Becker1996, Reference Becker1998, Reference Becker2001; Becker, Lazreq & Weddige, Reference Becker, Lazreq and Weddige2004; C. Dojen, unpub. Ph.D. thesis, Tech. Univ. Carlo-Wilhelmina, Braunschweig, 2005; Dojen, Valenzuela-Ríos & Carls, Reference Dojen, Valenzuela-Ríos, Carls and Over2009).
At the generic level, the Büyükdere ostracod fauna of the Pendik Formation shows generic links (e.g. Ctenoloculina, Semibolbina, Tricornina, Microcheilinella, Praepilatina, Acravicula, Baschkirina) with the Emsian Carnic Alps succession (Bandel & Becker, Reference Bandel and Becker1975), the latter being placed in a peri-Gondwanan setting during Devonian time (von Raumer, Reference Von Raumer1998). Lochkovian and Pragian ostracods of central Bohemia, which are similar to the Thuringian palaeo-ecotype, have Jenningsina, Selebratina, Semibolbina, Tricornina and Ulrichia in common (Přibyl, Reference Přibyl1988, Reference Přibyl1990) with the Istanbul Terrane. Peruncia (Bohemia) is considered part of the Armorican Terrane Assemblage, but Cocks & Torsvik (Reference Cocks, Torsvik, Gee and Stephenson2006) believed the two were separate in Early Palaeozoic time. The similarities of the early Pragian and Emsian shallow neritic ostracods from the Armorican Massif (see Lethiers et al. Reference Lethiers, Fèvre, Vannier, Weyant and Oertli1985) and the Büyükdere ostracods are also only at the generic level. There are no records of Devonian ostracods from the Adria and Hellene–Moesia areas.
Further afield from Gondwana and peri-Gondwanan Europe, the Büyükdere ostracod fauna shows some generic links (e.g. Kirkbyellina, Tricornina, Praepilatina, Poloniella) with Laurentia (e.g. Berdan & Copeland, Reference Berdan and Copeland1973; Berdan Reference Berdan, Murphy, Berry and Sandberg1977, Reference Berdan, McKerrow and Scotese1990).
Ostracod dispersal between palaeocontinents aided by mid-ocean islands, outer-shelf carbonate platforms or via other marine biota, e.g. transportation on floating algae, have been suggested (e.g. Lethiers & Crasquin-Soleau, Reference Lethiers and Crasquin-Soleau1995; Williams et al. Reference Williams, Floyd, Salas, Siveter, Stone and Vannier2003). More importantly, shallow water connections between Laurussia, Gondwana and peri-Gondwana are suggested for late Silurian to Early Devonian times (Dojen, Reference Dojen2009).
6.b. Location of the Turkish Pontides in Early Devonian time
In Early Devonian (Emsian) time, the Turkish Pontides were situated at some distance from the northern African part of Gondwana (Fig. 9), to the east of the Adria and Armorican Terrane Assemblage (Cocks & Torsvik, Reference Cocks, Torsvik, Gee and Stephenson2006, Fig. 9). However, Torsvik & Cocks (Reference Torsvik, Cocks and Basset2009, p. 8) noted that Silurian brachiopods from the Istanbul Terrane are similar to those in the Welsh Borderlands (Avalonian part of the peri-Gondwana), and therefore the palaeogeographical position of the Pontides in Early Palaeozoic time is unclear (see also Torsvik & Cocks, Reference Torsvik, Cocks, Van Hinsbergen, Buiter, Torsvik, Gaina C. and Webb2011). Brachiopods have wide dispersal mechanisms, and are known to produce planktonic larvae. Thus, more than one possibility exists and the interpretation of the biogeography does not just depend on the palaeogeography.
The Istanbul and Zonguldak terranes have been considered both as a single terrane (e.g. Okay & Tüysüz, Reference Okay, Tüysüz, Durand, Jolivet, Horváth and Seranne1999; Cocks & Torsvik, Reference Cocks and Torsvik2002; Kalvoda et al. Reference Kalvoda, Leichmann, Bábek and Melichar2003; Moix et al. Reference Moix, Beccaletto, Kozur, Hochard, Rosselet and Stampfli2008; Okay et al. Reference Okay, Bozkurt, Satir, Yiğitbaş, Crowley and Shang2008; Kalvoda & Bábek, Reference Kalvoda and Bábek2010) or as two separate terranes: the Istanbul Terrane around the Bosphorus and the Kocaeli Peninsula and further east, the Zonguldak Terrane (e.g. Göncüoğlu, Reference Görür, Monod, Okay, Sengör, Tüysüz, Yiğitbaş, Sakinç and Akkök1997, Reference Bozkaya, Yalçin and Göncüoğlu2012; Kozur & Göncüoğlu, Reference Kozur and Göncüoğlu2000; Stampfli & Borel, Reference Stampfli and Borel2002; Yanev et al. Reference Yanev, Göncüoğlu, Gedik, Lakova, Boncheva, Sachanski, Okuyucu, Özgül, Timur, Maliakov, Saydam, Robertson and Mountrakis2006; Sachanski, Göncüoğlu & Gedik, Reference Sachanski, Göncüoğlu and Gedik2008; Bozkaya, Yalçin & Göncüoglu, Reference Bozkaya, Yalçin and Göncüoğlu2012 a,b).
According to Göncüoğlu (Reference Göncüoğlu, Göncüoğlu and Derman1997) and Okay et al. (Reference Okay, Bozkurt, Satir, Yiğitbaş, Crowley and Shang2008), the Istanbul Terrane was one of the peri-Gondwanan terranes that drifted northward from Gondwana. A peri-Gondwanan (Avalonian) setting for the palaeogeographic position of the Pontides during Devonian time was proposed by e.g. Dean et al. (Reference Dean, Monod, Rickards, Demir and Bultynck2000), von Raumer, Stampfli & Bussy (Reference Von Raumer, Stampfli and Bussy2003) and Yalçin & Yilmaz (Reference Yalçin and Yilmaz2010). In general these assertions are supported by the ostracod data presented here.
7. Conclusions
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(1) An ostracod fauna with a mixture of Thuringian and Eifelian Mega-Assemblage elements is documented from the Büyükdere section of the Kozyatağı Member, Pendik Formation, Turkey. Ostracods present in the Kozyatağı Member indicate an offshore position in deeper, less agitated water, below normal wave base.
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(2) The Büyükdere section yielded several stratigraphically important short-ranging species (e.g. Semibolbina alcaldei, Berdanella igesohni, Simplicithlipsa cortes, Marginohealdia costata) that demonstrate correlation with upper Emsian formations elsewhere, and Ctenoloculina latisulcata with the lower Eifelian. There is no evidence for major faunal turnover at the Emsian–Eifelian boundary, excepting the first appearance of Ctenoloculina latisulcata.
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(3) The Büyükdere ostracod fauna demonstrates species-level biogeographical links with open marine environments of Gondwana and peri-Gondwana (Armorican Terrane Assemblage) and the Istanbul Terrane.
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(4) The palaeogeographical vicinity of NW Turkey, the northern margin of Gondwana and the Armorican Terrane is suggested by the ostracod assemblages during Early Devonian time.
Acknowledgements
This study was supported by the General Directorate of Mineral Research & Exploration (MTA) and the Council of Higher Education (Turkey). The authors are deeply indebted to Prof. Mark Williams, Dr Claudia Dojen and an anonymous reviewer for their constructive comments in the preparation of this manuscript.
