Conodont Fauna and Biostratigraphy of the Early-Middle Devonian Units in Beykoz, Şile and Kurtdoğmuş Areas, Istanbul, Turkey
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Mineral Res. Exp., Bull., 145, 1-21, 2012 CONODONT FAUNA AND BIOSTRATIGRAPHY OF THE EARLY-MIDDLE DEVONIAN UNITS IN BEYKOZ, ŞILE AND KURTDOĞMUŞ AREAS, İSTANBUL, TURKEY Dilek Gülnur SAYDAM-DEMİRAY* and Şenol ÇAPKINOĞLU** ABSTRACT.- Conodont faunas defining the delta-pesavis zones (upper Lochkovian, Lower Devonian) from Beykoz and Karamandere sections of the İstinye Formation (the Yumrukaya Group) and the laticostatus, serotinus, patulus and partitus zones (upper Emsian-lower Eifelian, Lower- Middle Devonian) from Büyükdere and Kokarpınar sections of the Kozyatağı member of the Kartal Formation were obtained. A total of 22 species/subspecies were described belonging to the genera Neopanderodus (2), Icriodus (8), Pelekysgnathus (1), Lanea (1), Polygnathus (4), Ozarkodina (2), Pseudooneotodus (2) and Belodella (2). Key words: Lower-Middle Devonian, conodont fauna, biostratigraphy, İstinye Formation, Kozyatağı member, İstanbul, Turkey INTRODUCTION The first conodont investigations in the İstanbul zone of the Pontides, Turkey were made by Abdüsselamoğlu (1963); followed by Haas (1968), Gedik (1975), Göncüoğlu et al. (2004), and Çapkınoğlu (1997, 2000, 2005a, 2005b) who described conodont faunas from Paleozoic and Triassic units in the vicinity of İstanbul and Kocaeli, Turkey. A total of 96 lime- stone samples for conodont were collected, for this study, from four measured stratigraph- ic sections in Beykoz, Şile and Kurtdoğmuş Figure 1- Location map of the study area. areas (İstanbul, Turkey) (Figure 1) of the Kozyatağı Member (the Kartal Formation) and acidizing techniques with formic- and/or ace- the İstinye Formation (the Yumrukaya Group). tic-acid. In the formic acid method, each kilo- The Lower-Middle Devonian conodonts were gram of rock is placed in a solution of 1500 ml found in 34 samples, which were used to carry formic-acid and 6000 ml water fro 24 hours. out the biostratigraphic zonation of the investi- In the acetic acid method, a solution of 100 ml gated stratigraphic sections. acetic acid and 900 ml water, is used per 1 kg of rock. MATERIALS AND METHODS Residue filtered from the nested sieves of 100 micron and 2 mm was washed by running Samples collected for conodonts were water until fully clear water flows. The residue broken down pieces in 2-3 cm diameter and on 100-micron sieve was transferred into a por- processed in plastic buckets using standard celain bowl or glass holder and dehydrated in * Maden Tetkik Arama Genel Müdürlüğü, Jeoloji Etütleri Dairesi, Ankara. ** Karadeniz Teknik Üniversitesi, Jeoloji Mühendisliği Bölümü, Trabzon. 2 Dilek Gülnur SAYDAM-DEMİRAY and Şenol ÇAPKINOĞLU an oven at 60°C. Dry residues were screened beige, thin- to medium-bedded limestone, bio- through nested sieves of 100 micron and 1 mm, clastic limestone, sandy limestone, laminated and conodonts were picked from the 100 mi- limestone and gray carbonated shales, and is cron to 1 mm fraction under the binocular mi- both laterally and vertically transitional with oth- croscope. er rock types forming the Kartal Formation. It comprises rather dense, reworked brachiopod STRATIGRAPHY and crinoid. Nodular limestones and/or nodu- lar limestone-shale alternation are observed at The lithostratigraphic units in the İstanbul some levels. Paleozoic sequence were given different names (Lower Ordovician–Visean) by differ- ent investigators in previous studies (Kaya, BIOSTRATIGRAPHY 1973; Önalan 1981, 1982; Gedik et al., 2004). In this study, the stratigraphic nomenclature The Lower Devonian conodont faunas were of Gedik et al. (2004) was taken as the basis obtained from the Beykoz and Karamandere (Figure 2). stratigraphic sections of the İstinye Formation (the Yumrukaya Group) (Figures 3, 4) and the The Dolayoba Formation, the basal unit Lower–Middle Devonian from the Büyükdere of the Yumrukaya Group, was first named as and Kokarpınar stratigraphic sections of the “the Dolayoba Limestone” by Kaya (1973), Kozyatağı member of the Kartal Formation and then, was changed to “the Dolayoba For- (Figure 5). mation” by Önalan (1981, 1982). It consists mainly of light-gray, sometimes pink to light- A direct correlation with common conodont brown reefal limestones. Yellow to beige, thin- zones of the pelagic biofacies was not possi- bedded shales are observed near the bottom. ble, because of the lack of conodonts in many It includes abundant corals, brachiopods, samples, the absence of (Klapper and Ziegler, orthoceratids and crinoid stems. The Dolay- 1979; Johnson et al., 1980; Johnson et al., oba Formation (100 m thick) is conformably 1985) zone-defining taxa due to shallow-water bounded by the Gözdağ Formation from the biofacies, the restricted diversity of species, lower and the İstinye Formation from the up- and the irregular vertical distributions of the per. The İstinye formation, the upper unit of the present taxa. Yumrukaya Group, was first defined by Kaya The Beykoz Measured Stratigraphic Section (1973). It was subdivided, in ascending order, (the İstinye Formation, the Yumrukaya Group) into three members: the Sedefadası (thinly laminated limestone-shale), Gebze (thin- to A total of 35 samples were collected medium-bedded limestones), and Kaynarca from the Beykoz Section (155 m thick), but (coarse nodular limestone–shale) members. only 4 samples produced conodont faunas The İstinye Formation, about 300 m thick, is (Figure 6). conformable and transitional with the under- Sample BG28 collected from gray to dark- lying Dolayoba Formation and the overlying gray, massive limestone bed, and sample BG34 Kartal Formation. from the lower part of gray, thick- or thinly-bed- The Kartal Formation consists of shale, ded limestones yielded Lanea eleanorae (Lane sandstone and limestone alternation. The and Ormiston) (Figure 6, Table 1). Sample BG30 Kozyatağı Member, the middle part of the Kar- from nodular limestone bed produced Icriodus tal Formation, was first defined by Kaya (1973) cf. vinearum Carls, Klapper and Murphy and as a stratigraphic formation, but was reduced Pseudooneotodus sp., and sample BG32 Icrio- in rank by Gedik et al. (2004) to a member. It dus rectangularis lotzei (Carls) and Icriodus cf. is made up of greenish-gray, gray and whitish- vinearum Carls. DEVONIAN CONODONT FAUNA IN BEYKOZ, ŞILE AND KURTDOĞMUŞ 3 Figure 2- Generalized columnar section of the İstanbul Paleozoic Sequence 4 Dilek Gülnur SAYDAM-DEMİRAY and Şenol ÇAPKINOĞLU Figure 3- Geological map showing the location of the Beykoz section. Table 1- Conodont distribution at the Beykoz section. DEVONIAN CONODONT FAUNA IN BEYKOZ, ŞILE AND KURTDOĞMUŞ 5 Figure 4- Geological map showing the location of the Karamandere section. 6 Dilek Gülnur SAYDAM-DEMİRAY and Şenol ÇAPKINOĞLU Figure 5- Geological map showing the locations of the Büyükdere and Kokarpınar sections. DEVONIAN CONODONT FAUNA IN BEYKOZ, ŞILE AND KURTDOĞMUŞ 7 Figure 6- The Beykoz measured stratigraphic section. 8 Dilek Gülnur SAYDAM-DEMİRAY and Şenol ÇAPKINOĞLU Based on the presence of Lanea eleanorae The Kokarpınar Measured Stratigraphic (Lane and Ormiston) with a range restricted to Section (the Kozyatağı member, the Kartal the delta Zone (upper Lochkovian) (Murphy and Formation) Matti, 1983, Figure 4; Murphy and Berry, 1983, Only 11 of 19 limestone samples that were Figure 2), samples BG28–BG34 in the Beykoz collected from the Kokarpınar stratigraphic section are referred to this zone (Table 1). section (4.65 m thick) produced conodont fau- nas (Figure 8). The section begins with 25 cm The Karamandere Measured Stratigraphic thick, gray, nodular limestone bed. A conodont Section (the İstinye Formation, the fauna consisting of Neopanderodus perlineatus Yumrukaya Group) Ziegler and Lindström, Belodella resima (Philip) Only 7 of 15 samples collected from lime- and Pseudooneotodus beckmanni (Bischoff and stone strata in the Karamandere Section of Sannemann) was recovered from sample KP1 the İstinye Formation (99.8 m thick) produced taken from this bed. conodont faunas (Figure 7). Sample ŞG3 from The following conodont faunas were ob- blackish-gray, thin- to medium-bedded, detri- tained from samples collected from limestone tal limestone bed with calcite veins produced strata within greenish-gray to gray, thin- to medi- Ozarkodina sp. Sample ŞG4 from a dark-gray, um-bedded limestone and shale sequence con- brachiopod bearing massive limestone bed stituting the majority of the section. yielded Icriodus angustoides alcoleae Carls and Sample KP10 produced Neopanderodus Icriodus cf. vinearum Carls. Icriodus angustoi- perlineatus (Ziegler and Lindström); sample des alcoleae Carls was recovered sample ŞG5 KP11 Belodella resima (Philip); sample KP12, taken from a light-gray, thin- to brachiopod and Neopanderodus transitans (Ziegler and Lind- crinoid bearing medium-bedded limestone bed . ström); sample KP13 Neopanderodus perlin- Sample ŞG8 produced Pseudooneotodus beck- eatus Ziegler and Lindström, and Pseudoone- manni (Bischoff and Sannemann) and Icriodus otodus beckmanni (Bischoff and Sannemann); angustoides alcoleae Carls. Samples ŞG9-10 sample KP13A Polygnathus linguiformis bul- and ŞG15 yielded Icriodus angustoides alcoleae tyncki Weddige beta morphotype, Neopan- (Carls and Gandl). derodus perlineatus (Ziegler and Lindström), Pseudooneotodus beckmanni (Bischoff and The presence of Icriodus angustoides alco- Sannemann), and Ozarkodina carinthiaca leae Carls and Gandl, identified by Valenzuela- (Schulze); sample KP13B Neopanderodus tran- Rios (1994) from the delta and pesavis zones sitans Ziegler and Lindström, Pseudooneotodus (upper