GEOLOGIJA 54/1, 91–96, Ljubljana 2011 doi:10.5474/geologija.2011.007 Devonian conodonts from the Fo~a–Pra~a Paleozoic complex (Durmitor Nappe, southeastern Bosnia and Herzegovina) Konodonti iz fo~ansko-pra~anskega paleozojskega kompleksa (durmitorski pokrov, jugovzhodna Bosna in Hercegovina) Tea KOLAR-JURKOVŠEK1, Hazim HRVATOVI]2, Ferid SKOPLJAK3 & Bogdan JURKOVŠEK4 1, 4Geolo{ki zavod Slovenije, Dimi~eva ulica 14, SI-1000 Ljubljana; e-mail: tea.kolar�geo-zs.si, bogdan.jurkovsek�geo-zs.si, 2, 3Federalni zavod za geologiju, Ustani~ka 11, 71000 Sarajevo, e-mail: zgeolbih�bih.net.ba Prejeto / Received 15. 3. 2011; Sprejeto / Accepted 13. 4. 2011 Key words: conodonts, Devonian, CR-17 borehole, Crna Rijeka, Bosnia and Herzegovina Klju~ne besede: konodonti, devon, vrtina CR-17, Crna rijeka, Bosna in Hercegovina Abstract Conodont study of the Crna Rijeka borehole CR-17, positioned in the frontal part of the Durmitor Nappe (Fo~a – Pra~a Paleozoic complex, SE Bosnia and Herzegovina) is presented. The obtained fauna indicates an Early-Middle Devonian age and due to poor preservation an identification at a generic level is possible only. The recovered cono- dont elements have a high Color Alteration Index (CAI = 6,5–7) indicating a degree of metamorphism correspon ding to a temperature interval from 440 °C to 720 °C. Izvle~ek Predstavljene so konodontne raziskave vrtine Crna rijeka CR-17 v ~elnem delu pokrova Durmitor (paleozojski kompleks Fo~a – Pra~a, jugovzhodna Bosna in Hercegovina). Konodontna favna dokazuje spodnje-srednjo devon- sko starost, vendar je zaradi slabe stopnje ohranjenosti mogo~a le dolo~itev na stopnji rodov. Dobljeni konodontni elementi imajo visok barvni indeks (CA I = 6,5–7), ki kaže na stopnjo metamorfoze v temperaturnem intervalu od 440 °C do 720 °C. Introduction The goal of the CR-17 borehole (Fig. 1) was to acquire knowledge about the thickness of Devo- nian carbonate in the Crna Rijeka area of Bosnia and to recognize the geological characteristics of the area to support the project of the »Crna Rijeka Dam«, near Sarajevo (BA{AGI} & SKOPLJAK, 2007). In this short report a documentation is presen- ted of a conodont study carried out in Paleozoic strata of the Crna Rijeka CR-17 borehole, inter- val from 12 to 203 meters. The obtained conodont fauna indicates an Early-Middle Devonian age of the investigated samples present in some of the oldest strata in Bosnia and Herzegovina. Geological setting Geographically, the Crna Rijeka is located southeast of Sarajevo (Fig. 1). The area of Crna Rijeka is included in the Fo~a-Pra~a Paleozoic Fig. 1. Location map of the Crna Rijeka CR-17 borehole. GEOLOGIJA_54_1_2011_internet.indd 91 30.6.2011 7:28:51 92 Tea KOLAR-JURKOVŠEK, Hazim HRVATOVI], Ferid SKOPLJAK & Bogdan JURKOVŠEK complex of southeastern Bosnia and Herzegovina Lower and Middle Devonian limestone (KOSTI}- and is positioned in the frontal part of the Durmi- PODGORSKA, 1958; žIVANOVI}, 1963; PANTI}, 1963). tor Nappe, which tectonically overlies the Bosnia Some Paleozoic formations of the Fo~a area are Flysch Nappe (Fig. 2). of a presumed Devonian age. The thickness of the Southeastern Bosnia and Herzegovina compri- Paleozoic formations attains up to 800 m in the ses the areas of Fo~a, Goražde and Pra~a. In the area (BUZALJKO, 1971). between the Fo~a and Goražde areas the oldest Devonian formations are overlain by Early Paleozoic formations crop out in which Variscian Carboniferous flysch that is up to 1000 m thick. age structures are preserved. Thick-bedded lime- The flysch sediments contain ammonoids (go - stone occurs at Ustikolina with Late Silurian niatites, orthoceratides), mollusks, gastropods, conodonts Ozarkodina and Panderodus present brachiopods and corals. At Podkoran, an occur- (BUZALJKO, 1971; RA MOV{, 1989). rence of Early Carboniferous strata containing Lower Devonian strata are represented by dark goniatites was studied in detail by KITTL (1904). gray platy limestone with conodonts (Neoprionio- Based on the goniatite data, FRECH (1906) and dus, Plectospathodus) and Upper Devonian lime- SCHMIDT (1924) supported a Visean age of some stone are marked by the presence of conodonts Paleozoic formations. POdgORSKA (1939) pub- (Palmatolepis), bryozoans and crinoids (BUZALJKO, lished data on fauna from crinoidal limestone 1971; RAMOV{, 1989). from the area of Pra~a. In the area of Klek on the easternmost slopes of KRSTI} et al. (1988) gave explanation of the ori- Mt. Jahorina, “Orthoceras limestone” with Early gin for the Silurian and Devonian limestones in and Late Silurian conodonts and tentaculides are the Pra~a area of SE Bosnia considering them as present in the Pra~a thrust below Triassic forma- allochthonous clasts and olistoliths in the Lower tions (KOSTI}-PODGORSKA, 1958). Here, a rich fauna Carboniferous „Culm“ flysch. FILIPOVI} & JOVA- of corals, stromatoporoids, hydrozoans, bryozo- NOVI} (1994) later provided new data for age and ans, brachiopods and crinoids was collected in characteristics of the same rocks in the Pra~a (SE Fig. 2. Main structures of the Dinarides of Bosnia and Herzegovina (HRVATOVI}, 2006): - CR-17 borehole. 1. Karst Nappe, 2. Una-Drežnica-Gacko Nappe, 3. Klju~-Radu{a Nappe, 4. Mid-Bosnian Schists Mts., 5. Bosnian Flysch Nappe, 6. Durmitor Nappe, 7. Ophiolite Nappe, 8. Golija Nappe, 9. Sana-Una Nappe, 10. Sava-Vardar Nappe. GEOLOGIJA_54_1_2011_internet.indd 92 30.6.2011 7:28:53 Devonian conodonts from the Fo~a–Pra~a Paleozoic complex (Durmitor Nappe, southeastern Bosnia and Herzegovina) 93 Bosnia) and Vlasenica (NE Bosnia) areas, and conodont analyses. All of them are composite they interpreted them as Upper Carboniferous samples, covering over one meter of the most per- olisto stromes connected with Asturian phase of spective divisions, i. e. in the less recrystallized Variscan orogenesis. and less tectonized parts of the drill hole. Three A break in sedimentation took place during the samples were composite samples embracing over Late Carboniferous and Early Permian. The Upper three to six meters of the borehole in order to ob- Permian is represented by reddish clastics overlain tain positive results. A standard technique for by Bellerophon limestone bearing gastropods (Bel- conodont extraction was applied by use of acetic lerophon) and calcareous algae (Gymnocodium). acid and then heavy liquid separation. The sam- The Bellerophon limestone was first recorded by ples were dissolved at the Geolo{ki zavod Sloveni- BIT TNER (1880) and documented later by KITTL je / Geological Survey of Slovenia. (1904) at Han Orahovica, KATZER (1926) at Zbi{}e Out of the 10 examined samples from the inve- and Musi}i, and KOSTI}-POdgORSKA (1958) at Vi- stigated interval, six samples were productive for hor, Lunji and Razboji{te. In the area of Tjenti- conodonts. However, conodont yields are rather {te, CADET (1966) reported finding of brachiopods, low (Fig. 4). The obtained elements are largely mollusks and gastropods in dark gray thick bed- fragmented. An identification at a generic level ded limestone of Latest Permian age. In the area is possible only due to poor state of preservation. of the Kolina Valley, Fo~anska Jabuka and further The conodont elements recovered have a high towards Pra~a sideritic-ankeritic limestone were Color Alteration Index (CAI = 6.5–7) indicating a di scovered with sulphides: pyrite, chalcopyrite, degree of metamorphism corresponding to a tem- ar senopyrite, galena and antimonite. BUZALJKO perature interval from 440 °C to 720 °C (REJEBIAN (1971) made a detailed stratigraphic subdivision et al., 1987). of the Permian rocks of the Southeast Bosnia area Most of the forms are identerminable and only (Fig. 3). the elements of the two samples (CR 74-79 m and CR-17 193-195 m) enable comparison with Early– Conodont study Middle Devonian taxa. The present study is based on collections from the borehole CR 17 of Crna Rijeka and made in Materials and methods 2006 (KOLAR-JURKOV{EK & JURKOV{EK, 2006). Ten carbonate samples were collected, averaging ap- Photographs of all illustrated conodont ele- proximately 2 kg each. They were processed for ments presented herein were taken on the JSM- M Age Lithology Environments Fossils <100 Bellerophon limestone, Shallow marine-lagoonal Bellerophon sp., P3 – sandstone, Archaeocidaris ladina, – gypsum, Gymnocodium sp. – redish schist, – siltstone Land? 850 – redish conglomerate, and quartz sandstone, Shallow marine to fluvial Naneionella, Mizzia cornuta, P1,2 – gray schist, marble, bedded limestone, Globivalvulina, Tubertina sp. – breccia 100 Sandstone, claystone, conglomerate, schist Trench Lepidodendron weltheimianum C3 Flysch: Trench Verneulites librovitchi C2 700 Flysch: Trench Lepidodendron lasseni, C1 Subgraywacke, sandstone, claystone, Glyphyoceras sphaericum, clayey-quartz-sericite schist, Aviculopecten pra~aensis, microconglomerate, massive limestone Cyathocarinia rasliana, Chonetes, Nereites 200 Bedded limestone Marine platform Hindeodella sp., D3 Palmatolepsis glabra pectinata, P. rhomboidea, Belodella triangularis 450 Massive reefal limestone Marine platform Favosites sp., D2 Polygnathus linguiformis 200 D Bedded limestone, layered schist Marine platform Neoprioniodus bicurvatus, 1 Plectospathodus, Panderodus unicostatus 100 S Massive limestone Marine platform Ozarkodina, 3 Panderodus Fig. 3. Geological description of Paleozoic strata of SE Bosnia (HRVATOVI}, 2006; after BUZALJKO 1971; KULENOVI}, 1985). GEOLOGIJA_54_1_2011_internet.indd 93 30.6.2011 7:28:54 94 Tea KOLAR-JURKOVŠEK, Hazim HRVATOVI], Ferid SKOPLJAK & Bogdan