GEOL. CROAT. 53/2 209 - 268 3 Figs. 1 Tab. 15 Pls. ZAGREB 2000 New Stratigraphic and Palaeogeographic Results from the Palaeozoic and Early Mesozoic of the Middle Pontides (Northern Turkey) in the Azdavay, Devrekani, Küre and Inebolu Areas: Implications for the Carboniferous - Early Cretaceous Geodynamic Evolution and Some Related Remarks to the Karakaya Oceanic Rift Basin Heinz W. KOZUR 1, Mustafa AYDIN2, Osman DEMIR 2, Huseyin YAKAR 3, M. Cemal GÖNCÜOGù LU4 and Ferudun KURU 3 Key words: Pelagic Upper Carboniferous and Permian, Middle Triassic oceanic crust, Upper Triassic to Middle Jurassic accretionary complex, Hallstatt Limestone, T o r l e s s i a, Microfauna, Northern Turkey, Middle Pontides, Paphlagonian Ocean, Küre Ocean and Karakaya oceanic rift basin. Abstract glomerate, sandstone) and Inaltõ Formation (shallow-water platform The Küre Complex of the Middle Pontides, northern Turkey, is carbonates). not a remnant of the Palaeotethys but consists of three different units The Küre Ridge Unit was split away from the Variscan Sakarya with differing geological history, the Küre Ridge Unit, the Küre Continent by the opening of the Karakaya oceanic rift basin during Ocean Unit and the Çalça Unit. The Küre Ridge Unit consists of the latest Permian (Dorashamian) and became a continental splinter Serveçay Group, a pre-Permian, low-grade metamorphic Variscan between the Karakaya oceanic rift basin and the Küre Ocean (opened oceanic sequence, and the Sırçalık Group, a Lower and Middle Trias- during the late Scythian). sic shallow-water sequence of North Alpine facies and event succes- Southward subduction began in the Küre Ocean during the mid- sion which disconformably overlies the Serveçay Group. Following a dle Carnian (beginning of the Karadagùtepe siliciclastic turbidites), hiatus, the Sõrçalık Group is overlain by marginal parts of the Akgöl whereas at the northern passive margin the deposition of Hallstatt Group with olistoliths of local origin which were derived mainly from Limestones continued until the latest Norian. The deposition of silici- the Sõrçalõk Group. The Küre Ocean Unit consists mostly of the clastic turbidites and olistostromes (Diskaya Unit) began in the entire Akgöl Group (siliciclastic turbidites and olistostromes of the Kara- Karakaya oceanic rift basin during the middle Carnian, and ocean d agùtepe Formation, which is a middle Carnian to Middle Jurassic basin deposits (radiolarites, pelagic limestones) and slope deposits accretionary complex from the southern, active margin of the Küre form the passive margin (e.g., Hallstatt Limestones) are no more pre- Ocean, and mainly Middle Jurassic molasse type shallow-water sand- sent in the Karakaya oceanic rift basin indicating that this basin was stones, siltstones. and shales of an unnamed formation) and of thick very narrow (only a few hundreds of kilometres). During the late oceanic basalts (Ipsinler Basalt). Tectonic slices of Middle Triassic to Norian, the Karakaya oceanic rift basin closed, whereas subduction at lower Carnian ophiolites and basalts are also present. The Kara- the southern (active margin) of the Küre Ocean continued. At the d agùtepe Formation contains numerous Middle Triassic exotic olis- northern margin of the (Upper Triassic?) Jurassic -Lower Cretaceous toliths and blocks of shallow-water and predominantly slope and basi- B e y k oz-Ç agùlayan turbidite basin (north of the Küre Complex) the nal limestones, ocean-floor deep-sea sediments (shales and radiolar- accretionary complex of an older ocean, the Late Palaeozoic Paphlag- ites), basalts and small clasts of ophiolites or ophiolitic detritus. The onian Ocean, was exposed that yielded clasts in the Beykoz-Ç agù l a- Çalça Unit consists of deposits from the northern, passive margin of yan turbidite basin. Among these clasts Carboniferous to Middle Per- the Küre Ocean with many Pelsonian to upper Norian Hallstatt Lime- mian (Capitanian) pelagic rocks (pelagic limestones, radiolarites) stones and Rhaetian-Lower Jurassic (?Middle Jurassic) deep-water could be dated. A Middle to Late Permian southward-directed sub- shales and marls. All three units are overlain following a period of duction is assumed for the Paphlagonian Ocean. Its closure occurred non deposition by the Upper Jurassic Bürnük Formation (red con- either at the end of the Permian or during the Scythian. 1 Rézsü u. 83, Budapest, Hungary. 2 Türkiye Petrolleri A.O., Exploration Group, Mustafa Kemal Mahallesi, 2. Cadde No. 86, 06502 Esentepe-Ankara, Turkey. 3 Türkiye Petrolleri A.O., Research Center, Mustafa Kemal Mahallesi, 2. Cadde No. 86, 06502 Esentepe-Ankara, Turkey. 4 Department of Geological Engineering, Middle East Technical University, Inönü Bulvari, 06531 Ankara, Turkey. 210 Geologia Croatica 53/2 1. INTRODUCTION AND GENERAL GEOLOGI- mounts of this age interval must be more than 1,000 km CAL SETTING OF THE MIDDLE PONTIDES long and had filled the entire ocean because basinal and AND IMMEDIATELY ADJACENT AREAS even slope sediments are unknown in this time interval. Moreover, these seamounts had to be persistent (throu- The Küre Complex of the Middle Pontides south of ghout most of the Pennsylvanian, the entire Early and Inebolu, northern Turkey (investigated area, Fig. 1) Middle Permian and the lower part of the Late Permian) plays an important role in the palaeogeographic recon- and covered by a facially stable carbonate platform. structions of the Late Palaeozoic and Early Mesozoic of Contemporaneous mafic volcanics and volcaniclastics Turkey and adjacent areas. Two conflicting palaeogeo- are not known from the Moscovian to middle Dzhulfian graphic models were developed by the S¸ E N G Ö R interval. All these features are in total contrast with school (e.g., S¸ENGÖR & YILMAZ, 1981; S¸ E N G Ö R , well-documented Permian seamounts in Panthalassa 1984, 1985; S¸ENGÖR et al., 1984; GENÇ & YILMAZ, studied by one of the authors (H.W. KOZUR) and also 1995; YILMAZ et al., 1997) on one side, and OKAY different from Palaeotethyan seamounts (KOZUR & and co-authors (e.g., OKAY & MOSTLER, 1994; S¸ENEL, 1999). OKAY et al., 1996) as well as ROBERTSON and co- The assumption of a large Carboniferous- P e r m i a n authors (e.g., PICKETT et al., 1995; USTAÖMER & (and Triassic) Karakaya Ocean by Okay and co-authors ROBERTSON, 1995, 1997, 1999; PICKETT & RO- was based on the fact that the youngest olistoliths of the BERTSON, 1996) on the other. largely broken Variscan basement are cherty limestones The first model regards the Küre Complex as a rem- of early Bashkirian age (OKAY & MOSTLER, 1994; nant of the southwards subducting Late Palaeozoic - KOZUR, 1999), whereas red radiolarites of the Dora- Triassic Palaeotethys, and the Karakaya oceanic rift shamian to Middle Triassic Çal Unit (OKAY et al., basin as a latest Permian - Triassic back-arc basin that 1991) were erroneously dated as Sakmarian-Artinskian was closed during the Upper Triassic by southward in one locality (OKAY & MOSTLER, 1994). Re-exam- subduction. ination of this locality SE of Çan in the Biga Peninsula, The second model regards the Karakaya Basin as northwestern Turkey (for precise locality data see the large, Devonian to Triassic Palaeotethyan Ocean OKAY & MOSTLER, 1994) by KOZUR (1999) yield- and the Küre Basin as a short-lasting, small, oceanic ed a rich late Dorashamian radiolarian fauna in all ex- basin which opened as a back-arc basin by the north- posed radiolarites confirming the former conodont- ward subduction of the Karakaya oceanic lithosphere. based dating of the opening of the Karakaya oceanic rift Some authors considered the Karakaya oceanic rift basin by KOZUR & KAYA (1994). The assumed Late basin as a Triassic ocean or rift basin (as in the first Permian mafic volcanics, mainly tuffs (OKAY & MO- model) without regard to the age of the Küre Complex STLER, 1994), were dated as post-latest Scythian beca- use they contain inclusions of conodont-bearing latest (OKAY,. 1991;. ALTINER & KOÇYIGIT, 1993), whe- reas YIGù IT B AS¸et al. (1999) regarded the Küre Com- Scythian limestones (KOZUR, 1999). plex as the remnants of a persistent Pa l a e o t e t h y a n The formerly assumed latest Permian opening of the ocean (as in the first model) without regarding the Karakaya oceanic rift basin (first model, see above) Karakaya Complex. These papers also support the first during the Dorashamian Stage could be confirmed pal- model. aeontologically by KOZUR & KAYA (1994), KOZUR A third model regarding the relation of the Kara- (1999) and KOZUR et al. (1999). Pelagic uppermost kaya oceanic rift basin and Küre Ocean was presented Dzhulfian and Dorashamian limestone olistoliths from by OKAY & TÜYSÜZ (1999) and OKAY (2000). the upper Diskaya Unit (KAYA et al., 1986; junior syn- According to these authors both oceanic basins repre- onym: Hodul Unit, OKAY et al., 1991) and late Dora- sent the same large Palaeotethyan ocean and the present shamian red radiolarites of the Çal Unit are the oldest separation is a later feature. The HP/LT metamorphic pelagic rocks of the Karakaya Complex. The oldest dat- Nilüfer Unit of the Karakaya Complex was regarded as ed mafic volcanics have a Scythian age (Table 1). The an oceanic plateau despite the fact that the lower half missing geochemical signals for subduction related contains shallow-water (?algal) limestones with mafic mafic rocks in the Nilüfer Unit of the Karakaya Com- metatuffs and also in the upper half the water-depth was plex (within plate basalts, USTAÖMER & R O B E R T- (according to the fauna) probably not below 100-200 m. SON, 1999) is no evidence for a large Late Palaeozoic- The view of Robertson and co-authors of a Car- Triassic Palaeotethyan Karakaya Ocean, as assumed by boniferous-Triassic age of the Karakaya oceanic rift USTAÖMER & ROBERTSON (1995, 1997, 1999), PI- basin is for the Palaeozoic (pre-Dorashamian) part CKETT et al. (1995), OKAY et al. (1996) and PICK- based only on an assumption which is in conflict with ETT & ROBERTSON (1996), but indicates early rift- the fact that in the post-Bashkirian pre-latest Dzhulfian ing in a shallow-water carbonate platform.