Late Cretaceous-Eocene Geological Evolution of the Pontides Based on New Stratigraphic and Palaeontologic Data Between the Black Sea Coast and Bursa (NW Turkey) (original) (raw)

Stratigraphic organisation, spatial distribution, palaeoenvironmental reconstruction, and demise of Lower Cretaceous (Barremian-lower Aptian) carbonate platforms of the Western Pontides (Black Sea region, Turkey)

Barremian-Lower Aptian platform carbonates (‘‘Urgonian limestones’’) of the northern margin of the Istanbul zone extend from Zonguldak to the Kurucasile area along the Black Sea coast. New stratigraphic data on the ‘‘Inpiri’’ Formation of the Inpiri-Kurucasile area are based on the identification of calcareous algae, foraminifera, and rudists. They show that this lithostratigraphic unit is stratigraphically and lithologically equivalent to the Oküsmedere Formation from Zonguldak. Some of the biostratigraphic markers are reported for the first time in Anatolia. Foraminifera are represented by several forms with a significant biostratigraphic potential used to distinguish the Barremian from the lower Aptian. Lower Aptian beds also yield relatively advanced caprinid rudists. The Oküsmedere Formation is relatively thin, terrigeneous-rich, and rudist-free or rudist-poor in the Kurucasile sector, and thick, terrigeneous-poor, and rudist-rich from Amasra to Zonguldak, with a set of marker beds including either charophytes or Palorbitolina and capped by a coral unit underlying ammonite bearing marls. Terrigeneous-rich carbonates from the eastern sector are interpreted as marginal marine coastal, infralittoral environments and grade distally, northward, to marly basinal sediments. By contrast ‘‘Urgonian type’’ limestones from the Zonguldak-Amasra region possess a wide extent and no transition to coastal or basinal sediments has been observed. A transition from a typical platform westward to a mixed siliciclastic-carbonate ramp eastward was controlled by both the nature of the adjacent exposed area and tectonic factors affecting the overall continental margin that is a northward downwarping. The exposed area was flanked southward by a belt of coastal siliciclastics grading southward and eastward to deep water sediments of the Ulus basin. In mid-Bedoulian time, carbonate platform demise from the western region was drowned below deeper marly sediments whereas the eastern siliscilastic-carbonate ramp was buried below coastal clastics.

New UPb and Rb-Sr ages from northwest Turkey; Early Cretaceous continental collision in the western Pontides

2009

Keywords: Intra-Pontide suture, Ä°stanbul Zone, Sakarya Zone, U-Pb zircon ages, Rb-Sr mica ages We provide new isotopic data from the Intra-Pontide Suture Zone, which indicate Early Cretaceous collision between the Sakarya and Ä°stanbul terranes following the consumption of the Intra-Pontide Ocean. The study area is located south of Sapanca Lake between the Ä°stanbul and Sakarya terranes in northwest Turkey. These two terranes show different geological histories, as reflected in their stratigraphic record, and are juxtaposed along the Intra-Pontide suture. The new U/Pb zircon and Rb/Sr mica ages come from south of the Sapanca Lake, south of the North Anatolian Fault in northwest Turkey. The Ä°stanbul terrane has a late Proterozoic basement (Chen et al., 2002; 570 Ma) overlain by a sedimentary sequence of Ordovician to Carboniferous age. The Sakarya terrane is characterized by Carboniferous (330-310 Ma) high temperature metamorphism (Okay et al., 2006), Paleozoic granitic plutonism (Topuz et al., 2007) and by the presence of Palaeo-Tethyan subduction-accretion units. South of the Sapanca Lake, three main tectonostratigraphic units have been differentiated forming a northeastward dipping thrust stack. At the top of the thrust stack is an amphibolite-facies metamorphic unit consisting of an intercalation of amphibolite, metaperidotite, metapyroxenite and gneiss representing a Proterozoic metaophiolite in the basement of the Istanbul Zone. This old metaophiolite is underlain by a Cretaceous accretionary complex of metabasite, metachert, slate and serpentinite. The lowermost tectonic unit in the thrust stack is a metasandstone, slate, phyllite and marble unit metamorphosed in greenschist facies. Our U/Pb geochronological data comes from the basement gneisses and the metasedimentary unit. The age of deposition and metamorphism of this metasedimentary unit were not constrained. The U/Pb ages of the clastic zircons from metasandstones are between 500-317 Ma. These new clastic zircon ages from the metasedimentary unit show that deposition of the sandstones must be later than Carboniferous (316±2,4 Ma). The Rb-Sr muscovite and biotite ages from metasedimentary unit and the basement gneisses give Early Cretaceous (138-111 Ma) ages. The muscovite ages of metasandstones are 138±1,5 Ma represents the metamorphic age of metasedimentary unit and the biotite Cretaceous cooling age of 111,3±1,1 Ma from the reheating of the Proterozoic basement. The new Rb/Sr ages indicate that the collision between the Istanbul and Sakarya terranes occurred during the Early Cretaceous. REFERENCES Chen, F., Siebel, W., Sati r, M., Terzioğlu, N., Saka, K., 2002. Geochronology of the Karadere basement (NW Turkey) and implications for the geological evolution of the Ä°stanbul Zone. Int. J. Earth Sci., 91, 469-481. Okay, A.I., Sati r, M. & Siebel, W., 2006, Pre-Alpide orogenic events in the Eastern Mediterranean region. In: European Lithosphere Dynamics (eds. Gee, D. G., and Stephenson, R. A.), Geological Society, London, Memoirs 32, 389-405. Topuz, G., Altherr, R., Schwartz,W.H., Dokuz, A.,Meyer, H.-P., 2007. Variscan amphibolites-facies rocks from the Kurtoğlu metamorphic complex (Gümüşhane area, Eastern Pontides, Turkey). Int. J. Earth Sci. 96, 861-873. Please fill in your abstract text.

Palaeontological, diagenetic and facies characteristics of Cretaceous/Paleogene boundary sediments in the Ordu, Yavuzlu and Uzunisa areas, Eastern Pontides, NE Turkey

Cretaceous Research, 2005

The region discussed in this paper is located in the eastern part of the Pontide tectonic unit in north-east Turkey. From north to south it comprises the Ordu, Yavuzlu and Uzunisa areas, which form part of the Pontide fore-arc basin. The region shows different facies developments through the Upper Cretaceous to the Eocene, and the K/Pg boundary section is represented by limestones, sandstones, and glauconitic sandstones. While investigating the palaeontological, diagenetic and facies characteristics of the boundary sediments, it was observed that the Maastrichtian age is represented by thicker successions than the Paleocene in the northern and southern parts of the study area. By contrast, in the centre, the Paleocene epoch is represented by a thicker sequence. It was also determined that the area has become deeper from north to south, owing to rifting during the MaastrichtianePaleocene and uplift to the north.

Late Cretaceous to Early Eocene Sedimentation in the Sinop–Boyabat Basin, North-Central Turkey: A Deep-Water Turbiditic System Evolving into Littoral Carbonate Platform

Sedimentary Processes, Environments and Basins

The Sinop-Boyabat Basin is a SE-trending, elongate basin in the Sakarya Zone of Central Pontides, northern Turkey, filled with a succession of Early Cretaceous to Middle Eocene deposits, nearly 7 km thick. The basin evolved from a forearc graben controlled by the process of Western Black Sea rifting into a foreland trough increasingly influenced and eventually inverted by compressional deformation associated with the Pontide/Tauride orogeny. This thesis summarized the results of a detailed sedimentological study of the Late Cretaceous to Early Eocene part of the basin-fill succession, ca. 2 km thick, which comprises three formations (Gürsökü Fm., Akveren Fm. and Atbaşı Fm.). The aim of the study was to reconstruct the basin's palaeogeographical and tectonic history on the basis of sedimentary facies analysis, supplemented with petrographical, micropalaeontological and ichnological data. Special emphasis was on the depositional processes involved and on the basin's responses to active tectonics and relative sea-level changes. The basin-fill succession studied has been described and its sedimentation processes interpreted in terms of eight component sedimentary facies, ranging from hemipelagites and turbidites to tempestites and shallow-marine calcarenites/limestones. These facies constitute four facies associations, stacked conformably upon one another with gradational boundaries: predominantly siliciclastic turbidites (FA 1), calcareous turbidites (FA 2), turbiditic to tempestitic carbonate-ramp deposits (FA 3) and ramp-drowning, predominantly hemipelagic deposits (FA 4). The Campanian-Maastrichtian Gürsökü Formation (up to 1200 m thick) consists of sheet-like turbidites interbedded with calcareous mudstones and marlstones (FA 1). These deposits represent the medial to distal reaches of a deep-marine turbiditic system that was supplied with siliciclastic and increasingly abundant bioclastic sediment from the basin's uplifted southwestern margin and was formed by unconfined, low-to high-density turbidity currents flowing eastwards along the basin axis. A sinuous turbiditic palaeochannel occurs in the lowermost part of the formation, but the system was subject to gradual headward backstepping and it is thus unknown if its proximal part involved many more channels. The Campanian uplift correlates with the accretion of Kirşehir microcontinent to the Sakarya margin of Eurasia, and this first pulse of compression, superimposed on the rifting-driven subsidence, marked the onset of a foreland regime in the basin. The overlying Maastrichtian-Palaeocene Akveren Formation (up to 600 m thick) consists of sheet-like calcarenitic turbidites interbedded with marlstones and calcareous mudstones (FA 2), passing upwards into a tempestite-dominated succession overlain by shoreface calcarenites and shallow-marine reefal limestones (FA 3). These deposits represent a turbiditic carbonate slope apron evolving into a carbonate ramp increasingly influenced by storms and covered by a basinward-expanding reefal platform. The rapid upward shallowing, from bathyal to littoral conditions, indicates a decline in subsidence, probably accompanied by mild compressional uplift of the basin floor. This pulse of compressional deformation correlates with the trench closure and the onset of continental collision in the adjacent Tauride-Anatolide Zone to the south. The Late Palaeocene-Early Eocene Atbaşı Formation (up to 200 m thick) consists of variegated calcareous mudstones interspersed with thin calcarenitic tempestites and turbidites (FA 4). These deposits represent a rapid rise in relative sea level that caused shoreline backstepping, cessation of sand supply, reduced sedimentation rate and extensive seafloor oxidation in the sediment-starved basin. This change indicates a strong pulse of rifting, with a rapid wholesale sinking of the basin and its footwall margin. The overlying Early-Middle Eocene Kusuri Formation (up to 1400 m thick), not covered in detail by the present study, is a siliciclastic turbiditic succession recording the last stages of the basin development, until its closure by tectonic inversion that correlates with the culmination of the Tauride-Anatolide orogeny. First of all I would like to thank my supervisor, Prof. Dr. Wojtek Nemec (Univ. of Bergen), for vital guiding during my field work as well as insightful and critical reading of the manuscript. I am also grateful to my co-workers at the larger project of which my thesis is a part of; Dr. Scient. student Nils Erik Janbu (Univ. of Bergen), M.Sc Łukasz Gągała (Wrocław Univ.), and M.Sc Ediz Kırman (Ankara Univ.). My thesis would not have turned out this way without our fruitful discussions and close collaboration. Nils Erik Janbu is especially thanked for constructive critics of my ideas and interpretations; Ediz Kırman is particularly acknowledged for vital help with drawing figures and for all those hours he spent behind the wheels during our fieldwork.

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 Ocean...

Geologia Croatica

The Küre Complex of the Middle Pontides, northern Turkey, is not a remnant of the Palaeotethys but consists of three different units with differing geological history, the Küre Ridge Unit, the Küre Ocean Unit and the Çalça Unit. The Küre Ridge Unit consists of the Serveçay Group, a pre-Permian, low-grade metamorphic Variscan oceanic sequence, and the Sırçalık Group, a Lower and Middle Triassic shallow-water sequence of North Alpine facies and event succession which disconformably overlies the Serveçay Group. Following a hiatus, the Sırçalık Group is overlain by marginal parts of the Akgöl Group with olistoliths of local origin which were derived mainly from the Sırçalık Group. The Küre Ocean Unit consists mostly of the Akgöl Group (siliciclastic turbidites and olistostromes of the Karad ag tepe Formation, which is a middle Carnian to Middle Jurassic accretionary complex from the southern, active margin of the Küre Ocean, and mainly Middle Jurassic molasse type shallow-water sandstones, siltstones and shales of an unnamed formation) and of thick oceanic basalts (I

Palaeostress analysis of Tertiary post-collisional structures in the Western Pontides, northern Turkey

Geological Magazine, 2002

Fingerprints of the opening of the Western Black Sea Basin and collision of Pontides and Sakarya Continent along the Intra-Pontide suture can be traced in the area between Cide (Kastamonu) and Kurucaşile (Bartin) in northern Turkey, along the southern coast of the Black Sea. The Western Black Sea Basin is an oceanic basin opened as a back-arc basin of the northward-subducting Intra-Pontide Ocean. Basement units related to this opening are represented by Lower Cretaceous and older units. The first arc magmatism related to this subduction began during Turonian times. Coeval with this magmatism, back-arc extension affected the region and caused development of horst-graben topography. This extensional period resulted in the break-up of continental crust and the oceanic spreading in the Western Black Sea Basin during Late Santonian times. During the Late Campanian–Early Maastrichtian period, the Sakarya Continent and Pontides collided and arc magmatism on the Pontides ended. After this c...

Upper Cretaceous stratigraphy of the Beydağları carbonate platform, Korkuteli area (Western Taurides, Turkey)

The Upper Cretaceous Korkuteli (Antalya) carbonate sequence of the Bey Dağları Autochthonous unit (western Taurides) comprises two formations. The Cenomanian-Santonian Bey Dağları formation lies at the base of this sequence and can be divided into two parts. Neritic part is characterized by platform-type, peritidal limestones and comprises an approximately 600-m-thick sequence that contains two main rudistid horizons corresponding to Cenomanian and early Santonian. The neritic limestones pass gradually upward into the 15-m thick, middle-upper Santonian massive hemipelagic limestones that form the upper part. The upper Campanian middle Maastrichtian Akdağ formation consists totally of pelagic limestones that indicate basinal conditions and disconformably overlies different stratigraphic levels of the Bey Dağları formation. Palaeogene pelagic marls form the base of the Tertiary sequence and disconformably overlie different stratigraphic levels of the Upper Cretaceous sequence. The presence of two erosional phases in the Upper Cretaceous sequence is obvious. The autochthonous unit was subaerially exposed after post-Santonian and middle Maastrichtian regressions.

The Upper Cretaceous to Palaeogene sedimentary history and tectonic evolution of the Bala Basin, Central Anatolia, Turkey

1985

The study area is situated on the northern extention of the Tuzgolu basin, (Central Anatolia) and contains Upper Cretaceous-Tertiary volcanic, clastic, and carbonate rocks with evaporites deposited on an ophiolitic melange basement, the Ankara Melange. The present structure of the area is the result of tectonism during late Alpine movements. The movements controlled the timing and conditions of sediment accumulation. The Bala basin evolved on the northern continental margin of the Kirsehir block. A brief period of south dipping subduction, which originated a continental island arc, was followed by oblique subduction, transform fault and continent to continent collision stages. These determined the shape and depositional characteristics of the basin. This is sup ported by independent magnetic evidence which suggests a 90° anti-clock wise rotation of the Kirsehir block during the Upper Cretaceous-Eocene period. Deposition of sediments occured in two phases. The Upper Cretaceous-Middle Eocene phase contains seven forma tions, Four are believed to have been deposited in a deep marine environment by mass movements and turdidity currents sometimes forming submarine fans, and two are shallow marine to continental deposits. The seventh is composed mainly of Andean type calc-alkaline volcanic rocks and their pyroclastics and was formed by subaerial lava flows. The formations reflect conditions of deposition in different parts of the basin and therefore some are the time equivalent of others. The Middle Eocene to probably Oligocene phase consists of two interfingering formations deposited in continental and marine environments of deposition. Palaeocurrent and pétrographie data suggest that during the first phase, the source area was to the southeast and formed by volcanic rocks of Sarikaya formation and Ankara Melange, while in the second phase sediments were derived from multiple marginal sources, including the sedimentary rocks of the first phase. ACKNOWLEDGEMENT The author is indebted to the Mineral Research and Exploration Institute for providing the grant as well as for the use of the Institute's facilities during the field work. The author gratefully acknowledges the unfailing support, encouragement and guidance of his supervisor Professor A.J. Smith, in every stage of the present research. This thesis would not have been completed without his constant interest and critical reading. Special thanks are extended to the academic and technical staff of the Geology Department of the Bedford College. Amongst the academic staff Dr. A. Saunders for stimulating discussions and suggestions on orogenic volcanic rock and their plate tectonic interpretation. Dr. G. Mariner for her help during the minerological and chemical analyses of rocks. Dr. D. Powell and Dr. P. Banham for fruitfull dis cussion on structural geology and magmatic rocks. Dr. T. Rose for his help and suggestions for the identification of fossils will be remembered. Miss R. Fricher and Mrs S. Bishop for their kind help and assistance. Mr. S Houlding, Mr. N. Sinclair, Mr. J. Mock and Mr. J. Keith for their technical assistance and help deserve special thanks. The author also wishes to thank Dr. A.G. Adams of the Natural History Museum and S. Tekler of M.T.A. for iden tification of microfossils, professor D.J. Shearman for use ful discussion in aspects of limestone diagenesis, Dr. 0. Varol of Robertson Research Institute for indentification of Nannofossils and Professor T.N. Norman of Middle East Technical University and Dr. F.Y. Oktay of Istanbul Technical University for useful discussions on the geology of the Central Anatolia.

Upper Cretaceous volcaniclastic complexes and calcareous plankton biostratigraphy in the Western Pontides, NW Turkey

TURKISH JOURNAL OF EARTH SCIENCES

This study describes and interprets Upper Cretaceous volcaniclastics interbedded with hemipelagic to pelagic limestones, marls, and turbidites from the Western Pontides, northwestern Turkey. The Dereköy Formation, the Unaz Formation (red pelagic limestone unit), and the Cambu Formation can be distinguished, overlain by the turbiditic Akveren Formation. Biostratigraphic ages from the predominantly volcaniclastic Dereköy Formation indicate Turonian (Dicarinella concavata planktonic foraminifera zone, CC13/UC8-9 nannofossil zones) to middle/late Santonian ages up to CC17/UC13. The Unaz Formation, deposited during the late Santonian (UC13, Dicarinella asymetrica Zone), is overlain by the volcaniclastic Cambu Formation of latest Santonian (CC17b/UC13) to early/middle Campanian (CC20/UC15a) age. However, turbidite intercalations are already present diachronously from CC19/UC14d onwards, and the turbiditic Akveren Formation ranges up into the late Maastrichtian (Abathomphalus mayaroensis Zone). Geochemistry of the volcaniclastic units reveals information about the volcanic series and tectonic setting, although element mobility has to be considered. An overall trend of calc-alkaline to high-K calc-alkaline series and basaltic to basalt-andesitic rock types was identified. A negative Nb anomaly with respect to Th and Ce in all samples confirms the existence of a volcanic arc, also indicated by a negative Ti anomaly. Biostratigraphic age constraints give evidence for volcanic arc activity mainly between Turonian and early Campanian, ca. 91-79 Ma. Various geochemical data, especially element variations normalized to N-MORB, show two types of volcanic arc basalts (VAB): (1) Calc-alkaline to high-K calc-alkaline VAB have increased Nb and Zr values, (2) more tholeiitic VABs are depleted in Nb, Zr, Ti, V. The volcaniclastics successions were deposited in an arc setting triggered by different stages of subduction of the Neotethys Ocean to the south and contemporaneous spreading in the Western Black Sea Basin to the north. An extensional regime caused formation of small but deeper-water sedimentary basins along the southern shore of the Black Sea where volcaniclastic complexes interfingered within short lateral distances with pelagic and mass-flow deposits.