Cretaceous pelagic red beds and black shales (Aptian-Santonian), NW Turkey: Global oceanic anoxic and oxic events

The study areas located near the towns of Goynok, Muclurnu and Nallihan in the central northwestern part of Turkey lie on the 'Sakarya Continent', which is one of the tectonic entities of the Cretaceous geology of Turkey. Measured stratigraphic sections comprise the Aptian pelagic carbonates and the overlying Albian-Coniacian turbiditic sequences, which are all capped by a Late Santonian red pelagic succession. Lower and Upper Aptian, Upper Albian and Cenomanian/Turonian marine black shales recognized in the sections are followed by Lower and Upper Aptian, Upper Albian and Turonian marine red beds. The black shales are generally silty, laminated, and include pyritized radiolarian and planktonic foraminifera. The red beds are composed of red-pink limestones, which are of packstone facies with abundant planktonic foraminifera, bivalve, echinoidea, iron infillings and coatings. They also include red silty maris with quartz, iron and glauconite minerals as well as bivalve fragments. Sedimentologic, sequence stratigraphic and cyclostratigraphic properties of black shales and red beds recorded along the measured stratigraphic sections have been determined and Fischer plot analysis has been applied for their correlation and coherency. Their sequence stratigraphic positions and cyclic nature indicate that black shales were generally deposited in the early transgressive system tracts. However, red beds represent the late transgressive/high-stand systems tracts. In some areas, the Upper Santonian red beds are observed in association with a drowning event and overlie a Type-3 sequence boundary. Their stratigraphic position and sedimentology are used to better understand the oceanic events and tectonic movements recorded in this basin. These black shales and red beds are recognized within coeval biostratigraphic intervals as in their global counterparts.


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The Late Cretaceous-Eocene geological evolution of northwest Turkey between the Black Sea and Bursa was studied through detailed biostratigraphic characterization of eleven stratigraphic sections. The Upper Cretaceous sequence in the region starts with a major marine transgression and lies unconformably on a basement of Palaeozoic and Triassic rocks in the north (Istanbul-type basement) and on metamorphic rocks and Jurassic sedimentary rocks in the south (Sakarya-type basement). Four megasequences have been...
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The Pontide magmatic belt in the Western Pontides, which developed in response to the northward subduction of the northern branches of the Tethys Ocean, consists of two different volcanic successions separated by an Upper Santonian pelagic limestone unit, the Unaz Formation. The first period of volcanism and associated sedimentation started during the Middle Turonian and lasted until the Early Santonian under the control of an extensional tectonic regime, which created horst-graben topography along the sout...
Upper Cretaceous volcaniclastic complexes and calcareous plankton biostratigraphy in the Western Pontides, NW Turkey
Boehm, Katharina; Wagreich, Michael; Wolfgring, Erik; Tuysuz, Okan; Gier, Susanne; Yılmaz, İsmail Ömer (2019-01-01)
This study describes and interprets Upper Cretaceous volcaniclastics interbedded with hemipelagic to pelagic limestones, marls, and turbidites from the Western Pontides, northwestern Turkey. The Derekey 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 Derekoy Formation indicate Turonian (Dicarinella concavata planktonic foraminifera zone, CC13/UC8...
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In the Central Pontides (Northern Turkey), south of Tosya, a tectonic unit consisting of not-metamorphic volcanic rocks and overlying sedimentary succession is exposed inside a fault-bounded elongated block. It is restrained within a wide shear zone, where the Intra-Pontide suture zone, the Sakarya terrane and the Izmir-Ankara-Erzincan suture zone are juxtaposed as result of strike-slip activity of the North Anatolian shear zone. The volcanic rocks are mainly basalts and basaltic andesites (with their pyroc...
Early-Middle Triassic echinoderm remains from the Istranca Massif, Turkey
Hagdorn, Hans; Göncüoğlu, Mehmet Cemal (2007-01-01)
In the northwestern part of the Istranca Massif close to the Turkish-Bulgarian border, recrystallized limestones above germanotype fluvial clastics (Buntsandstein-equivalents) yielded remains of echinoderms and bivalves. The limestones are lensoidal, flaser-bedded and bioturbated, like the Holocrinus lagerstatten, which are common in the germanotype Muschelkalk. The sufficiently preserved crinoid ossicles can be assigned to genus Holocrinus, a crinoid clade that occurs worldwide in Early and Middle Triassic...
Citation Formats
İ. Ö. Yılmaz, “Cretaceous pelagic red beds and black shales (Aptian-Santonian), NW Turkey: Global oceanic anoxic and oxic events,” TURKISH JOURNAL OF EARTH SCIENCES, pp. 263–296, 2008, Accessed: 00, 2020. [Online]. Available: