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Radiolarian rich, siliceous interval within Hauterivian pelagic succession in the central Sakarya, Pontides, NW Turkey
Ismail Omer Yilmaz, Ugur Kagan Tekin

Building: Muséum d'Histoire Naturelle de Genève
Room: Lobby /Hall/
Date: 2018-12-05 12:18 PM – 12:21 PM
Last modified: 2018-11-24


The study area lies on the Sogukcam village, central Sakarya region, central Pontides, in NW Turkey. 106 meters thick pelagic carbonates have been measured in detail within the Sogukcam Limestone. This limestone covers the underlying units with a transgression. Microfacies, sedimentary features and radiolarian biochronology of the Sogukcam Limestone have been carried out in this study.

In the Sakarya region, lithofacies can be observed as alternation of foraminifera and calpionellid bearing wackestones and mudstones at the basal part of the Sogukcam Limestone. Higher in the sequence, an interval characterized by thick-bedded, bioturbated, siliceous limestones with radiolarian and sponge spicule assemblages take place. Pyrites and iron mineralization have also been recorded within the same beds. Within this radiolarian rich, siliceous limestone interval, Spumellarian type radiolarian have been recognized (e.g., Dicerosaturnalis trizonalis dicranacanthos, Aurisaturnalis variabilis variabilis, Cecrops septemporatus, Crucella svinitzensis, Paronaella trifoliacea and Suna hybum) as major component whereas some Nassellerian type of radiolarians are also present (e.g., Stichomitra spp., Podobursa spp., Xitus sp., Crolanium sp. and Mictyoditra sp.) as minor component. Comparing the previous studies (e.g., Baumgartner et al., 1995; Dumitrica et al., 1997), age of this radiolarian rich limestones can be assigned as Hauterivian.

At the bottom of the succession, just below the siliceous interval, there is a shale/mudstone interval alternating with thin marls and calcareous sandstones. This siliceous interval in the studied area can be correlated to radiolarian bearing sequence encountered in the Sogukcam Limestone in other parts of the basin (Bragin & Tekin, 1999; Okay & Altıner, 2016, 2017). According to Bragin and Tekin (1999), pelagic deposits belonging to Sogukcam Limestone first appears in middle Oxfordian (Late Jurassic). Due to gradual deepening of the basin, radiolarian-rich, siliceous limestones of this formation took place in all of the basin in Hauterivian period (Okay & Altıner, 2016, 2017). Our findings are well-correlative to the previous studies. Geochemical analysis related to this formation will be carried out in the future studies.