Portail de Conférences / Conference Portal, JK2018

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The Jurassic-Cretaceous Boundary in marine sedimentary ‎successions in Turkey: A review
Ismail Omer Yilmaz

Building: Muséum d'Histoire Naturelle de Genève
Room: Amphithéâtre
Date: 2018-12-06 02:50 PM – 03:10 PM
Last modified: 2018-11-25


The Jurassic-Cretaceous boundary in Turkey can be observed within shallow water platform carbonates, pelagic carbonates and even deep basin facies in different parts of Turkey representing different zones in Sakarya and Tauride platforms and basins.

Many studies including Jurassic Cretaceous boundary have been published based on benthic foraminfera, dasyclad algae, calpionellids, radiolaria and even Sr isotopes (Altiner et al., 1991; Yilmaz, 1999; Yilmaz et al., 2016; Atasoy et al., 2018; Bartolotti et al., 2018, Kirmaci et al., 2018; Vincent et al., 2018) from different localities till now.

Platform carbonates display indistinct facies change along the boundary in both Taurides and Pontides. And mainly boundary can be tracked by Anchispirocyclina sp., Protopeneroplis striata, Campbelliella striata for Tithonian, and last occurrence of Clypeina sulcata (ex jurassica), presence of Haplophragmoides joukowski, Coscinoconus delphinensis, Coscinoconus campanellus, Charentia cuvillieri for the Berriasian (Altiner et al., 1991, Yilmaz, 1999; Yilmaz et al., 2016; Atasoy et al., 2018) But, the boundary line can be visible within couple of meters instead of centimeters.

Pelagic carbonate facies can display J/K boundary by presence of Saccacoma biozone, Tubiphytes morronensis, Calpionellid biozone A, and may be calcareous nannofossil biozones, like M. chiatius biozone, for the Tithonian, and calpionellid biozone B-C, and calcareous nannofossil biozones, like N. steinmanni biozone, for the Berriasian (Altiner et al., 1991; Yilmaz, 1999; Yilmaz et al., 2016; Atasoy et al., 2018).

In the eastern Pontides, NE Turkey, a hiatus around the Tithonian-Berriasian boundary is determined by Sr isotope age and foraminiferal biostratigraphy on the shallow-water platform carbonates (Vincent et al., 2018). In this region, volcanics in the Late Jurassic are more dominant. A possible effect of tectonics is more likely around the boundary in this region and can possibly be correlated with Caucasus. However, the J/K boundary can be tracked within dolostones in some localities in eastern Pontides too.

In the central western Turkey, late Tithonian age is obtained by radiolarian in the deep basin facies (basalt-chert facies) (Bartolotti et al., 2017), however a clear boundary just at the Tithonian and Berriasian is not recorded. However, radiolarian assemblage spanning the J/K boundary was recorded within clayey limestones and marls in NW Turkey, around Ankara city (Bragin & Tekin, 1999).