Original articleBenthic foraminiferal assemblages of the Cretaceous platform carbonate succession in the Yavca area (Bolkar Mountains, S Turkey): biostratigraphy and paleoenvironmentsAssociations de foraminifères benthiques des séquences de plate-forme carbonatée du Crétacé dans la région de Yavca (Montagnes de Bolkar, Turquie méridionale) : biostratigraphie et paléoenvironnement
Introduction
The Bolkar Mountains are situated in the eastern part of the Central Taurides (Fig. 1a). They are bounded by the Ereğli-Ulukışla Basin in the north and by the Mediterranean Sea in the south. Up to now biostratigraphic characteristics, as well as lithostratigraphy, of the Upper Cretaceous carbonates in the Bolkar Mountains have not been investigated in much detail. The Yavca area represents a small part of the Bolkar Dağ carbonate platform that existed during the Permian to Late Cretaceous (Demirtaşlı et al., 1984). This area is important because the Cretaceous carbonate succession represents the latest stage of platform conditions prior to the succeeding hemipelagic and pelagic carbonate deposition.
During detailed investigation of the Upper Cretaceous lithostratigraphy and basin development in the southern part of the Bolkar Mountains (Özer et al., 2002), abundant and diversified benthic foraminiferal assemblages have been observed in the Cretaceous platform limestones.
The aims of this study are:
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to document the benthic foraminiferal assemblages;
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to make chronostratigraphic interpretation of the Cretaceous platform carbonate sequence using the Standard European stages by means of the foraminiferal assemblages;
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to correlate the assemblages with those in other areas of the Mediterranean realm.
Section snippets
Material and methods
The material investigated comes from the Cretaceous carbonates in the Yavca area (Mersin) which is located at the southern part of the Bolkar Mountains (Fig. 1a). Three outcrop sections which form a 3 km SSW–NNE traverse between Kavaklıpınarı and Yavca (Fig. 1b) were sampled systematically. The Kavaklıpınarı section-II is characterized by a continuous stratigraphic record and has been chosen as the best representative of the Cretaceous sequence in the Yavca area (Fig. 2). This section was
Stratigraphy of the Bolkar Mountains
Stratigraphic data for the north of the investigated area (Bolkar Mountains) have been documented in Demirtaşlı et al. (1984) and references therein. İlker's (1975) report on the area investigated is a detailed work in which the Upper Cretaceous Yavca Formation was first described. The corresponding unit in the Bolkar Mountains was described by Demirtaşlı et al. (1984) under the name Arslanköy Formation.
In the southern part of the Bolkar Mountains, Demirtaşlı et al. (1984) have differentiated a
Biostratigraphy
As ammonites are absent and rudists are in shell debris, benthic foraminiferal assemblages are single biostratigraphic tool for subdivision of the Cretaceous platform carbonate succession in the Yavca area. The absence of stratigraphically important benthic foraminiferal taxa (especially orbitolinids and alveolinids) does not allow greater stratigraphic resolution within this carbonate platform domain.
Ranges of the foraminiferal taxa recognized in the Yavca Cretaceous sections are shown in
Demise of the Bolkar Dağ carbonate platform
The Cretaceous shallow-water carbonate succession of the Yavca area is conformably overlain by the Campanian pelagic gray limestones (Kavaklıpınarı Limestone). The Campanian age is confirmed by the presence of the following taxa (determined by Kemal Erdoğan, Ankara): Globotruncana linneiana (d'Orbigny), Globotruncana arca (Cushman), Globotruncanita cf. calcarata (Cushman), Globotruncana bulloides Vogler, Globotruncanita stuartiformis (Dalbiez), Globotruncanita elevata (Brotzen), Rosita fornicata
Discussion and conclusions
This study is the first approach to biostratigraphy and chronostratigraphy of the Cretaceous platform carbonates of the Bolkar Mountains. The Cretaceous succession of the Yavca area is dominated by inner platform carbonate deposits. Dolomitization is a common feature, either post-diagenetic or as alternating layers. The absence of deposition in early and middle Senonian is common all over the Taurus shelf (Farinacci and Köylüoğlu, 1982). As an exception for the Bolkar Dağ carbonate platform,
Acknowledgements
We are indebted to Danièle Grosheny (Strasbourg) and Rodolfo Coccioni (Urbino) for constructive and helpful reviews. Thanks also to Kemal Erdoğan (Maden Tetkik Araştırma, Ankara) for planktic microfossil determinations.
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