Elsevier

Geobios

Volume 39, Issue 4, July–August 2006, Pages 521-533
Geobios

Original article
Benthic 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

https://doi.org/10.1016/j.geobios.2005.05.002Get rights and content

Abstract

The microbiostratigraphic analysis of the three outcrop sections from the Cretaceous inner platform carbonate succession in the Yavca area (Bolkar Mountains) allows to recognize the four local benthic foraminiferal zones. These are: (1) Voloshinoides murgensis and Praechrysalidina infracretacea Cenozone in the Lower Aptian; (2) Pseudorhapydionina dubia and Biconcava bentori Cenozone in the Middle–Upper Cenomanian; (3) Ostracoda and Miliolidae Interval Zone in the probable Turonian, represented by dolomitized limestones without any significant markers; (4) Moncharmontia compressa and Dicyclina schlumbergeri Cenozone in the Coniacian-Santonian. The benthic foraminiferal assemblages correspond to those in other areas of the Mediterranean realm, with the exception of a lack of alveolinids and orbitolinids due to unfavorable environmental conditions (inner platform, restricted shelf). After the regionally well-known emergence during the late Aptian, Albian and early Cenomanian, very shallow subtidal to intertidal conditions were re-established during the middle–late Cenomanian time. The Coniacian-Santonian benthic foraminiferal assemblage shows an increase in diversity and abundance as a result of open marine influence, confirmed by the presence of larger foraminifera (Dicyclina), Rotaliidae and radiolitid fragments. Thaumatoporella and Aeolisaccus-bearing wackestone intercalations still indicate the existence of sporadic restricted environment conditions. The Cretaceous shallow-water platform carbonate succession of the Yavca area is conformably overlain by gray pelagic limestones with calcispheres and planktonic foraminifera. The Campanian flooding of the Bolkar Dağ carbonate platform resulted in drowning of the pre-existing biota and facies.

Résumé

L'analyse microbiostratigraphique de trois coupes d'affleurements à partir de succession de plate-forme carbonatée interne du Crétacé dans la région de Yavca (Montagnes de Bolkar) a permis de reconnaître les quatre biozones locales de foraminifères benthiques. Il s'agit de : (1) Cenozone à Voloshinoides murgensis et Praechrysalidina infracretacea de l'Aptien inférieur ; (2) Cenozone à Pseudorhapydionina dubia et Biconcava bentori du Cénomanien moyen-supérieur ; (3) Zone d'Intervalle à Ostracoda et Miliolidae du Turonien probable, représenté par des calcaires dolomitiques sans aucun marqueur significatif ; (4) Cenozone à Moncharmontia compressa et Dicyclina schlumbergeri du Coniacien-Santonien. Les associations de foraminifères benthiques correspondent à celles d'autres régions de la Méditerranée, excepté un manque d'alveolinids et d'orbitolinids en raison des conditions environnementales défavorables (plate-forme interne, shelf protégé). Après l'émersion généralisée bien connue durant l'Aptien supérieur, Albien et Cénomanien inférieur, les conditions marines peu profondes ont été rétablies au cours du Cénomanien moyen-supérieur. L'association de foraminifères benthiques du Coniacien-Santonien a montré l'augmentation du point de vue de la diversité et l'abondance à cause des influences marines ouvertes que se confirment par la présence de nombreux grands foraminifères (Dicyclina), Rotaliidae et débris du radiolitidés. Les wackestones intercalés à Aeolisaccus et Thaumatoporella abondants indiquent encore un milieu marin protégé sporadique. La succession de plate-forme carbonatée du Crétacé dans la région de Yavca est directement surmontée par des calcaires pélagiques gris à calcisphères et les foraminifères planctoniques. La transgression du Campanian de la plate-forme carbonatée des Montagnes de Bolkar, a eu comme conséquence la noyade du biota et des faciès préexistants.

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:

  • to document the benthic foraminiferal assemblages;

  • to make chronostratigraphic interpretation of the Cretaceous platform carbonate sequence using the Standard European stages by means of the foraminiferal assemblages;

  • 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.

References (36)

  • P. De Castro

    Sulla prezensa di un nouvo genere di Endothyridae nel Cretacico superiore della Campania

    Bollettino Societã dei Naturalisti in Napoli

    (1966)
  • Decrouez, D., 1976. Étude stratigraphique et micropaléontologique du Crétacé. d'Argolide (Péloponnèse septentrional,...
  • Demirtaşlı, E., Turhan, N., Bilgin, A.Z., Selim, M., 1984. Geology of the Bolkar Mountains. In: Tekeli, O., Göncüoğlu,...
  • R.J. Dunham

    Classification of carbonate rocks according to depositional texture

  • A. Farinacci et al.

    Evolution of the Jurassic–Cretaceous Taurus shelf (Southern Turkey)

    Estratto dal Bollettino della Società Paleontologica Italiana

    (1982)
  • A. Farinacci et al.

    Biostratigraphy and event-analysis of the Cenomanian–Maastrichtian carbonates of the Bey Dağları (Western Taurus, Turkey)

    Geologica Romana

    (1986)
  • E. Fourcade et al.

    Debarina hahounerensis n. gen. n. sp., nouveau Lituolidé (foraminifère) du Crétacé inférieur constantinois (Algérie)

    Comptes Rendus de l’Académie des Sciences de Paris

    (1972)
  • I. Gušić et al.

    Foraminiferal assemblages, facies, and environments in the Upper Cretaceous of the Island of Brac, Yugoslavia

    Revue de Paléobiologie, Volume Spécial

    (1988)
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