Stratigraphy and Larger Foraminifera of the Eocene Shallow-marine and Olistostromal Units of the Southern Part of the Thrace Basin, NW Turkey

Authors : ERCAN ÖZCAN, GYÖRGY LESS, ARAL I OKAY, MÁRIA BÁLDIBEKE, KATALIN KOLLÁNYI, İ ÖMER YILMAZ

Pages : 27-77

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Publication Date : 0000-00-00

Article Type : Research Paper

Abstract :The Eocene marine sequence in the southern part of the Thrace Basin insert ignore into journalissuearticles values(NW Turkey); involves a variety of platform and deep-marine olistostromal units, the stratigraphy of which have been vigorously debated in the past. A detailed analysis of larger foraminifera in these either foraminifera or foraminifera-coral-coralline algae-dominated platform and associated comparatively deeper-marine units permits us to establish a high-resolution biostratigraphy in the context of shallow benthic zonation insert ignore into journalissuearticles values(with SBZ zones); of Tethyan Paleogene. The oldest zone insert ignore into journalissuearticles values(SBZ 5, corresponding to the basal Ypresian); was observed only in olistoliths. An old erosional remnant of a transgressive shallow-marine to basinal sequence insert ignore into journalissuearticles values(Dişbudak series; late Ypresian−? middle Eocene); was recognized below the regionally most widespread carbonate platform unit, the Soğucak Formation. The Dişbudak sequence, previously considered to belong to the Soğucak Formation and formally introduced recently, contains larger foraminifera, such as orthophragmines, nummulitids and alveolinids in its shallow-marine package referred to SBZ 10 insert ignore into journalissuearticles values(late Ypresian);. The Soğucak Formation, which often exhibits patch reef developments, contains a rich and diverse assemblage of orthophragmines insert ignore into journalissuearticles values(Discocyclina, Orbitoclypeus and Asterocyclina);, nummulitids insert ignore into journalissuearticles values(reticulate and other Nummulites, Assilina, Operculina, Heterostegina and Spiroclypeus);, and other benthic taxa insert ignore into journalissuearticles values(Silvestriella, Pellatispira, Chapmanina, Orbitolina, Linderina, Gyroidinella, Fabiania, Halkyardia, Eoannularia, Sphaerogypsina, Asterigerina, Planorbulina and Peneroplis);. Their assemblages, referred to SBZ 15/16, 17, 18, 19 and 20 Zones, provide a precise tool for recording the history of marine events which resulted in the deposition of the Soğucak Formation during four main periods. Their spatial distribution, recorded as late Lutetian, early Bartonian, late Bartonian and Priabonian, suggests a marine transgression from WSW to ENE. The Çengelli flysch sequence overlying the Soğucak Formation in a limited area to the east of the Gelibolu Peninsula, contains benthic foraminifera, mainly from limestone olistoliths mostly derived from the Soğucak Formation, and also in the turbiditic strata. The assemblages in the olistoliths reveal the existence of various shallow marine limestone sequences ranging in age from late Bartonian to early Priabonian.
Keywords : southern Thrace, benthic foraminifera, biometry, taxonomy, biostratigraphy