Aral İ. OKAY, Michael D. SIMMONS, Ercan ÖZCAN, Stephen STARKIE, Michael D. BIDGOOD, Andrew R.c. KYLANDER-CLARK

Eocene-Oligocene succession at Kıyıköy (Midye) on the Black Sea coast in Thrace

A belt of Upper Eocene-Lower Oligocene marine sedimentary rocks extends from Kıyıköy on the Black Sea coast to Pınarhisar in the Thrace Basin, suggesting a marine connection between the Black Sea and the Thrace Basin during this period. The Cenozoic succession of this marine corridor was studied in the vicinity of Kıyıköy along two measured stratigraphic sections. The sequence lies unconformably over metamorphic basement rocks and consists of ~75 m of bioclastic limestone and sandstone of the Soğucak Formation, overlain by ~40 m of limestone, marl, mudstone, sandstone, and acidic tuff, which are assigned to the newly defined Servez Formation. Larger benthic foraminifera indicate that the lower part of the succession is Late Eocene in age, and nannoplankton from the upper part of the succession suggest an Early Oligocene age; these age determinations are also supported by the Sr-isotope data. A U-Pb age from zircons from a tuff bed is 33.9 ± 0.4 Ma, which falls on the Eocene-Oligocene boundary. The Kıyıköy Upper Eocene- Lower Oligocene sequence was deposited in shallow marine conditions below 50-m water depth. The depositional setting, as well as the relatively reduced thickness of the sequence, shows that any marine connection between the Black Sea and the Thrace Basin along the Kıyıköy-Pınarhisar corridor was not significant. The Late Eocene-Early Oligocene marine connection between the Black Sea and the Thrace Basin occurred along the Çatalca gap southeast of Kıyıköy. In the Çatalca gap the Upper Eocene-Lower Oligocene sequence is much thicker (350 m) and was deposited at much greater water depth.

Keywords:

Thrace Basin, Black Sea, Eocene, Oligocene, foraminifera, nannoplankton,

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