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

Aral I Okay,Michael D Bidgood,Michael D Simmons,Andrew R.C Kylander-Clark,Stephen Starkie,Ercan Özcan

doi:10.3906/yer-1907-5

Abstract

A belt of Upper Eocene-Lower Oligocene marine sedimentary rocks extends from Kiyikoy on the Black Sea coast to Pinarhisar 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 Kiyikoy 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 Sogucak 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 Kiyikoy 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 Kiyikoy-Pinarhisar corridor was not significant. The Late Eocene-Early Oligocene marine connection between the Black Sea and the Thrace Basin occurred along the Catalca gap southeast of Kiyikoy. In the Catalca gap the Upper Eocene-Lower Oligocene sequence is much thicker (350 m) and was deposited at much greater water depth.

Highlights

At the end of the Eocene, most of the Balkans, Anatolia, and Iran constituted a land area that divided the Tethys marine realm into the Black Sea–Caspian in the north and the Eastern Mediterranean in the south (Figure 1; e.g., Lüttig and Steffens, 1976; Popov et al, 2004)
The Thrace Basin existed as a distinct depocentre during the Eocene and Oligocene on the margin of the Paratethys; it was separated from the Black Sea by the metamorphic rocks of the Strandja Massif (Figure 2)
The Upper Eocene-Lower Oligocene sedimentary sequence at Kıyıköy consists of shallow marine bioclastic limestone, sandstone, mudstone, marl, and tuff

Summary

Introduction

At the end of the Eocene, most of the Balkans, Anatolia, and Iran constituted a land area that divided the Tethys marine realm into the Black Sea–Caspian in the north and the Eastern Mediterranean in the south (Figure 1; e.g., Lüttig and Steffens, 1976; Popov et al, 2004). At 76 m above the base of the Northern Servez section there is a sharp change in facies from bioclastic limestones to an alternation of dark grey marl and fine- to medium-grained planar bedded limestone devoid of any macrofossils (Figure 6e).

Results

Conclusion