Abstract:
Geographically, Thrace is a region located in southeastern Europe within the territories of Greece, Bulgaria and Turkey. In Turkish Thrace, karst occurs extensively in Eocene limestones, although some limited karst occurs in marble of the metamorphic series of Palaeozoic age. The karstification base is shallow to very shallow and most of the dolines and poljes have been captured by surface streams. Subsurface drainage has been changed to surface drainage in most parts of the region. Caves and cave relicts are concentrated mainly at three different altitudes, and almost all caves are horizontal or sub-horizontal. With these characteristics, Turkish Thrace hosts a distinct type of karst compared to that of other regions of Turkey, and particularly to the well-developed active Taurus karst. In this paper, the author discusses the major controls on karst evolution and consequently the occurrence of the present karst type with special emphasis on the geological history of the region. Tectonically, the area is weakly active, implying that a relatively steady continental uplift together with sea-level changes provided the source of the energy gradient required for karstification. The erosion base is controlled mainly by impermeable units. From the geological history of the region, it is concluded that no abrupt change in the energy gradient occurred due to continental uplift. However, fluctuation in sea level due to climate change has caused more sudden changes, particularly in erosion-base levels. This suggests that, in contrast to other karst provinces of Turkey, the impact of climate change has been more pronounced in this region. Reconstruction of karst evolution on the basis of the geological history of the region suggests that karstification processes have evolved without major interruption during the neotectonic period. Thus, the evolutionary character of the Thracian karst has produced relict karst with relatively local karst aquifers compared to those existing in the Taurus karst region. Morphological and hydrological aspects of the area indicate that karstification is in a cessation phase