Geodynamic Control of Hypogene Karst Development in Central Anatolia, Turkey

Abstract

Hypogene karst development in central Anatolia, Turkey is represented by unique collapse dolines (obruks) developed mainly in Neogene lacustrine limestone formations. Many of these obruks are located in two separate rectilinear zones, one of which appears to mark the suture zone between Tauride-Anatolian and Sakarya Zone tectonic blocks of the Anatolian plate. The other zone coincides with the alignment of three dormant volcanoes. Formation of obruks seems to be associated with upwelling of carbon dioxide released from deep-rooted igneous activity sources along these zones since Late Miocene. Formation of obruks still continues today, whereas the size of recent collapses is much smaller than ancient examples probably due to weakening volcanism. Recent obruk formations are observed in an area where the youngest volcanic activity seems to have occurred. Frequency of obruk formation increased in recent years because of the groundwater's accelerating piezometric head decline. The stable carbon and noble gas isotope data previously obtained from regional groundwater samples suggested both crustal and mantle sources for the carbon dioxide required for obruk formation. It seems likely that many of the large-scale karst cavity-collapse structures in the world are linked with excessive carbon dioxide release from mantle in orogenic plateaus like central Anatolia.