Geochemical variations in Quaternary hardgrounds from the Hellenic Trench region and possible relationship to their tectonic setting

The progressive lithification of Quaternary hardgrounds forming in the Hellenic Trench region of the eastern Mediterranean is documented by increasing 18O values and high-magnesium calcite contents, which reflect cold, penesaline waters. The presence of aragonite and dolomite in hardgrounds from the Strabo Trench, which are also enriched in 12C, indicates that the diagenetic solutions vary locally. The origin of this unusual mineralogy and carbon isotopic content could be explained by the upward migration of brines from the underlying Messinian evaporites and the subsurface oxidation of 12C enriched organic material. Shallow burial of the evaporites in the Strabo Trench, a region dominated by transcurrent motion, as opposed to deeper burial in the Matapan- and Poseidon Trench, regions dominated by subduction and thrusting motion, could be responsible for geochemical variations in the diagenetic solutions