Low-angle Normal Detachment Faults Research Articles

The Thrace basin in the Rhodope province of NE Greece — A tertiary supradetachment basin and its geodynamic implications

Detailed tectonic analysis and geological mapping on the Tertiary molassic and volcanosedimentary rocks of the Thrace basin in northeastern Greece, allowed us to reconstruct the structural evolution of the basin and its geotectonic setting, as well as the orientation of the regional paleostress field. Sedimentation was linked with a calc-alkaline and locally shoshonitic magmatism associated with the Tertiary syn- to late-orogenic extension in the Rhodope province. We interpret the molassic Tertiary Greek part of the Thrace basin as a supradetachment basin associated with sedimentary and volcanic infilling. Five (5) deformational events (T1 to T5) have been distinguished during basin evolution from Eocene to Quaternary time. T1 is related to a low angle normal detachment fault zone with a top to the SW to SSW sense of movement and initial basin subsidence during Middle–Late Eocene to Oligocene time, simultaneously with uplift and exhumation of the footwall Rhodope metamorphic rocks. Stacking and crustal thickening in the more external parts of the Hellenic orogenic belt have taken place during the same time. T2 evolved during Oligocene–Miocene time. It was characterized by transpressional tectonics and formation of large strike slip faults and extensional fractures, as well as conjugate thrust faults and folds with N–NW or S–SE sense of movement. During Miocene–Pliocene time the third T3 event took place. It was responsible for the high-angle normal faults, dismembering the Eocene–Oligocene molassic basin into Neogene grabens. The T4 event affected the Neogene sediments of the basin with minor reverse strike-slip faults, as well as normal faults. The following T5 event is related to large normal active faults. They coincided with the active tectonics of the study area defined by the earthquake focal mechanisms.