Timok fault and Tertiary strike-slip tectonics in part of western Bulgaria

The existence of NW-SE and NNW-SSE trending, regional-scale faults is well-known feature in the area of Tran and Breznik (West Bulgaria). Despite the numerous studies in the area, there is a lack of direct data about the kinematics of the main fault zones. Our investigations allow to define three groups of faults and also demonstrate the dominant dextral strike-slip kinematics of the faults from Pernik fault zone, as well as of several segments of Tran-Kosharevo fault. The field data, together with analysis of the existing maps, suggest the existence of another main strike-slip fault zone with almost N-S strike – the Timok fault. This fault is well-documented in Eastern Serbia, as its continuation in the area of Tran (Kraishte zone) was already suggested by Karaguleva et al. (1980) and Krautner and Krstic (2003). In the westernmost parts of Bulgaria, the Timok fault is traced along the fault segments, previously interpreted as parts of Tran-Kosharevo fault. To the Southward the zone is following the Serkirna fault. Unlike the northeast Serbia the translations along the Timok fault in western Bulgaria are much smaller – probably of not more than few kilometers. Additionally, our new data do not support the idea that these fault zones are part of Maritsa fault zone, well-defined southeast from Sofia.