Cenozoic tectonics of Macedonia and its relation to the South Balkan extensional regime

摘要

From Paleogene to Recent time, Macedonia was part of the South Balkan extensional region, the northern part of the Aegean extensional regime. Extension began in the middle to late Eocene in eastern Macedonia with the formation of a NNW-trending east-tilted half graben lying east of a forearc basin in central Macedonia. Following a short-lived period of localized shortening in late Oligocene to early Miocene time, a second period of Neogene extension began that continued to the present. Five cycles of Neogene extension are recognized, and associated sedimentation occurred in extensional basins of complex origins: (1) true graben, (2) tilted half graben, (3) pull-apart basins along strike-slip faults, (4) faulted silled basins filling topographic lows, and (5) complexly faulted basins of mixed fault origin. Neogene faulting and basin formation show a pattern that begins with both NNW- and EW-trending faults in mainly northern and eastern Macedonia progressing to younger times by dominantly NNW- to N-trending faults migrating into western Macedonia and E-W– and NW-trending faults dominant in eastern Macedonia. The origin of the Paleogene basins is interpreted to be related to trench rollback along the northern Hellenic trench and lateral spreading of thick hot crust within an arc. The short period of early Neogene shortening is related to the arrival of the small continental Kruja fragment at the subduction zone in Albania. The younger Neogene extension and westward migration of extensional faulting and basins is related to progressive rollback of the subducted slab in the northern Hellenic trench. The north-south extension in eastern Macedonia is related to the propagation of the North Anatolian fault in the northern Aegean Sea ca. 6 Ma and subsequent movement southward of south Balkan lithosphere north of the fault caused by the rapid SSW movement of the Aegean crust related to trench rollback along the southern Hellenic trench. The amount of southward extension within the Southern Balkan extensional region is much less than that in the Aegean south of the North Anatolian fault.