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.
Abstract The M essinian S alinity C risis is well known to have resulted from a significant drop of the M editerranean sea level. Considering both onshore and offshore observations, the subsequent reflooding is generally thought to have been very sudden. We present here offshore seismic evidence from the G ulf of L ions and re‐visited onshore data from I taly and T urkey that lead to a new concept of a two‐step reflooding of the M editerranean B asin after the M essinian S alinity C risis. The refilling was first moderate and relatively slow accompanied by transgressive ravinement, and later on very rapid, preserving the subaerial M essinian E rosional S urface. The amplitude of these two successive rises of sea level has been estimated at ≤500 m for the first rise and 600–900 m for the second rise. Evaporites from the central M editerranean basins appear to have been deposited principally at the beginning of the first step of reflooding. After the second step, which preceeded the Z anclean G lobal S tratotype S ection and P oint, successive connections with the P aratethyan D acic B asin, then the A driatic foredeep, and finally the E uxinian B asin occurred, as a consequence of the continued global rise in sea level. A complex morphology with sills and sub‐basins led to diachronous events such as the so‐called ‘ L ago M are’.This study helps to distinguish events that were synchronous over the entire M editerranean realm, such as the two‐step reflooding, from those that were more local and diachronous. In addition, the shoreline that marks the transition between these two steps of reflooding in the P rovence B asin provides a remarkable palaeogeographical marker for subsidence studies.
The South Balkan extensional system consists of normal faults and associated sedimentary basins within southern Bulgaria, Macedonia, eastern Albania, northern Greece, and northwestern Turkey. Extensional tectonism began during the final convergence across the Vardar, Intra-Pontide, and Izmir-Ankara suture zones, where oceanic regions closed between continental Europe and continental fragments that make up the Pelagonian, Sakar, and western Anatolian tectonic units. Earliest extension of latest Cretaceous– middle Eocene age appears to have occurred within a regional convergent tectonic setting and may be related to an increase in gravitation potential energy within a thickening continental lithosphere. Following diachronous closure across the suture zone, from the middle Eocene to late Oligocene, the transition from a regionally convergent to a regionally extensional tectonic setting occurred and was associated with abundant magmatism and formation of sedimentary basins. Extension was associated with lithospheric thinning probably related to changes in geometry of the subducted slab, dynamics of the mantle wedge, and beginning of slab rollback along the Hellenic subduction zone. A short period of local and diachronous (?) shortening (during latest Oligocene–early Miocene time) occurred in the Thrace basin of northwestern Turkey and in some basins in western Bulgaria and eastern Macedonia. Regional extension began in middle Miocene time and was related to the regional extensional tectonic setting that has dominated the Aegean extensional region to the present. Trench rollback was the dominant dynamic process, but during late Miocene time it was modified by the formation of the western part of the North Anatolian fault zone that partially decoupled the South Balkan extensional system from the Aegean extensional region. During late Cenozoic time, east-west–striking normal faults and associated sedimentary basins in the eastern part of the South Balkan extensional system propagated westward in tandem with westward migration of north-south–striking normal faults and sedimentary basins from western Bulgaria into eastern Albania. This migration was caused by evolution of the Hellenic subduction zone as it increased its curvature during trench rollback and clockwise and counterclockwise rotation of crustal fragments in the west and east, respectively. After formation of the western part of the North Anatolian fault zone, extension within the eastern part of the South Balkan extensional system was related to southward movement of its lithosphere at a slower rate than the extension within the Aegean extensional region. Active extension and basin formation show two provinces of extension that are nearly at right angles to one another and their overlap in the central South Balkan extensional system: east-west extension in central Albania to eastern Macedonia and north-south extension from northwestern Greece and eastern Macedonia to eastern Bulgaria and northwestern Turkey.
