RIFT FORMATION IN THE GAKOVA REGION, SOUTHWEST ANATOLIA - IMPLICATIONS FOR THE OPENING OF THE AEGEAN SEA

The time of the onset and the nature of the extension in the Aegean ar ea have been problematic owing to the confusion of neotectonic replace ment structures with neotectonic revolutionary structures. This paper concerns two rift systems of different ages and orientations in the Go kova region of southwestern Anatolia. The first system has a northwest -southeast trend with a Middle to Upper Miocene infill, whereas the se cond system is orientated in an east-west direction and filled with Pl io-Quaternary rocks. Structural and palaeomagnetic data indicate that the first system originally had a north-south trend, and then bodily r otated anticlockwise to its present orientation before the end of the Miocene. Both the orientations and the structural patterns of these cr oss-cutting rift systems suggest that they resulted from two different and successive tectonic regimes. Regional geology suggests that the g enerative regime of the older system was characterized by north-south compression and related to the palaeotectonic evolution of southwester n Anatolia, whereas that of the younger system is characterized by nor th-south extension and relates to the neotectonic evolution of this re gion. This inference contradicts, at least in southwestern Anatolia, s ome recent claims that the extensional tectonics and the related rift formation in the Aegean region began in the early Miocene, with the al leged demise of the compressional palaeotectonics during the late Olig ocene,but is consistent with older views that placed the onset of nort h-south extension into the later middle Miocene. The formation of the Aegean Sea seems to be the result of these two complicated and contras ting, succesive tectonic regimes that have affected this region since middle Miocene times.