Sur les etapes de la transgression du Miocene inferieur observee dans les fenetres de Goecek (Sud-Ouest de la Turquie)

102

The time of the onset and the nature of the extension in the Aegean area have been problematic owing to the confusion of neotectonic replacement structures with neotectonic revolutionary structures. This paper concerns two rift systems of different ages and orientations in the Gokova region of southwestern Anatolia. The first system has a northwest-southeast trend with a Middle to Upper Miocene infill, whereas the second system is orientated in an east-west direction and filled with Plio-Quaternary rocks. Structural and palaeomagnetic data indicate that the first system originally had a north-south trend, and then bodily rotated anticlockwise to its present orientation before the end of the Miocene. Both the orientations and the structural patterns of these cross-cutting rift systems suggest that they resulted from two different and successive tectonic regimes. Regional geology suggests that the generative regime of the older system was characterized by north-south compression and related to the palaeotectonic evolution of southwestern Anatolia, whereas that of the younger system is characterized by north-south extension and relates to the neotectonic evolution of this region. This inference contradicts, at least in southwestern Anatolia, some recent claims that the extensional tectonics and the related rift formation in the Aegean region began in the early Miocene, with the alleged demise of the compressional palaeotectonics during the late Oligocene, but is consistent with older views that placed the onset of north-south extension into the later middle Miocene. The formation of the Aegean Sea seems to be the result of these two complicated and contrasting, succesive tectonic regimes that have affected this region since middle Miocene times.

Section: Discussionmentioning

confidence: 82%

Rift formation in the Gökova region, southwest Anatolia: implications for the opening of the Aegean Sea

Görür¹,

Şengör²,

Sakinü³

et al. 1995

102

“…Görür et al (1995) interpreted the north trending structures as a product of a compressional regime, without taking into account the special location of the study area which is on top of Lycian nappes, and implied that this is applicable to the rest of western Turkey. The evidence presented in support of the existence of a compressional regime in Görür et al (1995) is the latest nappe emplacement (Guntic & Poisson, 1970;de Graciansky, Lorenz & Magne, 1970;Besang et al 1977). The claimed north-south compression (Görür et al 1995) during Middle to Late Miocene times should be restricted for the Lycian nap pile (see Seyitoglu, Scott & Rundle, 1992) due to the Early Miocene age of regionally distinct extensional structures (that is, Büyük Menderes graben: , and late Oligocene extensional shear zones (Bozkurt & Park, 1994) in southwest Turkey.…”

Section: Discussionmentioning

confidence: 93%

Late Cenozoic tectono-sedimentary development of the Selendi and Uşak-Güre basins: a contribution to the discussion on the development of east–west and north trending basins in western Turkey

Seyítoğlu

1997

104

This paper expands the K-Ar dating and palynologically controlled stratigraphical data base reported in earlier papers to the north trending Selendi and Uşak-Güre basins located to the north of east-west trending Alaşehir graben in western Turkey. These north trending basins began to form during Early Miocene times and most of their basin fills accumulated before 14 Ma, except for the youngest Asartepe formation. Recent studies of both east-west grabens and north trending basins show that they started to develop simultaneously during Early Miocene times under the north-south extensional regime, and the classification of the structures as 'replacement' and 'revolutionary' has no meaning for the Alaşehir graben and the basins located to its north.

“…Isparta (Gutnic & Poisson, 1970) and (3) Tortonian clastic sediments near Antalya (de Graciansky, Lorenz & Magne, 1970;Hayward, 1984). The nappes have been thrust onto rocks containing Tortonian monazite (11.9 ± 0.4 to 9.15 ± 0.2 Ma: Besang et al 1977) on the island of Kos.…”

Section: F Age Of Deformation and Metamorphic Phasesmentioning

confidence: 99%

Extensional v. contractional origin for the southern Menderes shear zone, SW Turkey: tectonic and metamorphic implications

Bozkurt

2006

The southern Menderes Massif in southwest Turkey consists mainly of orthogneisses and overlying Palaeozoic-Middle Paleocene schists and marbles. The contact between the two distinct rock types is almost everywhere structural, herein named the southern Menderes shear zone: a S-facing, high-angle ductile shear zone that separates metamorphic rocks of differing grade. Although there is a consensus that the shear zone was associated with top-to-the-S-SSW shearing and is of Tertiary age, its origin and nature have been highly debated over the last decade. Some claim the contact is a thrust fault, while others have argued for an extensional shear zone. Integration of field and microstructural data (the identification of different fabrics, associated kinematics and overprinting relationships) with fissiontrack thermochronology and the P-T paths of the rocks above and below the shear zone, supports the conclusion that the southern Menderes shear zone is an extensional shear zone and not a thrust. The data are consistent with a model that the exhumation and cooling of the southern Menderes Massif occurred after a period of extensional deformation. Pervasive top-to-the-N-NNE high-temperature-mediumpressure ductile shear structures (D 2 deformation) overprint an early HP event (D 1 deformation). The subsequent top-to-the-S-SSW greenschist shear band foliation (D 3 deformation) developed mostly around the orthogniess-schist contact and forms the most characteristic features of the massif. The topto-the-N-NNE structures are attributed to the main Alpine constructional deformation that developed during back-thrusting of the Lycian nappes during the latest Palaeogene collision between the Sakarya continent and the Anatolide-Tauride platform across the Neotethyan Ocean. The top-to-the-S-SSW structures are interpreted to be the result of the exhumation of the massif during the activity of the southern Menderes shear zone. The presence of these two distinct fabrics with differing kinematics suggests that the southern Menderes shear zone operated as a top-to-the-N-NNE thrust fault during early Alpine contractional deformation but was later reactivated with an opposite sense of movement (top-to-the-S-SSW) during subsequent Oligocene-Miocene extensional collapse.