EXTENSION PARALLEL FOLDING IN NORTHERN MENDERES MASSIF, WESTERN TURKEY

The northern part of the Menderes Metamorphic core complex in Western Turkey covers over 6,000 km² between the Alasehir Graben to the south and the Simav graben to the North. Our recent mapping between the northern margin of the Alasehir graben and southern margin of the Simav graben revealed the presence of mesoscopic to macroscopic scale antiforms and synforms in the metamorphic rocks of the region. The axial traces of all synforms and antiforms are parallel to the mylonitic lineations, which ranges from N10E to N30E. Considering that mylonitic lineations form parallel to the direction of extension, these folds suggest a compression direction perpendicular to the direction of extension. The age folding, however, remains to be studied.

The axial surface traces of the antiforms and synforms are approximately parallel to the axial surface trace of the Horzum Turtleback surface of the Alasehir graben. The turtleback is a part of the detachment surface which separates brittlely deformed Cenozoic sedimentary rocks of the upper plate from the strongly mylonitic ductilely deformed Paleozoic-Mesozoic lower plate rocks, containing mylonitic lineations which trend between N10E to N30 E. The detachment surface contains striations also trending between N10E to N30E, suggesting that the brittle deformation overprinted the ductile deformation during the exhumation of the northern Menderes Massif. These observations suggest that there may be a structural relationship between the Horzum Turtleback and the large-scale antiformal structures of the northern Menderes massif. However, detailed radiometric age dating and a precise geochemical study are needed to establish this relationship and the age of the ductile and brittle deformations in northern Menderes massif. These studies are also needed to reconstruct the Cenozoic extensional tectonics of Western Turkey and the Aegean region.