Testing Miocene Remagnetization of Bey Dağları: Timing and Amount of Neogene Rotations in SW Turkey

Authors: DOUWE J.J. VAN HINSBERGEN, MARK J. DEKKERS, AYTEN KOÇ

Abstract: Here we reassess the timing and amount of rotation of the eastern limb of the Aegean orocline, located in SW Turkey. The current model for this orocline involves a 25-30° counterclockwise (CCW) rotation of the Bey Dağları region, which exposes upper Cretaceous to Eocene platform carbonates and lower Miocene flysch deposits. In this model the rotation has to postdate a Miocene remagnetization, which would not exclude non-synchroneity between rotations of the western and eastern limbs of the Aegean orocline. To test this model a detailed palaeomagnetic study was conducted on lower Miocene strata in the Bey Dağları area. Two (composite) sections were sampled near Korkuteli and Doğantaş, spanning the lower Miocene foreland basin stratigraphy from the Aquitanian unconformity with the Bey Dağları limestones to the uppermost Burdigalian-lowermost Langhian, and a wide array of palaeomagnetic analyses were obtained. The natural remanent magnetization (NRM) in the Aquitanian limestones and Burdigalian blue clays resides dominantly in magnetite with minor greigite and haematite. A positive reversals test, a correlation of obtained polarity patterns to the geomagnetic polarity timescale, showing significant compaction following acquisition of the NRM, a scatter in NRM directions that can be confidently attributed to palaeosecular variation and a positive recently-proposed end-member model test of the acquisition curves of isothermal remanent magnetization (IRM) all show that the Miocene sediments on the Bey Dağları platform have not been remagnetized. Our new results, combined with a partial reassessment of existing data, imply that the Bey Dağları region underwent no rotation between the late Cretaceous and late Burdigalian, and 20° counterclockwise rotation between 16 and 5 Ma, i.e. during the middle to late Miocene and prior to deposition of previously reported non-rotated Pliocene sediments north of Antalya. The two limbs of the Aegean orocline thus rotated simultaneously: our new age constraints of 16-5 Ma in the east, compare with (largely) 15-8 Ma in the west, as published previously. The rotation of the Bey Dağları was probably bounded in the south at the plate boundary with Africa, and in the east by the Aksu thrust and Kırkkavak dextral strike-slip fault, which together partitioned dextral transpression induced by the rotating block. Accommodation of the western Anatolian rotations to the north and west of the Bey Dağları will be the subject of a future publication.

Keywords: Aegean, orocline, palaeomagnetism, IRM component analysis, remagnetization

Full Text: PDF