Abstract
The Lower Cambrian Kocayayla Group forms the stratigraphically lowermost part of the relative autochthonous Geyikdagi unit of the Taurus Range in the Sandikli (Afyon) region. It is represented by the Celiloglu Formation, Gögebakan Formation, Kestel Çayi volcanics and the Tasoluk Formation in the ascending order. The Celiloglu Formation consists of quartzites with intercalations of metapelites. The Gögebakan Formation overlies the Celiloglu Formation along a gradational boundary, and is composed of metapelites with mafic volcanic intercalations. The Gögebakan Formation grades laterally and vertically into the Kestel Çayi volcanics (Sandikli porphyroids) consisting of rhyolites with volcanosedimentary intercalations. The Tasoluk Formation is composed of yellow quartzites and it is the uppermost unit of the Kocayayla Group gradationally overlaying Kestel Çayi volcanics. The Kocayayla Group is overlain by the Sandikli unit and there is a pronounced unconformity between them. The Sandikli unit consists of white quartzites, brown dolomites, trilobite-bearing limestones and mudstones of the Middle-Upper Cambrian age. The Lower Jurassic Ilyasli Formation unconformably covers both the Kocayayla Group and Sandikli unit. The flat-laying Neogene volcanosedimentary rocks are the youngest succesion unconformably covering the all older rock units. The Kocayayla Group was deformed and underwent a low-grade metamorphism marked by sericite-chlorite-biotite/stilpnomelane-quartz paragenesis in the metapelites of the Gögebakan and Tasoluk formations and chlorite-epidote-albite-quartz and opaque assemblage in the mafic volcanic intercalations in the Gögebakan Formation, before the deposition of the trilobite-bearing Middle-Upper Cambrian succession. The Gögebakan and Tasoluk formations and the Kestel Çayi volcanics show a single penetrative foliation which mostly obliterated the primary structures whereas beds, trace fossils and cross-stratifications are partly preserved in the quarzite beds of the Celiloglu Formation. The Gögebakan Formation has rough foliation while the Kestel Çayi volcanics displays anastomizing and continuous foliation with a prominent stretching lineation. The attitude of the stretching lineation concentrates at 25/45 and 280/43 in the Kocayayla area, and s-clasts, s/c fabrics and quartz sigmoids indicate top-NNE and ESE shear sense. This difference in shear direction is related to the post-Liassic rotation in the core of southwest-verging asymmetric anticline. After removing this younger folding it is determined that, the linear fabrics has a concentration of 280/43 with top-ESE shear sense. In the Tasoluk area, the linear fabrics clusters at 320/43 with top-NW shear sense. The difference in orientation of foliation, linear fabric and shear sense in the Lower Cambrian Kocayayla Group indicate regional scale Alpine fold event(s) that rotated the earlier deformation fabrics in the Geyikdagi unit.
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