New Triassic finding in Andız Peninsula (İzmir, Western Turkey) and comparison of pre-Neogene sequences of Andız and Karaburun Peninsulas: Stratigraphic and tectonic implications

Authors: İSMAİL İŞİNTEK

Abstract: This study aims to review the geology of the Andız Peninsula and compare the pre-Neogene Andız succession with the middle part of the Karaburun Peninsula to discuss the nature of the Paleozoic-Mesozoic boundary in the Karaburun Peninsula. The pre-Neogene units of the Andız Peninsula are represented by the Paleozoic Dikendağı, Triassic Gu?vercinlik, and Jurassic Nohutalan Formations. In this study, the Triassic carbonate rocks in the Andız Peninsula are paleontologically defined for the first time. The Megalodont-bearing Gu?vercinlik Formation contains a late Norian-Rhaetian characteristic foraminiferal assemblage consisting of Aulotortus gr. sinuosus, A. tenuis, A. friedli, A. impressus, and Triasina hantkeni. The Thaumatoporella-bearing Nohutalan Formation conformably overlies the Gu?vercinlik Formation and yields a typical Liassic fossil assemblage of Orbitopsella praecursor, Siphovalvulina gibralterensis, S. colomi, Meandrovoluta asiagoensis, and Palaeodasycladus mediterraneus. In the Andız Peninsula, the Mesozoic Gu?vercinlik and Nohutalan Formations tectonically overlie the Paleozoic Dikendağı Formation along a displacement contact. In the middle Karaburun Peninsula, the Triassic Gerence Formation lies directly on the Dikendağı Formation along a displacement contact. Lateral continuation of this displacement contact is discovered between the Triassic Gerence and Camiboğazı Formations at the top and Paleozoic Dikendağı Formation at the bottom. Further north, the same displacement contact extends into the Paleozoic sequence where the Carboniferous Alandere Formation tectonically overlies the Dikendağı Formation. These observations suggest that the succession in the Karaburun Peninsula ranging from Bashkirian to Cretaceous, is a tectonic slice or a package of slices over the Dikendağı Formation.

Keywords: Andız Peninsula, Karaburun Peninsula, Triassic-Jurassic transition, Paleozoic- Mesozoic boundary, displacement contact

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