Abstract:

The Bornova Flysch Zone consists of large blocks of Mesozoic limestone, basalt, serpentinite and radiolarian chert in a highly sheared clastic matrix of latest Cretaceous to Paleocene age. We describe a condensed Mesozoic section from a limestone block near the village of Urbut, 27 km southwest of Bigadiç, north of İzmir. The section, 81 m thick, starts with massive, thickly-bedded Upper Triassic carbonates with megalodonts and foraminifera characteristic of Late Norian-Rhaetian. These are unconformably overlain by condensed, hemipelagic Tithonian-Middle Albian limestones, 19 m thick, with gaps in the succession. The condensed sequence is, in turn, unconformably overlain by red, pink Rotalipora- and Globotruncana-bearing pelagic limestones of Late Cretaceous age. The Upper Cretaceous section is at least 50 m thick, the basal parts contain foraminifera characteristic of late Cenomanian which pass up into lower-middle Turonian carbonates. The Turonian pelagic limestones contain Valanginian and Upper Triassic limestone clasts, and Tithonian and Upper Triassic carbonate olistoliths, several metres across. The stratigraphy of the Urbut section is similar to that of the Domuzdağ unit in the Lycian nappes and that of the Boyalı Tepe unit in the central Taurides; all are characterized by neritic Upper Triassic carbonates at the base, overlain unconformably by a condensed pelagic limestone sequence of Upper Jurassic-Lower Cretaceous age; pelagic Upper Cretaceous limestones lie unconformably above the Lower Cretaceous or directly on the Upper Triassic/Liassic carbonates. The Urbut section shows several foundering events in the Anatolide-Tauride carbonate platform; the latest one in the late Cenomanian is probably related to the inception of the ophiolite obduction. The Urbut section also provides additional data in favour of the derivation of the Lycian nappes and equivalent allochthonous units from north and northwest of the Menderes Massif.

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