Late Maastrichtian-Late Palaeocene planktic foraminiferal biostratigraphy of the matrix of the Bornova Flysch Zone around Bornova (İzmir, Western Anatolia, Turkey)

Abstract

The Bornova Flysch Zone (BFZ), located between the Menderes Massif and the İzmir-Ankara Suture in westernmost Anatolia (Turkey), forms the westernmost part of the Anatolide-Taurides. The BFZ comprises intensely sheared Upper Cretaceous-Palaeocene matrix and blocks of various origins. The matrix of the BFZ is mainly made up of unfossiliferous flysch-type sediments (alternations of sandstones and shales). In Bornova (İzmir, western Turkey) and its surroundings, these clastics locally include planktic foraminiferabearing pelagic micritic limestone and calcareous shale lenses and interbeds (Beytitepe Limestone). As a result of studies focusing on the planktic foraminifera-bearing pelagic interlayers in three areas (Gökdere, Işi{dotless}klar and Kocaçay areas) around Bornova, a detailed planktic foraminiferal biostratigraphy of the rocks is documented for the first time. The thickness of the laminated micritic limestones attains 360 m in the Gökdere area. Occurrences of late Maastrichtian species such as Abathomphalus mayaroensis (Bolli), Contusotruncana contusa (Cushman), Globotruncanita conica (White) and Racemiguembelina fructicosa (Egger) within planktic foraminifera assemblages obtained from the laminated micritic limestones and red calcareous shales in the three areas suggest a late Maastrichtian age for these rocks. The occurrence of various species of Globanomalina, Morozovella, Igorina and Parasubbotina within the calcareous shales in the Işi{dotless}klar area suggests a late Palaeocene age. The Kocaçay area has well-preserved outcrops showing the stratigraphy of the matrix, despite the more complex geology. The upper Maastrichtian laminated micritic limestones are gradationally overlain by upper Maastrichtian calcareous shales. The calcareous shales are represented by rich planktic foraminiferal assemblages and include blocks derived from laminated micritic limestones. The upper Mastrichtian calcareous shales are overlain by Palaeocene red calcareous shales. Poor assemblages including Parasubbotina varianta (Subbotina), Subbotina triangularis (White), Subbotina cf. velascoensis (Cushman), Globanomalina compressa (Plummer) and Globanomalina planoconica (Subbotina) indicate a late Palaeocene age for the lower part and a latest Palaeocene age for the upper part of the calcareous shale sequence. Therefore, the age of conglomerates and flysch overlying the calcareous shales should be latest Palaeocene or younger in the Kocaçay area. © TÜBITAK.