Authors: ÖMER FEYZİ GÜRER, YÜCEL YILMAZ
Abstract: On the Lycian Nappes of SW Anatolia, Neogene basins developed along two different trends in different periods. NNE-trending basins formed during the Early-Middle Miocene period as exemplified by the Ören and Yatağan grabens. These graben fills consist of three distinct rock units. At the base are (1) coarse clastics, sourced from elevated areas adjacent to the basin-bounding faults. These are linear river-valley fills. They give way upward to (2) alternating coal-bearing sandstone and limestone as the graben valleys were gradually widened, and the surrounding mountains were reduced by erosion. Finally, lake environment formed, invading the region during the advanced stage of graben development. In the lakes were deposited (3) extensive marls and limestones. The lake deposits gradually onlapped the graben shoulders. The NE-trending grabens extend SW toward the shore of the SW-NE-trending Kale-Tavas basin. The lake and the sea basin were apparently connected as evidenced by several marine incursions from the south into the Ören basin. The marine units wedge out to the north. On the graben shoulders, the Lower-Middle Miocene sediments were overlain unconformably by red, brown coarse clastic sediments as linear and axial fluvial deposits during Late Miocene time when N-S extensional tectonics began. Under this tectonic regime, some of the N-S-trending faults were reactived as oblique-slip faults with a dip-slip component. Later, the fluvial deposits were replaced by sediments of a new lake environment, in which extensive lacustrine limestones were deposited. The extents of the lakes were regional, stretching far beyond the limits of the grabens. The E-W-trending faults bordering the northern margin of the Gökova graben cut and postdate the Upper Miocene-Lower Pliocene lacustrine units. The Lower to Upper Miocene sequences were elevated on the graben shoulders. Along the northern edge of Gökova graben, more than 400 m of coarse fluvial conglomerates and debris were formed in front of this elevated region. The Gökova graben, mostly offshore, is about 150-km-long and enlarges westward from 5 to 30 km. The western margin of the graben rises steeply to over 1000 m, but the southern margin is less marked. The coastline has many bays and small offshore islands.
Keywords: Ören, Gökova, Neogene basin, extensional tectonics
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