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<p>The age, origin and consequences of the crustal extension in the Aegean region are a continuing debate among geologists. Thanks to the fact that recent studies lowered the age of inception of crustal extension to the Oligocene, some regional problems related to the Oligocene sedimentary units in the approximately EW trending basins of SW Anatolia became solved. The Datça-Kale Main Breakway Fault (Seyitoğlu et al. 2004), which lies in an SW-NE direction in the Aegean Region, has created a basin and a thick stratigraphic sequence. This basin has been grouped under different names (e.g., Ören-Gökova Havzası, Kale-Tavas Havzası, Denizli Havzası, Çivril-Çardak Havzası, Burdur Havzası, Dinar Havzası) by previous researchers and referred to as distinct basins. Sedimentological, paleontological, and stratigraphic studies have been conducted in these different basins. Stratigraphically, it has been determined that they share the same formations and members. Facies analysis conducted on these formations and members revealed the same facies and facies assemblages. Furthermore, it has been identified that these sequences are associated with the same normal fault (the Datça-Kale Main Breakway Fault), which has controlled the deposition processes. Due to the same stratigraphy and facies assemblages, it has been concluded that the area created by the fault constitutes a single basin, which we have named the DAKAC (Datça-Kale-Acıgöl) Basin. First proposed in this study, the DAKAC Basin is a depositional area that extends from the Gulf of Gökova to Acıgöl, measuring more than 400&#xa0;km in SW-NE direction. The DAKAC Basin has a quite simple stratigraphy that consists of Mortuma, Çardak and Hayrettin formations, and Üçtepe Member. Facies analysis of these units points to alluvial fan/alluvial, fan-delta, beach, shallow sea-shelf carbonate and offshore sedimentary environments. The geographic distribution of sedimentary facies indicates that a shallow sea from the west flooded the DAKAC Basin, and inland seas penetrated into Central Anatolia during the Oligocene. The lowest levels of the DAKAC Basin fill yielded ostracod, mollusk and some rodent fossils, which provide an Early Oligocene age. These age data show that crustal extension in the Aegean Region probably started in Late Eocene (?)—Early Oligocene times. In 11 measured sections, Oligocene units have normal fault contact relationships with the underlying Taurus basement units, and their materials are sourced from this basement and not from the Menderes Massif. Therefore, it is believed that DAKAC Basin opened by the Datça-Kale Main Breakaway Fault, and this fault continues eastward into Anatolia. It appears that the DAKAC Basin is a graben basin developed by extensional tectonics in Late Eocene (?)—Early Oligocene, and it is not composed of several piggy-back and molasse basins as proposed in some previous studies.</p>

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Oligocene palaeogeographic evolution of the DAKAC basin (Datça-Kale-Acıgöl): implications for the Cenozoic tectonic evolution of SW Anatolia

  • 期刊论文

  • 发表日期：

    2025年2月1日

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  • Levent Karadenizli

摘要

The age, origin and consequences of the crustal extension in the Aegean region are a continuing debate among geologists. Thanks to the fact that recent studies lowered the age of inception of crustal extension to the Oligocene, some regional problems related to the Oligocene sedimentary units in the approximately EW trending basins of SW Anatolia became solved. The Datça-Kale Main Breakway Fault (Seyitoğlu et al. 2004), which lies in an SW-NE direction in the Aegean Region, has created a basin and a thick stratigraphic sequence. This basin has been grouped under different names (e.g., Ören-Gökova Havzası, Kale-Tavas Havzası, Denizli Havzası, Çivril-Çardak Havzası, Burdur Havzası, Dinar Havzası) by previous researchers and referred to as distinct basins. Sedimentological, paleontological, and stratigraphic studies have been conducted in these different basins. Stratigraphically, it has been determined that they share the same formations and members. Facies analysis conducted on these formations and members revealed the same facies and facies assemblages. Furthermore, it has been identified that these sequences are associated with the same normal fault (the Datça-Kale Main Breakway Fault), which has controlled the deposition processes. Due to the same stratigraphy and facies assemblages, it has been concluded that the area created by the fault constitutes a single basin, which we have named the DAKAC (Datça-Kale-Acıgöl) Basin. First proposed in this study, the DAKAC Basin is a depositional area that extends from the Gulf of Gökova to Acıgöl, measuring more than 400 km in SW-NE direction. The DAKAC Basin has a quite simple stratigraphy that consists of Mortuma, Çardak and Hayrettin formations, and Üçtepe Member. Facies analysis of these units points to alluvial fan/alluvial, fan-delta, beach, shallow sea-shelf carbonate and offshore sedimentary environments. The geographic distribution of sedimentary facies indicates that a shallow sea from the west flooded the DAKAC Basin, and inland seas penetrated into Central Anatolia during the Oligocene. The lowest levels of the DAKAC Basin fill yielded ostracod, mollusk and some rodent fossils, which provide an Early Oligocene age. These age data show that crustal extension in the Aegean Region probably started in Late Eocene (?)—Early Oligocene times. In 11 measured sections, Oligocene units have normal fault contact relationships with the underlying Taurus basement units, and their materials are sourced from this basement and not from the Menderes Massif. Therefore, it is believed that DAKAC Basin opened by the Datça-Kale Main Breakaway Fault, and this fault continues eastward into Anatolia. It appears that the DAKAC Basin is a graben basin developed by extensional tectonics in Late Eocene (?)—Early Oligocene, and it is not composed of several piggy-back and molasse basins as proposed in some previous studies.