Quaternary deposits of the Büyük Menderes Graben in western Anatolia, Turkey: Implications for river capture and the longest Holocene estuary in the Aegean Sea Nizamettin Kazancı a, ⁎, Saliha Dündar b , Mehmet Cihat Alçiçek c , Alper Gürbüz a a Ankara Üniversitesi, Mühendislik Fakültesi Jeoloji Mühendisliği Bölümü 06100 Tandogan, Ankara, Turkey b Türkiye Petrolleri A.O., Ankara, Turkey c Pamukkale Üniversitesi Jeoloji Mühendisliği Bölümü, 23400 Denizli, Turkey abstract article info Article history: Received 20 October 2008 Received in revised form 22 April 2009 Accepted 27 May 2009 Communicated by J.T. Wells Keywords: Quaternary Büyük Menderes River marine incursion Holocene Estuary river capture The Büyük Menderes Graben is a seismically active depositional basin in the N–S extensional tectonic region of western Anatolia, Turkey. It extends in an E–W direction and is bounded by the Aegean Sea to the west. The infill of this tectonic basin comprises ca 850 m and 245 m thick clastic sequences of Neogene and Quaternary, respectively and the Quaternary part of the basin-fill is presented here by the help of seismic sections and boreholes. Results show that the studied succession was made of unconsolidated, mostly fine- grained clastic sediments of marine and continental sequences interfingered with each other. The marine counterpart forms three relatively short (approx. 30 km) and one long (approx. 100 km from modern coastline) sediment wedges representing sea transgressions onto the graben. The last one was a rapid incursion that occurred in the Middle Holocene, forming the longest estuary of the Aegean Sea in western Anatolia. The filling of this estuary caused the decline of some historical harbours and settlements in the region. While marine-based events occurred in the west of the graben, alluvial and fluvial processes produced marginal and axial deposits in the east of graben, respectively. In general, the continental succession of Quaternary is thinner than its marine equivalent, probably due to sea-level fluctuations. In addition, the sedimentation rate increased suddenly during deposition of the last marine sequence (estuarine deposits) in the Holocene. It is likely that this was the result of enlargement of the drainage area of the River Büyük Menderes due to a river capture that occurred in the latest stages of Pleistocene. © 2009 Elsevier B.V. All rights reserved. 1. Introduction The Büyük Menderes Graben (BMG) is an E–W trending seismically active depression in western Anatolia lying 175 km inland from the Turkish coasts of the Aegean Sea (Fig. 1). Among others initiated in Neogene (Fig. 1), it is the longest continental basin of western Turkey. The River Büyük Menderes (RBM; the river Maiandros of antique times), the longest stream of the region, drains and also fills this depression. Miletos, Priene and some other ancient settlements have been affected by sediments of the RBM and so they are all now land-locked harbours in western Anatolia (Fig. 2). Hence, the western end of the BMG is an important area for cultural, particularly maritime archaeological purposes (Franco, 1996; Brück- ner et al., 2002; Marriner and Morhange, 2007). In addition, the area is significant for its abundance of historical records on siltation and the seismic hazards of ancient settlements (Erol, 1976; Kayan 1999). The Neogene infill of the BMG basin is well exposed, particularly along the northern margin of the graben, and together with the bedrocks belongs to the Menderes massif owing to successive faultings (Figs. 1, 3). A reliable stratigraphy has been erected depen- dent on not only lithofacies and fossil assemblages but also mag- netostratigraphy (Sözbilir and Emre, 1990; Seyitoglu and Scott, 1992; Ünay et al., 1995; Sarıca, 2000; Saraç, 2003; Şen and Seyitoglu, 2002, 2009). The oldest unit was a clastic succession associated with lacustrine limestone of Early Miocene and the overlying units of Pliocene and Quaternary consisted of clastic sediments of alluvial origin (Fig. 3). As a matter of fact, sedimentary facies and chro- nostratigraphies of the extensional western Anatolian basins, included the BMG, resemble each other with only minor differences (Sözbilir and Emre, 1990; Alçiçek et al., 2007). Thus, the BMG is a convenient area to investigate the geological evolution of Anatolia together with the eastern Mediterranean, and various attempts have already been made, producing different interpretations (e.g. Dewey and Şengör, 1979; Seyitoglu and Scott, 1991; Westaway, 1994; Bozkurt, 2000, 2003; Purvis and Robertson, 2005; Rojay et al., 2005). The main debate is about basin development and the causes and timing of crustal extension (Seyitoglu and Scott, 1992; Bozkurt, 2000; Yılmaz et al., 2000; Seyitoglu et al., 2002; Şen and Seyitoglu, 2009). On the other hand, information, hence interpretations about the Quaternary evolution of the BMG and other basins, is scarce due to lack of exposure. The sedimentary characteristics of the graben-fill of Marine Geology 264 (2009) 165–176 ⁎ Corresponding author. Tel.: +90 312 203 33 73. E-mail address: kazanci@eng.ankara.edu.tr (N. Kazancı). 0025-3227/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.margeo.2009.05.003 Contents lists available at ScienceDirect Marine Geology journal homepage: www.elsevier.com/locate/margeo