Progressive development of the Büyük Menderes Graben based on new data, western Turkey

Abstract

Oblique and normal fault systems exposed in the Büyük Menderes Graben (BMG) region record two successive and independent complex tectonic events. The first group tectonic event is defined by an E–W extension related to N–S contraction and transpression. This group is responsible for the development of NW- and NE-trending conjugate pairs of oblique faults which controlled Early–Middle Miocene basin formation. Between the Early–Middle Miocene and Plio-Quaternary strata exists an unconformity, indicating a period of folding, uplift and severe erosion associated with N–S shortening. The second group of events was the change in tectonic regime from E–W extension to N–S extension which controlled the formation of the Büyük Menderes Graben by three progressive pulses of deformation. The first pulse of extensional deformation was initially recorded in the region by the exhumation of the deep part of the Menderes Massif (MM) with the development of the E-trending Büyük Menderes Detachment Fault (BMDF). The minimum age of this pulse is constrained by the older Plio-Quaternary fluviatile deposits of the Büyük Menderes Graben that range in age from the Plio-Pleistocene boundary interval to Late Pleistocene. The second pulse, which is marked by the rapid deposition of alluvial deposits, initiated the formation of approximately E–W-trending high-angle normal faults synthetic and antithetic to the Büyük Menderes Detachment Fault, on the northern margin during Holocene times. These faults are interpreted as secondary steeper listric faults that merge with the main Büyük Menderes Detachment Fault at depth. The third pulse was the migration of the Büyük Menderes Graben depocentre to the present day position by diachronous activity of secondary steeper listric faults. These steeper faults are the most seismically active tectonic elements in western Turkey. According to the stratigraphic and structural data, the N–S extension in the Büyük Menderes Graben region produced a progressive deformation phase with different pulses during its Plio-Quaternary evolution, with migration of deformation from the master fault to the hangingwall. The formation of diachronous secondary synthetic and antithetic steeper faults on the upper plate of the Büyük Menderes Detachment Fault, hence the southward migration of the deformation and of the Büyük Menderes Graben depocentre, should be related to the evolution of detachment in the region. The presence of the seismically active splays of secondary faults implies an active detachment system in the region. This young Plio-Quaternary N–S extension in the Büyük Menderes Graben may be attributed to the combined effects of the two continuing processes in Aegean region. The first process is back-arc spreading or probably the roll-back of African slab below the south Aegean Arc, which seems to be responsible for the change in the stress tensor from E–W extension to N–S extension. The second and later event is the southwestward escape of the Anatolian block along its boundary fault, that is, the North Anatolian fault (NAF).

Vegetation and climate in the Miocene deposits of southern side of the Büyük Menderes Graben, Șahinali-2 core, SW Turkey

“…Moreover, well preserved leaf flora from the Șahinali open cast mine was determined from the muddy sediments, and assigned to Serravallian by Mädler & Steffens (1979). Miocene sediments of the Söke Basin (Söke Formation) located about 70 km west of the current study area have similar lithologies to the Șahinali open cast mine and were dated as Early-Middle Miocene on the basis of mammal zone (MN4-6) (Gürer et al (2009). Ünay & Göktaș (1999) described a well-preserved mammal fauna from the Söke and Dededað Formations.…”

“…from the Dededað locality. Alçiçek (2010) studied the regional palaeogeography, stratigraphy and tectonism of the Neogene units in southwestern part of Turkey, and suggested middle Burdigalian-early Serravallian (Early-Middle Miocene) for the Söke Formation on the basis of mammal fauna studied by Becker-Platen (1970) and Gürer et al (2009). Unfortunately, the age of lignite-bearing sediments in the northern and southern sides of the Büyük Menderes Graben is still a matter of debate and more precise dating is needed.…”

An overview on the main stratigraphic and structural features of a geothermal area: the case of Nazilli-Buharkent section of the Büyük Menderes Graben, SW Turkey

“…Lastly, it was reactivated once more as a normal fault during the Quaternary neotectonic period. In the present, the Hasköy-Künüpe detachment fault segment works to be a southerly-dipping listric normal fault and is being used by geothermal fluids as indicated by hot water springs coming out of the Earth's surface such as the Gedik hot water spring in the Hasköy-Künüpe detachment fault zone (Figure 3) (Gürer et al, 2009;Koçyiğit, 2014;Koçyiğit, Yusufoğlu, & Bozkurt, 1999;Sözbilir & Emre, 1990).…”

“…In general, graben fills are about 2 km in thickness, Miocene-Quaternary in age and well-exposed not only in the Nazilli-Buharkent geothermal area but also throughout the Büyük Menderes and Denizli grabens located between Kuşadası-Söke to the west and Denizli to the east (Figure 1(b)). In the Büyük Mernderes-Denizli grabens, graben fills were studied locally, mapped, named formally to informally and dated differently by numerous researchers (Alçiçek, 2007;Cohen, Dart, Akyuz, & Barka, 1995;Gürer, Bozcu, Yılmaz, & Yılmaz, 2001;Gürer, Sarıca-Filoreau, Özburun, Sangu, & Doğan, 2009;Koçyiğit, 2005;Koçyiğit, Yusufoğlu, & Bozkurt, 1999;Ring et al, 1999;Sarıca, 2000;Şimşek, 1984;Sözbilir & Emre, 1990;Sun, 1990), but there is no a common agreement among previous workers on age and naming of the graben fills. This is seen obviously on Figure 5.…”

“…In addition, it is cut frequently, displaced (up to 6 km) in both dextral and sinistral directions (Figures 3 and 4) and so divided into numerous and diverse-sized (1-18 km) structural segments by the intervening N-NW-, N-S-and N-NE-trending transverse (ramp) faults such as the Böğrüdelik fault zone (Figures 3). The most general and diagnostic four characteristics of the Büyük Menderes detachment fault are as follows: (1) it is a low-angle normal fault in listric nature, (2) it determines incipient margin of the Miocene palaeotectonic graben and juxtaposes tectonically the Menderes Massif rocks with the Miocene graben fill, (3) both the palaeotectonic and neotectonic graben fills (Kızılburun group and Tosunlar Formation respectly), which comprise the southerly down-thrown hanging wall block of the Büyük Menderes detachment fault, have experienced a roll-over deformation to some extent owing to its listric nature, and (4) the Büyük Menderes detachment fault zone is being widely used by both the percolation of the cold meteoric waters and the upwelling geothermal fluids as indicated by the borehole data and the widespread occurrences of hot springs and fissure-ridge travertines exposed and actively growing within this fault zone (Gürer, Sarıca-Filoreau, Özburun, Sangu, & Doğan, 2009;Koçyiğit, 2014;Koçyiğit et al, 1999;Sözbilir & Emre, 1990). Along the northern margin of the Büyük Menderes Graben, the 50-140-m-thick topmost part of the Menderes Massif rocks is included in a detachment fault zone, namely the Büyük Menderes detachment fault zone (Gürer et al, 2009).…”