Nature and onset age of neotectonic regime in the northern core of Isparta Angle, SW Turkey

Abstract

The Isparta Angle (IA) is a reverse Λ-shaped morphotectonic structure located to the north of Antalya Gulf in the Eastern Mediterranean Sea. It resulted from the northward curvature of the originally E-W-trending Tauride orogenic belt owing to the nappe emplacements and related clockwise and anti-clockwise rotations in a time period of Early Paleocene to Early Pliocene. The IA is included in the southwest Anatolian tensional neotectonic domain and characterized by a series of grabens and horsts bounded by active normal faults of dissimilar length and trend. The evolutionary history of the graben-horst system is episodic. It is evidenced by two graben fills. These are older and modern (younger) graben fills separated by an intervening angular unconformity. The modern graben fill is nearly flat-lying (non-deformed) whereas older graben fill was deformed into a series of anticlines and synclines with ENE-trending curvi-linear axes by a short-term compressive tectonic regime operated in NNW-SSE direction during Late Pliocene. The diagnostic structures taking a part in the development of grabens and shaping the northern section of the IA are the margin-boundary normal faults. They occur in numerous single and several fault zones displaying a basin ward facing step-like land shape. Most of fault segments, particularly the master faults, are active and have a capacity of creating destructive earthquakes with a magnitude (up to Mw = 7.0). This is evidenced by both the historical and instrumental period earthquakes. Both the focal mechanism solution of earthquakes and the stereographic plots of slip-plane data, measured on the active margin-boundary faults of various grabens comprising the IA, on the Schmidt lower hemisphere net obviously reveal that the IA is under the influence of the tensional neotectonic regime, not a compressive tectonic regime, i.e. the sinistral strike-slip shearing along the Pliny arc has not propagated yet onshore, and its commencement age is Early Quaternary.

A Miocene onset of the modern extensional regime in the Isparta Angle: constraints from the Yalvaç Basin (southwest Turkey)

“…They claimed that the Yarıkkaya Formation was deformed by this short compressive tectonic episode. The field observations presented in Koçyiğit et al (2012) and also in our study show that folds developed in the Yarıkkaya Formation are only very gentle (interlimb angles are between 180° and 120°). This type of undulations can easily develop during extension al tectonic regime (Schlische 1995).…”

“…14) show that its motions are consistent with basin extension. Koçyiğit et al (2012) concluded that extension shaped the Yalvaç Basin, interrupted by a short-term contractional phase. They claimed that the Yarıkkaya Formation was deformed by this short compressive tectonic episode.…”

“…2). Focal mechanism solutions of moderate-size earthquakes along these faults in historic times indicate regionally multi-directional extension, with range-bounding major normal faults accommodating dip-slip NE-SW extension that occur in tandem with NW-SE extension accommodated along less prominent fault zones (Taymaz et al 2004;Ergin et al 2009;Poyraz et al 2014;Tiryakioğlu et al 2013;Koçyiğit et al 2012) (Fig. 2).…”

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

“…This deformation pattern is seen obviously in Kuşadası and Söke areas located at the westernmost tip of the Büyük Menderes Graben (Gürer et al, 2001), in the Halitpaşa graben (Kaya et al, 2004), along the northern margin of the Kiraz half graben located at the eastern tip of the Küçük Menderes graben (Bozkurt & Rojay, 2005), in the Künüpe section of the Büyük Menderes detachment fault zone, to the northeast of Kızıldere settlement located north-eastern margin of the Büyük Menderes Graben (Şimşek, 1985), around Acıdere village located on the southern slope of the Çökelezdağ which comprises the Çivril Graben (Koçyiğit, 2013b), in the apex of Isparta Angle (Boray, Saroğlu, & Emre, 1985), in the Deresenek section of the Akşehir-Afyon Graben (Koçyiğit, Ünay, & Saraç, 2000) and in the Yenigediz-Erdoğmuş Graben (Kütahya) (Gürboğa, Koçyiğit, & Ruffet, 2013). In addition, older graben fill is always folded in not only the Gediz and Büyük Menderes grabens shaped by the detachment normal fault zone, but also in and outside the whole of rest grabens, which lack detachment fault zones but included in the south-western Turkey neotectonic domain (Bozkuş, 1996;İnci, 1991Koçyiğit, 1983Koçyiğit, , 1997Koçyiğit & Deveci, 2007;Koçyiğit, Gürboğa, & Kalafat, 2013;Koçyiğit, Gürboğa, & Ruffet, 2013;Yağmurlu, 1991).…”

“…The short-term diachronic compressive events, which deformed the older graben fills of dissimilar facies and age range, can be classified into two groups based on their occurrence times and origins: (1) Late Langhian-Messinian compressive events and (2) Late Early Pliocene-Late Pliocene events. The first group of compressive events may be related to the emplacement of the Lycian Nappes onto the Beydağları, which comprises the western limb of the Isparta Angle, and the first phase of Aksu thrusting across the eastern limb of the Isparta Angle (Koçyiğit, Gürboğa, & Kalafat, 2013;Poisson, Wernli, Sagular, & Temiz, 2003). However, the first group of compressive events occurred in Miocene may be the most distinct reflections of the continent-continent collision of the Eurasian and Arabian plates and consequent formation of the Bitlis suture in south-eastern Turkey in late Middle Miocene (Dewey, Hempton, Kidd, Şaroğlu, & Şengör, 1986;Koçyiğit, 2013a;Şengör & Yılmaz, 1981).…”