Tracking the uplift of the Bolkar Mountains

17 Pages·2015·4.4 MB·English

Turkish Journal of Earth Sciences Turkish J Earth Sci
(2016) 25: 64-80
http://journals.tubitak.gov.tr/earth/ © TÜBİTAK
doi:10.3906/yer-1504-17
Research Article
Tracking the uplift of the Bolkar Mountains (south-central Turkey): evidence from
apatite fission track thermochronology
Fatih KARAOĞLAN*
Department of Geological Engineering, Faculty of Engineering and Architecture, Çukurova University,
Balcalı-Sarıçam, Adana, Turkey
Received: 15.04.2015 Accepted/Published Online: 23.11.2015 Final Version: 01.01.2016
Abstract: Apatite fission track (AFT) thermochronology is applied to the Horozköy granitoid, which outcrops within the Bolkar
Mountains (south-central Turkey). The region comprises the Niğde Massif to the north, the Inner Tauride Suture Zone, and the Central
Taurides to the south. The Niğde Massif and the Central Taurides collided during the Eocene following north-dipping subduction of the
Inner Tauride Ocean beneath the Niğde Massif. The Ulukışla Basin formed above this suture zone. The AFT ages range between 23 and
16 Ma, although there was no significant uplift or exhumation during this period. During the Oligo-Miocene, the region experienced a
slow uplift and the collapse of the Tauride belt, in response to the mantle processes (roll-back, break-off, and/or slab tearing) related to
the African plate and linked oceanic slab beneath the Anatolide-Taurides. The Central Taurides reached maximum height during the
latest Miocene. The AFT modeling results indicate a fast exhumation in the late Miocene-Pleistocene, consistent with the biostratigraphic
and field evidence.
Key words: Central Taurides, Bolkar Mountains, Horozköy granitoid, apatite fission track, exhumation, uplift
1. Introduction reaches as high as 3–3.5 km above sea level in east and
South-central Anatolia hosts two major units, namely central Anatolia along the suture zones, where the Central
the Central Anatolian Crystalline Complex (CACC) Anatolian Plateau reaches elevations of about 500–1500
to the north and the Central Taurides to the south. The m (Tezel et al., 2013). The westward escape of Anatolia
Bolkar Mountains, part of the Central Taurides, which are compounded the convergence and collision with the Afro-
bounded by the Ecemiş Fault to the east and the Kırkkavak Arabian plate along the Bitlis-Zagros Suture Zone (Dewey
Fault to the west (Blumenthal, 1960; Özgül, 1984), and the et al., 1986; Jolivet and Faccenna, 2000; McClusky et al.,
CACC juxtaposed following the subduction of the Inner 2000; Robertson and Mountrakis, 2006; Smith, 2006; Allen
Tauride Ocean during the Late Cretaceous-Eocene (Görür and Armstrong, 2008; Ring et al., 2010; Elitok and Dolmaz,
et al., 1984; Dilek et al., 1999a; Clark and Robertson, 2002; 2011; van Hunen and Allen, 2011) (Figure 1).
Pourteau, 2011; Robertson et al., 2012; Parlak et al., 2013; The exhumation of the CACC exhibits distinct features
Sarıfakıoğlu et al., 2013; Pourteau et al., 2014). The collision at its margins. The exhumation of the northern part of
between the Arabian platform and the Taurides occurred central Anatolia was related to the collision of Eurasia
during the Oligocene-Miocene, resulting in shortening, and Anatolia during the early-middle Paleocene, while
thickening, and uplifting in east Anatolia and westward the eastern part of the CACC was exhumed as a result of
extrusion of central and western Anatolia. Thus, the the Tauride-Arabia collision during the Oligocene (Boztuğ
Central and Eastern Anatolian plateaus span a transition and Jonckheere, 2007). The fission-track data suggest that
from crustal shortening in the east to westward block the southern margin of central Anatolia, linked with
extrusion and extension, accommodated mostly along Central Taurides, was exhumed at 17–11 Ma in a yo-yo
the North and East Anatolian faults (Şengör and Yılmaz, tectonic regime (Fayon and Whitney, 2007; Umhoefer et
1981; Şengör et al., 1985; Yılmaz, 1993; Yılmaz et al., 2007; al., 2007; Whitney et al., 2008).
Okay et al., 2010; Elitok and Dolmaz, 2011; Schildgen South-central Anatolia first emerged above sea level
et al., 2014; Karaoğlan et al., 2015). The thickened crust during the Eocene, where the southern flank of the Taurides
* Correspondence: [email protected]
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KARAOĞLAN / Turkish J Earth Sci
still remained under sea level (Aksu et al., 2005a; Jaffey and 1), and the relation between the exhumation/uplifting and
Robertson, 2005). The emergence of the Bolkar Mountains the mantle processes.
was a part of the regional south-central Anatolian uplift,
as a result of complex mantle processes (subduction roll- 2. General geology
back, slab break-off, slab tearing) that resulted from the South-central Anatolia comprises two main tectonic units
north-dipping southern branch of the Neo-Tethys Ocean separated by the Inner Tauride Ocean and the CACC to
beneath the Anatolide-Tauride continent during the the north and the Central Taurides to the south, where the
Oligo-Miocene (Barazangi et al., 2006; Dilek and Sandvol, Ulukışla Basin formed (Demirtaşlı et al., 1984; Görür et
2009; van Hinsbergen et al., 2009; Ring et al., 2010; Biryol al., 1984; Dilek et al., 1999a) (Figure 1). The CACC, first
et al., 2011; van Hunen and Allen, 2011; Cosentino et described by Göncüoğlu et al. (1991), was formed by
al., 2012; Schildgen et al., 2012a, 2012b, 2014). The uplift three metamorphic units, namely the Kırşehir, Akdağ, and
of the Bolkar Mountains within the Central Taurides Niğde massifs, distinguished by their metamorphism. The
shows temporal discrepancies against the exhumation of Kırşehir and Akdağ massifs experienced clockwise P/T
the CACC. The Bolkar Mountains appear to have been paths at moderate P/T conditions, with upper amphibolite
exhumed slightly earlier then the CACC during the late (highest) overprint, whereas the Niğde Massif underwent
Eocene-early Miocene (Dilek et al., 1999b; Lefebvre et al., two distinct metamorphisms between the Late Cretaceous
2015). The available low-temperature thermochronologic (Göncüoğlu, 1986; Whitney and Dilek, 1997; Whitney et
data suggest that the uplifting is propagated from south al., 2007) and early-middle Cenozoic (Whitney and Dilek,
to north or the paleogeothermal gradient was located at a 1997, 1998, 2000; Fayon et al., 2001; Whitney et al., 2001;
higher position in the south, where the Central Taurides Dilek and Sandvol, 2009).
were already at maximum height during the Oligocene- The Inner Tauride Suture Zone (ITSZ), bounding
Miocene (Dilek et al., 1999b; Fayon and Whitney, 2007; the southern margin of the CACC, was formed by the
Umhoefer et al., 2007; Lefebvre et al., 2015). During the late consuming of the Inner Tauride Ocean in a north-dipping
Miocene-Pleistocene, the crustal uplift rate changed and subduction beneath the CACC during the Late Cretaceous-
the late Miocene marine sediments uplifted up to 1.5–2 km early Cenozoic (Dilek et al., 1999a; Okay and Tüysüz, 1999;
(Schildgen et al., 2012a, 2012b). The field, biostratigraphic, Parlak and Robertson, 2004; Robertson, 2004; Kadıoğlu et
and cosmogenic dating data from CACC and the Central al., 2006; Kadıoğlu and Dilek, 2010; Pourteau et al., 2010,
Taurides suggest that the continuing slab break-off and/ 2013; Parlak et al., 2013; Sarıfakıoğlu et al., 2013). During
or slab tearing led to the fast uplifting of south-central Paleocene (Late Cretaceous?) and Miocene time, above
Anatolia and emergence above sea level starting at ~7 the ITSZ, the Ulukışla Basin formed in an E-W trending
Ma ago (Cosentino et al., 2012; Schildgen et al., 2012a, seaway. The Ulukışla Basin contains marine and terrestrial
2012b). Recent studies show that the Arabia-Africa and sedimentary rocks, evaporites, volcanosedimentary
Eurasia collision was responsible for the Oligocene- rocks, and volcanic and intrusive magmatic units with
early Miocene exhumation and/or uplifting, whereas the a thickness of up to 5 km (Demirtaşlı et al., 1973, 1984;
mantle processes beneath south-central Anatolia were Clark and Robertson, 2002, 2005; Kurt et al., 2008; Engin,
responsible for the high uplift rates within the CACC and 2013) (Figure 1). To the south, the basal units of the basin
Central Taurides (Cosentino et al., 2012; Schildgen et al., composed of conglomerates, calcarenite, and limestone
2012a, 2014; Cipollari et al., 2013; Radeff et al., 2015). The unconformably rest on the Central Taurides, represented
latest Miocene-Recent uplifting of the Central Taurides by the Bolkardağ Unit (Figure 2).
and CACC is well documented (Cosentino et al., 2012; The Bolkardağ Unit, to the south of the CACC,
Schildgen et al., 2012a, 2014; Yildirim et al., 2013; Radeff et comprises carbonate, siliciclastic, and volcanic rocks and
al., 2015); however, the Oligocene-early Miocene history their metamorphic equivalents with ages ranging from
is still under debate in the frame of timing of exhumation Upper Permian to Late Cretaceous (Demirtaşlı et al., 1973,
and the effect of subduction and collisional events on the 1984; Özgül, 1976). This unit is interpreted as a ribbon-
Central Taurides. shaped continent rifted off from Gondwana (Özgül, 1976,
In this study, apatite fission track (AFT) 1984; Robertson and Dixon, 1984; Görür et al., 1991;
thermochronology is applied to a postcollisional Garfunkel, 1998, 2004). The Bolkardağ Unit (Bolkar
granitoid, the so-called adakitic Horozköy granitoid, that Group of Demirtaşlı et al., 1984) may be divided into
intruded into the Bolkardağ Units (Central Taurides) four formations: 1) the Dedeköy formation (Permian),
during the early-middle Eocene. This paper discusses 2) Gerdekesyayla formation (Lower-Middle Triassic),
the thermochronologic (AFT) evidence related to the 3) Berendi limestone (Upper Triassic), and 4) Üçtepeler
exhumation and uplift of the Bolkar Mountains, located limestone (Jurassic-Cretaceous) (Demirtaşlı et al., 1973,
to the north of the easternmost Mediterranean Sea (Figure 1984). The lowermost part of the Bolkardağ Unit begins
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KARAOĞLAN / Turkish J Earth Sci
A 30°E 35°E 40°E
B l a c k S e a
İstanbul
40°N
40°N East Anatolian
high plateau
21
CACC
BZSZ
EFZ
Fig. 1B
s
Central Ta uride Adana 18
Arabian Plate
N
35°N
0 100 200 km
10
30°E 35°E
B Ulukışla EC
37º30’ ULUKIŞLA BASIN EMIS
2380m FAU
LT
N - CACC Alihoca KatrancıAlihoca ophiolBiteFF ZONE
SI
SLA BA Aktoprak Darboğaz Kızıltepe2975 m Horoz village
KI Horoz
ULU BFFn t a i n spluton Figure 2 EASTE
u R
CENTRALITSZTAURIDE BLOCK34º30’ B o lk a r M o 3580 m ECEMIS FAULT ZONE PoAlzaadang top5hi oBlkitmeele2m47e0d imkN TAURIDE BLOCK
LA BASIN AFTellylrusrvecishut mrdiae (lpQ douesapittose sr(inUtsa. r(EyOo)lcigeoncee)ne) EASTERNTAURIDES CNNaeerrrbiittiioccn llaiimmteee &sstt oocnnlaees t((iJMcu .rr oTarcsikasssic s(-iPCce-rJerumtaroac-seCsoiaucrs)b)oniferous)
S
ULUKI ÇvU(HAUokilafu.ltt claekkPaiaşhasntpalleieacinnpo viaeFcnor eotF lecFnromraeocrn-rmaaEmitlcaaioosattc initooaieo:n nnn(n:sdLe : ( a)(CsLUte.el a.dC PCsimrtaericelete atn&aoctc caeceeroaoynur ubesuso-?nE?-niL)toas.ctPeea nrloeeco)kcse,ne Cenrtal TauridesBolkardağ Unit MSMCcaaahrrrbbbisolltee na aaantnndedd ma ssnccedhhta iicssqlttau ((saPUtrie.ctPzr rmiatoelieca k(onLsz)o o(wLiceo-Lwr .Te Mrri aTesrsisaoicsz)soiicc))
INNER-TAURIDEOCEAN CRUST HOOopprhhoiiooz lliiGtteicr a (mCniérteolatidan cg(eYeop (urUes.s, Ci9ar4ne-,t7 a51c5 eM-4oa8u)Ms-aP)aleocene) Fault
Figure 1. A) Regional topography map (SRTM V4.1 data from Jarvis et al. (2008) showing
major tectonic boundaries. CACC: Central Anatolian Crystalline Complex; CP: Central
Pontides; BZSZ: Bitlis-Zagros suture zone; NAF: North Anatolian Fault; EAF: East
Anatolian Fault; DSFZ: Dead Sea Fault Zone; EFZ: Ecemiş Fault Zone; ES: Eratosthenes
Seamount; LV: Lake Van. Arrows with numbers inside represent plate movement (mm/
year) with respect to Eurasia (Reilinger et al., 1997); map modified after Schildgen et
al. (2014). B) Geological map of south-central Turkey. Data from Clark and Robertson
(2002), Dilek and Sandvol (2009), and Engin (2013).
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Katrancı
Sivri T.
FK 88 Horozköy
FK 89 FK 91
FK 90
Top Dağı
Katırgediği T.
N
0 250500m
Legend
Bolkardağ Unit
Talus (Quaternary)
(Permian)
Terrace sediments (Mio-Pliocene)
Urbanisation area
Granite
Horozköy granite (L.Eocene) Hill
Granodiorite
U
Conglomerate (Paleocene) lu Anticline
k
ış
Quartz-porphyry (U.Cretaceous-Paleocene) la Wrench fault
B
limestone (U.Maestrichtian-L.Paleocene) as FK 88 Sample location
in
Alihoca ophiolitic complex (Cretaceous)
BFF Bolkar Frontal Fault
Madenköy ophiolitic melange (Cretaceous)
Figure 2. Geological map of Horoz village and surroundings (modified after Çalapkulu, 1980; Çevikbaş
et al., 1995; Kadıoğlu and Dilek, 2010; Kocak et al., 2011).
with dolomitic limestones intercalated with micaceous oolitic and dolomitic limestone, dolomite, and limestone
slates (Dedeköy formation-Upper Permian). The (Üçtepeler limestone). The formation formed in an open
Dedeköy formation formed under stable shelf conditions marine and deep pelagic sedimentary environment
and has a thickness of 600 m. Upwards, this unit passes during the Jurassic-Late Cretaceous (Demirtaşlı et
into shale and clayey limestone alternation continued al., 1973, 1984). The Gerdekasyayla formation shows
with limestone, thick-bedded dolomitic limestone, and greenschist metamorphism, whereas biotite, tourmaline,
shale and clayey limestone alternation named as the and almandine crystals are formed near the contact zones
Gerdekesyayla formation, which was formed in an open of the Horozköy granitoid (Çalapkulu, 1980). The dykes
marine shelf during the Lower-Middle Triassic. The upper of the Horozköy granitoid intruded into the marbles
part of the Bolkardağ Unit is predominantly represented (Çalapkulu, 1980; Çevikbaş et al., 1995).
by a thick carbonate sequence including dolomite, fine- The Central Tauride block (including the Bolkardağ
grained limestone, and medium to thick-bedded dolomitic Unit) was shortened and thickened as a result of folding
limestone, formed in a shallow marine, stable carbonate and imbrication along the thrust faults such as the
platform during the Upper Triassic (Berendi limestone). Bolkar Frontal Fault (Demirtaşlı et al., 1984; Dilek et al.,
Upwards, the Berendi limestone passes into partly 1999b). The obduction of oceanic lithosphere (i.e. Alihoca
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KARAOĞLAN / Turkish J Earth Sci
ophiolite) from the north and continuous subduction biotite, and hornblende, and the granodiorite is composed
of the northern edge of the Central Taurides (Dilek of quartz, feldspar, biotite, and amphibole (Çalapkulu,
and Whitney, 1997; Dilek and Flower, 2003; Dilek and 1980; Çevikbaş et al., 1995; Kadıoğlu and Dilek, 2010).
Sandvol, 2009) was responsible for the shortening and Both rock types are intruded by mafic and felsic dykes
thickening of the Paleozoic-Jurassic tectonostratigraphic and include mafic microgranular enclaves, indicating that
units in the Tauride block during the Late Cretaceous magma mixing/mingling processes played an important
and Eocene (Dilek et al., 1999b; Dilek and Sandvol, 2009; role during crystallization (Kadıoğlu and Dilek, 2010;
Parlak et al., 2013, 2014). The isostatic rebound of the Kocak et al., 2011).
partially subducted continent, as a result of the subduction The Horozköy granitoid rocks were interpreted to have
processes, caused the northern edge of the entire Tauride formed in a postcollisional extensional environment as
block to be gradually uplifted along the normal faults (i.e. a result of the collision of the Central Taurides with the
the Bolkar Frontal Fault) during the Miocene, building CACC (Kadıoğlu and Dilek, 2010). The earlier suggestions
a southward-tilted asymmetric mega-fault block with a for the formation (crystallization) age of the Horozköy
rugged, alpine topography (Dilek and Whitney, 1997, 2000; granitoid were based on cross-cutting relationships with
Dilek et al., 1999b; Dilek and Sandvol, 2009; Kadıoğlu the Cretaceous ophiolitic mélange that rests tectonically
and Dilek, 2010) (Figures 1 and 2). In the study area, the on the Bolkardağ marbles, reported to be post-Lower
Bolkardağ Unit forms a big anticlinorium, where most of Paleocene to pre-Lower Eocene (Çalapkulu, 1980) and
the anticlines are asymmetrical and overturned towards pre-Paleocene or Late Cretaceous-Paleocene (Çevikbaş
the north along the Bolkar Frontal Fault (Demirtaşlı et al., and Öztunalı, 1992). Zircon U-Pb dates indicate a slightly
1984) (Figure 2). The Bolkar Frontal Fault has an ENE- younger formation age, ranging from 56 to 48 Ma (Dilek
trending left-lateral oblique-slip component and displays et al., 1999b; Kadıoğlu and Dilek, 2010; Kuscu et al.,
a top-to-the-north shear sense indicator. The fault system 2010; Engin, 2013; Parlak et al., 2013), whereas the 40Ar-
has multiple splays within the northern edge of the Tauride 39Ar cooling ages (hornblende, 47 Ma, and biotite, 54–50
block and is defined by mylonitic breccia composed of Ma) yield a similar age range (Kuscu et al., 2010). Dilek
ophiolitic and carbonate rocks (Dilek and Whitney, 2000). et al. (1999b) also reported an AFT age of 23.6 ± 1.2 Ma,
The structural trend of the normal faults is generally ENE- suggesting that the granitoid uplifted during the Miocene.
WSW in the study area (Figure 2). The undeformed Mio-Pliocene fluvial terrace unit within
The fluvial terrace unit, observed in the Horoz valley, the incised valley indicates that the Central Taurides were
is slightly tilted to downslope. This unit rests on the already uplifted during this period (Dilek et al., 1999b).
Horozköy granitoid and seals the normal faults along the
valley, containing mainly marble and granitoid pebbles
3. Analytical procedure
and blocks with up to 250 m in thickness. The age of
Four samples were taken from the fresh outcrops across a
the terrace unit was reported as Oligocene by Çalapkulu
range of altitudes to illustrate the exhumation rate (Table
(1980); however, Dilek et al. (1999b) proposed a Mio-
1). The mineral separation procedures including crushing,
Pliocene age for the unit.
sieving, wet sieving, electromagnetic, and heavy liquid
2.1. Horozköy granitoid techniques were performed in the Çukurova University
The Horozköy granitoid outcrops in an area of ~8 km2 Geological Engineering Department (Adana, Turkey).
within the Bolkardağ region in the eastern part of the The samples were mounted in epoxy resin, ground, and
Central Taurides, where it took the name of the Horoz polished prior to etching. The samples were etched in
village (Figure 2). The granitoid body intruded into the 5.5 M HNO3 medium for 20 s at 21 °C (Donelick et al.,
northern flank of a NE-SW trending anticline including 1999). The mounts were covered with 50-mm uranium-
the Lower Marble unit and the schists of the Bolkardağ free muscovite external detectors and irradiated in a BR-1
unit, whereas a Plio-Quaternary terrace unit overlies the research reactor in Belgium. Three age standards including
southern part. The granitoid, first described by Blumenthal the IRMM 540R uranium glass and the c-axis oriented
(1956), has a contact metamorphic aureole represented Durango apatites, prepared in the same manner as the
by hornblende hornfels and garnet fels facies rocks. The samples, were included in the irradiation can in order to
tonalite and diorite dykes intruded into the wall rocks ensure that the tracks were counted in the same faces in
(Demirtaşlı et al., 1973, 1984; Çalapkulu, 1980; Çevikbaş the standard as in the samples and to guarantee minimum
and Öztunalı, 1992; Çevikbaş et al., 1995; Kadıoğlu and separation between the standard glasses and apatite age
Dilek, 2010). Engin (2013) reported that the dykes of the standard to avoid possible radial fluence gradients for
Horozköy also intruded into the Eocene Ulukışla Basin minimizing the systematic error of individual z values
units. The unit is composed of two parageneses: the (Table 2). To calculate the neutron flux, a 1% Al-Co-
granite is composed of quartz, plagioclase, K-feldspar, monitor (IRMM-528R) of 0.01 mm in thickness was
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Stand. dev. 2.15 4.58 5.97 4.81 ated using crystals-1;
Mean mber track lengthgths 14.80 17.19 16.25 17.17 977); ages calcule v = number of Error [Z] 10.0 6.8 6.3 7.6  
Nuξ Age ± 1σ of Nd(Ma)len 453523.7 ± 1.382 466420.5 ± 1.078 479016.1 ± 1.78 489219.4 ± 1.255 Gleadow and Lovering, 1degrees of freedom, wher Error [ρ]Z [Ma]D 0.008134.8 0.008141.6 0.007116.1 0.029130.8   
ρ ± 1σd 0.505 ± 0.008 0.515 ± 0.008 0.520 ± 0.007 0.525 ± 0.007 correction factor (2ning χ value for v 6 –2ρd [10cm] 0.502 0.533 0.435 0.490  
2ρ ± 1σNP(χ)ii 51.00 ± 4.66168330.70 53.52 ± 5.86291824.85 33.86 ± 5.4447459.01 28.89 ± 1.99132965.88 g 0.5 for the 4π/2π geometry 2) is probability of obtai); P(χ Galbraith and Laslett, 1993). 221/Errorξ/Error 0.0082.262 0.0164.188 0.0164.386 0.04110.836   
n2 (
Table 1. Apatite fission track analytical data for Horozköy granitoid. Elevation Irradiation SampleGrainsρ ± 1σNss(m)step FK 881318FG-653317.94 ± 1.56592 FK 891188FG-654215.98 ± 1.58670 FK 901130FG-65147.86 ± 0.80110 FK 911080FG-65468.00 ± 0.59368 N: Numbers of tracks counted; Analyses by external detector method usidosimeter glass IRMM-540R; (apatite) ξ IRMM540R = 267 ± 5 (see Table ξ age is a modal age, weighted for different precisions of individual crystals Table 2. ξ calibration calculations. DURIrradiationStandardξError  FG 65DD 21268.410.9  FG 65DD 22266.08.0  FG 65DD 23266.67.8 Mean [1s](unweighted) 267.00.7 Mean [1s](weighted) 266.75.0
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N
Bolkardağ Unit
FK 89
FK 88 20.5±1.0
23.7±1.3
Horoz granite _ FK 91
FK 90 19.4±1.2
_ + 16.1±1.7
+
Horoz Village
Terrace Unit
Figure 3. Field photo of the Horozköy granitoid near Horoz village including sample
locations with AFT age data.
added above each standard in the irradiation can. After a sufficient number of confined tracks, the mounts were
irradiation, the induced tracks in the external detectors over-etched with the same medium as etching done at 15
were etched in 48% HF for 30 min. s prior to measurements. Trackscan software allows users
The track counts were carried out in transmitted light to measure not only horizontal but also oriented tracks.
at a magnification of 1250× with a Zeiss AxioImager Between 50 and 100 confined tracks were measured in
microscope. The counting procedure of Jonckheere et al. prismatic faces with the selection of only tracks in tracks
(2003) was followed for counting. During the counting (TINTs) (Table 1).
the external detectors were repositioned track-side down The track counts, track lengths with c-axis angles,
on the mounts, in the same position as during irradiation. and dpar values were used in the inverse modeling for
The fossil tracks were counted by focusing on the apatite calculating the thermal histories. The thermal histories
surface through the muscovite external detector, whereas were modeled with computer software HeFTy 1.8
the induced tracks were counted by focusing on the (Ketcham, 2005). The annealing equations of Donelick et
underside of the external detector, without moving the al. (1999) and c-axis projection of Donelick et al. (1999)
microscope stage. Three age standards were counted for were used during inverse modeling calculations. A
the determination of the z calibration factor. At least 2500 minimum of 50,000 (at least 250 good paths) candidate
fossil tracks were counted in the apatite, and over 3000 temperature-time (T-t) paths were generated at random
induced tracks in the muscovite external detector and (Monte Carlo algorithm) for each modeling run.
4000 tracks in the external detector irradiated against
the uranium glass were counted. The calculation of the z 4. Analytical results
calibration factors and the unweighted overall mean z are The combined geo/thermochronologic data suggest a fast
given in Table 2. Approximately 40 grains were counted in cooling through 300 °C (McDougall and Harrison, 1999)
each sample (only in one sample 14 grains were counted) after emplacement, which can be explained by either
to ensure the total number of fossils and induced fission shallow emplacement or fast exhumation above 10 km
tracks were sufficient for reasonable ages. The results and in depth for the Horozköy granitoid (Dilek et al., 1999b;
the age calculations are given in Table 1. Kuscu et al., 2010; Engin, 2013; Parlak et al., 2013). The
The track length measurements were carried out with a single-grain fission track ages show very low dispersion
Zeiss AxioImager microscope at a magnification of 2500× and are consistently younger than the intrusion age
equipped with an Autoscan stage and a digitizer connected of granitoid (Table 1; Figure 3). Samples were taken at
to a computer with Trakscan software. In order to reveal different altitudes of the granitoid around Horoz village
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1350 the age-elevation and cooling history. Sample FK89 was in
1300 Horoz granite FK 88 the total annealing zone before 25 Ma and has a cooling
m)1250 history similar to that of FK88. The grains ages of FK89
on (1200 FK 89 are concordant (P(χ2) = 24.85) and the confined TL shows
evati1150 FK 90 a unimodal distribution, ranging between 10 and 17 µm
El1100 with a mean length of 17.19 µm (Table 1). The very high
FK 91
1050 standard deviation of the TL implies that the samples
1000 remained long enough in the PAZ to shorten the old
0 5 10 15 20 25 30
Age (Ma) tracks, which is consistent with the slow cooling suggested
by the age-elevation profile. This sample spans a more or
Figure 4. Age-elevation diagram of the AFT results. FK91 deviates
less steady uplift in the PAZ, cooled below ~90 °C slowly
from the normal trend as a result of faulting after exhumation.
after 7–8 Ma, and afterward the cooling rate of the sample
increased (Figure 5). The age of sample FK91 indicates that
(Figure 3) to detect the possible age-elevation profile. AFT normal faulting was active after the early Miocene, when
ages range between 23.7 and 16.1 Ma, where the oldest AFT the samples had been exhumed above the PAZ. In contrast
age is similar to the age reported by Dilek et al. (1999b) to this early Miocene cooling age, the T-t modeling based
(Table 1; Figure 3). The ages show a clear correlation with on track length data indicates a rapid undercooling from
elevation, except FK91, which is separated from the others the PAZ to the total stability zone in a time span between
by a normal fault in the field (Table 1; Figures 3 and 4). 6 and 8 Ma (Figure 5) (Wagner and Van den Haute, 1992;
To calculate the cooling or exhumation rate, one can Van Den Haute and De Corte, 1998).
perform either the mineral pair method, using one rock
sample with multiple mineral cooling ages, or the altitude- 5. Discussion
dependence method, performing the same dating method The accumulating low-temperature data from central and
on two (or more) samples from different altitudes. The eastern Anatolia cluster into three groups (Dilek et al.,
latter requires no important vertical tectonic displacement 1999b; Fayon et al., 2001; Boztuğ and Jonckheere, 2007;
during or after exhumation. If any tectonic activity Umhoefer et al., 2007; Boztuğ et al., 2008, 2009a, 2009b,
occurred after the youngest isotopic age, then the linear 2009c; Okay et al., 2010; Karaoğlan, 2012; Karaoğlan
relationship between altitude and age will be disrupted et al., 2015). The oldest age group is Paleocene-Eocene
(Gallagher et al., 1998; Balestrieri et al., 2003; Gallagher from the granitoids, located to the northern edge of the
et al., 2005). After excluding FK91, the age-elevation plot CACC, related to the closure of the northern branch of
drawn with the ages obtained in this study indicates a slow the Neo-Tethys Ocean and the collision between Eurasia
exhumation (nearly steady) of ~0.03 mm/year for the Early and the CACC (Boztuğ and Jonckheere, 2007; Boztuğ
Eocene-aged Horozköy granitoid between 23 and 16 Ma et al., 2008, 2009c), whereas there are also Oligocene
(Early Miocene) (Figures 3 and 4). The AFT age reported cooling ages from the metamorphic rocks of the CACC
by Dilek et al. (1999b) cannot be used for the age-elevation (Fayon et al., 2001). The second age group is Eocene-
profile, as the elevation data and the methodology of AFT Oligocene, related to the first collision of the Anatolide-
age were not reported. Tauride platform and the Arabian platform, which is also
Three T-t paths were calculated using HeFTy related to the third and the youngest age group (Miocene)
computer software by inverse modeling to reconstruct (Fayon and Whitney, 2007; Umhoefer et al., 2007; Okay
the exhumation of the samples in the partial annealing et al., 2010; Karaoğlan et al., 2015) (Figure 6). According
zone (PAZ) (Ketcham, 2005). The number of track to the complexity of the collision events in the Anatolian
lengths within sample FK90 was insufficient to provide peninsula, one must use these data with care. The previous
a statistically meaningful result. The T-t path of sample fission-track data from south-central Anatolia indicate an
FK88, calculated by inverse modeling, indicated similar Early-Late Miocene cooling/uplift for this region (Dilek et
results with measured ages (Figure 5). The sample was al., 1999b) (Figure 6). The Niğde Massif and the Tauride
cooled below 100 °C after 25 Ma and remained in the PAZ block collided following the subduction of the Inner
until 2–3 Ma (Figure 5). The probability of the chi-square Tauride Ocean during the Late Cretaceous-Eocene (Dilek
test (P(χ2) = 30.70) for this sample indicates a uniform and Whitney, 1997; Kadıoğlu and Dilek, 2010; Parlak et
age distribution between intergrains. The track length al., 2013). Following the deposition of the Ulukışla Basin
(TL) distribution of FK88 shows a unimodal distribution above the suture zone, the Bolkar Mountains and the
with a mean length of 14.80 µm and standard deviation of Ulukışla Basin remained under sea level, whereas high
2.15 µm (Table 1; Figure 5). The TL distribution implies levels of the Niğde Massif emerged and eroded during the
a slow cooling rate in the PAZ, which is consistent with Eocene. During this stage the Ecemiş Fault activated and
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KARAOĞLAN / Turkish J Earth Sci
Model Age: 23.2 FK 88
Measured Age: 23.0±1.2
0.30
40 GOF: 0.90
C) Model TL: 11.89±2.89 0.25
e (° 60 GMOeaFs:u 0r.e9d4 TL: 11.84±1.73
atur 0.20
per 80
m
0.15
Te
100
0.10
120
0.05
FK 88
Model Age: 20.3 FK 89
Measured Age: 20.3±1.0
40 GOF: 0.96 0.35
Model TL: 14.45±1.04
Measured TL: 14.12±1.20
C)60 GOF: 0.77
e (° 0.25
atur80
er
p
m
Te100 0.15
120
0.05
FK 89
Model Age: 19.5 FK 91
Measured Age: 19.4±1.2
0.30
40 GOF: 0.95
Model TL: 13.51±1.35
0.25
Measured TL:13.14±1.39
60
GOF:0.59
C) 0.20
e (° 80
atur 0.15
er
mp100 0.10
Te
120 0.05
FK 91
50 40 30 20 10 0
Time (Ma)
2 6 10 14 18
Length (µm)
Figure 5. On the left, the time-temperature (T-t) paths for samples FK88, FK89, and FK91 modeled by HeFTy (Ketcham, 2005)
using a Monte Carlo algorithm are shown. The software plots envelopes in a T-t space from the paths, for which all statistical
parameters of the models are either greater than 0.50, corresponding to “good” (purple area) fit, or above 0.05, corresponding to
“acceptable” (green area) fit. The solid black line shows the best-fit curve. On the right, the measured track-length distributions
are shown. ‘Model Age’ is the fission-track age predicted by HeFTy. ‘Measured Age’ is the pooled age from the measured data.
‘Model TL’ is the mean and standard deviation of the track-length distribution predicted by HeFTy. ‘Measured TL’ is the mean
and standard deviation of the measured track length distribution. ‘GOF’ defines the value of the goodness-of-fit between the
model and measured ages and length distribution.
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KARAOĞLAN / Turkish J Earth Sci
Konur Danacıobası HasandedeÇamsarı Durmuşlu Buzlukdağ Akdağ Karaçayır Kösedağ
58.5±3.1 58.1±4.8 59.3±2.2 59.8±5.3 61.0±5.4 58.2±2.1 31.6±1.6 59.5±2.8 29.7± 1.2
60.5±2.8 58.7±3.2 59.0±4.9 58.3±3.3 35.1±1.8 61.1±2.6 29.3±1.2
59.8±2.0 60.1±2.8 59.7±2.0 29.1±1.2
59.3±2.3 58.6±6.6 58.8±2.4 29.5±1.2
58.8±3.7 58.4±2.3 29.4±1.2
59.1±2.2 28.5±1.5
29.0±1.3
29.3±1.2
28.9±1.1
28.8±1.1
29.3±1.2
29.5±1.1
28.6±1.0
28.6±1.0
Baskil
40.1±5.1
46.9±8.2
14.6±2.5 13.8±3.1
13.4±2.2
Hamit
60.1±2.2
60.6±2.2
Baranadağ Çayağzı
59.8±2.3 60.8±5.3
60.2±2.2 61.9±9.1
57.2±1.8 60.5±8.5
58.3±2.4 59.3±5.3
58.1±2.2 59.9±5.3
58.5±2.0 58.6±2.3
58.8±2.8 60.5±3.5
58.7±2.0 60.0±9.3
Üçkapılı
Niğde 16.6±1.9 17.5±2.8
Baranadağ 12.0±1.0 12.8±1.6
39.2±6.0 12.3±2.7 11.9±1.6 13.9±2.1
47.0±3.2 11.6±0.8
10.8±0.9
Horoz 1152..72±±10..58 18.0±1.8
23.6±1.2 15.8±1.8
23.7±1.3
20.5±1.0
16.1±1.7
19.4±1.2 Esence
29.3±3.8
29.1±3.6
Doğanşehir
31.8±3.1
29.6±7.3
52.8±5.6
Figure 6. AFT age data from central and southeast Turkey. Inset map: Turkey, with dashed line box showing the outer map (map
data from Yılmaz, 1993; Boztuğ et al., 2004, 2009b and AFT data from Dilek et al., 1999b; Fayon et al., 2001; Boztuğ et al., 2004, 2008,
2009a, 2009b, 2009c; Boztuğ and Jonckheere, 2007; Umhoefer et al., 2007; Okay et al., 2010; Karaoğlan, 2012).
remained active to recent times (Toprak and Göncüoğlu, Bolkar Mountains, Ecemiş Fault Zone, and Karsantı Basin
1993; Tatar et al., 2000; Jaffey and Robertson, 2001, 2005; in the east, and the Bucakkışla region in the west and Mut
Gautier et al., 2002). After the formation of the Ulukışla Basin and Adana Basin in the south (Yetiş and Demirkol,
Basin, the Niğde Massif units experienced a burial event 1986; Görür, 1992; Dilek et al., 1999b; Clark and Robertson,
starting at the Middle Eocene, which raised temperatures 2002, 2005; Jaffey and Robertson, 2005; Şafak et al., 2005;
to over 120 °C, causing a resetting of AFT ages (Whitney et Alan et al., 2007; Derman and Gürbüz, 2007; Cosentino
al., 2003, 2008; Fayon and Whitney, 2007) (Figure 6). The et al., 2012; Esirtgen, 2014). Following the emergence, the
Anatolide-Tauride platform underwent an extensional ophiolitic rocks, which were emplaced onto the Bolkar
collapse during the Oligocene-Miocene. South-central Mountains during the Late Cretaceous, eroded in the first
Anatolia emerged above sea level during the Oligocene, order and fed the adjacent basins (i.e. Ecemiş Basin) (Jaffey
as demonstrated by the deposition of Oligocene terrestrial and Robertson, 2001, 2005). Braided rivers transported
sediments in the Ulukışla Basin between the CACC and the ophiolitic sediments to the Oligocene-Early Miocene
73