Int J Earth Sci (Geol Rundsch) (2004) 93:314–328DOI 10.1007/s00531-004-0390-y

O R I G I N A L P A P E R

Faruk Ocakoglu

Mio-Pliocene basin development in the eastern partof the Cappadocian Volcanic Province (Central Anatolia, Turkey)and its implications for regional tectonics

Received: 16 July 2002 / Accepted: 1 February 2004 / Published online: 20 March 2004� Springer-Verlag 2004

Abstract The Cappadocian Volcanic Province (CVP)comprises predominantly of a thick succession of vol-canogenic rocks and interbedded siliciclastic sediments ofMiddle Miocene to Recent age in Central Anatolia,Turkey. The conditions of basin development in theeastern part of the CVP have been elucidated by usingsedimentological and geomorphological approaches. Theprevailing tectonic regime, its extent and causes are alsodiscussed. Sedimentological analysis supported by geo-morphological observations revealed a major NE-trendingprobably normal, border fault and its several synthetics.This tectonic element constitutes the SE margin of thebasin and divided the CVP from the Tauride range duringMiddle Miocene to Pliocene. The basin fill in the studyarea comprises gravelly alluvial fans near the border fault,while fluvial clastics and lacustrine carbonates dominatetowards the centre. Some pyroclastic rocks and lava flowsare also made part of the fill. The southeastern basinmargin is characterized morphologically by a number ofuplifted basement blocks, probably associated with syn-thetic faults, and some deeply incised canyons in thefootwall. These canyons were subsequently filled with aMid-Pliocene ignimbrite sheet, and represent the sedi-ment supply conduits to the basin. The cessation of fillingin the basin was determined by strike-slip faults thatuplifted and detached the basin about 2.6 Ma. This datealso marks the onset of the neotectonic period in theregion. The overall extensional tectonic regime inferredfor the eastern CVP appears coeval with events recogni-sed in the southern basins, i.e. Adana and Mut Basins andthe eastern Mediterranean. Some physical connectionsbetween these basins also have been demonstrated. It issuggested that the CVP and the southern basins wereall created during a phase of extension resulting fromcontinued northward subduction of the African platebeneath the Eurasia during the Late Cenozoic.

Keywords Adana Basin · Basin development ·Cappadocia · Extension · Fault-controlled deposition ·South Central Anatolia

Introduction

In Central Anatolia, which forms part of a complexcollision zone within the Alpine-Himalayan collage, anextensive volcanic realm extends in a NE–SW directionfor more than 300 km parallel to the main regionalstructures (Fig. 1). Known generally as the CappadocianVolcanic Province (CVP), this realm comprises a Neo-gene-Quaternary succession of volcanic and siliciclasticrocks, and constitutes the central part of the AnatolianVolcanic Arc (Innocenti et al. 1975; Pasquar� et al. 1988;Dirik and G�nc�oglu 1996). The latter is generallyinterpreted as the consequence of the convergence be-tween Afro-Arabian and Eurasian plates in Tertiary times(Smith 1971; Dewey et al. 1973; Pearce et al. 1990;Yılmaz 1990).

The Cappadocian Volcanic Province, especially itscentral and western parts, has been investigated exten-sively for various objectives. Among others, geochrono-logical, geochemical and petrographical studies werecarried out on volcanics for the clarification of magmatichistory (Pasquar� 1968; Innocenti et al. 1975; Batum1978; Ercan et al. 1990; Temel et al. 1998; Aydar et al.1995; Le Pennec et al. 1994; Pearce et. al. 1990). Therelationship between magmatism and regional tectonicsalso has been evaluated (Toprak 1998; Yılmaz 1990;Pasquar� et al. 1988; Dhont et al. 1998). Geographicallymore comprehensive accounts of the basin, especially inthe west of the province, where large amounts of vol-canic materials are deposited, has also been considered bysome researchers (Dirik and G�nc�oglu 1996; Toprak andG�nc�oglu 1993; Pasquar� et al. 1988). However, theeastern sector of the Cappadocian Volcanic Province, i.e.to the east of the Erciyes stratovolcano, has attracted lessgeological attention. Following early work (Blumental1952; Pasquar� 1968), the area was re-examined for

F. Ocakoglu ())Department of Geological Engineering,Osmangazi University,Eskisehir, Turkeye-mail: focak@ogu.edu.tr

various purposes (coal exploration, geological map-ping and volcanologic investigation) by geologists fromMineral Research and Exploration General Directorate(MTA) in 1970s and 80s (Yigitel 1975; Erkan et al. 1978;Metin 1986; T�rkecan et al. 1998). These works aremostly unpublished but provide the detailed geologicalmaps of the eastern part of the CVP.

Although largely neglected up to now, the area fromYahyalı to Pınarbası, comprises a “frozen Mio-Pliocenelandscape”. The fault-controlled NE-trending basin mar-gin uplift, similarly running intrabasinal highs and deeplyincised valleys on the margin are the manifestations thatpreserved through the complex interplay between tecton-ics and erosion. Moreover, the well-exposed stratigraphicsequence in the area, dominated by coarse-grained sili-ciclastic rocks encourages the use of sedimentology as atool for elucidating the basin history. More importantlyfrom a geodynamic viewpoint, the position of the studyarea provides opportunities to assess the role of the CVPin models dealing with genesis and evolution of the southcentral Anatolian Basins (e.g. Kelling et. al. 2001). Therelation of the CVP to the larger scale depositional centresto the north, such as the Sivas Basin, has been discussedelsewhere (Dirik et al. 1999; Pasquar� et. al. 1988).However, the relationship of the extensional tectonicregime (although changing in stress orientation) prevalentfrom the Early Miocene up to the Recent in the Adana andMut Basins, and in the high Taurus Mountain Range(Ocakoglu 2001) with that of the CVP has not beenconsidered in detail (Pasquar� 1968). It is believed thatthe analysis of the more easterly basin considered in thispaper can also provide some insights concerning thisquestion.

Tectonic framework

Convergence between the Afro-Arabian and Eurasianplates from Mid-Cretaceous times onwards largely deter-mined the nature and timing of geological processes inthis part of the Alpine-Himalayan orogeny (Biju-Duval etal. 1977; Seng�r and Yılmaz 1981). The Eocene andEarly Oligocene correspond to the time of completeclosure of the northern branch of the Neo-Tethys ocean,by means of massive nappe movements southwards(forming the Taurus Mountain Range), and also witnessedcollision and total emergence of the Pontides (Seng�r andYılmaz 1981). Late Miocene-Pliocene times experienceda radical change in tectonic style all over Anatolia due toformation of the East and North Anatolian Fault zones,following the climax of collision between the Arabianpromontory and Eurasia (McKenzie 1972; Dewey et al.1973; Seng�r and Kidd 1979; Seng�r and Yılmaz 1981).As a result, the Anatolian plate was created, and thedominantly calc-alcaline Anatolian Volcanic Arc devel-oped on it, above the still-subducting oceanic slab of theAfro-Arabian plate (Innocenti et al. 1975; Pasquar� et al.1988).

Fig. 1 a Location of the Taurides; b Geological map of south-central Anatolia (simplified after the 1/2000000 scale GeologicalMap of Turkey; MTA 1989)

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The Cappadocian Volcanic Province represents thecentral part of the Anatolian Volcanic Arc, and has beenactive from Middle Miocene to Recent times (Pasquar� etal. 1988). The main depression, in which a dominantlyvolcanic succession accumulated, formed as a conse-quence of NW-SE extension (Toprak and G�nc�oglu1993; Toprak 1998; Pasquar� et al. 1988; Pasquar� andFerrari 1993; Dhont et al. 1998). The oldest volcanicrocks (the Ke�ikalesi and Kızıl�in volcanics) belonging tothe province are Middle Miocene (13.7–12.4 Ma) in age(Besang et al. 1977; Batum 1978). These, together withinterstratified fluvial-to-lacustrine sediments are consid-ered to have been deposited in a 50–60-km-wide exten-sional basin whose northern and southern margins weredetermined by the Central Kızılırmak Fault Zone and theNigde Fault Zone respectively (Fig. 2, Toprak andG�nc�oglu 1993). Having a strike of N35E, this latterzone comprises a group of steeply northward dippingfaults and is traced to the south of Nigde for more than100 km (Fig. 2c). In places, a vertical offset more than500 m has been recorded on some ignimbrite layers ofMio-Pliocene age (Toprak and G�nc�oglu 1993). Alsonoteworthy is the alignment of volcanic vents parallel tothe basin margin faults to the NW of Nigde (Fig. 2;Toprak 1998). The eastern part of the basin, where thepresent study focussed, appears to constitute the easterncontinuation of the southern margin (Fig. 2). Here thebasin fill is generally undeformed. The coarse-grainedalluvial-to-fluvial sediments, which are intercalated withsome pyroclastic rocks, are found at lower stratigraphiclevels. Upwards—and also northwestwards—lacustrinelimestone and mudstone appear (Pasquar� 1968). Thissuccession, presumably Middle Miocene-to-Early Plio-cene in age, is covered throughout the area by anignimbrite sheet 2.7–3 Ma old (Valibaba tepe ignimbrite;lnnocenti et al. 1975; Schumacher et al. 1990). Theignimbrite level serves as a key horizon useful forcorrelation over great distances, as well as for recon-structing the Mio-Pliocene palaeogeography. The basinfill is mostly horizontal, with the exception of theKaranfildag Fault Zone to the south where a lateraldisplacement of about 20 km in the Late Mioceneagglomerates has occurred (Fig. 3). As a whole, theMio-Pliocene basin filling episode was terminated in theMid-Pliocene, due to renewed E–W compression attribut-ed to Anatolian “escape” tectonics. Under this still-ongoing tectonic regime, the spectacular Erciyes strato-volcano and the related Sultansazlıgı depression havesubsequently developed (Toprak 1998; Toprak andG�nc�oglu 1993; Ko�yigit and Beyhan 1998; Erol 2001).

Mio-Pliocene basin evolution

Shape and extent

The Cappadocian Volcanic Province (CVP) expressesitself as a generally low-lying area (though containingvolcanoes over 3,000 m such as Mt. Erciyes and Melen-

diz) north of the NE-trending Tauride range (Fig. 2).Towards the northeast, volcanic rocks are less abundantand several uplifted carbonate basement blocks, partlysurrounded by Mio-Pliocene sediments, appear within thecorridor. The investigated area is situated in the easternpart of the CVP, and extends parallel to the mountainrange for about 80 km from the region SE of Mt.Develidag to Pazar�ren (Figs. 1, 2). Since this area alsocoincides with the course of the SW-flowing ZamantıRiver, the sedimentary cover is slightly eroded through-out, providing good exposures for sedimentological stud-ies. A sharp topographic break, having a strike of N35E,determines the eastern margin of the Mio-Pliocenesediments. This contact with the Tauride range is highlyindented due to heavy slope wasting and deeply incisedvalleys (Fig. 3). Two spectacular examples of the latter,either perpendicular or subparallel to the margin, arelocated near Ozluce and Arslantas in the central part. Thehigh altitude basement limestone within the corridor alsoexhibits deep erosion and subsequent filling by ignimbritesheets during the Pliocene (see the valleys near Hacıpasaand Kalek�y, Fig. 3). To the south of Deresimli, the trendand the morphological expression of the margin changeabruptly. Throughout the N55E-running contact with thebasement, the Mio-Pliocene sediments are folded andfaulted, signalling a large-scale dextral displacement ofthe NE basin margin in post-Mid-Pliocene times. Thisregional structure was previously named as the “Karan-fildag segment” of the Central Anatolian Fault Zone(Ko�yigit and Beyhan 1998) (Fig. 3).

Stratigraphy

The study area comprises a relatively thin succession(80–300 m) ranging in age from Middle Miocene toearly Late Pliocene, resting on a basement of Palaeo-zoic-Mesozoic carbonates and ultramafic rocks. Twoseparate outcrops expose brick-red mudstone-conglom-erate alternations in the central part near Deresimli andK�seler that are in thrust contact with underlyingophiolites (Fig. 3). This unfossiliferous unit lithologi-cally resembles the infill of the Oligocene KarsantıBasin and the Oligocene Selimiye formation of the SivasBasin (�nl�gen� et al. 1993; G�k�en and Kelling 1985),and probably belongs to the earlier compressionalhistory of the region. The Mio-Pliocene deposits showcomplex lateral and vertical facies changes, due bothto the nature of depositional environments and thepalaeotopography. The oldest rocks of the Mio-Pliocenebasin are the coal-bearing Yaylacık conglomerates,which were compared with the Yesilhisar conglomerates(Pasquar� 1968). The Yaylacık unit consists dominantlyof well-consolidated greyish to reddish conglomeratesinterbedded with reddish sandstone and siltstone, andsuch rocks are closely associated with the basin margin.They also crop out in the vicinity of the Karanfildagfault to the south (Fig. 3). Mammalian fossils discoveredin an abandoned coalmine south of Yaylacık (Sanraz

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Fig. 2 a Main tectonic ele-ments of Anatolia (NAF NorthAnatolian Fault, EAF EastAnatolian Fault); b Digital El-evation Model (DEM) of thesouth central Anatolia; c Lin-eaments drawn from DEM(CVP Cappadocian VolcanicProvince, KB Karsantı Basin)

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river) substantiate a Middle Miocene age for the lowerpart of this succession (G. Sara�, 2001, personal com-munication). Further SW, in the Dikme Basin (Fig. 1),the mammalian and marine faunas in this unit demon-

strate the existence of both Lower and Middle Miocene(Ocakoglu 2002).

Within the Yaylacık conglomerates, a pyroclastic unitwith a maximum thickness of about 40 m occurs. This

Fig. 3 Geological map of the investigated area. Map is compiled from the archives of Mineral Research and Exploration GeneralDirectorate (MTA), and revised by the author

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includes large (up to 1 m) olivine basalt blocks embeddedin a lapilli-sized pyroclastic material. Mapping the distri-bution of these volcanic bodies, two distinct pyroclasticcentres are inferred, each 3 km in diameters, in thevicinity of Bakırdag and Yaylacık (Fig. 3). To the NE,several elongated lava flows, 4 to 7 km long and 1 to 3 kmwide, probably related with a fissure eruption, are en-countered near Toklar, Kara�ren and Cinliyurt. These areblack olivine basalts exhibiting columnar jointing inplaces. Two large basaltic lava ridges near Toklar alsoshow distinct orientation in NE–SW and N–S directions(Fig. 3). Regarding the stratigraphic position and miner-alogical composition, the lava flows to the north and thepyroclastic cones to the south are thought to be correlative(see also Pasquar� 1968). A radiometric age of 7.9 millionyears (Tortonian) was obtained (D�nmez et al. 2003) forthe correlatives of these agglomerates from the Agcasarvillage in the Develidag complex to the West.

Lacustrine limestone appears above the Yaylacıkconglomerates, and sometimes rests directly over thebasement, depending on the palaeotopography. This unitreaches a maximum thickness of about 30 m, and iscomposed mostly of pisoids, in situ skeletal algae andtheir remains. The limestone is particularly widespread inthe north of the study area, and shows complex interfin-gering with the Yaylacık conglomerates. The Mid-Pliocene Valibaba tepe ignimbrite (Fig. 3) conformablyoverlies the lacustrine carbonates and their subaerialcorrelatives within the basin. At the sides of narrowpalaeovalleys (such as Arslantas and Hacıpasa), and nearthe basinal palaeohighs (eg. Kızıldag), it directly comesupon the basement rocks (Fig. 3). Towards the easternmargin, the ignimbrite sheet is covered by the alluvial andcolluvial fans that have been shed to the west from themountain front.

Sedimentology and basin fill architecture

The variations in sedimentary facies parallel and perpen-dicular to the eastern basin margin are shown (Figs. 4, 5).Although rapid facies changes frequently occur, thelacustrine unit and, more particularly, the ignimbritesheet form reference levels in this correlation.

A belt of Yaylacık conglomerates occupies the prox-imal parts of the NE margin, especially near the mouths ofcanyon-like valleys. Since the base of the measured logsis always taken at the basement contact due to smoothtopography, only a relatively thin (generally less than50 m) stratigraphic record could be analysed in the NE (Dto H in Fig. 4). These marginal facies are typicallycrudely stratified to massive, well-consolidated cobble toboulder conglomerates. The colour is dominantly grey.Their clasts are moderately rounded, and derived mostlyfrom recrystallized limestone and ultramafic rocks to theeast. Large blocks of basalt are also encountered nearToklar (Fig. 3). Thin, laterally discontinuous (pinchingout over several metres) sand lenses, less than 10 cmthick, are frequently interbedded within the gravelly

package. In the vertical organisation, 2–3-m-thick grav-elly sands are also encountered in places. In rare cases,some of these sandy intervals are loose and include tracesof vertical plant rootlets (K���kcanlı section, Fig. 4).Proceeding way from the margin towards the west, thegrain size of the Yaylacık conglomerates considerablydecreases over several kilometres, accompanied by achange of sedimentary facies (Fig. 4, Culha, Hankoy andCinli Magara sections). As a result, almost half of thesection comprises phytoturbated massive gravelly sand-stone, and mudstone in the �ulha area. Proceeding north,and also away from the basin margin, the basin fillsimilarly becomes finer material, and is composed mostlyof caliche-bearing red/grey mudstone and channelisedsandstone and conglomerates (Fig. 4). Towards the SWbasin margin, where the whole stratigraphic record hasbeen uplifted due to post-Mid Pliocene structure (Fig. 3),the marginal areas are represented by similar sedimentaryfacies, although their thickness varies considerably inaccordance with the initial topography, rate of sedimentsupply and subsidence. In areas close to the basin margin,alluvial fan conglomerates make up the bulk of thesuccession, attaining 310 m thickness in places (I inFig. 5). Although some fining upward cycles are apparent,the majority of the section is composed of massive-to-crudely bedded boulder conglomerates. Oblique to thebasin margin, grain size decreases considerably towardsthe Yaylacık section where a thin coal seam (30 cm)occurs within the interbedded sandstones and conglom-erates (B in Fig. 5). Thin red mudstones and cross-stratified conglomerates are also frequent in this area.

On the basis of the observed facies, the Saraycık,Sorkun Dere, K���kcanlı and the lower coarse part of theTafdere sections are interpreted as proximal braided riverdeposits, mainly bars and limited overbank areas. Dom-inantly finer grained deposits nearer the basin centre(Hankoy and Cinli Magara sections, Fig. 4) probablycorrespond to extensive floodplain and related fluvialchannel and overbank systems. Distribution of the faciesindicates a passage to the distal reaches of the alluvialfans.

Two arrays of measured sections show facies changesfrom the basin margin towards the basin interior (Fig. 5).In the north (Fig. 5, logs N-S), the channelised conglom-erates alternate with red mudstones near the basin margin,while thick algal limestone occurs towards the basincentre. Palaeocurrent measurements deduced from gravelimbrication and cross-bedding are consistent (flow toNW) with this facies distribution (Fig. 5). In the south, thethick alluvial fan conglomerates already mentioned (I inFig. 5) pass northwestwards (away from the basin margin)into relatively fine-grained thinning and thickening up-ward cycles. The gravels are mostly pebble-sized, and aconsiderable amount of sand and mud grade material isfound within the cycles. In certain intervals laterallydiscontinuous lignite beds and fossiliferous marls alsooccur. In this medial area the sequence is capped bylacustrine limestone with abundant algal remains (K inFig. 5). Further NW, in the Bakırdag section, the grain

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Fig. 4 Correlation of sedimentological logs parallel to the basin margin

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Fig. 5 Two arrays of sedimen-tological logs across the basinfrom margin to centre of thebasin (I-M in the south; N-S inthe north; for legend see Fig. 4)

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size decreases to sand-pebble grade at the base, and verywell rounded gravels show abundant bedforms (mainlyplanar cross-bedding, large scale epsilon cross-bedding).A 50-m-thick agglomeratic package is sandwiched withinthese conglomerates, and hence is overlain by coal-bearing fossiliferous mudstone, limestone and finer con-glomerates. Upwards, two distinct intervals of boulderconglomerate with different textures and directions oftransport sit on the underlying fine-grained sediments(Fig. 5, Bakırdag section 120–160 m). Lastly, in thewesternmost area, the Beskardesler section includes 20 mthick fossiliferous marl, certain levels of which turn toblackish organaceous mud. All these sediments arecovered conformably by the widespread Valibaba tepeignimbrite.

In this southern sector of the basin, the thick Saraycıksection is interpreted as proximal braided river facies,probably related to alluvial fans. As indicated bypalaeocurrent directions, the whole system flows north-westward. The system passes first to distal fluvial facies(with finer grained gravels and well developed finingupward cycles) in the base and medial part of theBakırdag section, and then to lacustrine facies in theBeskardesler section.

To conclude, the eastern basin margin of the CVP ischaracterized by coarse-grained conglomeratic facieswhose age ranges from Middle Miocene to LowerPliocene. Regarding the sedimentary facies, they showevidence of deposition by braided rivers in proximalreaches of alluvial fans, and some of their main canyons(see the following chapter) are still preserved in theTaurus basement. In the downfan direction, a decrease inthe thickness of coeval deposits is typically accompaniedby fining of maximum clast size. As a result, lacustrinefacies are observed in areas distant from the basin margin.

Preserved morphological features of the basin

The eastern CVP includes several geomorphologicalevidences explaining the dynamics of the basin develop-ment. They are found both in the margin and within thebasin.

The eastern margin of the basin manifests itself as amorphologically mature, highly sinuous uplift, cut bydeeply incised canyons excavated into the Tauride cal-careous basement (Figs. 2, 3). Kilometer-size ellipsoidalbasement highs (such as Kızıldag and B�y�kkızıldag) onthe downthrown block elongated parallel to the basinmargin are also prominent (Fig. 3). Field observations andmap inspections indicate that the base of the mountainfront is mantled by alluvial and colluvial fans, whichcoalesce to form a continuous belt of mountain-toesediments (Fig. 6). Colluvial fans have rather smallercatchment areas, while the alluvial fans drain larger areas,and have typical lobe shapes, 2–3 km in diameter. Thealluvial fans are dissected by deep channels and arecurrently under erosion. In addition to these depositionalfeatures, the canyons and their extension towards the

basin interior confer a highly indented appearance on thebasin margin. These canyons are situated sub-parallel tosub-perpendicular to the basin margin, and probablycorrespond to the feeder systems of the ancient largeralluvial fans. The Arslantas canyon, a spectacular exam-ple, has a sub-perpendicular outlet to the basin (Fig. 7).Towards the mountain front, a sudden change in thedirection of the canyon occurs, although there are stillsome smaller feeder channels from the east. The canyonextends for 9 km in this manner towards northeast (to theeast of the Arslantas Village), and then turns eastward toterminate against the mountain front. The canyon fillcomprises a relatively thin sequence, several tens ofmetres of well-consolidated boulder conglomerates at thebase, and the overlying ignimbrites. Observations on theSW margin of the canyon reveal NE-trending faults andrelated slivers of ophiolites. The �zl�ce canyon, furthernortheast, constitutes another feeder system (Fig. 7). Itruns eastward, sub-perpendicular to the basin margin for7 km, and has a similar fill. The gray-coloured, 40-m-thick boulder conglomerates overly unconformably thelimestone basement, and in turn overlain by the ign-imbrites. Both cover units are dissected down to ancientvalley floor by the recent fluvial system (Fig. 7c).

Another systematic morphologic feature is the pre-ferred alignment of variously-sized spherical to ellip-soidal basement blocks on the hanging wall of the mainbasin margin fault. From SW to NE, these highs areKızıldag, B�y�kkızıldag, Kocadag and another unnamedhill to the east of �zl�ce (Figs. 3, 7). These appear tocorrespond to the eroded and partly buried shoulder of thehanging wall block, under the basin margin coarsesediments. A very similar geometry, if not identical, isseen just to the east of B�y�kkızıldag, where the Elkıranuplift was surrounded by canyon fill to the southeast, andby the main basin fill to the northwest (Fig. 7).Thegeomorphological features within the basin comprise theHacıpasa and Yenik�y basement highs with the preservedpalaeovalleys on them, and the Toklar elongated volcanicridges. The Hacıpasa basement uplift has a NNW-strikinglinear contact, probably faulted against the overlyingignimbrite. The ignimbrite sheet fills also a maturepalaeovalley heading up to the Hacıpasa village perpen-dicular to the contact for 10 km (Fig. 3). The Yenik�ybasement high is bordered to the west by Develidagvolcanics (lava flows and pyroclastic rocks). To the east,a network of mature valleys filled with reddish muds andoverlying ignimbrite justify again the antiquity of therelief (Fig. 3).

In the literature, similar buried landforms under thesheet of ignimbrite flows exist. The “Valley of TenThousand Smokes” ignimbrite that flowed for 22 kmdownstream in a 2-km-wide valley is a prominentexample (Curtis 1968). The Valibaba tepe ignimbritewhose source is situated 80–90 km to the north in theKayseri area (Pasquare et al. 1988) seems more spectac-ular, filling not only the parallel-to-flow valleys but alsothe perpendicular-to-flow valleys as the cases in theHacıpasa and Yenik�y areas. Regarding the mobility of

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flow, the Valibaba tepe ignimbrite is modest, surmountingonly 100 m high relief in the Bakırdag area (Fig. 3). Amagnificent example from Japan, the Ito pyroclastic flow(Yokoyama 1974) climbs the obstacles higher than 600m, probably due to larger volume and close distance toobstacles with respect to Valibaba tepe example.

The Toklar elongated volcanic edifices comprises twoelongated lava flows (Fig. 3). The smaller volcanicedifice borders the Toklar village and extends for 4 km.The greater volcanic structure is found just to the NE andruns northwardly for 7 km. It creates a 200-m-high relief

within the basin. Both volcanic edifices are envelopedunconformably by the fluvial conglomerates.

Tectonic control during the basin development

The revealed sedimentary architecture and facies distri-bution of the basin fill strongly suggest a NE-trendingfault-controlled basin margin, whose southwestern partwas dissected and translated dextrally for more than20 km by the post-Mid-Pliocene strike slip KaranfildagFault Zone (Ocakoglu 2001).

Fig. 6 a Detailed geology andmorphology of the basin marginin the central part; b I-I’ geo-logical section; c Postulated re-construction of palaeomorpho-logical features (For legend seeFig. 3)

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The well-preserved morphological elements associatedwith the main basin margin are thought to be generatedwithin an overall extensional tectonic regime (Fig. 8).Taking into account the still-preserved morphologies ofalluvial and colluvial fans, and the location of elongatehighs developed on the hanging-wall adjacent to mainfront, it is clear that the major basin margin fault issituated just at the toe of the mountain front. Throughoutthe considerable length of this structure, ophiolites andrecrystallized limestones abut each other, indicating thatthe ophiolites were initially sheet-like slivers of signifi-

cant extent, which subsequently dismembered by almostvertical basin margin faults. Additional evidence clearlydemonstrates the occurrence of synthetic faults both in thebasin and in the hinterland (Fig. 8). The 4 km long NE-trending volcanic ridge near Toklar is interpreted as themanifestation of a parallel fracture zone within the basin.Another elongated volcanic edifice just to the north has aN–S axis, and is likely linked with another extensional ortranstensional structure. The most prominent of thesynthetic lineaments in the hinterland delimits the Ar-slantas valley. This valley runs parallel to the main basin

Fig. 7 a Appearance of the SE basin margin and the palaeo-valleys on Digital Elevation Model; b Geological map of the same (for legendsee Fig. 3). c I- I’ geological section of the �zl�ce palaeo-valley

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margin, and is filled with Pliocene conglomerates andignimbrites. Equally prominent features that delimit thetwo larger intrabasinal basement uplifts (the Hacıpasa andunnamed one north of the study area) on their SWmargins (Fig. 8) seem to be strike-slip faults with aconsiderable dip-slip normal offset. The Hacıpasa palaeo-valley is developed perpendicular to the SW faulteduplifted margin. The Late Miocene-aged pyroclasticbodies near Bakırdag and Yaylacık may be also relatedwith this lineament. The resulting picture of the natureand distribution of tectonic controls operating during thedevelopment of the eastern CVP is best explained interms of a regional extensional regime (Fig. 8) with anextension direction of N55 W. The N35E-striking fault setcorresponds to pure dip-slip normal faults.

Discussion

The development of the Anatolian Volcanic Arc, not onlyrequires northwards subduction of an oceanic slab be-

neath the Eurasian plate, but also implies an overallextensional tectonic setting as indicated by the alkalinecharacter and geochemical signature of the volcanics(Innocenti et al. 1975; Temel et al. 1998). A majortectonic control on volcanism has been exerted by N 58–80 E-trending lineaments, termed the “East Anatolian set”in view of the parallelism to the East Anatolian FaultZone (Pasquar� et al. 1988). Subsequently, basin analysisto the west of the Ecemis Fault zone identified a 50–60-km-wide, NE-trending extensional basin in which themajority of the Mio-Pliocene volcanics were accumulated(Toprak and G�nc�oglu 1993; Dirik 2001). In the EcemisFault Zone, Late Miocene deposits that overlay uncon-formably an Oligo-Miocene succession of deformed stratain a NW-SE directed compressional stress frame weredocumented (Jaffey and Robertson 2001). Although theyfavoured a transtensional setting for this poorly dated LateMiocene succession by interpreting subsidence curves, itseems that they are lithological equivalent of thoseobserved in the central CVP (Toprak and G�nc�oglu1993). More controversially, in recent years it has been

Fig. 8 Depositional model andtectonic controls in the eastern-most part of Cappadocian Vol-canic Province

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suggested that the tectonic activity and associated depo-sition in that trough were re-arranged in Mid-Pliocenetimes when the NNE-striking Central Anatolian FaultSystem was initiated (Toprak 1998; Ko�yigit and Beyhan1998; Ko�yigit and Erol 2001).

The results obtained in the present study of the regioneast of the CVP, closely resemble those from morewestern areas. The direction of the control faults, as wellas their nature, is similar, i.e. NE-trending extensionalfaults. The architecture of the dominantly siliciclasticinfill, and the preserved palaeo-morphology, which isgenerally less evident to the west, due to the intensevolcanic activity, yield convincing evidence for a dom-inantly extensional basin during this magmatic phase.Additionally, the deformation history of this sector of thebasin matches well with the western part.

However, fundamental questions arise regarding thedistribution of this extensional regime, its position in theoverall structural framework of south Central Anatolia,and its ultimate cause(s). The early plate tectonic inter-pretations regarded this basin, like all others in CentralAnatolia, as a product of escape tectonics, which wasbelieved to have commenced in the late Serravalian-earlyTortonian (Seng�r and Yılmaz 1981). Later studies haveadvanced this date (which corresponds to the initiation ofthe East Anatolian Fault Zone-EAFZ) to Mid-Pliocenetimes (~2,6 Ma) (Toprak 1998; Ko�yigit and Beyhan1998; Ko�yigit and Erol 2001), although the ancestor ofthe EAFZ, the Malatya-Ovacık Fault, is believed to beslightly older (~5 Ma) (Westaway and Arger 2001).Hence, genesis of the CVP and related basins by escapetectonics appears unlikely. Instead, a comprehensive eval-

uation of the CVP should take into account all the coevalbasins and tectonic lineaments on a regional scale(Fig. 9). As the main components of the first category,the Adana and Mut Basins to the south and the SivasBasin to the NE were active during the Middle Miocene-Pliocene interval. The coeval structural belts on the otherhand were the Central Anatolian Fold- and-Thrust Belt tothe north, the Bitlis Suture and its western extension (theMisis-Andırın-Kyrenia lineament), and the Dead SeaFault Zone further south (Fig. 9).

The extensional origin of the Adana Basin and itscoeval evolution with the Mut Basin to the west is widelyaccepted in the Taurus literature (G�r�r 1992; Williamset al. 1995; Kelling et al. 2001), although the overalltectonic setting remains controversial. A recent study(Ocakoglu 2002) in the high Taurus Mountains (NEAladag) as a key area identified a coeval south-facingextensional basin with Middle Miocene marine interca-lations (Dikme Basin (DB), Fig. 9). The stratigraphic/structural connection of this basin with the successions inthe eastern CVP reported here, and the subsequent upliftand disintegration of the Dikme Basin due to escape-related post-Mid-Pliocene tectonics were also document-ed (Ocakoglu 2001). These observations, coupled with theresults of the present study enable a common evolutionaryline between these two realms to be identified.

As to the Sivas Basin (Fig. 9) which was initiated as aforeland basin through closure of the Erzincan suture(G�r�r et al. 1998), the Miocene evolution of this easternregion is governed by extensional tectonics up to thePliocene (Poisson et al. 1996). The geochemical imprint(the elevated values of La/Nb, Th/Nb, K2O/P2O) of the

Fig. 9 Major sedimentary ba-sins and controlling structurallineaments in south CentralAnatolia during Mio-Pliocenetimes ( CVP Cappadocian Vol-canic Province, SB Sivas Basin,AB Adana Basin, MB Mut Ba-sin, DB Dikme Basin, CAFTBCentral Anatolian Fold andThrust Belt). Map is compiledfrom MTA 1989; Toprak andG�nc�oglu 1993; Ocakoglu2002. Inset map denotes theposition of the Anatolian Vol-canic Arc (after Dhont etal.1998)

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Middle Miocene volcanic rocks within the basinal suc-cession of the Sivas Basin implies subduction-relatedmagma sources with variable degrees of crustal involve-ment (Parlak et al. 2001), a pattern similar to that of theCVP (Temel et al. 1998).

All this information fit into a simple regional model,parts of which have been put forward by several previousresearchers (Fig. 9). This model comprises the Bitlissuture and its westerly oceanic continuation beneathMediterranean, and wide extensional basins realm tothe original north (Adana, Mut and CVP-related basins)that was diachronously formed from Late Oligocene toPliocene times, in response to ongoing subduction. Ex-tensional tectonics and exhumation of the Nigde massif inthe central region was previously explained by roll-backof the subducting oceanic slab, while the uplift of themountain front was ascribed to the thermal effect of thethinned lithosphere (Whitney and Dilek 1997; Dhont et al.1998). This geodynamic picture was terminated in Mid-Pliocene times by major strike-slip movements through-out the region (Toprak 1998; Ko�yigit and Beyhan 1998;Ko�yigit and Erol 2001).

Conclusions

The basin history of the eastern part of the CappadocianVolcanic Province (CVP) has been elucidated from adetailed study of its sedimentology, geomorphology andtectonics. Evaluation of the sedimentary fill, from theviewpoint of geometry and sedimentary processes, sug-gests that the basin was defined by a N35E-trendingmaster border fault and several synthetic splays, and wasfilled with terrestrial deposits (mainly coalescing alluvialand colluvial fans) from Middle Miocene to Mid-Pliocenetimes. Two separate Tortonian-aged agglomerate bodiesand their lava correlatives also interfingered within thebasinal succession. The whole basin fill was covered by aMid-Pliocene ignimbrite sheet. Geomorphological data,especially deeply incised palaeo-valleys (filled withignimbrites) cutting through the basin margin, substanti-ate this tectonic element as a regional feature whichseparated the CVP from the southern sedimentary basinssuch as those of Adana and Mut during the MiddleMiocene-Pliocene interval. The ENE-trending strike-slipKaranfildag fault dissected the basin fill just following theignimbrite deposition, probably 2.6 Ma. This representsthe onset of neotectonic period and erosion in this part ofthe CVP. Taken in conjunction with existing studies ofcentral Anatolia, these results suggest that extensionaltectonics probably driven by continuing northwards sub-duction of the African plate beneath the Eurasian plate,was responsible for basin initiation and developmentthroughout this region, prior to the inception of Anatolianescape tectonics.

Acknowledgements This study was carried out as a part of the“Mining Geology of Eastern Taurides” Project in behalf of MineralResearch and Exploration General Directorate (MTA). I am in-

debted to Dr. M. Senel, the chief of the project, for his encour-agements. I extend my special thanks to Prof. G. Kelling whoimproved the text both scientifically and grammatically.

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