Emplacement of volcanic vents and geodynamics of Central Anatolia, Turkey

22 Pages·1998·3.53 MB·English

JournalofVolcanologyandGeothermalResearch85(cid:14)1998.33–54
Emplacement of volcanic vents and geodynamics of Central
Anatolia, Turkey
D. Dhont a,), J. Chorowicz a, T. Yu¨ru¨r b, J.-L. Froger c, O. Ko¨se b, N. Gu¨andogdu b
De´partementdeGe´otectonique,ESA-CNRS7072,case129,Uni˝ersite´Paris6,4placeJussieu,75252Pariscedex05,France
bDepartmentofGeology,HacettepeUni˝ersity,Beytepe,Ankara,Turkey
c CentredeRecherchesVolcanologiques,Uni˝ersite´BlaisePascal,5rueKessler,63038ClermontFerrand,France
Observations on Synthetic Aperture Radar ASbAsRtracstc(cid:14)enes .of the European Remote Sensing ERS sa(cid:14)tellite.and Digital
Elevation Models (cid:14)DEMs., complementedby field structural analysis permit a new understandingof relationshipsbetween
tectonics and volcanism since the late Miocene (cid:14)10 Ma. in Central Anatolia. Volcanic edifices form elongate stratovolca-
noes,linearclustersandvolcanicridges.Theyindicateemplacementontensionfracturesandtail-crackorhorsetailfeatures.
Forinstance,theKaraDagvolcanoisrootedonatail-crackwhichaccommodatesahorizontalleft-lateralthrowcomponent
at a fault termination. Caldera complexes of Cappadocia are associated with horsetail fault patterns. The emplacement of
volcanoesalsobenefitsfromlarger-scaletectonicstructures:theErciyesDagvolcanoislocalizedbytheSultanSazreleasing
bendwhichopensalongthesinistralstrike-slipEcemisfault.Deformationhasbeenanalysedfromtensionfractures—which
areperpendiculartothedirectionof extension—andfromfieldstructuralanalysis. Ona regionalscale, thetectonicregime
responsible for the distribution of volcanic vents in this area of convergence and lateral extrusion, is not compression but
extension. The Central Taurus range is the thermally uplifted shoulder of the Adana–Cilicia basin, which is related to
lithospherethinning.Westwardmovementsinthenorthwesternpartofthestudiedareaareinfluencedbytheactiveback-arc
Aegean extension situated to the west. Farther to the south, the direction of motion turns southwest and south, under the
influenceoftheopeningoftheAdana–Ciliciabasin.WeinterpretedthatextensionintheCentralAnatolianplateauisrelated
tocrustalblocksmovingabovesub-horizontaldetachmentsurfaceslocatedinthelowercrust.Thisisbasedonseveralfacts:
¨ ¨ ¨ ¨
otherwise it would have been bordered by thermally uplifted shoulders; movements change trend within a small (cid:14)50 km.
region. q1998ElsevierScienceB.V. All rightsreserved.
Keywords:CentralAnatolia;Taurus;neotectonics;volcanism;tensionfractures;detachment;satelliteimagery;DEM;faultmechanisms
1. Introduction and types of volcanic vents provides information on
the geodynamics (cid:14)e.g., Dengo et al., 1970; Stoiber
Observation of geometric relationships between
and Carr, 1973; Nakamura, 1977; Hamilton, 1979;
volcanism and tectonics is a fruitful approach in
Chotin et al., 1980; Francis, 1993.. On the other
geology. On one hand, analysis of the distribution
hand, tectonic analysis explains the location of vol-
canic vents, related for instance to tension fractures
)Corresponding author. Tel.: q33-1-44275089; Fax: q33-1- e.g., Nordlie, 1973; Opheim and Gudmundsson,
44275085;E-mail:[email protected] 1989; Takada, 1994; Koyaguchi and Takada, 1994;
0377-0273r98r$19.00q1998ElsevierScienceB.V.Allrightsreserved.
PII: S0377-0273(cid:14)98.00048-1
34 D.Dhontetal.rJournalofVolcanologyandGeothermalResearch85(1998)33–54
Chorowicz et al., 1997., fissures (cid:14)e.g., Macdonald, tolia and Africa–Arabia, and Eocene–early Oligo-
1972., pull-apartstructures(cid:14)e.g., Bellierand Sebrier, cene (cid:14);30 Ma. collision and emersion in the Pon-
1994., rifting (cid:14)Smith et al., 1995. or reactivation of tides (cid:14)Sengo¨r and Yilmaz, 1981.. Red Sea continen-
ancient faults (cid:14)N’ni et al., 1986; Deruelle et al., tal rifting and individualization of Arabia began at
1987; Brousse and Lefe`vre, 1990.. the Oligocene–Miocene boundary (cid:14)Le Pichon and
Recent and active tectonic and volcanic features Gaulier,1988..Inthemid-Miocene(cid:14);13Ma.,initi-
have distinct geomorphic expressions. High ground ation of left-lateral motion along the Dead Sea Fault
resolution (cid:14)10–30 m. satellite images and Digital zone occurred (cid:14)Joffe and Garfunkel, 1987., coeval
ElevationModels(cid:14)DEMs.expressthelandformsand with collision in the Eastern Taurus and related
yield synoptic views, permitting detailed mapping westward lateral extrusion of Anatolia bounded by
over large surfaces. Shadowed DEM images have theNorthandEastAnatolianfaults(cid:14)McKenzie,1972;
proved to be efficient in structural analysis (cid:14)Choro- Dewey et al., 1973; Sengo¨r and Kidd, 1979; Sengo¨r
wicz et al., 1995a,b.. Images acquired by the Syn- and Yilmaz, 1981; Yilmaz, 1993.. Subduction in the
thetic Aperture Radar (cid:14)SAR. of the European Re- Aegean region initiated during the late Miocene (cid:14)Le
mote Sensing (cid:14)ERS. satellite are particularly sensi- Pichonand Angelier, 1979;Lyberis, 1985.. We shall
tive to variations in ground slope. consider the late Miocene (cid:14);10 Ma. to present-day
The Central Anatolian region in Turkey (cid:14)Fig. 1A. time globally and take into account only finite dis-
has been subjected to deformation and volcanism placements and deformation during this interval.
over the past 10 Ma (cid:14)Innocenti et al., 1982; Sengo¨r
et al., 1985; Pasquare` et al., 1988; Aydar, 1992;
2.2. Regional geology
Temel, 1992; Aydar et al., 1993; Le Pennec et al.,
1994.. This region is part of the Anatolia block
which is moving westward by lateral extrusion as a Themostprominentrecenttectonicfeaturesofthe
consequence of north–south convergence between studied area are the Tuz Go¨lu¨ and Ecemis fault
Africa–ArabiaandEurasia(cid:14)McKenzie,1972;Sengo¨r zones, the Central Taurus range and the Adana basin
et al., 1985; Dewey et al., 1986.. The aim of this (cid:14)Fig. 1B.. They overprint crystalline and Mesozoic–
paper is to analyze the emplacement of volcanic Paleogene sedimentary or metamorphic rocks de-
vents and tectonics in Central Anatolia, using satel- formed in late Eocene–early Oligocene times (cid:14);30
lite and DEM images, complemented with field Ma. by folds, thrusts and transcurrent faults.
structural analysis. We shall argue that regional vol- VolcanisminCentralAnatoliahasdevelopedsince
canism in Central Anatolia is associated with exten- the late Miocene (cid:14)Innocenti et al., 1975, 1982;
sion, not compression. Pasquare` et al., 1988.. This volcanism has been
considered to be related to compression (cid:14)Pearce et
al., 1990; Yilmaz, 1990. but it may also be the
2. Regional structural framework
consequence of regional extension (cid:14)Temel, 1992.. It
has mainly produced calc-alkaline rocks (cid:14)Innocenti
2.1. Geodynamic context
et al., 1982. and has been interpreted as an arc
Convergence between Africa–Arabia and Eurasia related to the north-dipping oceanic slab of the
(cid:14)Fig. 1A.beganinthemid-Cretaceousataround100 African plate (cid:14)Innocenti et al., 1975, 1982. (cid:14)Fig.
Ma (cid:14)Biju-Duval et al., 1977; Livermore and Smith, 1A.. The volcanics comprise late Miocene stratovol-
1984; Yazgan and Chessex, 1991., inducing Campa- canoes (cid:14)e.g., Melendiz Dag., late Miocene–Pliocene
nian–Maestrichtian(cid:14);70Ma.obductionsoverAna- ignimbritic units of Cappadocia (cid:14)Le Pennec et al.,
Fig.1.(cid:14)a.GeodynamiccontextofCentralAnatoliasincethelateMiocene.LargearrowsshowAfrica–ArabiaandAnatoliaplatemotions
relativetoEurasia.Thicklines:plateboundaries.Rectangle:locationof(cid:14)b..DSF:DeadSeaFault;EAF:EastAnatolianFault;NAF:North
AnatolianFault.(cid:14)b.GeologicsketchmapofCentralAnatolia,compiledfromthe1r2,000,000geologicalmapofTurkey(cid:14)MTA,1989..DD:
Develi Dag volcano; DF: Derinkuyu fault; ED: Erciyes Dag; HD: Hasan Dag; KD: Kara Dag; KcD: Karaca Dag; KoD: Koc¸ Dag; MD:
MelendizDag.
D.Dhontetal.rJournalofVolcanologyandGeothermalResearch85(1998)33–54 35
36 D.Dhontetal.rJournalofVolcanologyandGeothermalResearch85(1998)33–54
1994.,Quaternarystratovolcanoes(cid:14)e.g.,ErciyesDag, Ma.,depositedinthezonewheretheAfricanplateis
Hasan Dag. and scattered vents of mafic or acidic subducting underneath Anatolia (cid:14)Jackson and
volcanism. McKenzie, 1984; Karig and Kozlu, 1990.. These
The NW-striking Tuz Go¨lu¨ fault zone forms the rocksareoverlainbyMessinian(cid:14);6Ma.evaporites
northeasternboundaryoftheTuzGo¨lu¨ basin(cid:14)Arikan, and Pliocene(cid:14);5–2 Ma. marinesediments(cid:14)Kelling
1975; Go¨ru¨r et al., 1984; MTA, 1989., situated at etal.,1987..Thebasinemergedfrombelowsea-level
mean elevation 1000 m. The basin forms a in the Quaternary but remains a low plain. In late
northeast-dipping half-graben, infilled with 2000 m Miocene–Plio-Quaternarytime(cid:14)since ;10Ma., the
of Neogene sediments and volcanics, lying above Adanabasinmayberegardedasapull-apart(cid:14)Sengo¨r
several thousand meters of Eocene–Oligocene sedi- et al., 1985; Dewey et al., 1986. or a releasing bend
ments.SouthwestoftheHasanDagvolcano,theTuz basin (cid:14)Chorowicz et al., 1994a,b., developed along
Go¨lu¨ basin is partly overlain by volcanoes which faults which mark the prolongation of the left-lateral
form a NE-trending belt that extends as far as the East Anatolian fault, related to the lateral expulsion
Kara Dag stratovolcano in the SW. The Tuz Go¨lu¨ of Anatolia (cid:14)Fig. 1A..
basin is bordered to the northeast by the Nevsehir Accordingto Sengo¨r et al. (cid:14)1985., Central Anato-
plateau and the Kirsehir massif, with crystalline lia presently undergoes moderate NE–SW-trending
basement rocks at mean elevations up to 1200 m, compression, but Pasquare` et al. (cid:14)1988. and Toprak
overlain by volcanic materials up to 2700 m at the and Go¨ncu¨oglu (cid:14)1993. have associated the Central
summit of the Melendiz Dag. Anatolia grabens with a late-Miocene to early
The Ecemis fault zone strikes northeasterly in the Pliocene (cid:14);10–4 Ma. east–west-trending tension.
north and turns around the transtensive (cid:14)Pasquare` et Pasquare` and Ferrari (cid:14)1993. and Borgia et al. (cid:14)1994.
al., 1988. Sultan Saz basin to strike NNE further have suggested that there is a N-trending, 100-km-
south where it cuts the Central Taurus range. The long, buried graben in the central part of the Nevse-
Ecemisfaultzonecomprisesinthesouthanarrow(cid:14)1 hir plateau and that the Tuz Go¨lu¨ and Ecemis faults
km. strip of Paleocene(cid:14)?.–Lutetian marl and sand- are reverse faults formed as a result of the intrusion
stone, interbedded with clastic and detrital marine of a large batholith.
limestone, disconformably overlain by Oligocene to
Quaternary continental detrital and evaporitic rocks
(cid:14)Yetis,1984..TheEcemisfaultzonecutsthrust-units
emplaced during the late Eocene–Oligocene (cid:14);30 3. Data and methodology
Ma. compressive event. It may have accommodated
about 80 km of left-lateral slip motion since the
Eocene and is considered to be still active (cid:14)O¨zgu¨l, 3.1. Data
1976; Scott, 1981; Sengo¨r and Yilmaz, 1981..
The Central Taurus range has been raised since A DEM of the whole area has been developed
the late Miocene (cid:14)O¨zgu¨l, 1976.. It is made up of using a kriging method, from the digitization of
marine lower to middle Miocene sediments now at elevation contour lines (cid:14)25 to 100 m vertical contour
elevations of more than 2000 m, which uncon- intervals. of nine topographic maps at 1r250,000
formably overlie ophiolites and platform carbonate scale. It covers 260=320 km with 500 m horizontal
rock units thrust during the Late Eocene–Early ground resolution (cid:14)Fig. 2..
Oligocene (cid:14);30 Ma. event. WehaveanalyzedfourERS-1SARimages(cid:14)Figs.
The Adana basin is partly filled with turbiditic 3–6.. We applied standard processing to generate an
rocks spanning from Aquitanian to Tortonian (cid:14)24–8 image from each original digital scene covering 100
Fig.2.Shadowedimage(cid:14)a.oftheDEMofthestudiedarea,at500mhorizontalgroundresolution,illuminatedfromsouth,andstructural
interpretation(cid:14)b..A:Aksaray;B:Bor;DF:Derinkuyufault;ED:ErciyesDag;F1andF2:inactivefaults;FT:normalfaultsoftheCentral
Taurusrange;GF:Gumuskentfault;HD:HasanDag;KD:KaraDag;MD:MelendizDag;RB:rhombshapedbasins;S:Sereflikoc¸hisar;
SSB:SultanSazbasin;TGF:TuzGo¨lu¨ fault.X:theTuzGo¨lu¨ faultterminationsagainsttheEcemisfault.
D.Dhontetal.rJournalofVolcanologyandGeothermalResearch85(1998)33–54 37
38 D.Dhontetal.rJournalofVolcanologyandGeothermalResearch85(1998)33–54
=100km,at25mgroundresolution.Illuminationis various gray tones on the slopes backing the illumi-
fromtheWSW.Wehaveproducednegativeprintsin nation.
order to express in black the slopes facing the radar High ground resolution (cid:14)10 m. panchromatic
source. Detailed information is well revealed by SPOT images have also been processed in order to
Fig. 3. SARERS-1image(cid:14)negativeview. of the Nevsehirplateauand Kirsehirmassif(cid:14)a. and structuralinterpretation(cid:14)b.. F are curved
faultsinplanview,interpretedasextensionalspoonfaults.LocationonFig.2.
D.Dhontetal.rJournalofVolcanologyandGeothermalResearch85(1998)33–54 39
Fig.4.SARERS-1image(cid:14)negativeview.oftheTuzGo¨lu¨ fault(cid:14)TGF.area(cid:14)a.andstructuralinterpretation(cid:14)b..A:Aksaray;DF:Derinkuyu
fault;F1andF2:inactivefaults;f:curvedfaultsinplanviewatsoutheasternterminationoffaultF1;GF:Gumuskentfault;HD:HasanDag;
NACC:Nevsehir–Acigo¨lCalderaComplex;t1andt2:horsetailstructures.LocationonFig.2.
40 D.Dhontetal.rJournalofVolcanologyandGeothermalResearch85(1998)33–54
D.Dhontetal.rJournalofVolcanologyandGeothermalResearch85(1998)33–54 41
obtain detailed views of particular areas. We have tionofstriatedfaultplanes(cid:14)Fig. 10.. Specialempha-
mainly used scene KJ 113–273 (cid:14)Fig. 7. and KJ sishasbeenplacedonstriationsdirectlyobservedon
114–272 to make a small mosaic (cid:14)Fig. 8.. the major mapped fault planes, on which the main
partoftheregionaldisplacementsoccurred.Wehave
3.2. Methodology alsotakenintoaccountstriationsobservedonsmaller
faults paralleling the nearby major fault, assuming
Observations from ERS-1 SAR, SPOT and DEM
that in a given local stress field parallel faults have
images have been used to map the recent faults and
the same mechanism, for a given tectonic phase. We
locate the volcanic vents. These features have been
have plotted on the trace of the main faults the
consolidated onto a single map (cid:14)Fig. 9..
plunge of striations, with indications of the sense of
Recent faults interpreted as active or inactive are
movement (cid:14)Figs. 9 and 10.. Along the major faults
determined from their distinct, poorly eroded scarp
we have generally found only one set of striations
orbecausetheyaffecttherecent(cid:14);10–0Ma.rocks.
which we assume to be related with the latest dis-
We systematically have compared our images with
placements. In a few sites not located along major
geological maps in order to carefully separate the
mappedfaults,wehaveusedstriationsonthevarious
scarps formed by fault planes (cid:14)active. from those
minorfaultsurfacestoestimatetheorientationofthe
resulting from differential erosion of contrasted
local paleostress pattern, using the right dihedral
lithology (cid:14)ancient.. In some cases, Quaternary de-
method of Angelier and Mechler (cid:14)1977.. We consid-
positsoverliethefaulttracewhichisintheprolonga-
ered that all measurements from any one site are
tion of distinct scarps, as is the case for the Gu-
related to a single finite deformation and paleostress
muskent–Derinkuyu fault (cid:14)Fig. 9.. This pattern indi-
pattern unchanged since 10 Ma. The fact that the
cates that the fault is recent but inactive.
results of our calculations are consistent from place
We have speciallysearchedfor the volcanicvents
to place throughout the Central Anatolian region
and related volcanic cones or craters. Following
justifies this hypothesis. However, when two defor-
Nordlie (cid:14)1973., we have considered the outlines of
mation events were supposed to have occurred, be-
lowermost floors of volcanic edifices, which are
cause of incompatibilities in the data or several
generally horizontal. Some volcanoes and craters are
striation sets on fault planes, the measurements were
clearly elongate. Aligned and adjacent volcanoes
sorted by relative age at each site. To characterize
define what we refer to as volcanic linear clusters the paleostress at each site, we used parameter w(cid:14)s2
(cid:14)Takada, 1994; Gudmundsson, 1995.. Elongate vol- ys3.r(cid:14)s1ys3.x which ranges from 1 to 0. The
canoes and volcanic linear clusters are related to
stress ellipsoid has three well distinguishable axes
hidden tension fractures which permit lavas to reach
when values of this parameter are close to 0.5.
the surface (cid:14)Chorowicz et al., 1997.. Tension frac- Values approaching 0 indicate that s3 is equal to
tures are perpendicular to the direction of extension. s2.
On the map of Fig. 9, we have drawn the tension
fractures inferred from elongate volcanoes and vol-
canic linear clusters and have indicated the direction 4. Structural observations
of local extension.
To complement this information relative to the 4.1. Tuz Go¨lu¨ structure
strain, we have carried out structural analysis in the
field, searching for local slip movements along the 4.1.1. Tuz Go¨lu¨ fault zone
main faults and for local strain or paleostress pat- The main Tuz Go¨lu¨ fault trace (cid:14)Fig. 9., well
terns.Ourobservationsconsistedofmeasurementsof expressed on the DEM (cid:14)Fig. 2. and SAR or SPOT
tension fractures and orientations and sense-of-mo- images (cid:14)Figs. 4 and 7. cuts the Quaternary Hasan
Fig. 5. SAR ERS-1 image (cid:14)negative view. (cid:14)a. and structural interpretation (cid:14)b. of the Sultan Saz basin (cid:14)SS. and part of the Cappadocia
region, including the Gumuskent and Derinkuyu faults (cid:14)GF and DF.. h: NNE-striking faults south of Nevsehir (cid:14)N. forming a horsetail
pattern.l:NW-SEstructurallinesaffectingtheErciyesDag(cid:14)ED..LocationonFig.2.
42 D.Dhontetal.rJournalofVolcanologyandGeothermalResearch85(1998)33–54
Fig.6.SARERS-1image(cid:14)negativeview.ofpartoftheCentralTaurus(cid:14)a.andstructuralinterpretation(cid:14)b..B:Bor;C:linearclustersof
volcanoes;CTR:CentralTaurusrange;EF:Ecemisfault;F:normalfault;X:terminationoftheTuzGo¨lu¨ faultagainsttheEcemisfault;V:
elongatevolcanoes.LocationonFig.2.
Dag stratovolcano, attesting to recent movements ward, up to the point where it ends against the
(cid:14)Aydar, 1992; Toprak and Go¨ncu¨oglu, 1993.. The Ecemis fault (cid:14)X on Figs. 2 and 6.. The Tuz Go¨lu¨
main crater of Hasan Dag is not on the fault but 8 fault dips ;SW 658 in sites 1 and 4 (cid:14)Fig. 10..
km away (cid:14)Fig. 2.. Both DEM and SAR imageries Striations on the main fault plane are indicative of
clearlyindicatetheTuzGo¨lu¨ faultextendssoutheast- W-oriented oblique-slip dextral transtensive dis-