The geodynamics of the Aegean and Anatolia: introduction

16 Pages·2007·0.8 MB·English

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The geodynamics of the Aegean and Anatolia: introduction
T.TAYMAZ1,Y. YILMAZ2 & Y. DILEK3
1Departmentof Geophysical Engineering, ˙Istanbul Technical University,Maslak,
TR–34469,˙Istanbul, Turkey (e-mail: [email protected])
2KadirHasUniversity, Fatih, I˙stanbul, Turkey
3Department of Geology, Miami University, Oxford,OH45056,USA
The complexity of the plate interactions and and volcanism in Anatolia and the Aegean region
associated crustal deformation in the Eastern (Taymazetal.2004).
Mediterraneanregionisreflectedinmanydestruc-
tive earthquakes that have occurred throughout Regional synthesis
its recorded history, many of which are well
documented and intensively studied. The Eastern Given its location in the Alpine–Himalayan
Mediterranean region, including the surrounding orogenic belt, and at the collisional boundary
areasofwesternTurkeyandGreece,isindeedone between Gondwana and Laurasia, the geological
ofthemostseismicallyactiveandrapidlydeform- historyoftheAegeanregionandAnatoliainvolves
ing regions within the continents (Fig. 1). Thus, the Mesozoic–Cenozoic closure of several Neo-
the region provides a unique opportunity to tethyan oceanic basins, continental collisions and
improve our understanding of the complexities of subsequent post-orogenic processes (e.g. Sengo¨r
continental tectonics in an actively collisional & Yılmaz 1981;Bozkurt & Mittwede 2001;Okay
orogen. The major scientific observations from et al. 2001; Dilek & Pavlides 2006; Robertson &
this natural laboratory have clearly been helping Mountrakis2006).Theopeningofoceanicbranches
us to better understand the tectonic processes in of Neotethys commenced in the Triassic and
active collision zones, the mode and nature of they closed during the Late Cretaceous to Eocene
continentalgrowth,andthecausesanddistribution time interval. The closure of Neotethyan basins
of seismic, volcanic and geomorphological events is recorded by several suture zones (e.g. Vardar,
(e.g. tsunamis) and their impact on societal life Izmir–Ankara–Erzincan, Bitlis–Zagros, Intra-
and civilization. The tectonic evolution of the Pontide, Antalya sutures), along which Jurassic–
Eastern Mediterranean region is dominated by the Cretaceous ophiolites and me´langes are exposed
effects of subduction along the Hellenic (Aegean) (e.g. Sengo¨r & Yılmaz 1981; Robertson & Dixon
arc and of continental collision in eastern Turkey 1984; Dercourt et al. 1986; Stampfli 2000; Okay
(Anatolia)andtheCaucasus.Northwardsubduction et al. 2001; Parlak et al. 2002; Elmas & Yılmaz
of the African plate beneath western Turkey and 2003; Parlak & Robertson 2004; Robertson &
the Aegean region is causing extension of the Ustao¨mer2004;Robertsonetal.2004a,b;Stampfli
continental crust and volcanism in the overlying &Borel2004;Bagcıetal.2005,2006;Dileketal.
Aegean extensional province. Eastern Turkey has 2005;C¸eliketal.2006;Dilek&Thy2006;Parlak
been experiencing crustal shortening and thicken- 2006, and references therein). The polarity of
ingasaresultofnorthwardmotionoftheArabian subduction,thetimingofoceanbasinopeningand
plate relative to Eurasia and the attendant post- closure, and the location of Neotethyan suture
collisional magmatism (Taymaz et al. 1990, zonesremainsomewhatcontroversial.Thedestruc-
1991a,b;McCluskyetal.2000,2003;Dilek&Pav- tion of oceanic basins was also accompanied and
lides 2006, and references therein; Fig. 2). The followed by: (1) Cretaceous to early Palaeocene
resulting combination of forces (the ‘pull’ from arcmagmatism(e.g.Pontidearc:Okay&Sahintu¨rk
the subduction zone to the west and ‘push’ from 1997; Yılmaz et al. 1997); (2) development of
the convergent zone to the east) is causing the accretionary-type forearc basins (e.g. Haymana–
Turkishplatetomovesouthwestward,boundedby Polatlı Basin; Koc¸yigˇit 1991; Tuz Go¨lu¨ Basin,
strike-slip fault zones: the North Anatolian Fault Go¨ru¨retal.1998);(3)latePalaeocenetoMiocene
Zone (NAFZ) to the north and the East Anatolian and younger post-collisional magmatism (Aldan-
Fault Zone (EAFZ) to the south. Interplay mazetal.2000;Keskin2003;Boztug˘ etal.2004,
between dynamic effects of the relative motions 2006; Karslı et al. 2004; Aslan 2005; Innocenti
of adjoining plates thus controls large-scale et al. 2005; Altunkaynak & Dilek 2006); (4) the
crustal deformation and the associated seismicity development of several blueschist belts (e.g. Late
From:TAYMAZ,T.,YILMAZ,Y.&DILEK,Y.(eds)TheGeodynamicsoftheAegeanandAnatolia.
GeologicalSociety,London,SpecialPublications,291,1–16.
DOI:10.1144/SP291.1 0305-8719/07/$15.00#TheGeologicalSocietyofLondon2007.
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2 T.TAYMAZETAL.
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Fig.1. (a)SeismicityoftheEasternMediterraneanregionandsurroundingsreportedbyUSGS–NEICduring1973–2007withmagnitudesforM.3superimposedona 1
9
shadedreliefmapderivedfromtheGTOPO-30GlobalTopographyDatatakenafterUSGS.BathymetrydataarederivedfromGEBCO/97–BODC,providedbyGEBCO(1997)
andSmith&Sandwell(1997a,b).(b)SummarysketchmapofthefaultingandbathymetryintheEasternMediterraneanregion,compiledfromourobservationsandthose
ofLePichon&Angelier(1981),Taymaz(1990),Taymazetal.(1990,1991a,b);S¸arogˇluetal.(1992),Papazachosetal.(1998),McCluskyetal.(2000)andTan&Taymaz(2006).
LargeblackarrowsshowrelativemotionsofplateswithrespecttoEurasia(McCluskyetal.2003).BathymetrydataarederivedfromGEBCO/97–BODC,providedbyGEBCO
(1997)andSmith&Sandwell(1997a,b).ShadedreliefmapderivedfromtheGTOPO-30GlobalTopographyDatatakenafterUSGS.NAF,NorthAnatolianFault;EAF,East
AnatolianFault;DSF,DeadSeaFault;NEAF,NorthEastAnatolianFault;EPF,EzinepazarıFault;PTF,PaphosTransformFault;CTF,CephaloniaTransformFault;PSF,
Pampak–SevanFault;AS,ApsheronSill;GF,GarniFault;OF,OvacıkFault;MT,Mus¸ThrustZone;TuF,TutakFault;TF,TebrizFault;KBF,Kavakbas¸ıFault;MRF,MainRecent
Fault;KF,KagˇızmanFault;IF,IgˇdırFault;BF,BozovaFault;EF,ElbistanFault;SaF,SalmasFault;SuF,Su¨rgu¨Fault;G,Go¨kova;BMG,Bu¨yu¨kMenderesGraben;Ge,Gediz 3
Graben;Si,SimavGraben;BuF,BurdurFault;BGF,Beys¸ehirGo¨lu¨Fault;TF,TatarlıFault;SuF,SultandagˇFault;TGF,TuzGo¨lu¨Fault;EcF,Ecemis¸Fau;ErF,ErciyesFault;DF,
DelilerFault;MF,MalatyaFault;KFZ,Karatas¸–OsmaniyeFaultZone.
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4 T.TAYMAZETAL.
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Fig.2. (a)GPShorizontalvelocitiesandtheir95%confidenceellipsesinaEurasia-fixedreferenceframefortheperiod1988–1997superimposedonashadedreliefmapderived
fromtheGTOPO-30GlobalTopographyDatatakenafterUSGS.BathymetrydataarederivedfromGEBCO/97–BODC,providedbyGEBCO(1997)andSmith&Sandwell
(1997a,b).LargearrowsdesignategeneralizedrelativemotionsofplateswithrespecttoEurasia(inmma21)(recompiledafterMcCluskyetal.2000).NAF,NorthAnatolianFault;
EAF,EastAnatolianFault;DSF,DeadSeaFault;NEAF,NorthEastAnatolianFault;EPF,EzinepazarıFault;CTF,CephaloniaTransformFault;PTF,PaphosTransform
Fault;CMT,CaucasusMainThrust;MRF,MainRecentFault.(b)SchematicmapoftheprincipaltectonicsettingsintheEasternMediterranean.Hatchingshowsareasofcoherent
motionandzonesofdistributeddeformation.Largearrowsdesignategeneralizedregionalmotion(inmma21)anderrors(recompiledafterMcCluskyetal.(2000,2003).NAF, 5
NorthAnatolianFault;EAF,EastAnatolianFault;DSF,DeadSeaFault;NEAF,NorthEastAnatolianFault;EPF,EzinepazarıFault;CTF,CephaloniaTransformFault;PTF,
PaphosTransformFault.
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6 T.TAYMAZETAL.
Cretaceous Tavs¸anlı Zone in Turkey: Okay et al. coversalargeareathatincludesGreece,Macedonia,
1998;Sherlock1999;C¸amlıcametamorphicbeltin Bulgaria,AlbaniaandSWTurkeyandformsoneof
NW Turkey: Okay & Satır 2000, and references the most spectacular and best-studied continental
therein;Eocene–OligoceneCycladicblueschistbelt extensionalregions.Thecauseoftheonsetofexten-
inthecentralAegean:Altherretal.1979;Avigad& sion is controversial and may be (1) slab retreat
Garfunkel 1989, 1991; Okrusch & Bro¨cker 1990; along the Aegean subduction zone and consequent
Jolivet et al. 1994, 2003; Avigad et al. 1997; back-arcextension,(2)collapseofanoverthickened
Bro¨cker et al. 2004; Ring et al. 2001; Trotet et al. crust, (3) westward escape of Anatolia along its
2001;Bro¨cker&Pidgeon2007;LycianNappesand plateboundaries,theNAFSandEAFS,or(4)differ-
Menderes Massif: Oberha¨nsli et al. 2001; Okay ential rates of convergence between NE-directed
2001; Rimmele´ et al. 2003, and references therein; subduction of the African plate relative to the
BolkarMountainsintheCentralTaurides:Dilek& hanging-wall Anatolian plate; that is, rapid south-
Whitney1997);(5)high-tolow-grademetamorphism westwardmovement ofGreecerelativetoAnatolia
affectinglargerareas. (e.g. McKenzie 1978; Dewey & S¸engo¨r 1979;
The nappe translation and burial of large areas LePichon&Angelier1981;Rotstein1984;S¸engo¨r
beneath advancing ophiolite nappes has resulted et al. 1985; S¸engo¨r 1979, 1987; Dewey 1988;
in regional metamorphism and consequent for- Jackson & McKenzie 1988; Kissel & Laj 1988;
mationofcrustal-scale metamorphic massifs,such Taymaz et al. 1990, 1991a; Seyitogˇlu & Scott
as the Rhodope Massif, Strandja Massif, Cycladic 1991,1992;Taymaz&Price1992;Bozkurt&Park
Massif, Menderes Massif and Central Anatolian 1994;Meulenkampetal.1994;Taymaz1996;Saun-
CrystallineComplex(S¸engo¨retal.1984;Whitney dersetal.1998;Thomsonetal.1998;Koc¸yigˇitetal.
& Dilek 1997; Bozkurt & Oberha¨nsli 2001a, b; 1999; Bozkurt 2000, 2003; McClusky et al. 2000,
Okay et al. 2001; Gautier et al. 2002; Whitney 2003; Yılmaz et al. 2000; Okay 2001; Doglioni
et al. 2003; S¸engu¨n et al. 2006; Bozkurt 2007, et al. 2002; Purvis & Robertson 2004; Sato et al.
andreferencestherein). 2004; Seyitogˇlu et al. 2004; Seyitogˇlu et al. 2004;
Theclosureofoceanicbasinsresultedincrustal Bozkurt& So¨zbilir 2004,2006;Purviset al. 2005;
thickening and subsequent post-orogenic extension andreferencestherein).
and magmatism in the west (Aegean extensional The AES is currently under the influence of
system)andcollisionalintracontinentalconvergence forces exerted by northward subduction of the
ineasternTurkeyandtheCaucasusthatstillprevail African plate beneath the southern margin of the
in the region. The present-day configuration of the Anatolian plate along the Hellenic–Cyprean
Aegean region is therefore the manifestation of trenches and dextral slip on the North Anatolian
threemajorstructures:(1)theHellenic–Cypriansub- fault system. The continental extension has
duction zone; (2) the dextral North Anatolian fault expresseditselfintwodistinctstructuralstyles:
system(NAFS);(3)thesinistralEastAnatolianfault
system (EAFS). Along the Hellenic–Cyprian (1) Rapid exhumation of deep-burial meta-
trenches the African plate is subducting NNE morphic rocks in the immediate footwall of cur-
beneaththeAnatolianplateatvaryingratescausing rently low-angle brittle–ductile normal faults
lithospheric tearing and intra-plate deformation (detachment fault and metamorphic core com-
(Dilek2006).TheNAFSandEAFSareworld-class plexes). The footwall deformation preserves evi-
examplesofintracontinentaltransformfaultsystems dence for a progressive transition from ductile to
thatintersectatacontinentaltriplejunctioninnorth- brittlewheremylonitesareoverprintedbybreccias
eastern Turkey (e.g. Bozkurt 2001; S¸engo¨r et al. and, in turn, by cataclasites. Exhumation was
2005). The continuum of deformation along the accompanied by synchronous deposition of conti-
NAFSandEAFShasresultedintheWSWextrusion nentalredclasticsedimentsinthebasin(s)located
of the intervening Anatolian plate onto the Eastern inthedetachmenthangingwalls.
Mediterranean lithosphere, accompanied by its (2) Late stretching of crust and a consequent
counter-clockwiserotation,betweentheconverging grabenformationalongPlio-Quaternaryhigh-angle
Eurasian and Arabian plates (Rotstein 1984). normalfaults(themodernphaseofextensionorrift
ThesinistralDeadSeafaultsystem(DSFS)facilitates mode). Several core complexes (e.g. Rhodope,
the northward motion of Arabia and also plays an Cycladic, Kazdagˇ, Menderes, Nigˇde core com-
importantroleintheactivetectonicsoftheregion. plexes: Lister et al. 1984; Dinter & Royden 1993;
Subsequenttoaseriesofcontinentalcollisionsand Gautier et al. 1993, 1999; Bozkurt & Park 1994;
the demise ofthe Neotethyan seaways, the Aegean Gautier&Brunn1994;Dinteretal.1995;Vanden-
region experienced roughly NNE–SSW-oriented berg&Lister1996;Whitney&Dilek1997;Hetzel
extension since the latest Oligocene to Early et al. 1998; Jolivet & Patriat 1999; Jolivet & Fac-
Miocenetimes(Dilek2006,andreferencestherein). cenna 2000; Lips et al. 2001; Bonev & Stampfli
Thisregion, the Aegeanextensional system (AES), 2003; Ring et al. 2003; Gessner et al. 2004;
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INTRODUCTION 7
Beccaletto & Steiner 2005; Bonev 2006; Bonev referred to these publications for additional infor-
et al. 2006a, b; Bozkurt et al. 2006; Bozkurt mation (Robinson 1997; Gourgaud 1998; Bozkurt
2007; Re´gnier et al. 2007, and references therein) & Rowbotham 1999a, b; Durand et al. 1999;
andoverprintingapproximatelyeast–west-trending Bozkurt et al. 2000; Bozkurt & Mittwede 2001,
grabens(e.g.GulfofCorinth,Bu¨yu¨kMenderesand 2005; Aksu et al. 2002, 2005; Akıncı et al. 2003;
Gedizgrabens)thereforeformthemostprominent Taymaz et al. 2004; S¸engo¨r et al. 2005; Bozkurt
elementsoftheAES. 2006; Dilek & Pavlides 2006; Robertson &
Mountrakis2006).
TheAegeanregionisthereforeconsideredasa
perfect natural laboratory to study mechanisms of
core-complex formation, synchronous basin evol- Research themes
ution and subsequent graben formation during its
post-collisional extensional tectonic evolution. This Special Publication includes a wide range
of contributions, illustrating both the diversity of
The papers in this book shed some light on
various aspectsof this extensionaltectonics of the study regions being actively researched and of
techniques now available to investigate crustal
Aegeanregion,buttherearestillmanycontentious
issues concerning the origin, timing and evolution deformation. It also complements the recent
of Neogene crustal extension in this broad zone compilationsonthisregionaslistedabove.Cover-
agerangesfromtheLevantineregionintheeastto
of convergence between Africa and Eurasia (see
Taymaz & Price 1992; Taymaz 1993; Taymaz SW Bulgaria in the west, with emphasis on the
et al. 2004; Bozkurt & Mittwede 2005; Dilek & Aegean extensional province and the adjacent
Pavlides2006,andreferencesthereinfordetails). western part of the North Anatolian FaultZone as
The Aegean region is also characterized by well as the Hellenic and Cyprean subduction
zones.Wehavegroupedpapersintothefollowing
widespread post-collisional magmatism expressed
byextensivevolcanicsequences,hypabyssalintru- keythemes.
sions and granitoid bodies (Fytikas et al. 1976,
1984;Altherretal.1982;Bingo¨letal.1982;Inno- The Aegean Seaand the Cyclades
centietal.1984,2005;Gu¨lec¸1991;Seyitogˇluetal.
1992, 1997; Hetzel et al. 1995a, b; Richardson- Katziretal.reviewthetectonicpositionandfield
Bunbury 1996; Ercan et al. 1997; Yılmaz et al. relations of major ultramafic occurrences in the
2001; Is¸ık et al. 2003; Erku¨l et al. 2005; Ring & Cyclades and document in detail the petrography
Collins 2005; Tonarini et al. 2005; Yu¨cel-O¨ztu¨rk and chemical compositions of ultramafic and
et al. 2005; Aldanmaz 2006; Altunkaynak & associated rocks on the islands of Evvia, Naxos,
Dilek 2006; Bozkurt et al. 2006; Pe-Piper & Tinos and Skyros. They then discuss the origin
Piper2006;Dilek&Altunkaynak2007,andrefer- and mode of emplacement of these rocks and the
ences therein). The extant data suggest that orogenic evolution of the Cyclades. Widespread
there may have been close temporal and spatial serpentinization of most of the ultramafic rocks
relationships between magmatism and subduction suggests denudation prior to reburial causing
roll-back processes and/or Neogene continental Alpine metamorphism. Relict mantle assemblages
extensionintheAegeanregion,wheretheageofvol- and mantle-like oxygen isotope ratios from Naxos
canicactivitybecomesyoungersouthwards.There meta-peridotites are attributed to the emplacement
are good examples of synextensional granites ofthesemantlerocksontoacontinentalmarginvia
emplaced into the footwall rocks of detachment collisionandsubsequenthigh-pressure(HP)meta-
faults (i.e. Simav and Alasehir detachment morphism(M )at550–6508Cand(cid:2)14kbar.The
1
faults), providing crucial evidence for the age of meta-basites of the Skyros and Evvian me´langes
core-complexformation.Therefore,geochronology record M temperatures of 450–5008C and
1
andthermochronologicalstudieshaverecentlycon- 400–4308C,respectively.Thus,fromEvviasouth-
centratedonthesegranitoidbodiesintheregion(e.g. eastwards progressively deeper (i.e hotter) levels
Ring&Collins2005;Thompson&Ring2006). of the subducted plate are exposed. Interestingly,
This introduction is aimed at presenting a temperatures of the M overprint also increase
2
synopticoverviewoftheregionalgeologyandgeo- from Evvia through Skyros to Naxos. The diverse
physics based on the existing literature, as well as P–TpathsoftheCycladicblueschistsarepredicted
outliningtheresultsofrecentliteratureonexisting bythermalmodellingoftectonicallythickenedcrust
controversies about the tectonic and geodynamic unroofedeitherbyerosionorbyuniformextension.
evolution of the Aegean region. The geology of Mehletal.presentdetailedstructuraldatafrom
thisregionhasbeenreviewed inaseriesofrecent the islands of Tinos and Andros documenting the
special publications, providing in-depth coverage exhumation of HP metamorphic rocks in the
of the extant data and models, and readers are Cyclades.Thedataareconsistentwithlocalization
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8 T.TAYMAZETAL.
of deformation and its progressive evolution Thedatacomefromtwodistinctlocations:eastern
wherebyearlyductilefabricsaresuperimposedby Rhodope–Thrace of Bulgaria–Greece and the
low-angle semi-brittle shear planes and, in turn, BigaPeninsulaofNWTurkey.Thestructuraldata
by steeply dipping late brittle structures. The from the metamorphic rocks are consistent with
authors also confirm the role of boudinage for- top-to-the-NNW–SSE-toNE–SW-directedexten-
mation in localizing ductile–brittle transition and sion in dome-shaped core complexes in the foot-
emphasize the continuum of strain from ductile to walls of low-angle detachment faults. The results
brittle domains during exhumation. One of the ofthisstudycombinedwiththeavailableliterature
main conclusions of the paper is that the strain fromotherpartsoftheAegeanregionsuggestthat
localization process depends on both rheological the extensional history in the region comprises
stratificationandcompositionalheterogeneity. syn- and post-orogenic episodes during the Paleo-
Pe-Piper & Piperdocument the occurrence of cene–Eocene and the latest Oligocene–Early
Miocene igneous rocks on the island of Samos as Miocene,respectively.Theformereventwasattrib-
part of a Late Miocene–Quaternary back-arc uted to gravitationally induced hinterland-directed
setting in the Aegean Sea. Three groups of Late exhumation of the orogenic stack during the
Miocene igneous rocks are differentiated: (1) an closure of the Vardar Ocean, whereas the latter
intrusivecomplexofmonzodioriteandminorgran- wastheconsequenceofwidespreadback-arcexten-
ites; (2) potassic trachytes and minor rhyolite; (3) sion. The recognition of southward migration of
bimodal rhyolites and basalts. New K–Ar ages extension and magmatism from the Rhodope
combinedwithexistinggeochronologyandbiostra- complexinthenorthtothepresentpositionofthe
tigraphysuggestanagesof10–11Maforthefirst Hellenic trench in the south supports subduction
two groups and 8Ma for the bimodal volcanic roll-back processes that have prevailed in the
rocks. Radiogenic isotope and trace element com- regionsinceLateCretaceoustime.
positions suggest partial melting of an enriched Georgievetal.reporttheresultsofrecentglobal
garnet lherzolite mantle source for the origin of positioning system (GPS) campaigns aimed at
monzodioriteandbasalt.Theauthorsshowthattra- monitoringand studyingthe active deformationin
chyteandmonzodioriterocksmayhaveevolvedby SW Bulgaria. The analyses of GPS data for the
fractional crystallization of a parental magma 1996–2004periodprovidefirmevidenceforactive
similartothatoftheyoungerbasalt.Emplacement faultingintheregion.Theregionisdivided,based
and eruption of the monzodiorite, minor granites, on geology and geodetic data from 38 GPS sites,
potassic trachytes and rhyolite are attributed to into five blocks of homogeneous kinematic beha-
regionalextensionandlistricfaulting,whereasthe viour with average motions varying between 1.3
younger basalt extrusion was probably associated and3.4mma21.Therateofmotionforthewhole
with north–south strike-slip faulting that provided regionisc.1.8+0.7mma21inaN1548direction
pathwaysfordifferenttypesofmantlemelts. (totheSSE)withrespecttothestableEurasia;this
Piper et al. interpret marine seismic reflection result correlates well with the geological data on
profiles from around Santorini to show the distri- neotectonicmotionsinSWBulgaria.
bution of active faults and the occurrence of
submarinevolcanicrocksinterfingeringwithstrati- The Hellenic and the Cyprus arcs region
fied basinal sediments in the south Aegean arc.
Two distinctphases of recent volcanismappear to Karagianni & Papazachos present a database of
have taken place in the area: the 1.6 ka and regionalearthquakesrecordedbyaportablebroad-
0.6520.55Ma Akrotiri episodes. Accordingly, the band three-component digital station and a shear
agesofsubsurfacesubmarinevolcanichorizonsof velocity model of the crust and uppermost mantle
Santorini (lower and upper volcanic units) are beneaththeAegeanareausingsimultaneousinver-
estimatedaslatestPlioceneandtheyoungerAkro- sion of Rayleigh and Love waves. The results are
tiri episode. Because Santorini is located at the consistent with strong lateral variations of the
intersectionofseveralfaultsetsofdifferentorien- S-wave velocities for the crust and uppermost
tations (east–west, ENE–WSW and NE–SW) mantleintheAegean.Theauthorsconfirmthepre-
anddifferentages,LateNeogenebasinsubsidence sence of thin crust (,28–30km) for the whole
and volcanism are interpreted to have resulted Aegean Sea region and even thinner (20–22km)
from changing fault patterns associated with crust in the southern and central Aegean Sea. On
the collision of the African and Aegean– the other hand, the crust on land is much thicker,
Anatolianplates. around40–45kminwesternGreeceandameanof
Bonev & Beccaletto document structural evi- 35km in the rest of the country. A significant
denceonthelatestOligocenetoPresentextensional sub-Moho upper mantle low-velocity zone (LVL
tectonics within a back-arc setting in the mantle) identified in the southern and central
northAegeanabovetheHellenicsubductionzone. AegeanSeacorrelateswellwiththehighheatflow
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INTRODUCTION 9
inthemantlewedgeabovethesubductedslaband shift of depositional environment from lacustrine
withtherelatedactivevolcanismintheregion. to the present marine conditions. The change of
Meier et al. investigate the structure and grain size from sand- to gravel-sized particles at
dynamics of the plate boundary in the area of thebasetosiliciclasticmudupwardsinthesucces-
Cretebyreceiverfunction,surfacewaveandmicro- sion is interpreted to mark changes in the Pleisto-
seismicity using temporary seismic networks, and cene–Holocene conditions. The widespread
summarize the results with special emphasis on occurrences of faults, synsedimentary structures
their implications for geodynamic models. The and submarine slides or slumps interpreted on
authors then propose that the island of Crete rep- seismic profiles form the most important records
resents a horst structure in the central forearc of active tectonics in the canyon and prove once
of the retreating Hellenic subduction zone. The morethemajorroleoffaultingandassociateddefor-
reportedpropertiesofthelithosphereandtheplate mationonsedimentationintheSeaofMarmara.
interface beneath Crete are attributed to extrusion Taymazetal.investigatetheseismotectonicsof
of material from a subduction channel, driving theNorthAnatolianFault(NAF)inthevicinityof
differentialupliftoftheislandbyseveralkilometres theOrta–C¸ankırıregion(centralTurkey)byanalys-
sinceabout4Ma. ing a moderate-sized (M ¼6.0) earthquake that
w
Yolsal et al. inspect historical tsunamis known occurred on 6 June 2000. The authors correlate
tohaveoccurredintheEasternMediterraneanSea source rupture characteristics of this event with
region identified from verified catalogues in three thoseobtainedfromthefieldmapping(neotectonic)
groups and correlate them with the seismogenic and geodetic (InSAR) studies. The authors then
zones such as the Hellenic and the Cyprus arcs, discuss the faulting in this anomalous earthquake
the left-lateral strike-slip Dead Sea Fault and the inrelationtothelocalgeometryofthemainstrike-
Levantine rift. The authors conduct numerical slip system (NAF), and speculate that this event
simulationsinvolvingtheinitiationandpropagation may not be a reliable guide to the regional strain
of tsunami waves as series of large sea-waves of fieldinNWcentralTurkey.Theauthorstentatively
extremely long wavelength and period generated suggestthatonepossibleexplanationfortheoccur-
by an impulsive undersea disturbances or activity renceofthe6June2000Orta–C¸ankırıearthquake
nearthecoasts(i.e.earthquake-inducedtsunamis). could be localized clockwise rotations as a result
The authors then compute water surface elevation ofshearingofthelowercrustandlithosphere.
distributions and theoretical arrival times (i.e. Gu¨rsoyetal.stresstheimportanceoftravertine
calculated travel times) for the Paphos, Cyprus occurrencesinthestudyofactivefaulting,asthese
earthquakeof11May1222andfortheCreteearth- deposits are commonly linked to earthquake
quakeof8August1303,whichareknowntobethe activity during which geothermal reservoirs are
largest and well-documented tsunamigenic events reset and activated by earthquake fracturing. They
in the region. The authors confirm that the coastal studythepalaeomagneticrecordofthreetravertine
topography, sea bottom irregularities and near- fissures in the Sıcak C¸ermik geothermal field near
shore bathymetry are crucial components in Sivas in central Anatolia to understand the
tsunami wave simulations, and they further ambientfieldatthetimeofdepositionandtoident-
suggest that improvement of the resolution of ify cycles of secular variation of the geomagnetic
bathymetric maps, particularly for the details of field, with the aim of estimating the rate of
the continental shelf and seamounts, would facili- travertine growth. Thetravertinesaredatedbythe
tate a better understanding of tsunami generation U–Th method and vary in age between 100 and
andtsunami-pronemechanisms. 360ka.Theauthorsanalysesequentialsamplescol-
lectedfromthemargins(earliestdeposition)tothe
centres (last deposition) of fissure travertines and
Structural complexities associated with conclude, based on the assumption that these
strike-slip faulting inAnatolia cyclesrecordtimeperiodsof1–2ka,thattravertine
layersidentifyresettingofthegeothermalsystemby
Ergin et al. report on the influences of the Late earthquakes with magnitudes of 4.5–5.5 at every
Quaternarytectonicsandsea-levelchangesonsedi- 50–100 years. Travertine precipitation appears to
mentationintheSeaofMarmara,asobservedinthe have occurred at rates of 0.1–0.3mm a21. The
Sarko¨yCanyoninthewesternpartofthissea.They data are also consistent with the occurrence of
present the results of detailed sedimentological major earthquakes (M c. 7.5) at approximately
work on several sediment cores collected from every10ka.
thissubmarinecanyon.Theworkisalsosupported Themajorityofthepapersinthisthematicbook
by the interpretation of seismic section profiles were presented at the International Symposium on
and 14C dating of base sections in the sediment the Geodynamics of Eastern Mediterranean:
cores.Thedatedsediments(12kaBP)markedthe Active Tectonics of the Aegean, held at the Kadir
Downloaded from http://sp.lyellcollection.org/ by guest on January 4, 2019
10 T.TAYMAZETAL.
Has University, ˙Istanbul, Turkey, during 15–18 We finally thank the contributors to this book for their
June 2005. This meeting was organized in time and effort, and active participation in producing
memory of Professor Kaˆzım Ergin (1915–2002), thisexcitingvolumeonthegeodynamicsoftheAegean
asourceofprideforthe˙IstanbulTechnicalUniver- andAnatolia.
sity.KaˆzımErgin(MehmetKaˆzımErgin),knownto
hiscolleaguesand studentsas Kaˆzım Hoca, was a
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