Western Anatolia

22 Pages·2005·0.46 MB·English

Turkish Journal of Earth Sciences(Turkish J. Earth Sci.), Vol. 14,2005, pp. 145—166.Copyright 'T(cid:134)B(cid:220)TAK
Geotectonic Setting and Origin of the Youngest Kula
Volcanics (Western Anatolia),
with a New Emplacement Model
MURAT TOK(cid:130)AER1, SAMUELE AGOSTINI2& MEHMET YILMAZ SAVA(cid:222)(cid:130)IN1
1 Dokuz Eyl(cid:159)l (cid:134)niversitesi, M(cid:159)hendislik Fak(cid:159)ltesi, Jeoloji M(cid:159)hendisli(cid:219)i B(cid:154)l(cid:159)m(cid:159),
Bornova, TR—35100 (cid:220)zmir, Turkey (E-mail: [email protected])
2University of Pisa, Istituto di Geoscienze e Georisorse-CNR, Department of Earth Sciences, Pisa I-56124, Italy
Abstract:The Quaternary Kula volcanics are Na-dominant in character while all the older volcanic rocks of western
Anatolia are generally definitive K-dominant rocks. As a unique example in western Anatolia, the existence of a
huge amount of plateau basalts at Kula indicates rapid uplift of mantle material, as confirmed by new geochemical
data.
Based on our field observations, the oldest Kula volcanics are the plateau basalts with more than one main lava
flow. At the beginning of volcanic activity (first-period plateau basalts), this plateau was vast. Subsequently, parts
of the first-period plateau basalts were uplifted and partly eroded while other parts were covered by younger lavas,
tephra and sediments. The horsts, covered by plateau basalts, are well protected because of their resistance to
erosion. During extensional activity, the development of cinder cones continued without hiatus. During the last
period of volcanic activity, the youngest craters once again produced lava flows to form the second-period plateau
basalts. As a result, there are more than 80 cinder cones with quite different erosional stages between the first
and second plateau-basalt periods.
The Kula basalts are the only example of rapid uplifting of asthenospheric material in western Anatolia, and
are interpreted to form due to the opening of a horizontal slab window as a consequence of the more rapid
southwestward movement of the Aegean microplate overriding Africa, with respect to the Anatolian plate.
Key Words:western Anatolia, extensional tectonics, Kula volcanics, geochemistry
Gen(cid:141) Kula Volkaniklerinin Jeotektonik Konumu, K(cid:154)keni ve
Yeni Yerle(cid:223)im Modeli (Bat(cid:221) Anadolu)
(cid:133)zet:Kuvaterner ya(cid:223)l(cid:221) Kula volkanikleri Na(cid:213)ca bask(cid:221)n karakterde olmalar(cid:221)na kar(cid:223)(cid:221)n (cid:154)nceki di(cid:219)er t(cid:159)m Bat(cid:221) Anadolu
volkanikleri K(cid:213)ca egemen volkanik kayalard(cid:221)r. Bat(cid:221) Anadolu i(cid:141)in tek bir (cid:154)rnek olan bu b(cid:159)y(cid:159)k miktardaki plato
bazaltlar(cid:221)n(cid:221)n varl(cid:221)(cid:219)(cid:221) jeokimya sonu(cid:141)lar(cid:221) ile de desteklenen h(cid:221)zl(cid:221) bir manto materyalinin y(cid:159)kselimini i(cid:223)aret eder.
En ya(cid:223)l(cid:221) Kula volkanikleri, birden fazla lav ak(cid:221)nt(cid:221)s(cid:221)ndan olu(cid:223)an plato bazaltlar(cid:221)d(cid:221)r. Volkanik aktivitenin
ba(cid:223)lang(cid:221)c(cid:221)nda geni(cid:223) bir yay(cid:221)l(cid:221)m sunan bu plato bazaltlar(cid:221) 1. evre plato bazaltlar(cid:221) olarak adlan(cid:221)rlar. Birinci evre plato
bazaltlar(cid:221) kimi yerde y(cid:159)kselmi(cid:223) kimi yerlerde a(cid:223)(cid:221)nm(cid:221)(cid:223) ve kimi yerde ise daha gen(cid:141) lavlar ve tortullarca
(cid:154)rt(cid:159)lm(cid:159)(cid:223)lerdir. Plato bazaltlar(cid:221) ile kapl(cid:221) horstlar bazaltlar(cid:221)n dayan(cid:221)ml(cid:221)l(cid:221)(cid:219)(cid:221)dan dolay(cid:221) cok iyi korunmu(cid:223)lard(cid:221)r.
B(cid:154)lgedeki a(cid:141)(cid:221)lma d(cid:154)nemi s(cid:159)resince volkan konilerinin olu(cid:223)umu kesintisiz devam etmi(cid:223)tir. Volkanik aktivitenin son
d(cid:154)neminde en gen(cid:141) volkan konileri bir kez daha lav (cid:159)reterek ikinci plato bazaltlar(cid:221)n(cid:221) olu(cid:223)turmu(cid:223)lard(cid:221)r. Bu iki plato
bazalt evresi aras(cid:221)nda farkl(cid:221) a(cid:223)(cid:221)nma derecelerine sahip 80(cid:213)den fazla volkan konisi vard(cid:221)r.
Kula bazaltlar(cid:221), Bat(cid:221) Anadolu(cid:213)da astenosferik mantonun h(cid:221)zl(cid:221) y(cid:159)kselmesine tek (cid:154)rnektir ve bu GB(cid:213)ya hareket
eden Ege mikroplakas(cid:221)n(cid:221)n Afrika (cid:159)zerine bindirme h(cid:221)z(cid:221)n(cid:221)n, Anadolu plakas(cid:221)n(cid:221)n Afrika (cid:159)zerine bindirme h(cid:221)z(cid:221)ndan
daha fazla olmas(cid:221) sebebiyle a(cid:141)(cid:221)lm(cid:221)(cid:223) olan bir (cid:141)e(cid:223)it yatay pencerenin varl(cid:221)(cid:219)(cid:221)na ba(cid:219)lanabilir.
Anahtar S(cid:154)zc(cid:159)kler: Bat(cid:221) Anadolu, genle(cid:223)me tektoni(cid:219)i, Kula volkanikleri, jeokimya
145
NEW EMPLACEMENT MODEL FOR KULA VOLCANICS
Introduction with some remarks. Canet & Jaoul (1946) remarked that
cinder cones in the area are roughly situated on two
The widely distributed small bodies of alkaline basalts
straight lines whose strikes are sub-parallel to the graben
occurring in all of the various sectors of the Aegean-
edge. This is also observable on the geological map of the
Anatolian realm are derived from OIB-type rocks. The
area published by Hamilton & Strickland (1841).
time-space distribution of volcanism in the Aegean and
western Anatolia — with their main rock associations and Later researchers (Erin(cid:141) 1970; Ercan 1981) made a
the involved magma sources — definitely show a transition similar classification of the basalts of the area with some
from calc-alkaline, mantle-wedge source rocks to insufficient criticism of Hamilton & Strickland (1841).
alkaline, OIB-type mantle-source rocks. Southwestward Recent studies of the tectonic setting and volcanism of the
migration of calc-alkaline, shoshonitic and lamproitic Kula area have yielded diverse opinions. The most
magmas in the hanging wall was accompanied by prominent neotectonic features of western Anatolia are
southwestward migration of the subduction hinge. With a E—W-, NE—SW- and NW—SE-trending grabens (e.g.,
higher enrichment of the more incompatible elements, Ko(cid:141)yi(cid:219)it et al. 1999; Bozkurt 2000, 2001a, 2003;
the trace-element distribution is similar to OIB-type Bozkurt & S(cid:154)zbilir 2004 and references there in). Shortly
basalts as seen in the primordial-mantle (PM) normalized after the concentration of extension into two grabens ~ 2
spider diagrams. The mainly potassic alkaline-basaltic Ma, the generation of alkali-basalt magmas was
magmatism, with its diverse geochemical compositions, generated in Kula area (Richardson-Bunbury 1996).
reflects the extension-related activities prior to the Kula According to G(cid:159)len (1990), the Kula basalts contain
volcanism. The sodic — phonolitic plateau basalts, craters, mantle xenoliths and represent volatile-rich,
and lava flows of the Kula volcanics are therefore metasomatised asthenospheric melts (the best
products of the final activity where the mostly representative mantle material in western Anatolia).
uncontaminated material of the Aegean mantle rapidly
Besides the geotectonic setting and origin of the Kula
erupted as a new episode in a strongly extensional regime
volcanics, explanation of the evolution of the volcanism
during the neotectonic period. The stretching between
and the emplacement of volcanic rocks in the Kula area is
Greece and Anatolia, and the differential velocity of
possible with some modifications of Hamilton &
convergence with the underlying slabs, should have
Strickland(cid:213)s model — another aim of the present study.
generated (cid:212)horizontal windows(cid:213) both in the hanging wall
The Kula volcanics are the youngest volcanic rocks of
and in the footwall of the subduction, allowing
western Anatolia and, in contrast to the older volcanics of
asthenospheric upwelling and consequently its partial
the area with their general potassic affinity, are mainly
melting. Thus, the OIB magmatism was generated after
sodic and have geochemical and isotopic characteristics
regular subduction/collision evolution. With this new
typical of OIB-type intraplate magmatism.
model, it is much easier to explain the one-of-a-kind and
characteristic evolution of the Quaternary Kula volcanics.
Kula is a small town on the main (cid:220)zmir-Ankara road, Tectonic Framework of Western Anatolia
which has a number of interesting volcanological aspects
After the closure of N—dipping subduction zone between
(Figure 1). The youngest volcanics of western Anatolia,
the Pontides to the NNW and the Anatolide Tauride
with widespread plateau basalts and well-preserved
platform to the SSE (Late Palaeocene to Early Eocene),
craters and lava flows, are excellent examples of an alkali-
the (cid:220)zmir—Ankara suture zone was formed ((cid:222)eng(cid:154)r 1979;
basalt province in an area of active rifting. These volcanics
(cid:222)eng(cid:154)r & Y(cid:221)lmaz 1981).
have been investigated by several researchers from the
According to a new tectonic model, developed in order
nineteenth century to present.
to explain the Cenozoic magmatic activity of western
The important tectonic, stratigraphic and
Anatolia (Doglioni et al.2002) as the most prominent
sedimentologic characteristics of the Kula volcanics were
geodynamic factor in shaping the area, the African plate
reported previously by Hamilton & Strickland (1841).
(Cyprus-Aegean subduction zone) was subducted beneath
According to those authors, topographic inversion of the
the Greek and Anatolian microplates at different
basalt stratigraphy within three periods is common in the
velocities, causing a diffuse extensional margin between
Kula area. Philippson (1914) confirmed this classification
146
M. TOK(cid:130)AER ETAL.
a N
Lesvos
BLACKSEA
İstanbul
A A
E E
S ˙anakkale Ankara S
N N
EGEA İzmir GEA MANİSA Study
A AE area
İZMİR
MEDITERRANEANSEA
0 320Km 0 40km
b
İZMNİRZ-OANNEKARA SİMAVGRABEN Simav
G(cid:246)rdes
Selendi
m
Da
mirk(cid:246)pr(cid:252)
De
Salihli ALAŞEHİR KULA
GRABEN
Alaşehir
0 20km
alluvium EarlyMiocene,normalfaults,
probablesetsofreactivated
Quarternarybasalt olderthrustfaults
flowsandcones
EarlyMiocene,normalfaults,
Neogenesedimentary reactivatedthrustfaultbetween
andcalc-alkalinevolcanic theMenderesMassifand
rocks,Quaternarydeposits İzmir-AnkaraZone
crystallinerocksofthe
MenderesMassif, low-anglenormalfault
Palaeogenegranitoids
İzmir-AnkaraZone(İAZ): postulatedtensionfractures
ultramafics,olistostrome leadingtobasalticeruptions
Figure 1. Location of study area (a)with generalized geological map of the Kula area (b)(taken
from Sava(cid:223)(cid:141)(cid:221)n et al.1999).
147
NEW EMPLACEMENT MODEL FOR KULA VOLCANICS
the Aegean Sea and western Anatolia (Doglioni et al. and N—S- trending left-lateral transtensional faults
2002); considering Africa as fixed, the faster (Figure 3).
southeastward motion of Greece relative to Cyprus-
Such a post-orogenic extension, caused by the
Anatolia determined the Aegean extension (Figure 2). In
hanging-wall plate overriding the slab (Doglioni et al.
this point of view, at least from the Early Miocene, the
2002), led to the coexistence of lacustrine sediments and
previous horizontal NE—SW direction of the (—1) in the
coeval volcanic rocks overlying the basement
compressive stage become the trend of (—3), explaining
(metamorphic rocks, ophiolitic nappes and flysch
the formation of NW—SE-trending normal faults and
sediments) — a typical section of western Anatolia
grabens, E—W-trending right—lateral transtensional faults
(Innocenti et al.2005).
a
N
0
40N X
boundariesof
ANATOLIA plates
subductionzone
GREECE
extension zone
350N betweenGreece
Aegean andAnatolia
subduction
Plate-motion
AFRICAN ARABIA vectors
X PLATE 250E 300E 350E 400E
b
SW NE
compression extension
Anatolia
Africanplate Aegean
lithosphere
foldedslab?
mantle asthenosphere
X flow upwelling asthenosphere X
Figure 2. (a)Considering a fixed Africa, Greece is overriding Africa faster than Cyprus and Anatolia. This implies extension between Greece
and Anatolia (thick double arrow). Thin arrows indicate present-day plate-motion vectors with respect to a fixed Africa, inferred
from space geodesy (Doglioni et al. 2002), after NASA data base (from http://sideshow.jpl.nasa.gov/mbh/series.html); (b)
Schematic cross-section of overriding western Anatolia and Greece to African Plate. African slab should be folded by isostatic uplift
of the mantle in the rift. This should result in a sort of window in the hanging-wall lithosphere that is splitting apart into two
independent plates, i.e., Greece and Anatolia. It would hypothetically be coupled with a sort of horizontal window in the underlying
stretched slab, allowing melting and ascent of OIB basalts (Doglioni et al.2002).
148
M. TOK(cid:130)AER ETAL.
mildly alkaline rocks with mainly potassic (locally, also
N sodic) affinity, forming scattered outcrops in western
Anatolia and Aegean Sea (e.g., Ezine, Urla, Fo(cid:141)a, Bodrum,
Dx transtension
Karaburun, U(cid:223)ak, K(cid:159)tahya, Simav, Kaloyeri, Patmos).
These products generally display a within-plate character,
even if a slight subduction-related geochemical signature
is also found locally. The radiometric ages from the
second-stage alkaline volcanics (Borsi et al.1972; Benda
n et al.1974; Besang et al.1976; Ercan et al.1985, 1997;
o
si
n Seyito(cid:219)lu & Scott 1996; Innocenti et al. 2005) are
e
xt
e consistent with those of the intercalating sediments.
Indeed, according to new radiometric age
determinations (Ercan et al.1997; Seyito(cid:219)lu et al.1997;
Sx transtension Innocenti et al.2005) there is no significant time gap
between the first-period volcanics of calc-alkaline to
shoshonitic types and the succeeding ultrapotassic (U-K)
Figure 3. Main trends and tectonic implications of
and lamproitic types (Figure 4, columnar section). Some
Miocene—Quaternary faults in the western Anatolia and
Aegean areas (Doglioni et al.2002). new ages of these ultrapotassic shoshonitic and lamproitic
rocks indicate that these rocks cropped out locally before
The petrogenesis of the younger alkaline association the end of the first orogenic period (Table 1).
and its relations with Neogene sedimentation and
As a third phase of volcanism, the Na-basaltic rocks of
extensional tectonics are reviewed in this study within the Kula cover an area over 350—400 km2, and are located at
framework of the relative movements of the Aegean-
the intersection of NE-trending tectonic lineaments with
Anatolian, Eurasian and African plates.
the youngest WNW-trending Ala(cid:223)ehir Graben (Figure 1b).
This youngest volcanic field of western Anatolia
comprises plateau basalts, several cinder and spatter
Cenozoic Volcanism in Western Anatolia
cones dating back to prehistoric times (Ercan et al.1985,
Early to Middle Miocene orogenic magmatism was
1997; Bunbury 1992; Richardson-Bunbury 1996;
followed by Late Miocene to Quaternary alkaline-basaltic
Sava(cid:223)(cid:141)(cid:221)n et al.1999).
volcanism (e.g., Francalanci et al.1990; Sava(cid:223)(cid:141)(cid:221)n & G(cid:159)le(cid:141)
These temporal variations in volcanic phases are
1990; Y(cid:221)lmaz et al.2001).
interpreted to have resulted from changing the
The first calc-alkaline and shoshonitic rocks were
geochemical features of the magma sources from supra-
characterized by stratostratovolcano-type occurrences
subduction (calc-alkaline to lamproitic associations) to
and formed large centers with intercalated terrestrial
sub-slab mantle (Agostini et al. 2003a, b). (1) In the
sediments. Some investigators considered that these K-
orogenic calc-alkaline and shoshonitic associations
dominant, calc-alkaline to shoshonitic- type initial
(mantle wedge metasomatized by subduction-related
volcanics (23—15 Ma) were related to compressional
components), 87Sr/86Sr and 143Nd/144Nd isotopic ratios and
(subduction) tectonism (Dora et al.1987; Y(cid:221)lmaz 1989;
trace—element variations suggest that interaction with the
Sava(cid:223)(cid:141)(cid:221)n & G(cid:159)le(cid:141) 1990; Sava(cid:223)(cid:141)(cid:221)n 1990), while others
crust was moderate, so that the geochemistry of these
(Seyito(cid:219)lu & Scott 1992; Seyito(cid:219)lu et al. 1992)
rocks is considered to reflect mainly the heterogeneous
suggested that the entire Oligocene—Miocene volcanism of
chemical nature of their mantle source. (2) The
western Anatolia was related to the extensional tectonic
ultrapotassic and lamproitic rocks are characterized by a
regime.
high 87Sr/86Sr and low 143Nd/144Nd isotopic ratios and are
Following the Middle Miocene, basins were enlarged strongly enriched in K and Rb with respect to Ba,
and they accumulated still thicker deposits. The second indicating a phlogopite-bearing lithospheric source. (3)
phase was limited to the Middle Miocene—Early Pliocene The low 87Sr/86Sr and high 143Nd/144Nd isotopic ratios,
and is characterized by the eruption of poorly evolved together with low LILE/HFSE ratios, reveal an OIB-type
149
NEW EMPLACEMENT MODEL FOR KULA VOLCANICS
NANATOLIANNICS(WAV) VVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVV VVVVVVVVVVVVVV VVVVVVVVVVVVVV VVVVVVVVVVVVVVVVVVVVVVV BF:Burdurfault ASF:Alaşehir-Simavfault WAV:westernAnatolianvolcanics n taken from Agostini 2004).
RA ee
WESTEVOLC 2-0Ma 8.4Ma 5-14.2Ma 7-16.3Ma 18-15Ma 21-16Ma rocks dimentsedimentsans) ric ages have b
ACKSEAN VVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVV V VVnVVVVVVVV15.VVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVV16.AVVVVVVVVVVVVVVVVSVVVVVVVVFVVVVVVVVVVVVVVVVVVVVVVVVVVVVV DITERRANEANSEA KshoshonitesVVVVVVVVVVcalc-alkalineVVVVVVVVVVVVVVVVVV Neogeneseper-alkalinerocks(lacustrinesmproitic,HK-UK)andalluvialf oshonitesbasement estern Anatolia with characteristic columnar sections (radiomet
BL Kırka Afyo sparta FB ME U hy(la sh ks in w
V V V V I VVV roc
VVVVVWAVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVAkhisarVVVVVVVVVVVVVVVVVVKulaVVVVV Denizli VVQuaternaryVVsediments Kulavolcanics LateMiocenealkalinebasalts Distribution of Miocene volcanic
AE S N EAE GEA V V 4.
VVV e
VVVVVV gur
VVV Fi
150
M. TOK(cid:130)AER ETAL.
Table 1. Some new age determinations from alkaline and hyper-alkaline rocks.
Locality Rock Type Age (Ma) Data Source
Akhisar UK-latite 16.9–0.3 Ercan et al.(1997)
Akhisar UK-latite 16.72–0.15 Innocenti et al.(2005)
Simav-Na(cid:223)a alkali basalt 15.2–0.3
15.8–0.3 Ercan et al.(1997)
Selendi UK-rock 15.5–0.4 Seyito(cid:219)lu et al.(1997)
G(cid:159)re lamproite 14.20–0.12 Innocenti et al.(2005)
Il(cid:221)caksu lamproite 15.87–0.13 Innocenti et al.(2005)
nature for the Kula volcanics, which originated from a Two different generalized stratigraphic columnar
sub-slab asthenospheric mantle (Agostini et al.2003a, b; sections from Kula and surrounding area are given in
Innocenti et al. 2005). Furthermore, ultrapotassic Figure 6a (Bunbury 1992) and Figure 6b (Kaya; an
shoshonites and Upper Miocene basalts have been unpublished report for the Municipality of Kula).
generated by interactions of source (1) with sources (2) Regionally metamorphosed units of the Menderes
and (3), respectively (Agostini et al.2003a). crystalline rocks include gneiss, schist and marble
(Brinkmann 1966; Dora et al.1987). This metamorphic
basement is poorly exposed only in the southern part of
Geology of the Kula Region
the study area (W and E of Kula and Demirk(cid:154)pr(cid:159) Dam),
Stratigraphy and Tectonics and is covered by listwaenite as relicts of the ophiolitic
nappes (Kaya; an unpublished report for the Municipality
The WNW-trending Simav and Ala(cid:223)ehir grabens
of Kula), Neogene sediments and Kula volcanics.
(Seyito(cid:219)lu 1997; Bozkurt 2001a, 2003; Seyito(cid:219)lu et al.
Seismotectonic data indicate that the tilted Kula block
2004 and references therein), filled from Pleistocene to
comprises up to 10—15 km of crystalline rocks from the
present, are well represented by gravity anomalies
upper crust (Eyido(cid:219)an 1988; Taymaz et al.1991).
(Sava(cid:223)(cid:141)(cid:221)n et al.1999) and bound the study area to the
north and south, respectively (Figure 1b). Kula is located Following tilting and uplifting of the Menderes Massif
on a block of crystalline rocks of the Menderes Massif assemblage, there was a a period of erosion in Kula
(e.g., Bozkurt 2001b; Bozkurt & Oberh(cid:138)nsli 2001; (Richardson-Bunbury 1996; Tok(cid:141)aer 2000). Small hills
Erdo(cid:219)an & G(cid:159)ng(cid:154)r 2004; Koralay et al.2004; Seyito(cid:219)lu were formed in the peneplain. Fluviatile and overlying
et al.2004 and references therein), which is delimited by lacustrine sediments of Neogene age include
a southward-tilted footwall block of the Simav Graben or conglomerate, sandstone, limestone and marl.
a southward-tilted hanging-wall block of the Ala(cid:223)ehir
The Kula area is characterized tectonically by regularly
graben (Figure 5). The readers are referred to recent
ordered NE-trending normal faults that separate the
literature about the continental extensional tectonics in
crystalline rocks, the Neogene sediments and the
western Turkey and the Menderes Massif (Bozkurt
volcanics from one another. According to Sava(cid:223)(cid:141)(cid:221)n et al.
2001b, 2003, 2004; Bozkurt & Oberh(cid:138)nsli 2001;
(1999), they acted as growth faults during the Miocene.
Seyito(cid:219)lu et al.2002, 2004; Akal 2003; Altunel et al.
NE-trending gravitational anomalies coincide in most
2003; England 2003; I(cid:223)(cid:221)k et al. 2003, 2004;
places with these NE-trending fault blocks (Sava(cid:223)(cid:141)(cid:221)n et al.
Karamanderesi & Helvac(cid:221) 2003; Ko(cid:141)yi(cid:219)it & (cid:133)zacar 2003;
1999). This NE-trending fault system reflected an older
Lenk et al.2003; Westaway 2003; Bozkurt & S(cid:154)zbilir
graben—horst structure with older Neogene sediments
2004; Erdo(cid:219)an & G(cid:159)ng(cid:154)r 2004; Kaya et al. 2004;
and, in the Kula region, have been partially reactivated in
Koralay et al.2004 and references therein).
the Quaternary. To the NE of the study area, NE-trending
151
NEW EMPLACEMENT MODEL FOR KULA VOLCANICS
LATEST MIOCENE ? - PLIOCENE
extension + uplift
S 2 2 N
1 1
M
S
P
PLEISTOCENE
RECENT degraded extension + uplift
tiltedKulafaultblock
alkalibasalt SİMAVGRABEN
ALAŞEHİRGRABEN volcanism
ex
Alaşehirfootwall Simavfootwall
? magmachamber
Figure 5. An alternative model for the latest Miocene—Pliocene to recent structural development of the Kula area (Sava(cid:223)(cid:141)(cid:221)n et al.1999). 1—
master share plane (MSP), reactivated older weakness zone; 2— tension fracture as the product of regional updoming, or reactivated
older strike-slip fault along with regional updoming; ex— prominent exhumation in the north.
faults also cut the first-period plateau basalts of Kula dominant in character while all of the older volcanic series
(Figure 7). of western Anatolia are generally K-dominant rocks.
The Kula volcanic field is a rectangular area about 15
km N—S by 40 km E—W. The volcanic rocks consist of
Volcanics of Kula
lavas and tephra originating from ~ 80 small cinder cones
In western Anatolia, during three distinct phases, the
(Richardson-Bunbury 1996).
volcanism changed from orogenic to K-alkaline and finally
Basaltic cinder cones are commonly small compared to
to sodic alkaline (Pliocene to Quaternary Kula volcanics;
other types of volcanic edifices, e.g., they are orders of
Richardson-Bunbury 1996). As the youngest volcanic
magnitude smaller than those of the Andes (Bunbury
rocks of western Anatolia, the Kula volcanics are Na-
152
M. TOK(cid:130)AER ETAL.
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basalt one,m one,m rocks
Pliocene-Quaternary UpperNeogeneunit(pebblestone,sandstandlimestone) LowerNeogeneunit(pebblestone,sandst olistostromeunit listwaeniteunit Menderescrystalline ort) (b).
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Alluviumunconformity 2,34,5,627,27B,28171 244,5,6B62,63,23 8,9,10,1120732 47,47B,47Karaoba33,34,351948,49,51Palankaya52,533250tongue56,355954 CiftÝbrahim 57,5873,7475unconformityredNeogenesedimentslacustrinelimestonefluviatileconglomerate arbleschistophiolitesequence :numberofcones ure 6.Two generalized stratigraphic colu
a 1 m 2,3 Fig
153
NEW EMPLACEMENT MODEL FOR KULA VOLCANICS
Explanations
N
Tibv QTTkhhvyy1 y Qa alluvium
ar
n
Qkv1 er Burgazvolcanics
at Qkv1
u
Q
Qkv1 Qat Asartepeformation
Pzse
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unconformity
Qat Tiu Ulubeyformation
Qa e
n
e
Qkv1 oc Tibv Beydağvolcanics
Pli
Tiah Ahmetlerformation
e unconformity
n
Qkv1 m e
Hachallar Pzse Qat Kv oc Thy Yenikoyformation
Tiah usMi unconformity
o
Tiu e
ac Kvm Vezirlermelange
Qat Tiu Tiu Cretzoic unconformity
o
ae Pzse Esmeformation
al
P
0 1 2 3km strike-slipfault
probablefault
Figure 7. Reactivation of older NE-trending faults (modified from MTA map of the Kula area). Explanation from the MTA map (not
our own).
1992). The diminutive size of the Kula cinder cones is (plateau or hilltop) around which flowing later the
probably a result of a very low flow rate of magma to the younger lavas(cid:213) (Hamilton & Strickland 1841). The
surface (Richardson-Bunbury 1996). geological map of Kula made by Hamilton & Strickland
(1841) clearly illustrates the important role of NE—SW-
Basaltic eruption in the Kula area started 1.6 Ma ago
and WNW—ESE-trending lineaments in the development
(Richardson-Bunbury 1996) and continued up to the
of the cinder cones and on lava flow directions. According
recent. These volcanics developed in more than three
to those authors, the development of the Kula volcanics
phases, or perhaps their evolution was without hiatus.
occured in three periods: (1) plateau basalts with more
Age determinations of the Kula lavas gleaned from
than one flow, (2) subsequent erosional valleys and
various publications (and also from different periods) are
eroded cinder cones with vegetation, (3) fresh non-
illustrated in Figure 8.
eroded cinder cone without vegetation.
The important tectonic, stratigraphic and
Philippson (1914) confirmed this classification with
sedimentological characteristics of the Kula volcanics
some remarks. According to him, the time interval
were reported previously by Hamilton & Strickland
between the second and third periods was not short.
(1841). According to those authors, topographic
Rather, it was long, and there were also cinder-cone
inversion of the basalt stratigraphy is widespread in the
phases between the second and third periods.
Kula area. (cid:212)It occurs where lava flows onto a plain, or into
a valley of material more easily eroded than the basalt. Canet & Jaoul (1946) remarked that the cinder cones
Following erosion the flow leaves as a topographic height in the area are situated along two straight lines whose
154