Geology of the Ören and Surrounding Areas, SW Anatolia

13 Pages·2002·4.81 MB·English

Turkish Journal of Earth Sciences(Turkish J. Earth Sci.), Vol. 11,2002, pp. 1-13.Copyright 'T(cid:134)B(cid:220)TAK
Geology of the (cid:133)ren and Surrounding Areas, SW Anatolia
(cid:133)MER FEYZ(cid:220) G(cid:134)RER1& Y(cid:134)CEL YILMAZ2
1 University of Kocaeli, Engineering Faculty, Department of Geological Engineering, Vinsan,
TR-41100 Kocaeli - TURKEY (e-mail: [email protected])
2(cid:220)stanbul Technical University, Faculty of Mines, Department of Geological Engineering, Maslak,
TR-80626 (cid:220)stanbul - TURKEY
Abstract:On the Lycian Nappes of SW Anatolia, Neogene basins developed along two different trends in different
periods. NNE—trending basins formed during the Early-Middle Miocene period as exemplified by the (cid:133)ren and
Yata(cid:219)an grabens. These graben fills consist of three distinct rock units. At the base are (1) coarse clastics, sourced
from elevated areas adjacent to the basin-bounding faults. These are linear river-valley fills. They give way upward
to (2) alternating coal-bearing sandstone and limestone as the graben valleys were gradually widened, and the
surrounding mountains were reduced by erosion. Finally, lake environment formed, invading the region during the
advanced stage of graben development. In the lakes were deposited (3) extensive marls and limestones. The lake
deposits gradually onlapped the graben shoulders. The NE—trending grabens extend SW toward the shore of the
SW-NE—trending Kale-Tavas basin. The lake and the sea basin were apparently connected as evidenced by several
marine incursions from the south into the (cid:133)ren basin. The marine units wedge out to the north. On the graben
shoulders, the Lower-Middle Miocene sediments were overlain unconformably by red, brown coarse clastic
sediments as linear and axial fluvial deposits during Late Miocene time when N-S extensional tectonics began. Under
this tectonic regime, some of the N-S—trending faults were reactived as oblique-slip faults with a dip-slip
component. Later, the fluvial deposits were replaced by sediments of a new lake environment, in which extensive
lacustrine limestones were deposited. The extents of the lakes were regional, stretching far beyond the limits of
the grabens. The E-W—trending faults bordering the northern margin of the G(cid:154)kova graben cut and postdate the
Upper Miocene-Lower Pliocene lacustrine units. The Lower to Upper Miocene sequences were elevated on the
graben shoulders. Along the northern edge of G(cid:154)kova graben, more than 400 m of coarse fluvial conglomerates
and debris were formed in front of this elevated region. The G(cid:154)kova graben, mostly offshore, is about 150-km-
long and enlarges westward from 5 to 30 km. The western margin of the graben rises steeply to over 1000 m,
but the southern margin is less marked. The coastline has many bays and small offshore islands.
Key Words:(cid:133)ren, G(cid:154)kova, Neogene basin, extensional tectonics
(cid:133)ren ve (cid:130)evresinin Jeolojisi, G(cid:159)neybat(cid:221) Anadolu
(cid:133)zet: G(cid:159)neybat(cid:221) Anadolu(cid:213)da, Likya Naplar(cid:221) (cid:159)zerinde iki farkl(cid:221) zamanda ve iki farkl(cid:221) y(cid:154)nde Neojen havzalar(cid:221)
geli(cid:223)mi(cid:223)tir. KKD gidi(cid:223)li, (cid:133)ren ve Yata(cid:219)an havzalar(cid:221) Erken-Orta Miyosen d(cid:154)neminde geli(cid:223)mi(cid:223)tir. Bu grabenlerde (cid:159)(cid:141)
farkl(cid:221) kaya toplulu(cid:219)u vard(cid:221)r; tabanda fayl(cid:221) havza s(cid:221)n(cid:221)r(cid:221)na kom(cid:223)u alanlardan derlenmi(cid:223) kaba klastikler yer al(cid:221)r. Bunlar
(cid:141)izgisel akarsu vadi dolgular(cid:221)d(cid:221)r. Bu (cid:141)(cid:154)keller, graben vadisinin giderek geni(cid:223)lemesi ve (cid:141)evre y(cid:159)kseltilerin erozyonla
a(cid:223)(cid:221)nd(cid:221)r(cid:221)lmas(cid:221) ile k(cid:154)m(cid:159)r ara katk(cid:221)lar(cid:221) i(cid:141)eren kumta(cid:223)(cid:221), siltta(cid:223)(cid:221) ardalanmas(cid:221)na ge(cid:141)er. Graben geli(cid:223)iminin ileri evresinde
g(cid:154)l ortam(cid:221) olu(cid:223)mu(cid:223) ve b(cid:154)lgeyi kaplam(cid:221)(cid:223)t(cid:221)r. G(cid:154)llerde ba(cid:223)l(cid:221)ca kire(cid:141)ta(cid:223)(cid:221) ve marn (cid:141)(cid:154)kelmi(cid:223)tir. G(cid:154)l (cid:141)(cid:154)kelleri tedrici olarak
graben omuzlar(cid:221)n(cid:221) a(cid:223)m(cid:221)(cid:223)t(cid:221)r. KD y(cid:154)nl(cid:159) grabenler, GB-KD y(cid:154)nl(cid:159) Kale-Tavas havzas(cid:221)n(cid:221)n GB k(cid:221)y(cid:221)s(cid:221)na do(cid:219)ru
geni(cid:223)lemi(cid:223)tir. G(cid:154)l ve denizel havzalar, (cid:133)ren havzas(cid:221)n(cid:221)n g(cid:159)neyinde denizin bu graben i(cid:141)ine do(cid:219)ru birka(cid:141) kez
ilerlemesi ile k(cid:221)smen birle(cid:223)mi(cid:223)tir. Bu alanda denizel birimler kuzeye do(cid:219)ru kamalanmaktad(cid:221)r. Kahverengi-bej renkli,
k(cid:154)m(cid:159)r arakatmanl(cid:221) g(cid:154)lsel ince detritikler ve marnlar temel (cid:159)zerinde uyumsuzlukla (cid:141)(cid:154)kelmi(cid:223)tir. Graben
omuzlar(cid:221)nda, Alt-Orta Miyosen (cid:141)(cid:154)kelleri (cid:159)zerine, Ge(cid:141) Miyosen(cid:213)de, K-G gerilmeli tektonikle ba(cid:223)layan lineer ve aksiyal
fluviyal ortamda, k(cid:221)rm(cid:221)z(cid:221), kahve renkli klastikler (cid:141)(cid:154)kelmi(cid:223)tir. Bu tektonik rejim ile K-G y(cid:154)nl(cid:159) faylardan baz(cid:221)lar(cid:221),
e(cid:219)im at(cid:221)m bile(cid:223)enleri olan oblik faylar (cid:223)eklinde yeniden hareket ge(cid:141)irmi(cid:223)tir. Daha sonra, fluvial birimler yerlerini
yeni bir g(cid:154)l(cid:159)n kire(cid:141)ta(cid:223)lar(cid:221)na b(cid:221)rakm(cid:221)(cid:223)t(cid:221)r. G(cid:154)l(cid:159)n yay(cid:221)l(cid:221)m(cid:221) b(cid:154)lgesel olup K-G grabenlerin s(cid:221)n(cid:221)rlar(cid:221)n(cid:221) a(cid:223)m(cid:221)(cid:223)t(cid:221)r. G(cid:154)kova
grabeninin kuzey kenar(cid:221)n(cid:221) s(cid:221)n(cid:221)rlayan D-B do(cid:219)rultulu faylar, (cid:134)st Miyosen-Alt Pliyosen g(cid:154)lsel (cid:141)(cid:154)kellerini kesmektedir.
Alt ve (cid:134)st Miyosen istifleri graben omuzlar(cid:221)nda y(cid:159)kselmi(cid:223)tir. G(cid:154)kova grabeninin kuzey kenar(cid:221) boyunca, y(cid:159)kselen
blo(cid:219)un (cid:154)n(cid:159)nde, 400 metre(cid:213)den daha kal(cid:221)n iri akarsu (cid:141)ak(cid:221)lta(cid:223)lar(cid:221) ve moloz birikmi(cid:223)tir. G(cid:154)kova grabeni, b(cid:159)y(cid:159)k
b(cid:154)l(cid:159)m(cid:159) deniz i(cid:141)inde, 150 km uzunlu(cid:219)unda ve bat(cid:221)ya do(cid:219)ru 5 km(cid:213)den 30 km(cid:213)ye kadar geni(cid:223)leyen bir grabendir.
Grabenin kuzey kenar(cid:221)nda, bat(cid:221) ucu 1000 m(cid:213)yi a(cid:223)an y(cid:159)kseltilere ula(cid:223)maktad(cid:221)r. G(cid:159)ney kenar(cid:221)nda ise, bir (cid:141)ok k(cid:159)(cid:141)(cid:159)k
koy ve adalar(cid:221)n olu(cid:223)tu(cid:219)u, daha az belirgin bir morfoloji ve k(cid:221)y(cid:221) (cid:141)izgisi geli(cid:223)mi(cid:223)tir.
Anahtar S(cid:154)zc(cid:159)kler: (cid:133)ren, G(cid:154)kova grabeni, Neojen havzas(cid:221), gerilmeli tektonik
1
GEOLOGY OF (cid:133)REN AND SURROUNDING AREAS (SW ANATOLIA)
Introduction al. 1999, Bozkurt 2000; Sar(cid:221)ca 2000). The proposed
synthesis of previously available data ((cid:222)eng(cid:154)r et al.1985;
There is a controversy concerning the age of development
Walcott 1988) or (commonly) of inadequate data was
of the E-W—trending graben basins of western Anatolia
mostly obtained from the rocks cropping out along the
(Figure 1). The two main views are: (1) the E-W grabens
immediate borders of the grabens (Seyito(cid:219)lu & Scott
began to form during the Late Oligocene-Early Miocene,
1992, 1996; Cohen et al.1995). To test and compare
and have been continuously evolving ever since (Seyito(cid:219)lu
the two models, we undertook a field-mapping project to
& Scott 1991); and (2) the E-W grabens are rather young
study the (cid:133)ren area (Figure 2) because there and in the
tectonic features, and began to form in Late Miocene time
surrounding regions, morphologically active and distinct
(McKenzie 1972; (cid:222)eng(cid:154)r & Y(cid:221)lmaz 1981; Mercier et al.
young faults of various trends, together with thick
1989; Paton 1992; Y(cid:221)lmaz et al.1997, 2000; Ko(cid:141)yi(cid:219)it et
Gulf of Edre IA
39(cid:176) BEG
N
(cid:221) GDG
38(cid:176) BH assif
M
A
A
E BMG
S es D
er
N nd T
e K
A M
E
G
37(cid:176) E M
A (cid:214)G YG
GulfofG(cid:246)kova
Kos S
E
F. D
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A L.
T (
0 20 40km Thrust
36(cid:176) Normaland
27 strike-slipfaults 29 30
mainlyophiolite, Tauridetectonic Neogenetorecent
mØlangeCretaceous unit sedimentaryrocks
JurassictoCretaceous Neogenevolcanic
Cretaceousflyschand
Limestoneanddetritalrocks rocks
olistostromeassoc.
(Bornovaflyschzone) metamorphicrocks
ofMenderesMassif graniticplutons
Figure 1. Geological map of western Anatolia (modified from Y(cid:221)lmaz et al.2000). BEG— Bergama graben; GDG— Gediz
graben, BMG— B(cid:159)y(cid:159)k Menderes graben; KT— Kale-Tavas basin, LN— Lycian Nappes; LNF— Lycian Nappe front;
BH— Bozda(cid:219) horst; (cid:133)G— (cid:133)ren graben; YG— Yata(cid:219)an graben. A, D, I and M are cities of Ayd(cid:221)n, Denizli, (cid:220)zmir
and Mu(cid:219)la, respectively. Inset shows the location of the study area.
2
(cid:133). F. G(cid:134)RER& Y. YILMAZ
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QUATERNARY E.PLIOCENE ENECOIM.L E.-M.MIOCENE E.MIOCENEL.OLIGOCENE MESOZOICPALEOZOIC P(cid:253)nar(cid:246)ren MS +A_ B(cid:146) LFO dified from Y(cid:221)lmaz et al.
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g
Fi
3
GEOLOGY OF (cid:133)REN AND SURROUNDING AREAS (SW ANATOLIA)
Neogene successions, are present. In this paper, the new direction. Grain size decreases toward the north, where
data resulting from this study are first presented and the red clastic sediments pass laterally and vertically into
then the data are discussed to shed light on the geological grey conglomerates, which in turn, pass vertically and
evolution of these Neogene basins. laterally into grey, well-sorted sandstones with some
limestones lenses. Locally these pass laterally into grey
The G(cid:154)kova graben is one of the major E-W—trending
shales containing lignite beds. These shales are lagoonal
grabens of western Anatolia. (Figure 2). The (cid:133)ren area is
and shallow-marine clastic sediments which contain
located to the north of the G(cid:154)kova graben where there
gastropods, bivalves and benthic foraminifers of Late
are large Neogene outcrops. This Neogene is commonly
Oligocene-Early Miocene age (Becker-Platen 1970;
referred to as the (cid:133)ren basin, which extends from the
Ko(cid:141)yi(cid:219)it 1984; Hakyemez 1989; Akg(cid:159)n & S(cid:154)zbilir
Gulf of G(cid:154)kova in the south to Milas in the north (Figure
2001). The sandstones are overlain by a flysch-like
2). The (cid:133)ren Neogene basin is bounded, for the most
sequence, composed mainly of alternating sandstones and
part, by steeply dipping oblique-slip faults with
marls. This sequence has numerous fluvial channel
considerable amount of normal slip component.
deposits, ranging in thickness from a few meters to a few
tens of meters; these were emplaced as turbidite deposits
Geology of the Basins which incised the underlying soft sediments and also
disturbed their original attitudes. Therefore, locally
In the G(cid:154)kova region, basins of various ages and
developed unconformities were formed in the succession.
orientations have been identified. The oldest basin, the
Upward in the section, the high energy of the depositional
Kale-Tavas molasse basin of (cid:222)eng(cid:154)r & Y(cid:221)lmaz (1981), is
environment decreases, as evidenced by fining-upward
orientated ENE-WSW. The youngest basin is the modern
profiles, and eventually the clastic sediments are gradually
G(cid:154)kova graben. Between the development of these
replaced by limestones of the Kale formation. Fauna from
approximately ENE-WSW or E-W basins, roughly
the limestones yield Aquitanian-Burdigalian ages
N-S—trending basins formed during the Early Miocene
(Hakyemez 1989; G(cid:154)r(cid:159)r et al.1995; Akg(cid:159)n & S(cid:154)zbilir
and Late Miocene. The major geological characteristics
2001).
of these basins are briefly described below.
The (cid:133)ren Basin
The Kale-Tavas Basin
The (cid:133)ren and Yata(cid:219)an basins are subparallel basins
The Kale-Tavas is the oldest basin of the region, and its
trending approximately NNW-SSE (Figures 1 and 2).
sedimentary fill ranges from Upper Oligocene to Lower
These basins display identical strata of Early to Middle
Miocene. The fill of the Kale-Tavas basin is best-observed
Miocene age. Typically, the basin units rest
in the area that extends from northeast of Denizli in the
unconformably on the slightly metamorphosed rocks of
east to the G(cid:154)kova graben in the west (Figure 2).
the western Taurides. In places, the lowermost clastic
The Kale-Tavas basin units rest on the Lycian Nappes
rocks rest unconformably on the fossiliferous marine
along an angular unconformity. The lowermost unit of
limestones of the Kale-Tavas basin. Development of the
the basin is a red, thick, massive to poorly-bedded and
(cid:133)ren and Yata(cid:219)an basins was controlled by oblique-slip
poorly-sorted coarse conglomerate assigned to the
fault systems, having major dip-slip components coupled
G(cid:154)k(cid:141)e(cid:154)ren formation. This conglomerate unit is devoid of
with a subordinate dextral strike-slip component. The
fossils, and is composed predominantly of ophiolitic
basin sediments and their substrate are disrupted by E-
materials derived from the underlying ophiolite, which
W—trending normal faults around the Gulf of G(cid:154)kova.
forms the uppermost tectonic slice of the Lycian Nappes.
The (cid:133)ren basin fill consists mainly of two rock units
These materials, which were accumulated to the north of
(Figure 3). The lower unit is composed predominantly of
an approximately NE-SW—trending fault zone, are mainly
clastic rocks of the G(cid:154)kbel conglomerate. This unit is a
debris flow and fluvial deposits, sourced from these fault-
massive to poorly bedded and poorly sorted grey, coarse
induced structural highs. Clast imbrication indicates an
conglomerate with well-rounded clasts derived from the
approximately southeast to northwest palaeocurrent
4
(cid:133). F. G(cid:134)RER& Y. YILMAZ
Y
R n
A eb
N Alluvium a
r
TER G(cid:246)kovafm conglomerate,sandstone gavllif
A o
k
U (cid:246)
Q G
unconformity
Denizciklms
-E limestone,marl
ENN 75m -u n l
EEC sa ag lif
COIMOILP Ya1ta0(cid:240)0amnfm continentalredbeds caraK odzoB nebar
.. g
LE
unconformity
E Sekk(cid:246)yfm Sekk(cid:246)yfm limestone,marl
N
E 150-200m
C
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M 75m
l
l
i
f
E Turgutfm n
L
e
D b
DI .b 100-1100m tuffite gra
M r 250m n
e
-Y g lignitebeds lli (cid:214)r
L f
R n
A y is
sandstone,siltstone a
E b
a
G(cid:246)kbelcong. coarseconglomerate sa
v
(cid:231)
unconformity aT
k Akb(cid:252)kls -e
l
NE A 2000m aK
E shallow marine
TEOC G(cid:246)k(cid:231)e(cid:246)renfm conglomerate,sandstone
AG
LI
L 50-400m >400m
O
unconformity
LycianNappes ophiolite,and
CC
IOIO sedimentaryrocks nt
ZOZO me
ELSE Tauridetectonicunit recrystallisedlimestone, ase
AM phyllite B
P
Figure 3. Generalized stratigraphic section of the Milas-(cid:133)ren area.
5
GEOLOGY OF (cid:133)REN AND SURROUNDING AREAS (SW ANATOLIA)
underlying recrystallized limestones and phyllites. The forming the Gulf of G(cid:154)kova. The northern margin is
conglomerates are of debris flow and fluvial origin. bounded by a linear mountain front, which rises steeply
Upward in the succession, the coarse conglomerates are to >1000-m. E-W—trending listric normal faults, together
replaced by sandstones of the Turgut formation. The with a set of N60…-80…E—trending oblique-slip faults,
upper unit is a shale-marl-dominated, fine clastic characterise the northern margin. The E-W—striking
succession having a number of lignite beds. The top of the faults commonly cut and offset the oblique-slip faults.
sequence is a white marl and limestone unit called the The southern margin of the graben is topographically less
Sekk(cid:154)y formation (Atalay 1980). steep and marked by many bays and small offshore
islands.
The NW-SE—trending basin fills are composed
generally of sediments deposited in a continental The graben-bounding faults of the G(cid:154)kova graben
environment. Toward the south where the ENE- have apparently controlled deposition of a thick post-
WSW—trending, partly coeval, marine Kale-Tavas basin Miocene-Pliocene sedimentary sequence which constitutes
was located, a number of marine incursions into the N-S the G(cid:154)kova Formation. The E-W faults cut the N-
troughs occurred intermittently, as evidenced by the S—trending graben bounding faults and the rock groups
presence of marine-fossil-bearing sandstone layers of the Miocene grabens. The sediments, deposited along
interbedded with the lacustrine sediments (Figure 4). The the margin of the G(cid:154)kova graben, consist of coarse clastic
marine beds wedge out toward the north. The age of sediments, formed as scree deposits, unconsolidated
these rock units has been variously assigned to the slope debris and lateral fan deposits. Their source is
Aquitanian (Tchihatcheff 1869), the Aquitanian- undoubtedly the uplifted horst block lying in the
Burdigalian (Nebert 1957), or the Oligocene-Lower immediate vicinity. The graben fill is rotated gently (10¡-
Miocene (Erent(cid:154)z & (cid:133)ztemur 1964). 15…) northward due to rotation on the major E-
The lacustrine limestone is overlain unconformably by W—trending, south-dipping listric faults. The age of the
a 100- to 200-m-thick, brown to red continental unconsolidated sediments in the graben may be inferred
conglomerate and sandstone unit, the Yata(cid:219)an to be post-Pliocene from stratigraphic evidence, insofar
Formation. In places, the red clastic sediments rest as debris from rocks of Late Miocene-Early Pliocene age
directly on the Lycian Nappes. The red beds yield a rich sourced from the adjacent horst blocks have been
mammalian fauna that ranges in age from Middle incorporated into the present graben fill.
Astracian to Turolian in the Mu(cid:219)la region (Atalay 1980).
The Yata(cid:219)an formation is composed of fluvial and debris-
Geological Evolution
flow deposits, laid down within fault-bounded,
approximately N-S—trending troughs. At top of the In the light of the data presented above the major stages
sequence is white lacustrine limestone of the Denizcik of the geological evolution of this region may be
formation. The limestones are not confined to the limits summarised as follows.
of the fault-controlled depressions where the clastic rocks
accumulated; they cover a vast region as a capping
First Stage
limestone that extended from the gulf areas in the west
to the Denizli area in the east. This distribution indicates The first stage corresponds to the period when the Lycian
that the N-S graben depressions were filled and lost their Nappes, as a nappe package, consisting of slices of the
topographic expression before deposition of the western Taurus metamorphic basement and the overlying
limestones. Mesozoic platform carbonates, together with the
dismembered ophiolites that form the uppermost nappe,
travelled southward during Early Miocene time. The
The G(cid:154)kova Graben
nappes were finally emplaced onto the Lower Miocene
This is the southernmost graben of western Anatolia. It is basin fill of the Antalya basin before the Late Miocene
150-km-long, and widens westward from 5 to more than time (Figure 5) (Robertson 2000).
30 km (Figure 1). A major part of the graben is offshore,
6
(cid:133). F. G(cid:134)RER& Y. YILMAZ
M. K.
E
G R C LITHOLOGY FOSSIL CONTENT
A O HI
F T
E m
N
f
E a
C v conglomerate
O o
k
LI ö
P G
unconformity
marl
N
NA m
AI f m
IN y
GO ö 5
NT k 7
k
AR e sandstone
LO S
T
Monodonta(Osilinus)cf.Elegans
N
FAUJAS
A fosilliferous
I m Turritellacrossei
L sandstone
DACOSTA
A 0
G 0 Turritella(Haustator)sp.aff.
2
I - Terrebraliabidentata
D 0
R 5 (DEFRANCE)
1
U Tympanotonusmargaritaceous
m
B (BROCCHI)
f
t Potamidesgirondicus
u
g marl, (MAYER)
ru coal beds Pirenellaplicata
T (BRUGUIERE)
N Rostellariadentata
A fosilliferous GRATELOUP
I
N m sandstone Galeodeslainei
AT 0 (BASTEROT)
A 02 Arca(Anadora)cf.Montensis
U sandstone, MAYER
Q siltstone, limestone Carditasp,
A
Cerithiumsp,
conglomerate
unconformity
C c
I ni
O o
Z ct recrystallised
SO deteunit limestone, dolomite
E ri
u
M a
T
Figure 4. Measured stratigraphic section of the Turgut and Sekk(cid:154)y formation (in the north of Alakilise town) (Modified from Nebert 1957)
7
GEOLOGY OF (cid:133)REN AND SURROUNDING AREAS (SW ANATOLIA)
N S
KALE-TAVAS BASIN
LLL
YYY
CCCIIIAAA
NNN
NNN
AAAP
PPP
PPE
EES
MENDERES
MASSIF
Oligocene
Figure 5. Pre-extension stage and development of the Kale-Tavas basin. The Lycian Nappes were moving south while a piggy-back basin, the Kale-
Tavas basin, developed above the Lycian Nappes during Oligocene time. The listric normal faults controlled the southern edge of the basin,
and the consequent coarse clastic deposition.
The Kale-Tavas basin began to form during this The E-W Extension Stage
period. Within this basin, sediment deposition started
The earlier stage of the N-S extension.N-S extension
during the Late Oligocene, indicating that this graben
began during Late Miocene time. During this period the E-
began to form slightly earlier than the N-S grabens.
W—trending Bozda(cid:219) horst, located in the middle of the
Mostly ophiolite-derived, coarse clastic materials at the
Menderes Massif, was elevated (Y(cid:221)lmaz et al.2000). Low-
base of the Kale-Tavas basin were sourced from a
angle detachment faults are recognised along both the
structural high formed from the Lycian Nappes. The high
southern and northern flanks of the Bozda(cid:219) horst. The
was located to the south of the basin. The southern
detachment faults appear to have been active mainly
margin of the basin, bounded by this structural high was
during Late Miocene time (Hetzel et al. 1995; Emre
characterised by NE-SW—trending normal faults. For this
1996; Ko(cid:141)yi(cid:219)it et al.1999; Y(cid:221)lmaz et al.2000; Bozkurt
reason, the Kale-Tavas basin, which was situated above
2001; S(cid:154)zbilir 2001) in that the Upper Miocene fluvial
the contemporaneously southerly advancing Lycian Nappe
lateral fan deposits derived from the horst were
package, may be regarded as a piggy-back basin (Y(cid:221)lmaz
transported into the surrounding low topography as
et al.2000). coarse clastic marial. Away from the structural high the
The N-S trending (cid:133)ren and Yata(cid:219)an grabens, that are clastic rocks gave way gradually to lacustrine limestones.
generally bounded by the oblique-slip faults, possibly This situation suggests that the horst was possibly
developed in a N-S compressional stress field (Figure 6) surrounded by interconnected lake basins (Figure 7).
in that the southern as well as the northern parts of Farther away from the horst, to both the south and
western Anatolia suffered N-S compressional deformation north, approximately N-S—trending accommodation faults
during this period (Y(cid:221)lmaz & Polat 1998; Y(cid:221)lmaz et al. began to develop on the upper plates of the detachment
2000; Robertson 2000) faults. These grabens were long, narrow troughs
bounded by the oblique-slip faults which controlled the
8
(cid:133). F. G(cid:134)RER& Y. YILMAZ
N S
L
Y
CI
A
N
N
YATAGAN GRABEN APPE
ÖRENGRABEN
Early-Middle Miocene
Figure 6. Differential stretching within the piggy-back basin areas formed N-S—trending faults and narrow grabens.
N S
BOZDAGHORST KARACASU
GRABEN
YATAÐANGRB
ÖRENGRB.
Late Miocene
Figure 7. During the Late Miocene, N-S extension began. The Bozda(cid:219) horst was elevated and major breakaway faults were formed. Above the
detachment surfaces, approximately N-S—trending grabens began to form as cross-grabens.
9
GEOLOGY OF (cid:133)REN AND SURROUNDING AREAS (SW ANATOLIA)
deposition of Upper Miocene sediments. Some of these have a sharp boundary with a steep slope of the newly
faults appear to have been spatially associated with the developed graben valleys (Figure 9) (Y(cid:221)lmaz et al.2000).
Early Miocene basin-bounding fault system, an example
The present morphology of the region formed later,
of this being the (cid:133)ren graben.
during the development of a set of E-W—trending faults in
Finally, a new lake developed during Late Miocene- Quaternary time (Figure 10).
Early Pliocene time. This new lake basin covered the
entire northern area and extended into present offshore
Conclusions
areas (Figure 8).
Structures and sediments in the northern G(cid:154)kova region
suggest different episodes of basin development.
The interruption stage of the N-S extension. N-S
1. The E-W—trending Kale-Tavas basin began to form
extension appears to have been interrupted at the end of
during Oligocene time above the
Late Miocene-Early Pliocene period when a regionwide,
contemporaneously southerly-transported Lycian
low-relief erosional surface formed on rocks as young as
Nappe package, as a piggy-back basin.
Early Pliocene. The limestones and red clastic rock of Late
Miocene-Early Pliocene age, flat or tilted, were eroded 2. The N-S—trending (cid:133)ren basin formed slightly later
and lie below this surface. during Early Miocene time, under an E-W
extension, N-S compression. The (cid:133)ren and Kale-
Tavas basins were interconnected.
The later stage of the north-south extension.
3. A new group of basins developed along reactivated
Following the development of the erosional surface, N-S
NNW-SSE—trending faults during Late Miocene
extension was reactivated and the E-W—trending grabens
time when N-S extension began, and possibly
began to form. As a result, the erosional surface, as well
survived into Early Pliocene time. The basins were
as the older structures and the Miocene-Lower Pliocene
filled and lost their morphological expression at
strata, were cut by faults that bound the east-west
the end of Late Miocene time.
grabens. The low-relief erosional surfaces on the plateaux
N
S
Denizli
B
O
Z
D
A
G
H
O
R
S
T Aydýn
MENDERES MASSIF
Early Pliocene
Figure 8. A new lake was developed during latest Miocene-Early Pliocene time, and it gradually invaded the flanks of the previously
elevated Bozda(cid:219) horst.
10