South Offshore Domain of the Central Anatolian Plateau

32 Pages·2014·13.81 MB·English

5
South Offshore Domain of the
∗
Central Anatolian Plateau
Contents
5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104
5.2 Background and setting . . . . . . . . . . . . . . . . . . . . . . 106
5.2.1 Offshore domain: Outer Cilicia Basin . . . . . . . . . . 108
5.2.2 Onshore domains bounding the Outer Cilicia Basin . . 108
5.3 Reflection seismic data . . . . . . . . . . . . . . . . . . . . . . 110
5.3.1 Seismic facies, seismic ties, and onland correlations . . 110
5.3.2 Seismic line A . . . . . . . . . . . . . . . . . . . . . . . 112
5.3.3 Seismic line B . . . . . . . . . . . . . . . . . . . . . . . 114
5.3.4 Seismic line C . . . . . . . . . . . . . . . . . . . . . . . 117
5.4 Structural domains in the Outer Cilicia Basin . . . . . . . . . 117
5.4.1 Northern domain . . . . . . . . . . . . . . . . . . . . . 117
5.4.2 Southern domain . . . . . . . . . . . . . . . . . . . . . 118
5.5 RegionalstructuresandtectonicevolutionoftheOuterCilicia
Basin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120
5.6 Linking the Mut and the Cilicia basins . . . . . . . . . . . . . 124
5.6.1 Mut-Cilicia geologic onshore-offshore section . . . . . . 124
5.6.2 Tectonic regime and displacements . . . . . . . . . . . 126
5.7 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128
5.7.1 The Central Cyprus Arc and its forearc basin system . 128
5.7.2 Uplift in the southern margin of the Central Anatolian
Plateau . . . . . . . . . . . . . . . . . . . . . . . . . . 130
5.8 Conclusions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130
∗To be submitted integrally to GSA Bull as: D. Ferna´ndez-Blanco, G. Bertotti, F. Pepe, A.
Aksu and J. Hall, Neogene Tectonics of the Central Anatolia Plateau South Margin: Linking the
MutandOuterCiliciaBasins
101
“In theory, there is no difference between theory and practice.
But, in practice, there is.”
Jan L.A. van de Snepscheut
CAP Offshore Domain 103
Abstract
The causes behind the growth of the southern margin of the Central Anatolian
Plateau remain elusive. We use seismic, fieldwork, and literature constraints to
study the Neogene kinematics and tectonic evolution of the transitional area
between the uplifted onshore Mut Basin and the subsided offshore Outer Cilicia
Basin, and link the latter to the Kyrenia Range, farther south. We constructed
offshore-onshore sections along south Turkey and farther south to define the
geometry and assess the syntectonic growth of a regional-scale Miocene monocline.
In the northern margin of the Outer Cilicia Basin a system of top-to-the-south
reverse faults, related with the monocline, offsets both the Miocene and the
erosional unconformity underneath the Pliocene. Pliocene reflections onlap against
the truncation surface and show syntectonic wedges and synsedimentary
unconformities that indicate pre-Pliocene uplift and erosion followed by Pliocene
and younger deformation. This large-wavelength kink-band fold has a 20–25 km
(horizontal length) flank along the studied sections, in which we estimate a relative
vertical displacement of 3.8km, rates of ∼0.5mm/y, and very low horizontal
shortening values (<1%). Contractional structures developed also in the center and
south of the Outer Cilicia Basin in relation to the Kyrenia thrust belt by
mid-Pliocene or younger times. These data suggest that the ∼8 Ma surface uplift of
the southern margin of the Central Anatolian Plateau is driven by compressional
stresses, and that the modern Central Taurus behave as the forearc high of the
Cyprus subduction system.
104 Chapter 5
5.1 Introduction
Avarietyofmodelsexplaintheupliftmechanismsandrelatedtopographiesobserved
in orogenic plateau systems around the world. Thermo-mechanical and structural
models propose explanations such as thickening of the crust, ductile flow or delami-
nation of the lower/middle crust, tectonic/magmatic underplating, or delamination
of the mantle lithosphere [e.g. Bird, 1979; Powell, 1986; Nelson et al., 1996; All-
mendinger et al., 1997; Yin and Harrison, 2000; S¸eng¨or et al., 2003; Rowley and
Currie, 2006; G¨o˘gu¨¸s and Pysklywec, 2008; Biryol et al., 2011]. Precipitation-erosion
drivenmodelsstatethataridconditionsduringreliefinitiationcreatelargesediment
loads in the interior of the system and transfer tectonic shortening toward its exter-
nal areas, developing higher topographic relieves and triggering feedback processes,
such as humid shadow and sediment trapping [e.g. Sobel, 2003; Mulch et al., 2006b;
Garc´ıa-Castellanos, 2007; Ballato et al., 2010].
The Neogene Central Anatolian orogenic plateau (CAP) in Central Turkey, has
proven qualities to be considered an orogenic plateau, i.e. endorheism and aridity in
theflatCentralAnatoliaregion,high-dischargeriversintherainygorgedTaurusand
Pontides mountains, a thick crust, and a thin lithospheric mantle [e.g. Ate¸s et al.,
2005;Faccennaetal.,2006;MutluandKarabulut,2011]. Differentmechanismshave
been recently proposed to explain the formation of the CAP. Some contributions
consider the CAP, from the Black Sea to the Mediterranean, a single system in
which surface uplift developed by sub-crustal detachment-delamination of the lower
crust at around 5Ma [Aydar et al., 2010] or by delamination of the lithospheric
mantle at ∼8Ma [Bartol et al., 2010]. Even though surface uplift is roughly coeval
in both margins of the CAP, i.e. Late Miocene to Early Pliocene, other studies
propose different growth mechanisms for the northern and southern margins. The
North Anatolian Fault is considered to have been driving the tectonic inversion of
Neogene basins and piecemeal uplift in the northern flank of the CAP since the end
oftheMiocene[Yıldırımetal.,2011]. InthesouthernmarginoftheCAP,slabbreak-
off and subsequent asthenospheric mantle upwelling are proposed as the engine for
post-8Masurfaceuplift,eitherjointlyto[Schildgenetal.,2012a]orseparatelyfrom
[Cosentino et al., 2012] other causes behind a possible second post-1,6Ma uplift.
Our goal is to constrain the mode of (de)formation of the southern margin of
the CAP (SCAP), to better understand its regional tectonic frame, and to discuss
the possible causes behind its formation. Our approach to the problem is to con-
sider the SCAP as an integral part of a larger system continuing farther south, a
domain controlled by subduction beneath the Cyprus arc [Calon et al., 2005a, b].
WestudytheoffshoreOuterCiliciaBasin(OCB),betweenTurkeyandCyprus, and
its relationship with its bounding landward basins (Fig. 5.1). Whilst the growth of
the southern limit of the OCB, the Kyrenia Range, has been related to a southward
verging thrust belt [e.g. Calon et al., 2005a; McCay et al., 2013], the origin of the
OCBnorthernmargin,theCentralTaurusMountains,isstillamatterofdebate[e.g.
Cosentinoetal.,2012]. Therefore,wefocusspecialattentionontheOCBlinktothe
north, i.e. the Mut Basin, which is on top of the Taurus Mountains. These basins
are the (subsided and uplifted) components of the southern margin of the CAP. To
study the sediments and structures developed before and during the formation of
the SCAP we adopt a multi-scale geometric approach in which:
CAP Offshore Domain 105
32ºE 34ºE 36ºE 38ºE
N
36º30´ 0 Km 500 36º30
´N
N 3
36º s AB 6ºN
MaB Taurus MoMuBn t ain
Z
T
N A
35º30´ OAn ▲ Z K ▲ A▲ ▲ ▲K y rO▲▲ e C n i B▲▲a R ▲ ▲ a n ▲ ▲g e ▲ M▲ ▲I Ce ▲BB ▲ K M▲ ▲ 0 K10m0 200 35º30´N
32ºE 34ºE 36ºE 38ºE
AB Adana Basin KMATZ Kyrenia-Misis-Adrın Thrust Zone MeB Mesaoria Basin
AKZ Anamur Kormakiti Zone MB Mut Basin OAn Offshore Antalya Basin
ICB Inner Cilicia Basin MaB Manavgat Basin OCB Outer Cilicia Basin
Figure 5.1: Location map, showing the main marine Miocene basins in and around the
study area of this contribution (onshore basins are in yellow, offshore basins are marked
by their acronyms). The structures depicted in this map are based on the analysis of 1-arc
DEM and LandSat 7 images from NASA. We depict the motion of the structures as known
in the available literature.
(i) We interpreted and depth-converted three N-S seismic lines in the offshore
OCB and performed a detailed kinematic analysis of structures and sediment
geometries.
(ii) We produced two geologic cross sections from fieldwork data in the onshore
Mut Basin, the northern counterpart of the OCB.
(iii) Welinkedtheobtaineddatainaregionalonshore-offshoregeologiccrosssection
delineating the monocline described by C¸iner et al. [2008], which was then
geometrically analized to evaluate the timing and mode of formation of such
structure, and thus that of the SCAP.
(iv) We finally integrated these results with available data from the literature on
northCyprustounderstandthetectonicsettinginwhichtheSCAPdeveloped
and discuss its geodynamic drivers.
This onshore-offshore approach allowed us to understand the latest Miocene-
Pliocene tectonic transition in the SCAP, both geometrically and in time, and pro-
vided constraints on the possible modes of plateau formation.
106 Chapter 5
5.2 Background and setting
A broad marine basin formed by the Late Oligocene-Early Miocene times, in the
northeasternmost Mediterranean that was then segmented into its present-day do-
mains in Late Miocene. This idea is supported in southern Turkey by stratigraphic
evidence for the Miocene sediments of the Manavgat, Mut, and northern Adana
basins[Karabıyıko˘gluetal.,2000;C¸ineretal.,2008]. Stratigraphiccorrelationwith
theoffshoreareastothesouthhasalsobeenestablished[I¸sleretal.,2005;Halletal.,
2005a; Calon et al., 2005a; Burton-Ferguson et al., 2005; Aksu et al., 2005a, b] (see
Fig. 5.2). Farther south, in the vicinity of the Kyrenia Range, deposition of the
mostly deep-water upper Oligocene to upper Miocene sequence preceded shallow
deposits, broadly similar to basins to the north and north-east, and with a common
Tauride source [McCay and Robertson, 2012].
Mut Cilicia Kyrenia Mesaoria
Basin Basin Range Basin
Quaternary Fanglomerate
Unit 1 Athalassa
(1700 m∙s-1)
Pliocene
Mirtou Nikosia
Unit 2
Messinian Lapatza Kalavasos
(4000 m∙s-1)
Tortonian Koronia
Sertavul
Serravall. Unit 3a
Köselerli (3000 m∙s-1) Kythrea Pakhna
Langhian Group
Mut
Burdigal.
Aquitanian Derinçay Unit 3b Aalogrea - Terra
(3000 m∙s-1) Ardana
Basement CKoızmıldpaleğx Unit 4 LTarpyipthao Gs rGour.p TroLoedfkoasr Ca m/ plx.
Figure 5.2: Seismic stratigraphy of the Cilicia Basin, showing the correlations between
seismic stratigraphic units (and their associated velocities) and the onland sedimentary
successions and exploration wells. Modified following Aksu et al. [2005a] and Calon et al.
[2005b].
ThenorthernsectorofthisMiocenebasinispresentlyoutcroppingontheTurkish
mainland and exposes a sedimentary sequence in excess of 1km in the Mut Basin,
ontopoftheTaurusMountains. Thetopofthissequence,upliftedat2km,isdated
as ∼8 Ma, Late Tortonian [Cosentino et al., 2012]. To the south, in the offshore
Cilicia Basin, the bottom of the Messinian reaches ∼2,5km depth. More to the
south, sedimentary deposits belonging to the previously continuous Miocene basin
are now outcropping in the Kyrenia Ridge (Fig. 5.3). Therefore, two main periods
ofdifferentialtectonicactivityareseen. IntheEarlyMiocene,aregionalsubsidence
took place that continued until the Late Miocene. Then, the subsequent surface
uplift of the northern and southern areas, coupled with continued subsidence in the
central domain, led to the presently differentiated domains (Figs. 5.3 and 5.4).
CAP Offshore Domain 107
N Taurus Mountains S
Cilicia Basin Kyrenia Range
~40 km
V.e.~2,5
pre-Miocene basement Continental Shallow water Deep water Salts Siliciclastics
Figure5.3: SchematicN-Sregionalcrosssectionacrossstudyarea(approx.fromKaraman
to Nicosia), showing the main type of depositional environment. Vertical exagg. ∼2.5.
N S
- 1 km
Early Miocene
- 1 km
- 2 km
Middle Miocene - 3 km
1 km
- 1 km
- 2 km
Late Miocene - 3 km
Figure 5.4: Schematic cross section showing the interpretation of the first order vertical
motions and the overall scale of movements along the study area. The vertical scale is
estimated as an approximation to the depth of deposition of the rocks of the area. The
black line represents the position of the basement at every time-step, and the green area
shows the location of the basement in the last time-step. Arrows depict the relative vertical
displacement between the last and the present time-step.
108 Chapter 5
5.2.1 Offshore domain: Outer Cilicia Basin
TheoffshoreOuterCiliciaBasin(OCB)liesintheEastMediterraneanSeabetween
the mainland areas of south Turkey and north Cyprus (Fig. 5.1). The sea floor
between these areas has a concave shape that opens and deepens westward, ranging
from 800m to 1100m in depth. Loose boundaries can be defined to the east, where
the sea floor gradually shallows as the OCB connects with the Inner Cilicia and
Adana basins, and to the west, where the sea floor deepens abruptly to depths of
2km in a horizontal distance of ±20km, in relation to the offshore Antalya Basin.
We consider the OCB as an elongated basin extending for ca. 120km in the N-S
direction and approximately 160km in the E-W direction.
The OCB can be seen as a forearc wedge top basin of the Cyprus arc-trench
system. The OCB is bounded by the Taurus Mountains to the north and by the
KyreniaRangetothesouth. Totheeast,theInnerCiliciaandtheAdanabasinsare
progressively in-filled portions of the same system [Evans et al., 1978], the Cilicia-
Adana basin complex. This foredeep of the Taurus Mountains [Aksu et al., 2005a]
is bounded to the south and southeast by the Kyrenia-Misis-Adrin Thrust Zone
(see Fig. 5.1). The topographic-bathymetric expression of this arcuate thrust zone
embayssedimentswithsourcestotheeastandnortheast[Evansetal.,1978;McCay,
2010] and has led to the asymmetrical deposition of the thick Miocene and younger
sediment infill of the Cilicia-Adana basin complex, as well as its relatively flat and
markedly shallow basin floor.
5.2.2 Onshore domains bounding the Outer Cilicia Basin
Present-dayonshoredomainsboundtheOuterCiliciaBasintothenorthandsouth.
The northern component encloses the Central Taurus Range (Fig. 5.1). When con-
sidered in a regional context, the modern Taurus Mountains are in a forearc high
positionwithregardtotheCyprusarc-trenchsystem. LowertoUpperMiocenesed-
iments, mostly marine, were deposited in the Mut Basin on top of the pre-Miocene
Taurus substratum [Monod, 1977; Andrew and Robertson, 2002; Bassant et al.,
2005; Eri¸s et al., 2005] (Fig. 5.3) and then uplifted. Toward the north, the marine
sediments of the Mut Basin are coeval with fluvio-lacustrine deposits known from
seismics for the Tuz G¨olu¨ area [G¨oru¨r et al., 1984; Huvaz, 2009; Fern´andez-Blanco
et al., 2013], both of which are in turn unconformably covered by terrace and allu-
vial fan Pliocene to Quaternary continental deposits [Monod et al., 2006; O¨zsayın
et al., 2013]. In the southern margin of the Mut Basin, the Miocene rocks shape a
monocline on top of the basement with a roughly flat surface in the hinterland that
progresses into gently south-dipping geometries in its southward offshore continua-
tion [C¸iner et al., 2008] (see Fig. 5.5).
The E-W trending Kyrenia Range and the Messaoria plain, in Cyprus, form the
southern onshore domain bounding the OCB. It is now accepted that the Kyrenia
Rangeoutcropsinrelationwithaprominentdeep-rootedsouthvergingthrustsystem
[Calon et al., 2005a, b; McCay, 2010]. In the Kyrenia Range, this imbricate system
thrusts basement and Miocene rocks on top of Pliocene sediments and is in turn
covered by Pleistocene deposits [Calon et al., 2005b; McCay et al., 2013]. Toward
the south, the asymmetric Mesaoria Basin is a foredeep of the Kyrenia belt formed
by Palæogene up to recent successions [McCay, 2010] (Fig. 5.5).
C
33oE 34oE
A
Leyend Main features
P
O
Pliocene-Miocene
f
37oN 37oN erosional contact fs
h
o
r
e
D
e.g. Monod, 1977
o
m
Miocene monocline
a
i
s.l. n
? ?
Quaternary Middle Miocene ? ?
e.g. Çiner et al, 2008
?
Transition
Pliocene Lower Miocene Mut - Outer Cilicia basins
36oN 36oN and regional integration
(this study)
?
Upper Miocene Paleogene Miocene thrust system
s.l.
Up-Mid Miocene Pre-Cenozoic
Basement e.g. Calon et al, 2005b
Miocene asymmetry
Km
0 30 60 90
33oE 34oE 35oN e.g. Mc Cay, 2010
Figure5.5: Mapshowingthedifferentcomponentsinandaroundthestudyarea. ThegeologicmapofSouthTurkeyandCenter-NorthCyprus
depicts a common age nomenclature for the Cenozoic units. The age integration is based on the ages shown for the MTA geologic maps of
1
Adana and Konya 1:500.000 [Ulu, 2002; S¸enel, 2002], and the geologic map of Cyprus 1:250.000 [Constantinou, 1995], and the stratigraphic 09
correlation shown in Fig. 5.2. On the right hand, the main geometric and contact relationships for the area and one representative study for
each of them are shown.
110 Chapter 5
33º E 34º E
Taşuku
N Bosyayι N
35º 35º
Line C - Fig. 10Sadrazamk9ö .giF - By eniL 8 .giF - A eniL Tatlιsu21 .giF 0ininr PesttehieKflrlir2iieinsmp s5Rce rmsteseitoituicesnddy50 Finitgeurprreet5ed.6:seLisomcaitcionlinmesapinof tthhee
Outer Cilicia Basin.
33º E 34º E
5.3 Reflection seismic data
Three N-S multichannel seismic reflection lines have been analyzed (Fig. 5.6). The
seismicprofileswereobtainedin1991and1992bytheMemorialUniversityofNew-
foundland in collaboration with the Institute of Marine Sciences and Technology,
Dokuz Eylu¨l University. The seismic lines cover an area south of Turkish onland
locations Bozyayı and Ta¸suku, almost reaching Sadrazamk¨oy and Tatlısu cities in
the north coast of Cyprus. These N-S seismic profiles, between 70km and 100km
long, are ca. 30–35 km apart from each other in the east-west direction. Appendix
A shows the raw seismic images of these lines. A small inset of a fourth line to the
east is also shown (Fig. 5.6).
Theseismiclines,originallyin.pdfformat,weretransformedtoSegYforanalysis
of the seismic signal and seismic interpretation, and then converted to true depth.
We performed these operations with GeoSuite AllWorks®. The seismic velocities
shown in Aksu et al. [2005a] (and Fig. 5.2) were assigned to the different units for
depth conversion of the interpreted time profiles.
5.3.1 Seismic facies, seismic ties, and onland correlations
Seismicfaciescharacteristicsofspecificpackagesofreflectionsallowthedistinctionof
fourseismicunitsintheOCB(Fig.5.7). Theseseismo-stratigraphicunitscorrespond
tothosepreviouslydefinedbyAksuetal.[2005a]forthisarea. Thereaderisreferred
to the aforementioned paper for a more detailed description of the seismic facies.
Biostratigraphic and lithostratigraphic data used in this study were compiled by
the Memorial University of Newfoundland from several onshore and offshore wells
(see Fig. 6 in Aksu et al. [2005a], and the references therein). The ages of the
seismo-stratigraphicunitsandtheirtentativecorrelationwiththestratigraphicunits
outcropping onland were found by the same team by means of ties with exploration
wells in the Inner Cilicia and Adana basins [Aksu et al., 2005a; Calon et al., 2005b].
The correlated ages for these units will be used in this contribution as shown in
Fig. 5.7.