Morphotectonic characteristics of Lefkas Island during the Quaternary

GEOLOGICA BALCANICA, 38. 1—3, Sofia, Dec. 2009, p. 23—33.
Morphotectonic characteristics of Lefkas Island
during the Quaternary (Ionian Sea, Greece)
George D. Bathrellos1, Varvara E. Antoniou2, Hariklia D. Skilodimou1
Department of Geography & Climatology, Faculty of Geology & Geoenvironment, National & Kapodistrian
University of Athens, University Campus (Panepistimiopolis), Zografou, ZC 15784, Athens, Greece;
e-mails: [email protected]; [email protected]
2
Department of Dynamic-Tectonic-Applied Geology, Faculty of Geology & Geoenvironment,
National & Kapodistrian University of Athens, University Campus (Panepistimiopolis), Zografou,
ZC 15784, Athens, Greece; e-mail: [email protected]
(Submitted: 13.03.2008; accepted in revised form: 13.05.2009)
1
Abstract. This paper focuses on the study of the Quaternary morphotectonic evolution of the
Lefkas Island using morphological and tectonic data. Based on our mainly morphological studies, two principal tectonic structures have been distinguished: (i) the Nydri-Vasiliki Fault Zone
(NVF) and (ii) the Ionian Zone overthrust onto the Paxos Zone, which both divide the island into
three morphotectonic units of Karya (KMTU), Maradochori (MMTU) and Athani (AMTU).
Paleogeographically, it has been suggested that the broader Lefkas area was dominated by a
NE—SW to ENE—WSW compressional regime since the early Pliocene that continuous in our
days, resulting in the uplift of the southwestern part of the island and the submergence of the
northeastern part of the island. This deformation is characterized by principal fault structures of
a N110°—130° strike. These structures, combined with a fault system of N40°—60° strike representing an older Miocene fault zone, control the main morphological characteristics such as
watersheds and streams and are responsible for the KMTU formation producing a northeastward plunging monoclinal en-echelon structure.
During the Early Pleistocene, a shift of the compressional regime towards the east was responsible for the formation of a N70°—90° strike fault system. These faults had a morphotectonic
effect throughout the island, controlling the watersheds and stream evolution. The continuous
compressional regime recorded in our days results in the formation of fault structures, striking
N20°—40° and N170°—190° that bound almost exclusively the coastal area of the island.
Bathrellos, G. D., Antoniou, V. E., Skilodimou, H. D. 2009. Morphotectonic characteristics of Lefkas Island during the Quaternary (Ionian Sea, Greece). Geologica Balcanica
38(1—3), 23—33.
Key words: surface analysis, drainage network, hydrological basins, morphotectonic units,
Lefkas Island, Greece.
INTRODUCTION
The island of Lefkas is one of the seven Ionian Sea
islands, the nearest one to the western coast of mainland Greece, from which is separated by a narrow
artificial straight, in the area of an extended shallow
lagoon (Fig. 1). The island has an elongated shape
with principal development axis of N360° strike and
covers an area of approximately 300 km2.
The greater part of Lefkas Island can be characterized as mountainous to semi-mountainous (high-
est elevation of 1158 m) with small intramountainous valleys and coastal basins. Its coastline has a total length of approximately 116.7 km and is steep in
general. The western coasts present linear development while the eastern, northern and southern coasts
form many small elongated bays.
The island of Lefkas presents significant geological for several reasons. First, to the west of the island, in the area of the Ionian Sea, the Hellenic
Trench (Fig. 1a) is bounded by the subduction of the
Eastern Mediterranean lithosphere under the Aegean
23
Fig. 1a. Map of Greece showing the study area in the western margin of the Hellenic trench (from Mountrakis et al., 1986; Flotte et
al., 2005 ) Le I = Lefkas Island, Am G = Amvrakikos Gulf, Sp = Sperchios. Fig. 1b. Map of western Greece showing the extension
of the main geological zones of Hellenides (based on Sotiropoulos et al., 2003; Kamberis et al., 2005) and the location of the study area.
lithosphere (Middle East, Eurasian lithospheric plate
margin; McKenzie, 1972; Mountrakis et al., 1986;
Underhill, 1989; Le Pichon et al., 1995; Papazachos
and Kiratzi, 1996; Sotiropoulos et al., 2003; Flotte et
al., 2005; Kamberis et al., 2005; Kokinou et al., 2005).
Second, the dominant geological formations of
the southwestern part of the island are attributed to
the most external geotectonic zone of the Hellenides
Mountain belts, known as the Paxos Zone (Renz, 1940)
or Pre-Apulian Zone (Aubouin, 1959) (Fig. 1 b).
Third, in a great area of the island, mainly along
its western coasts intense seismic activity has been
recorded with numerous submarine active seismic
epicenters, (Fig. 2, time period 1469—2003) that have
generated earthquakes of small to medium focal
depth (<40 km) with magnitude of >5R (Seismotectonic map of Greece, 1989; Kassaras et al., 1993;
Hatzfeld et al., 1995; Papazachos and Papazachou,
1997; Louvari et al., 1999; Kokinou et al., 2006; Papadimitriou et al., 2006).
Forth, the morphology of the island during the Quaternary presents interest mainly due to its alpine structure and to its post-alpine active tectonics controlled
directly from the Hellenic trench area processes characterizing it as an evolving morphotectonic structure.
This paper focuses on the study of the morphotectonic evolution of the island during the Quaternary.
24
Fault distribution, linear morphological features such
as the coastline, the watersheds and the streams of the
island have been analyzed and their statistical process-
Fig 2. Seismic epicenter map (based on Kassaras et al., 1993;
Papadimitriou et al., 2006)
ing and correlation has been carried out in order to
investigate the effect of the tectonic structures on them.
The systematic correlation of the morphological
features with the tectonic elements determines indirectly the effect of the tectonic activity on the development of important morphological features in the
area, providing important information for its morphotectonic evolution (Devi and Singh, 2006).
The aim of this paper is to present principal morphological features indicating diachronic shifts that
can be related or attributed to active tectonic structures as detected in Lefkas Island due to its proximity to the Hellenic Arc.
DATA AND METHODOLOGY
We used the following sources for data collection
and analysis and processing purposes of our study
in order to determine the morphotectonic structure
of Lefkas Island during the Quaternary:
1. Base maps from H.A.G.S. in 1:50000 scale,
“LEFKAS” sheet (1971) and “Ag. Petros” sheet (1971)
from which the following elements were used: (a) the
20 m spacing contour lines, (b) the hydrographic
network and (c) the island coastline.
2. The geological map “LEFKAS” sheet (1963) in
1:50000 scale, modified for the aims of the paper.
3. H.A.G.S. aerial photographs (scale 1:33000,
1987) and Landsat satellite image 7 ETM+ (path/
row: 185/033, Date: 22-08-2000, Cloud=0% (cloud
free), 7 multiphasmatic (analysis of 28 m) + 1 panchromatic (analysis of 15 m), mainly used to obtain
lineaments and to determine morphological characteristics that could not be identified on the base maps.
4. Field work focused on the certification of the
primary morphotectonic structures.
The geographical data processing, the correlations
and the construction of a digital elevation model
(DEM), followed by the production of a morphological gradients map are carried out with the use of
Arc/GIS 9.0, while the processing of the satellite im-
Fig. 3. Geological map of Lefkas Island (modified from Bornovas, 1963, 1964)
4 Geologica Balcanica, 1—3/2009
25
age and the tectonic features is carried out with the
use of ILVIS 3.3 Academic.
The data are recorded and processed based on
their linear characteristics and, more specifically,
based on their strike and length. For the investigation of the principal strikes of the linear elements
the calculation method of frequency is used and for
the investigation of their intensity the density method is used. The calculation method results are expressed with frequency and density rose diagrams
for every linear feature using Rockware/2004 Revision 4.7.9.
Finally, the principal trends of the linear features
are classified and characterized and the effect of
the fault distribution on the morphological features
is evaluated.
tic sediments (pebbles, sands, marls, clays, etc). The
thickness of these deposits varies from a few to several tenths of meters that in places exceeds 100 m.
The orogenic Alpine phase was expressed on the
Ionian Zone towards the end of the Oligocene and
resulted in intense tectonism of its formations with
folds and thrusts following a general direction of
N350°—10°. According to Mercier et al. (1987), this
phase was completed during the early Pliocene in the
most external region of the Hellenides mountain belts
with a NE compressional strain field (N40°—50°)
direction causing the overthrusting of the Ionian
Zone on the Paxos Zone.
RESULTS
Tectonics
GEOLOGY
Regarding the geological structure of the island,
Alpine and post-Alpine formations and deposits are
involved (Fig. 3). The Alpine formations include the
Paxos Zone formations and the overthrusted formations of the Ionian Zone.
The Paxos Zone formations are located on the
southwestern part of Lefkas Island and are composed
of a continuous sequence of Late Jurassic to Oligocene carbonate rocks grading towards the upper
members to a Miocene sequence of siliceous limestone (Bornovas, 1964; Stamatakis and Hein, 1993).
The Ionian Zone formations (Philippson, 1898;
Nopcsa, 1921; Renz, 1940; Aubouin, 1959; Bornovas, 1964; Dercourt et al., 1980) dominate the island
and are composed of a series of Late Triassic — Late
Eocene carbonate formations grading into flysch
formations (Late Eocene — Oligocene). The lower
stratigraphic members of the carbonate series of the
Ionian zone are composed of Triassic evaporites.
The post-Alpine formations include Upper Miocene molassic type formations and Quaternary deposits. The Upper Miocene formations unconformably overlie the Ionian Zone formations and are composed of conglomerates, sandstones, marls, marly limestones and breccia-conglomerates. The total thickness of these formations is approximately 500 m. The
Quaternary deposits are located on the mountainous
— semi-mountainous basins and on the coastal area
mostly at the eastern coastal zone. These deposits
include mainly fluvial and coastal deposits of clas-
The Paxos Zone formations on the island are folded,
with inclined folds of a N20°—40° axial plane strike
and 50° axial plane dip. The Ionian Zone formations are intensely folded, in closed inclined folds of
a N350°—20° axial plane strike and a 30°—50° axial
plane dip. Also, they present a strong brittle deformation with the presence of many internal thrusts of
a N350°—10° strike and 40°—60° dip (Fig. 4).
The Ionian Zone overthrusts the Paxos Zone. The
thrust plane has a N330° strike and 40°—50° dip. At
the base of this overthrust, intense tectonism was identified with the presence of extensive slump structures.
The Lefkas Island formations are faulted, mostly
from the neotectonic brittle deformation. The main
faults or fault zones classification and prioritization
regarding frequency, density and type (Fig. 4) are
presented in Table 1. The dip of the fault planes,
according to field work measurements, has a mean
value of 60°.
Based on the distribution and evaluation of the
fault structures, the most important is that of NydriVassiliki Fault (NVF). It has a N40°—60° strike and
is characterized according to field work data as a
strike-slip fault.
This dominant tectonic features along with the
thrust structure, divide the island into three morphotectonic units: (a) the central-northern unit, (b) the
southeastern unit and (c) the southwestern unit. For
the needs of this research the morphotectonic units
are named from main villages which are located in
each unit. More specifically, the central-northern unit
Table 1
Frequency, density and character of the main fault systems in Lefkas Island
Principal Fault
Strikes
N20°–40°
N40°–60°
N70°–90°
N110°–130°
Classification
Frequency
Density
Medium
Medium
Medium
Medium
Medium
Major
Medium
Major
N170°–190°
Major
26
Medium
Outcrop areas
Coastal zone, Athani, Karya
Karya, Maradochori
Coastal zone, Athani,,Maradochori
Karya
Coastal zone, Athani (primary),
Maradochori, Karya
Character
Oblique – normal
Strike slip
Oblique strike slip
Oblique – normal
Oblique – normal
Fig. 4. Tectonic map of Lefkas Island with the rose diagram of faults as linear features (a: frequency, b: density)
is named as Karya morphotectonic unit (KMTU),
the southeastern unit as Maradochori morphotectonic unit (MMTU) and the southwestern one as
Athani morphotectonic unit (AMTU).
In Lefkas Island, five fault systems were identified with the following principal strikes: N20°—40°,
N40°—60°, N70°—90°, N110°—130°, and N170°—190°.
The statistical processing of these fault systems was
performed with the use of 192 linear features.
The N20°—40° striking faults are characterized as
oblique/normal-slip faults, presenting lower density
compared to their frequency. They are developed
parallel or sub-parallel to the main fold and thrust
trends, with mostly counterbalancing dips. These
faults affect mainly the western coastal zones of
KMTU and AMTU and do not appear in the central area of the island.
The N40°—60° striking faults are characterized
mainly as strike-slip faults. These faults interrupt the
Alpine formations, the fold axes and thrusts, causing intense tectonic deformation with fracture zones
and locally tectonic mélange in the Miocene formations. In several locations, these faults are intersected by the other fault systems. Based on the statistical
analysis, they are classified as medium distributed
and are identified in KMTU and MMTU. In many
locations these faults have a right-lateral obliqueslip character such as Nydri-Vassiliki fault zone.
The N70°—90° striking faults are characterized as
oblique right-lateral faults presenting high-density
compared to their frequency. They are identified in
many locations on the island, mainly on the southern
coastal zone of MMTU and AMTU, where they vertically intersect the Alpine and Miocene formations.
The N110°—130° striking faults are characterized
as oblique/normal-slip faults. They present high-density in relation to their frequency in this direction
and are found mainly in KMTU, interrupting both
the Alpine formations of the Ionian Zone and the
post-Alpine formations. Frequently, they are observed
as the margins of the Quaternary basins. The general
trend of these faults follows the main thrust trend. In
27
the area of Eglouvi-Lazarata-Lefkas (S to N), they
form en-echelon monoclinal displacements essentially forming three main surfaces of gentle slopes
(<10%) at 800—900 m (Eglouvi), 300—400 m (Lazarata) and 0—100 m (Lefkas). A significant feature is
that these faults are not identified within AMTU while
they affect only the northern section of MMTU where
they locally intersect the NVF structure.
The N170°—190° striking faults are characterized
as oblique/normal-slip faults and although they have
a dominant frequency, they exhibit a very low-density (length). They are parallel to the main fold axes
and thrusts directions but mainly with counterbalancing dip. These faults are located on the coastal
zones of AMTU, MMTU and KMTU, while they are
absent from the central area of the island. Their relation to the N20°—40° striking fault system could
not be identified.
The N20°—40° faults follow the fold and the thrust
structures being parallel to the main development
axis of the island. The N40°—60° fault system repre-
sents a Miocene fault zone. The N70°—90° faults are
attributed to an intense compressional episode during the Late Pleistocene (Mercier et al., 1987; Cushing, 1985; Sorel et al., 1988). The N110°—130° fault
system is related to the deformation of Early Pliocene,
compressional regime (Sorel and Cushing, 1982;
Cushing, 1985). The N170°—190° faults like the
N20°—40°, follow the fold and thrust structures, parallel to the trench axis. The above mentioned fault
structures of different orientation represent an expression of compressional tectonic regime that had
influence to the morphology of the island.
Geomorphology
In general, the relief of the island is steep, with the
morphological slopes ranging from 10° to 65° (Fig. 5).
In the AMTU and MMTU the altitude is 700 m, while
in the KMTU is 1100 m. The higher morphological
slope (65°) was observed at the west coastal zone of
the AMTU area. Gentle slopes (<10°) develop on the
Fig. 5. Morphotectonic units — morphological gradients map of Lefkas Island with the rose diagram
of the coastline as linear features (a: frequency, b: density)
28
Table 2
Frequency, density and main outcrop areas, of coastline linear features of Lefkas Island
Principal Strike
Frequency
Density
Outcrop areas
N20°–40°
N40°–60°
N70°–90°
N110°–130°
Medium
Minor
–
–
Medium
Minor
–
–
N170°–190°
Major
Major
Coastal zone, Karya
Mainly Karya
–
–
On the western (primary) and
eastern coastal zone
mountainous — semi-mountainous regions of Eglouvi
at altitude 800—900 m and in Lazarata and Maradochori areas at 300—400 m.
The Englovi and the Lazarata plateau as well as
the Lefkas lowland compose an en-echelon morphological structure with a general direction towards the north.
The hydrographic networks of the island are
eroded in depth and their pattern is parallel and
rectangular type, while they mainly develop singlestreams. Only few hydrological networks, mainly in
KMTU, present pattern of dendritic type on the
Miocene formations.
The results of statistical processing of the coastline using 198 linear features are presented in Table 2. It can be concluded that as far as the coastline is concerned, the frequency follows the density
with a primary N170°—190° strike and a secondary
N20°—40° strike (Fig. 5). The rest of the strikes contribute scarcely on the coastline development.
The plot of the streams on a frequency and density
rose diagram is presented in Fig. 6. In Table 3 the
principal development directions are presented based
on their classification, character and area of appearance. The statistical processing of the streams is carried out with the use of 2064 linear features.
Fig. 6. Drainage basins map of Lefkas Island with the rose diagram of streams as linear features
(a: frequency, b: density) and of watersheds as linear features (c: frequency, d: density).
29
Table 3
Frequency, density, character and main outcrop areas of the streams in Lefkas Island
Principal strikes
Frequency
Density
Character
Outcrop areas
N20°–40°
Minor
Minor
Karya
N40°–60°
Medium
Medium
N70°–90°
Major
Major
N110°–130°
Medium
Major
Tributaries
Main streams and
tributaries
Single streams and
tributaries
Main streams
N170°–190°
Minor
Minor
Mainly tributaries
In all stream categories the frequency follows the
density. An exception is the N110°—130° striking
system that exhibits a greater density of streams compared to its frequency, a fact that is attributed to
the main direction that the principal river branches follow.
Lefkas Island includes twenty drainage basins that
present significant variety regarding their dimensions
and importance based on their morphological characteristics (Fig. 6). From these twenty basins, the
number 13 and 15 essentially represent one drainage
basin, since they are drained by the same stream to
the Vassiliki Bay. However, based on different structural and tectonic features they were separated in
two. Most of the basins are open towards the sea. The
exceptions are numbers 4, 12 and 14 that represent
closed karstic basins.
The frequency and density rose diagrams of the
watersheds are presented in Fig. 6. In Table 4 their
main evolution strikes are presented based on prioritization, character and outcrop area. The statistical
processing of the watersheds was performed with the
use of 121 linear features.
The comparative study of frequency and density
indicates that the watersheds of N70°—90° strike
present higher density than frequency while the opposite is observed with the N20°—40° strike. In the
rest of the strikes the frequency follows the density.
The comparison of the statistical processing of
frequency and density among streams, watersheds
and coastlines indicates that:
1. The N20°—40° strike, although it is major/medium for the watersheds (mainly in AMTU) with a
minimum contribution on the streams (tributaries of
KMTU), appears as medium for the coastlines mainly
at the western coastal zone of Karya.
Karya, Maradochori
Athani,Maradochori,
Karya
Karya, Maradochori
Maradochori, Karya,
Athani
2. The N40°—60° strike, although it is medium for
the streams and watersheds in KMTU and MMTU,
has a minor participation on the KMTU coastline
and is absent from the AMTU and MMTU area.
3. The N70°—90° strike, although it is major for
the streams (throughout the island) and medium/
major for the watersheds (KMTU, MMTU), is essentially absent on the coastline. A notable observation
is the absence of watersheds in AMTU compared to
the significant stream evolution in that direction.
4. The N110°—130° strike is medium for the watersheds and medium/major for the streams (main
streams in KMTU and MMTU), while it is essentially absent from the coastline.
5. The N170°—190° strike, although it is major for
the coastlines of the western main and eastern coastal zone of the island, appears as minor in streams
and watersheds throughout the island.
Morphotectonic correlation
The N20°—40° fault system, identified mainly on the
coastal zone, has contributed on the coastline formation and scarcely on the stream development. The
high density that it exhibits throughout the island
and mainly in AMTU can be attributed to the fact
that this direction mainly follows the fold and thrust
structures.
The N40°—60° strike-slip faults with the NVF as
dominant structure are scarcely expressed on the
coastline, while they have significant presence on the
main streams, tributaries and on the watersheds of
the KMTU and MMTU. They are absent from
AMTU. Along with the dominant tectonic fold structures and the thrust, they form basic watersheds and
streams. These faults could be considered important
Table 4
Frequency, density and outcrop area of the watersheds in Lefkas Island
30
Principal strikes
Frequency
Density
Outcrop area
N20°–40°
N40°–60°
N70°–90°
N110°–130°
N170°–190°
Major
Medium
Medium
Medium
Minor
Medium
Medium
Major
Medium
Minor
Athani, (mainly), Karya, Maradochori
Karya, Maradochori
Karya, Maradochori
Karya, Maradochori
Karya, Athani, Maradochori
for the formation of the early morphotectonic structure of the island and for the dynamic compressional strain distribution that dominates in KMTU,
MMTU and AMTU.
The N70°—90° fault system identified throughout
the island, with significant presence in the MMTU
and AMTU, forms watersheds (high-density) and
mainly streams. Moreover, it is not present on the
coastline. It is considered that the high-density of
the system has contributed significantly to the increase of the watersheds lengths, as well as to the
frequency and density of the streams.
The N110°—130° fault system having limited frequency and significant density forms watersheds and
streams but it does not control the coastline. In general, the KMTU area is morphotectonically controlled by the geological and tectonic structure expressed
through this system.
The N170°—190° fault system, showing high-frequency and low-density, controls mainly the western
and the eastern coastline of the island and limited
streams and watersheds. This fact leads us to suggest
that this system represents active structures under development. These faults follow the fold and thrust
structures and are parallel to the trench axis.
The N40°—60° strike-slip faults caused the formation of the early morphotectonic structure of the
island. The initial formation of these faults could be
related to the generation mechanism of the Miocene
molassic basins in the Ionian Zone. Towards this hypothesis, the outcrop of these faults as the margins
of the Miocene formations is reinforcing. Reactivation of these faults as oblique strike-slip faults and
possibly as oblique right-lateral faults during the emplacement on Paxos Zone should be considered since
the Miocene formations on the NVF fault zone are
intensely tectonized and frequently outcrop under
the Ionian Zone formations (Maradochori area).
Moreover, along these fault zones the Ionian Zone
formations migrated further to the west interrupting
the continuation of the thrust surface towards the
south. However, these faults do not displace the Paxos Zone formations.
Additionally, the N110°—130° faults that control
watersheds and streams are frequently interrupted by
the N20°—40° fault system and for this reason they
are considered as older from the latter. Possibly, they
were formed during the early Pliocene-early Pleistocene, a period when, according to Sorel and Cushing (1982) and Cushing (1985), the tensional regime
was compressional.
Many researchers suggested that during the Quaternary the Lefkas Island was under compression of
a N40°—60° direction (Drakopoulos and Delibasis,
1982; Cushing, 1985). Mercier et al. (1987) proposed
that this compressional phase dominates the area since
the middle Pliocene. According to Cushing (1985),
this compressional regime gradually decreases in our
days. Angelier et al. (1982) suggested that in the broader area of the Ionian Islands, the lower values of extension can be recorded, â<1.0.
The N70°—90° fault system, according to Mercier et al. (1987), Cushing (1985) and Sorel et al.
(1988), during the late Pleistocene was attributed to
an intense compressional episode of a WSW—ENE
direction. This compression resulted in the development of a right-lateral horizontal slip and the
formation of the E—W trending Sperchios-Amvrakikos fault zone (Fig. 1a). For many researchers,
the Sperchios-Amvrakikos fault zone, which has a
significant right lateral horizontal slip, represents
the western projection of the North Anatolian Fault
(Aubouin and Dercourt, 1975, Papanikolaou and
Dermitzakis, 1981; Mariolakos et al., 1985). This
zone is regarded as an active structure (McKenzie,
1972; Lyberis, 1984, Lekkas et al., 2001). Based on
the EBASCO (1979) map, the Sperchios — Amvrakikos zone was defined as an extensional rift, while
Doutsos et al. (1987) suggested that the formation
of Amvrakikos Bay is related to the action of numerous faults without systematic horizontal WNW—
ESE direction.
Since the N20°—40° fault strike coincides with
the fold axes strike and with the main development
axis of the island, it can be suggested that this area
is under compression and these faults represent
active structures as the result of strain release towards the east and west. Moreover, based on the seismotectonic map of Greece, the most recent terrestrial faults recorded on the western coasts of Lefkas
Island are of middle Pleistocene — Holocene age
and have a 0°—30° strike.
Finally, although the N170°—190° fault system
relative correlation was not possible during the
fieldwork, it can be considered that this system and
the N20°—40° fault system were active during the
same period.
CONCLUSIONS
Based on two principal tectonic surfaces, the NVF
zone and the thrust, Lefkas Island was divided into
three main tectonic units that developed as morphotectonic units corresponding to the Karya (KMTU),
Maradochori (MMTU) and Athani (AMTU).
We suggest that the a large area of Lefkas Island
was under a NE—SW to ENE—WSW directed compressional regime since the Early Pliocene till now.
It caused the uplift of Paxos Zone in the western
region and the parallel submergence of the Ionian
zone in the eastern region.
Therefore, after Early Pliocene emplacement on
Paxos zone the continuous deformation caused fault
structures of N110°—130° direction. These faults
along with the N40°—60° strike fault system, morphotectonically formed the area of the Ionian zone formations and mainly the KMTU. They controlled the
watersheds and streams, while they shaped the KMTU
to a monoclinal en-echelon structure of northeastern plunge. This structure create three main surfaces
of gentle slopes at altitude of 800—900 m, 300—400 m
31
and 0—100 m, resulting in the transgression of the
lower fault blocks from the sea on the northeastern
area of the island.
During the Early Pleistocene, the change of the
direction of the compression from N40°—60° to N90°,
created the N70°—90° fault system. These faults morphotectonically affected the island controlling the
watersheds and streams.
The continuous compressional regime resulted in
the formation of fault structures with N20°—40° and
N170°—190° strikes that defined the coastal area.
Acknowledgment
We would like to thank Professor G. Migiros for his
constructive reviews on the manuscript.
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