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Paleogene deep-water sedimentation and paleogeography of

foreland basins in the NW Peloponnese (Greece)













Hellenic Petroleum, Kifissias Av. 199, 15124 Maroussi, Athens, Greece

2*Corresponding author:

 Agricultural University of Athens, Laboratory of Mineralogy-Geology, Iera odos 75, 11855 Athens, Greece;


University of Patras, Department of Geology, 26110 Patras, Greece


I.G.M.E., Messoghion str. 70, 11527 Athens, Greece

(Manuscript received July 30, 2004; accepted in revised form June 16, 2005)

Abstract: The NW Peloponnese (Greece) belongs to the west-verging Alpine thrust-fault belt. Deep-water sedimentation
ensued, in the Gavrovo-Tripolitza and Ionian foreland basins, as relief was being built-up and the Tertiary compression
migrated westwards. The deep-water sedimentation and the deep structure of the thrust-fault belt are hereby assessed on
the basis of interpreted seismic profiles, borehole and field data. The sedimentation is controlled by sea-level changes and
thrust activity. The highest sedimentation rates for the Gavrovo-Tripolitza and Ionian Zones are observed during the
Early Oligocene. In the Late Eocene, within the Gavrovo-Tripolitza Basin, middle to outer fan associations prevailed
(Drossia-Charavghi Formation) changing to a channeled sea floor (Roupakia Formation) as the Pindos thrust front
approached. A deceleration of the Pindos’ advancement, combined with sea deepening, changed the environment to
distal fan and hemi pelagic (lower Skouras Formation). On top of the Skouras Formation a regressive episode is marked.
In Late Eocene, clastic sedimentation was installed in the Ionian Basin. First, distal fan facies overwhelmed the Ionian
carbonate sedimentation (Mavri Miti Formation). In the Early Oligocene the Santameri Formation witnesses basin
stability with distal characteristics in its lower parts. The lower Peta Formation, during the Late Oligocene is similar to the
previous one. A rapid and important uplift of the Pindos hinterland is marked in Peta’s upper members.

Key words: Greece, NW Peloponnese, Paleogene flysch, deep-sea fan evolution, foreland basins, fold and thrust belt,
seismic—borehole—field sedimentary data analysis.


The continuous deformation of the continental margin of the
Adria microplate, during its collision—subduction with the Eu-
ropa since the latest Cretaceous, has resulted in the formation
of numerous foreland basins associated with fold-thrust belts.
Beaumont (1981), Stockmal et al. (1986), and others, using a
variety of mechanical descriptions for lithospheric flexure,
have modeled foreland subsidence and the resulting thickness
of the foreland basin fill. These geodynamic models showed
that a lithospheric flexure caused by overthrust loading, cou-
pled with the resulting topographical expression across the
thrust belt, is an adequate mechanism for generating a foreland
basin and the stratigraphy of the deposits within it. The eustatic
sea-level changes and the thrusting activity control the evo-
lution of the clastic facies of the submarine fan formations
in the foreland basins. The combined action of these factors
is recorded by the patterns of the clastic sediments as well as
by their stratigraphic organization and depositional geometry.

After Brunn (1956) and Aubouin (1959) the External Helle-

nides s.l. in Western Greece (Pindos, Gavrovo-Tripolitza, Ion-
ian and pre-Apulian Zones), consist of a series of sub-parallel,
north—south trending tectono-stratigraphic zones including
several east-dipping thrust sheets and west verging folds.

From the Late Triassic to Eocene, a deep basin (Pindos

Ocean) developed between the Adrian and Eurasian plates,

comprising deep-water carbonate, siliciclastic and siliceous
rocks (Alexander et al. 1990; Degnan & Robertson 1998).
The collision—subduction between these plates, mainly dur-
ing the Tertiary, has progressively affected the External Hel-
lenides by compressive tectonics giving rise to folding and
thrusting of the previously mentioned zones. The deforma-
tion started in the Late Eocene within the Pindos Zone while
the Gavrovo-Tripolitza, the Ionian and the pre-Apulian
Zones were progressively involved during the Neogene—
Pleistocene (Underhill 1989; Kamberis et al. 1996).

In this paper new data are presented concerning the sub-

marine fan (flysch) facies of the Gavrovo-Tripolitza and the
Ionian Zones in the NW Peloponnese during the Late
Eocene to Late Oligocene (Fig. 1). Furthermore an attempt
is made in order to interpret the depositional environments
and their control mechanisms acting during the deposition
of the flysch sediments.

The study of the deep sea sediments and their paleogeo-

graphical significance are mainly based on the turbidite me-
soscale facies concept of Mutti (1974, 1977), Mutti &
Ricci-Lucchi (1972, 1975) and Ricci-Lucchi (1975). In a
smaller scale, the Bouma (1962) elementary sequence was
used where applicable.

Furthermore the present structural geometry of the Exter-

nal Hellenides, based mainly on subsurface geology such as
seismic information and borehole data, has been outlined.

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Gavrovo-Tripolitza Zone

The Gavrovo-Tripolitza Zone represents a stable shallow

carbonate dominated platform (Dercourt 1964). The Gavro-
vo-Tripolitza sediments include Middle Triassic to Upper
Eocene / earliest Oligocene limestones and Eocene to Lower
Oligocene flysch (Fleury 1980). The permanent shallow-wa-
ter sediments (Late Jurassic to latest Cretaceous) are distin-
guished by successive regressive episodes (Bernier & Fleury
1980). Gavrovo-Tripolitza Zone is considered as part of the
Adria microcontinent (Sorel 1976; Thiebault 1982; Under-
hill 1989). According to Alexander et al. (1990) this unit
structurally underlies the Pindos thrust sheets.

Carbonate sequences

The carbonate sequences, exposed in Skolis Mt (Fig. 2),

comprise Upper Cretaceous to Eocene thick-bedded carbon-
ates starting with Senonian rudist limestones. According to
previous studies the uppermost limit of the carbonate sedi-
ments, including the transitional beds, are of Early Oligocene
age (Izart 1976; Fleury 1980). The transitional beds (3—10 m

Fig. 1. Location map of the study area with the tectono-strati-
graphic zones of the External Hellenides. PTF – Pindos thrust
front, GTF – Gavrovo-Tripolitza thrust front.

thick) are composed of a thin horizon of bioclastic carbonates
with small-sized nummulites, marly limestones and marls. Ac-
cording to our field and micropaleontological analysis the
transition between the carbonate and the clastic deep-water
sedimentation was gradual without any interruption during the
Eocene. This situation is typical in the northern flanks of Sko-
lis Mt as well as further to the east, close to the Pindos thrust
slices (Alepochori village, Fig. 2) but, due to the tectonic ac-
tivity, it is not observed in the southern part of Skolis Mt.
In the C—D section (Fig. 3) the contact between the limestones
and the flysch of the Gavrovo-Tripolitza Zone is clearly
marked by a strong well-organized reflector.

Turbiditic fan facies

The turbiditic fan facies, east of Skolis Mt, consist of three

distinct formations. The prevailing typical facies types of these
formations are presented in Fig. 4:

1 – The Drossia-Charavghi  Formation is composed of

Upper Eocene (Priabonian, biozone of Turborotalia cerroazu-
lensis  and  Areosphaeridium diktyoplokus) to Lower Oli-
gocene (biozone of Globigerina ampliapertura) pelitic facies.
The lower horizons crop out close to the Pindos thrust front in
three successive thrust slices near the Drossia and Alepochori
villages. In these areas, the normal contact between the carbon-
ates and the flysch sediments (Facies D


, D


 and G) is locally

disturbed due to tectonic movements producing collapse

Near the village of Charavghi, on the eastern flank of Skolis

Mt, the uppermost horizons of the Drossia-Charavghi Forma-
tion are exposed. This part of the flysch consists of siltstones
and thin-bedded alternations of very fine sandstones with
small scale ripple marks (Facies D


 and D


). The sandstones in-

clude incomplete Bouma (1962) sequences (T


, T


). The

above-mentioned flysch facies associations are interpreted as
outer fan deposits, marking a sea transgression episode during
the Early Oligocene.

2 – The Roupakia  Formation, overlying the Drossia-

Charavghi Formation, marks an important change in the sedi-
mentation, characterized by the predominance of stacked
channel sequences (Fig. 4). At the base of each sedimentary
unit conglomerates (Facies A


) and massive sandstone beds

(Facies B) have been observed, while more pelitic intervals (Fa-
cies D) are progressively intercalated. The conglomerates
have been deposited on the highly eroded upper surfaces of
the pelitic beds of the underlying unit. Between these con-
glomerates are intercalated horizons presenting more chaotic
structure expressed by slumps, olistostromes and olistoliths
(Facies F) and rarely normal graded bedding corresponding
to Facies A


. In rare cases, imbricate pebbles indicate a rough-

ly east-to-southwest current direction. Sandstones of Facies C
succeed these conglomerates. Flute and groove casts show the
same as above paleocurrent flow direction (Fig. 4). Mud clasts,
fragments of lignite and vertical burrows, up to 60 cm in
length, also exist suggesting an important input of sediments
controlled by relatively strong turbidity currents during Early
Oligocene times (biozone of Globigerina ampliapertura and
Wetzeliella gochtii). From the base to the top of this formation,
the lithofacies associations contain an increasing amount of

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Fig. 2. Geological map of the NW Peloponnese.

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Fig. 3. Interpreted seismic profile C—D showing the faulted structure of the Gavrovo-Tripolitza Zone. 1 – Quaternary, 2 – Neogene (L. Mi-
ocene (?)—L. Pliocene, facies undivided), 3 – Flysch of Gavrovo-Tripolitza Zone, 4 – Gavrovo-Tripolitza limestones, 5 – Flysch of Ionian
Zone, 6 – Ionian limestones, 7 – Ionian evaporites, KLF – Kalfas Fault, DS – Décollement surface. For location of the profile see Fig. 2.

pelitic material showing a decrease of the overall energy of
the sedimentary gravity flows. The sandstones present an up-
wards fining and thinning sedimentary sequence with dis-
persed pebbles and small-scale synsedimentary structures
such as slumps and ripple marks. Facies E are also presented.
The above mentioned facies are interpreted as proximal and
belonging to a levee environment.

3 – The Skouras Formation is mainly composed of pelitic

facies overlying the Roupakia Formation (Fig. 4). The lower-

most horizons are composed of alternations of coarse sand (C



and clays in positive sequences (middle fan). The intermediate
parts of the Skouras Formation are dominated by thick pelitic
intervals of facies D


 and G, while upwards they alternate with

coarser sandy facies of C


 and D


 type. These lithofacies are

deposited during the Early Oligocene (biozone of Globigerina
ampliapertura and Wetzeliella gochtii) in a deep marine envi-
ronment (outer fan to basin plain). Abundant sedimentary
structures, such as ripples, flute casts and slumps have been ob-

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Fig. 4. Submarine fan facies of the Gavrovo-Tripolitza Zone with
representative mesoscopic scale sequences.

served in the upper members of Skouras Formation sandstones
suggesting a proximal marine environment. Finally, the upper-
most part of the Skouras Formation is characterized by the pres-
ence of thick conglomerates, well exposed in the Kombovouni
Mt (Facies F and A


 mainly). These conglomerates include

angular to subangular clasts derived from the Pindos Zone,
indicating a relatively short distance of transport (Pavlopou-
los & Tsagalides 1991). In the earliest Oligocene (Drossia-
Charavghi Formation) the paleocurrent flow direction was
towards the NW, while in a later stage (Early Oligocene) the di-
rection was towards the SW (Roupakia and Skouras Forma-
tions). This remarkable change of the paleoflow direction may
reflect a continuous change of the foreland basin topography
(Pavlopoulos & Tsagalides 1991; Alexander et al. 1990).

The total thickness of the flysch formation in Gavrovo-

Tripolitza Zone, deduced mainly by seismic and borehole
data, is estimated about 3700 m.

 Ionian Zone

The Gavrovo-Tripolitza carbonate platform passed west-

wards into an important intra-platform rift basin, the Ionian
Zone. The oldest known strata of this zone are the evaporites
including halite, anhydrite and gypsum accumulated in the
Triassic basins and later mobilized. Although the evaporites
crop out only in the Kyllini Peninsula, outside of the study
area, they were drilled in several locations in the NW
Peloponnese (Kamberis 1987; Kamberis et al. 2000).

Carbonate sequences

In continental Greece the lower parts of the sequence are

composed of shallow water carbonates (Pantokrator Forma-
tion) corresponding to a pre-rift sequence of Early Lias
(Aubouin 1959). Since the Late Lias a syn-rift period (Dercourt
1964; Karakitsios 1995) favours, in basinal areas, the deposi-
tion of pelagic sediments such as marls, carbonates, Posidonia
shales and Ammonitico Rosso facies. Micritic cherty lime-
stones (Vigla Formation) of the latest Malm to Early Creta-
ceous reflect the post-rift period. In the study area only the
upper calcareous part of the Vigla Formation is exposed near
the Cape Araxos, while the lower parts were identified in the
well Sosti-1, located out of the studied area, close to the Peris-
teri-1 well (Fig. 2). The Upper Cretaceous to Lower Eocene
deposits comprise alternations of microbrecciated and pelag-
ic limestones. These carbonate facies, as well as in the Vigla
Formation, include characteristic upwards thickening and
coarsening carbonate sequences including ripple bedding
levels indicating a deep-sea deposition environment.

During the Late Eocene meso- to large scale slumps and

olistostromes are observed within the limestones expressing
instability of the sea bottom during this period. This instabil-
ity is also marked in the lower parts of the Ionian flysch sedi-
ments, as it is the case of the Mavri Miti Formation (s. next). A
21 m thick (1965—1986 m depth) carbonate-flysch transition
zone has been found in the AR-1 well (Fig. 2) composed of
limestones, marly limestones and subordinate sandstones, in-
dicating an open marine to bathyal environment.

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Turbiditic fan facies

The turbiditic fan facies, west of Skolis Mt, can be divid-

ed into three distinct formations, which have been recog-
nized in field sections as well as in the AR-1 borehole
lithology log (Figs. 5 and 6):

1 – The lower Mavri Miti  Formation consists of upper-

most Eocene turbidites (biozone of Turborotalia cerroazulen-
sis and Areosphaeridium diktyoplokus), which are exposed in
the Cape Araxos. In Klematia—Paramythia region, to the north
in Epirus, a Middle Eocene age of the lowest parts of the Ionian
flysch is reported (Avramidis et al. 2000). The lower parts of the
Mavri Miti Formation are composed of Facies D



turbidites. These deposits are succeeded by Facies G including
olistoliths of reddish Eocene limestone, with small-sized num-
mulites. These beds include chaotic deposits with olistoliths,
sandstone olistostromes, slumps and flame structures.

Above these members, Facies C have been deposited sepa-

rated from the previous ones by an erosional surface marked
by the presence of mud clasts and fragments of lignite. The
sandstone beds (Facies C) show a thickening and coarsening
upwards trend and locally exhibit ball-and-pillow structures,
in a lenticular sand body. Above the erosion surface the fly-
sch sediments expose a fining-upward trend. The non-graded
sandstones of Facies C


 are bounded by even and parallel

surfaces, including small scale ripple marks showing a weak
current flow. The thickening upward trend of the pelitic in-
tervals seems to be indicative of the deep marine conditions.
Furthermore, in the upper part of this unit turbiditic se-
quences (Facies D


) have also been observed.

In the upper members of the Mavri Miti Formation the

flysch sedimentation is characterized by progressive coars-
ening-upward sequences. They are composed of Facies E, C


and D


. Conglomeratic sandstones (Facies C) predominate at

the top of this unit. Usually the top surfaces of the sandstone
beds are in sharp contact with the overlying pelitic layers.
The upper horizons of the Mavri Miti Formation are of Early
Oligocene age (biozone of Globigerina ampliapertura and
Areosphaeridium diktyoplokus), but contain an undeter-
minable fauna, while in previous works a post-Ypresian age
has been reported (Tsoflias 1993).

In the section E—F (Fig. 7) the Mavri Miti Formation, as

litho-seismic unit, is represented by the lower group of well
organized reflectors. More sandy intervals correspond to
the top of this unit and are composed of thin layered parallel

2 – The Lower Oligocene flysch sediments (Fig. 5) are

well exposed near the Santameri village, in the western side
of the Skolis Mt. Pliocene-Quaternary sediments cover the
transition between the Mavri Miti and the Santameri Forma-
tions. Thus, there is a lack of observation for about 700 m
when compared to seismic sections.

The  Santameri  Formation consists mainly of very fine

grained facies sediments (Facies D


 and D


) with sandstone in-

tercalations (Facies C) especially in the lower part. A minor tec-
tonic activity within this time interval (Early Oligocene)
generated high energy turbidity currents capable of transport-
ing coarser material. In this lower part the presence of Helm-
inthoidea and Paleodictyon ichnofacies suggest a relatively

Fig. 5. Submarine fan facies of the Ionian Zone with representative
mesoscopic scale sequences.

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Fig. 6. Log of the Ionian deep-sea fan sequences (see also Fig. 5)
issued from the AR-1 well. For location see Fig. 2.

and sandstones (Facies B and A


) with high relief erosional

surfaces mark a relatively shallow marine environment (inner
to slope fan). These facies (B and A


) are normally arranged in

graded coarsening upwards beds. The pelites contain high
amounts of sand and scattered pebbles. Field measurements
of flute casts imply paleocurrents flowing to the southwest
during the deposition of the Ionian flysch (Fig. 5). The Peta
Formation  corresponds to the uppermost part of the E—F sec-
tion (Fig. 7) and it is represented by well marked thick paral-
lel reflectors. The coarser material on the top of the Peta
Formation corresponds to the well marked thickest reflec-
tors, observed on the top of the E—F section (Fig. 7).

The total thickness of the Ionian flysch formation, as deduced

from drillings (AR-1 well), seismic profiles and field observa-
tions is estimated at 2700 m, including the transitional beds.

Tectonic setting

On the basis of field observations and seismic profile in-

terpretation, numerous compressional structures have been
recognized, formed during westward thrust propagation.

The Pindos Zone is considered to be the main tectonic

nappe in Western Greece. At the eastern part of the study
area, the Pindos Zone is thrusted over the Upper Eocene-
Lower Oligocene flysch successions of the Gavrovo-Tri-
politza Zone inferring a post-Lower Oligocene westward
movement. Likewise the Gavrovo-Tripolitza Zone has been
affected by the westward migration of the orogenic front.

Between the Skolis Mt and the Pindos thrust front (PTF) sev-

eral imbricated compressional structures are recognized (Fig. 2
and Fig. 9). The main structures correspond to intermediate-
scale hanging wall anticlines and footwall synclines associat-
ed with high angle thrust and reverse faults, dipping to the east,
as is the case near to Kalfas village (KLF), in Skouras (SKF) and
Roupakia (RFZ) (Figs. 2 and 8). This results in the overall in-
crease of the Gavrovo-Tripolitza flysch thickness (Fig. 8). In
several cases, these faults seem to present a listric geometry
passing downwards progressively into a low angle and finally
subhorizontal surface situated at the top of the Ionian Zone fly-
sch that is considered to be the décollement surface of the
Gavrovo-Tripolitza Zone. This surface lies approximately at a
depth of 4 to 5 km (0 to 2.5 sec T.W.T.) below the outcropping
Gavrovo-Tripolitza flysch deposits, while it becomes deeper
towards the Pindos thrust front (Fig. 9). In the C—D (Fig. 3) sec-
tion, the décollement surface between the Gavrovo-Tripolitza
limestone and the Ionian flysch is clearly outlined expressing a
low angle thrust surface, dipping eastwards. The development
of the hanging wall anticlines and imbricate fans has also been
reported north of the study area, in Etolia-Acarnania region
within the same foreland basin (Sotiropoulos et al. 2003).

This tectonic and structural style has been described in

several foreland folds and thrust belts around the world such
as in Southern Canadian Rocky Mountains (Bally et al.
1966), Southern Appalachians (Sachnic & More 1983) and
Appeninnes (Kruse & Royden 1994).

The western limit of the décollement surface is a high angle

east dipping surface corresponding to the Gavrovo-Tripolitza
thrust front (GTF, Figs. 7 and 9) of Skolis Mt. As a result, the

deeper marine environment (biozone of Turborotalia opima
opima and Wetzeliella gochtii). The above mentioned lithofa-
cies (D


, D


 and C) are mainly composed of fining upwards se-

quences. Within the uppermost horizons positive sequences
are observed indicating the beginning of an important change
of the depositional system (Mutti 1974). Furthermore, within
these sequences, SW of Portes village conglomeratic lenses
and limestone olistoliths are intercalated (Facies A



In the section of the Fig. 7 the middle to lower parts of the

Santameri Formation are composed of fair to roughly marked
reflectors. Towards the middle to upper parts of this formation
the reflectors are relatively better portrayed marking the sand-
iest interval of this formation (see also Fig. 6, AR-1 well).

3 – In the Upper Oligocene Peta  Formation  (Turborotalia

opima opima and Chiropteridium partispinatum) the domi-
nant coarse sediments of Facies B and C, alternate with more
pelitic intervals, mainly in the basal parts. In the uppermost
strata (exposed north of Peta village) thick conglomerates

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Cretaceous-Eocene limestones of Skolis Mt may be consid-
ered as a characteristic narrow hanging wall half-anticline
related to the thrust front. West of Skolis Mt the upper hori-
zons of Ionian flysch successions are of Late Oligocene age
(Peta Formation). Consequently it is considered that the
Gavrovo-Tripolitza thrust activity started, at least since the
earliest Miocene or earlier.

The Ionian Zone, successively, has been involved in the

westward propagating thrust belt resulting in thrusts and
large-scale folds. In contrast to the Gavrovo-Tripolitza
Zone, the Ionian Zone is characterized by open anticlines

(E—F section, Fig. 7) and synclines, reflecting a more ductile
style deformation related to the presence of Triassic evapor-
ites (Kamberis et al. 2000). It is assumed that these evaporites
played an important role in the geodynamic evolution of
the more External Hellenides.

The thrust faults, formed in the Ionian Zone, seem to sole

downwards in the evaporitic layer considered as the detach-
ment horizon of this zone (C—D section, Fig. 3). At the location
of the above-mentioned compressional structures diapiric
movements have been developed since the Pliocene, affecting
the Pliocene-Quaternary sedimentation (Kamberis et al. 1996).

Fig. 7. Interpreted seismic profile E—F showing imbricate reverse faults in the Ionian Zone, close to the Skolis thrust (right uppermost
part). Faults are marked in the footwall as well as in the basement of Triassic evaporites. The latter are involved in the shortening process in
a relatively later time period. Note the normal fault IoF, underneath the Skolis thrust characterized by a significant throw (0.8 sec / TWT).
1 – Neogene-Quaternary, 2 – Flysch of Ionian Zone, 3 – Ionian limestones, 4 – Evaporites, 5 – Flysch of Gavrovo-Tripolitza Zone,
6 – Gavrovo-Tripolitza limestones, IoF – Ionian normal fault, GTF – Gavrovo-Tripolitza thrust front, AGN – Aghios Nikolaos fault,
MAM – Mavri Miti Formation, SA – Santameri Formation, PE – Petas Formation, MMF – Moni Maritsas fault zone, DC – Drossia-
Charavghi Formation. For location of the profile see Fig. 2.

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Fig. 8. Cross-section through the Skolis Mountain and the Pindos thrust (A—A’ in Fig. 2) showing the main contractional structures of the
Gavrovo-Tripolitza and the Ionian Zones (modified from Kamberis et al. 2000).

Fig. 9. Interpreted seismic profile A—B showing the internal structure of the Gavrovo-Tripolitza Zone in the Kato Achaia Basin. Notice the
flexible deformation of the underlying Ionian Zone related to the presence of the Triassic evaporites. 1 – Neogene—Quaternary, 2 – Pin-
dos Zone (facies undivided), 3 – Flysch of Gavrovo Zone, 4 – Gavrovo limestones, 5 – Flysch of Ionian Zone, 6 – Ionian limestone,
7 – Triassic evaporites, GTF – Gavrovo-Tripolitza thrust front, DS – Décollement surface, PTF – Pindos thrust front. For location of
the profile see Fig. 2.

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In the eastern part of the E—F seismic profile (Fig. 7) a shal-

low group of prominent seismic reflectors is distinguished and
interpreted as the top of the Gavrovo-Tripolitza carbonate se-
quences. These limestones are covered by a few hundred
meters thick of shaly flysch at Skolis area, west of the main
Gavrovo-Tripolitza thrust. Thrust fault planes of lower order
locally exist in the lower sandy flysch members of the San-
tameri Formation, as it is the case of Portes village and WNW of
Arla village, near Maritsa Monastery. In these locations a typ-
ical ramp-flat geometry is observed in several outcrops. In the
same seismic profile the lower group of reflectors correlates
with the base of the flysch sequence. Ramp-flat thrust geome-
try is also recognized at the base of the Ionian carbonate series.

Furthermore, field observations in the Gavrovo-Tripolitza

and Ionian Zones reveal the existence of several secondary
WNW—ESE and ENE—WSW trending, sinistral and dextral re-
spectively, strike slip faults (MMF and AGN, Fig. 2), which cut
almost perpendicularly the previously mentioned thrust zones.
These faults are considered as accompanying features, formed
during the westwards thrust propagation in Miocene times (Ka-
mberis et al. 2000). Some of these faults are reactivated, during
the latest Cenozoic, as normal faults with quasi vertical angle
of pitch. This is the case of MMF and AGN fault zones.

Moreover in the study area numerous mesoscale faults

have been measured on Tertiary to Quaternary sediments.
The WNW—ESE trending normal faults affect both the flysch
and the Pliocene sediments, reflecting a more recent faulting
process. This type of faulting has also been reported for an
area adjacent to the southern coastline of the Patraikos Gulf
(Fig. 2, Kamberis 1987; Zelilidis et al. 1988). In many cases,
the WNW—ESE faults coexist with W—E and ENE—WSW
trending normal faults in the previously mentioned areas.

The formation of these faults is related to the late north-south
extensional stage since the Late Pliocene.

Tectonosedimentary evolution of the foreland basins

– Discussion

The examined deep-sea fan formations were deposited in

foreland basins developed in front of an active thrust belt as the
typical characteristics of this kind of basins are fulfilled:

– There is a horizontal compression generated by coupling

at the contact between subducting and overriding plates
(e.g.  Kanamori 1986).

– There is a pre-existing thick pile of layered strata (e.g.

Allmendiger et al. 1983) corresponding to the Pindos Zone for
the Gavrovo-Tripolitza Basin and the Pindos and Gavrovo-
Tripolitza Zones for the Ionian one.

– The foreland basins are a result of the deformation of a

foreland fold-thrust belt (Fig. 10).

The long-term accumulation in a foreland basin requires tec-

tonic subsidence. Nonetheless, surface processes impact such a
strong influence on the stratigraphy that many times the pure
tectonic signal is obscured. The main types of controls that are
independent of the local tectonic activity are craton lithology,
climate, eustatic sea-level and geological age.

In order to correlate the different types of the flysch se-

quences to the tectonic activity and / or other processes the
following observations are made: the Gavrovo-Tripolitza
submarine fan sequences, east of Skolis Mt, start in Late
Eocene with the Drossia-Charavghi facies associations that
correspond mainly to middle to outer fan deposits, indicat-
ed by weak turbidity currents with rare hemipelagic inter-

Fig. 10. Generalized situation of the foreland basins during Eocene—Miocene.

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Fig. 11. Comprehensive diagram showing the tectonic events and the corresponding sedimentary formations in relation to the eustatic
curves. The formations’ thickness is based on well and seismic data.

beds. The approach of the Pindos thrust pile, in the Early
Oligocene, caused an important change of the sedimentary
facies to inner fan / slope type deposits (Roupakia).

A calmer interval of the thrust advancement is clearly ob-

served in the middle—upper members of the lower part of the
Skouras Formation, which continue the up section evolution.
Later on the environment changes to outer fan turbidites. The
upper parts of the Skouras Formation indicate a new prograd-
ing phase of the thrust front, as the facies become coarser cor-
responding to an inner fan to slope / canyon environment.

From the above it is concluded that the flysch sediments east

of Skolis Mt represent a deep-sea fan influenced by an impor-
tant regressive sea level episode that took place in the Early
Oligocene, during the deposition of Roupakia Formation.
Progressively, a sea transgression followed, and resulted in the
deposition of the Skouras Formation (Fig. 11). The sedimento-
logical data of the Roupakia Formation imply a high-energy
depositional environment. The high-energy conditions, which
controlled the Skouras sedimentation, are not in accordance
with the general trend of the eustatic curve (Haq et al. 1987;
Fig. 11). This fact is related to the important tectonic activity
along the Pindos thrust. The Kombovouni conglomerates, on
the top of the Skouras Formation, mark the end of the sea
transgression and correspond to the beginning of a new rapid
regressional episode, which can be related to the combined
action of tectonics and the rapid fall of the sea level.

West of Skolis Mt the Upper Eocene Mavri Miti Forma-

tion, in Araxos region, shows a prograding tendance of the

compressional front. This is underlined by the proximal fa-
cies corresponding to an inner fan and slope environment.
The overlying members show a more even area of deposi-
tion that favours the formation of an inner to middle fan en-
vironment with channel fill and overbank facies. Rapid
deposition of sand produced flame and ball-and-pillow
structures. The more or less important synchronous seismic
activity has facilitated this procedure.

The lowermost part of the Mavri Miti Formation (Late

Eocene) is mainly influenced by the tectonic activity to the
east related to the Pindos thrust (Fig. 11). Progressively a
more proximal environment (inner fan) was installed. The
Lower Oligocene Santameri Formation corresponds mainly
to a more distal environment. The presence of abundant trace
fossils underlines a relative stability during the deposition of
the Santameri Formation. The lithoseismic characters ex-
pressed by non-deformed thin layered, well-organized, con-
tinuous and parallel reflectors confirm this stability (Fig. 3).
This event is in accordance to the corresponding eustatic
high sea level. Towards the upper parts of the Santameri For-
mation a more proximal environment was installed.

The Upper Oligocene Peta Formation shows a rapid upward

coarsening due to a more westwards progradation of the orogen
as well as to the contemporaneous fall of the sea level (Fig. 10A).

The overall evolution of the Ionian turbiditic flysch depos-

its, considered together as a great scale unit, exhibit a prograd-
ing trend that becomes more important in the upper
conglomeratic members of the Peta Formation.

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The paleocurrents in both zones (Figs. 4 and 5) have a

general W to SW flow direction with the exception of the
Drossia-Charavghi Formation (Gavrovo-Tripolitza Zone)
where the direction is NW. This is in agreement with the
paleocurrent measurements reported from Piper et al.
(1978) in the flysch of Etolia, north of the Patraikos Gulf
and in Makrynoros area, west of Gavrovo Mt (Pavlopoulos
1983; Vakalas et al. 2001). In contrast they only partly
correspond to the measurements of Gonzalez-Bonorino
(1996) in the east of the Amvrakikos Gulf area.

In the studied area the progressive overthrusting to the

west has resulted in the increase of the tectonic load and
caused a lithospheric flexure towards the orogene (Fig. 8).
Underhill (1989) has also reported the same assumption in
the islands of Zakynthos and Kefallinia. Due to this over-
loading, a foreland basin was formed in front of the oro-
genic belt, where synorogenic sediments were deposited
in deep water conditions. Furthermore, mountainous areas
have been progressively formed reflecting the underlying
footwall ramps as in Erymanthos and Skolis Mt. During
this process, the more external parts have progressively
formed a tectonic wedge migrating westwards.

The resulting overloading of the lithosphere, due to the

Ionian thrust emplacement on the Preapulian Zone, since
Early Pliocene, caused a further lithospheric flexure.

In order to calculate the sedimentation rates of the studied

flysch formations, in both zones, the true thicknesses of these
formations were calculated (Table 1). The calculation was a
product of field observations, as on Fig. 8, combined with
seismic information (Fig. 7) after conversion of the time scale
to a depth one. The results are presented in Fig. 12 from where
it is observed that the sedimentation rates in the Gavrovo-Tri-
politza Zone are generally higher than those of the Ionian
Zone. This is related to the combined action of the sea deep-
ening during the Rupelian (Fig. 11) which provided more ac-
commodation space, and the important thrust activity in the

Pindos Zone to the east. During this period the sedimentation
was extended to the most distal parts of the relatively deeper
Ionian Basin. In the higher horizons of the Gavrovo-Tripolit-
za flysch (Skouras Formation) the sedimentation rate remains
high compared to the partly synchronous Peta Formation of
the Ionian Zone.


The stratigraphic and map pattern of lithofacies classifi-

cation infer the depositional setting of ancient submarine
fans within the foreland basins of the Gavrovo-Tripolitza
and the Ionian Zones. This setting is related either to the
eustatic sea-level changes and / or the thrust tectonic activ-
ity, which occurred during the Paleogene in the External

The Gavrovo-Tripolitza turbiditic fan sediments corre-

spond, generally, to a more proximal depositional envi-
ronment than that of the Ionian one. In addition, during
distinct periods the deposition of the Gavrovo-Tripolitza
flysch was more affected by the thrust activity along the
Pindos thrust to the east than the Ionian flysch sedimenta-
tion. In the Gavrovo-Tripolitza sequences two major pro-
grading cycles are distinguished:


 – The older one that ends with the Roupakia Formation is

mostly related to a more intense tectonic activity. This event
does not fit the general trend of the eustatic sea-level change.


 – The younger one includes the basal parts of the Sk-

ouras Formation. The Kombovouni Conglomerates, on the
top of the Skouras Formation correspond to the beginning
of an important sea level regressional episode.

The greater part of the Ionian turbiditic fan facies were de-

posited in a relatively deeper sea-fan environment than that
of the Gavrovo-Tripolitza Zone. The lower part of the Ion-
ian flysch (Mavri Miti Formation) is marked by two major
overlapping fan prograding episodes. The end of the first
one is marked by a well developed erosion surface and other
typical structures of slope environment, while the second
one is incomplete. The upper part of the Ionian flysch (San-
tameri and Peta Formations) reflects mainly a progradation-
al sequence. The upper members of Peta Formation express
an intense orogenic thrust activity, accompanied by a well
marked important sea level regressive episode.


 The authors wish to thank Dr. J. Soták,

Dr. A. Robertson and an unknown reviewer for their con-
structive criticism which improved the first manuscript.
They are, also, indebted to the Hellenic Petroleum Compa-
ny for its permission to use the seismic data.

Table 1: Thickness and sedimentation rates during the deep-water sedimentation in the Gavrovo-Tripolitza and Ionian zones.

Gavrovo-Tripolitza Zone 

Ionian Zone 




Time span 









Time span 










Skouras (+Kombovouni) 










Roupakia 1100 









Drossia-Charavghi 1200 










Fig. 12. Curves expressing the sedimentation rates during the fly-
sch deposition in the Gavrovo-Tripolitza and Ionian Zones.

background image



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