Pindos Flysch Research Articles

HYDRAULIC AND STATISTICAL GRAIN-SIZE PARAMETERS OF PINDOS TURBIDITE DEPOSITS

Final closure of the Pindos ocean, resulted in collision of Apulia with Pelagonian microplates, produced voluminous clastic sediments that flowed southwards as turbidity currents in the form of submarine fans, giving rise to Pindos flysch during early Tertiary. Samples coming from thinbedded sandstones were collected from five cross-sections throughout Pindos flysch in order to determine the characteristics of the turbidity current between different areas. The hydraulic and grainsize statistical parameters showed that low energy turbidity currents deposited the analyzed sediments. Almost all samples show a positive skewness due to the competency of the unidirectional flow of the transporting media, where the coarse end of the size frequency curve is "chopped off'. The kurtosis values in combination with the sorting values are plotted to the turbidity filed. A correlation between the mean palaeoflow velocity and the grain size showed that the mean palaeoflow velocities related to sandy silt samples whereas the higher velocities with sandy samples.

EXHUMATION OF THE HELLENIC ACCRETIONARY PRISM – EVIDENCE FROM FISSION-TRACK THERMOCHRONOLOGY

Below the Potamos extensional detachment fault exposed in northern Kythera, the phyllite-quartzite unit (PQU) shows very consistent zircon FT cooling ages of c.11 Ma reflecting the time just after the rapid exhumation through the brittle-ductile transition. In contrast, a wide range of Mesozoic and some Paleozoic zircon FT cooling ages from Eocene-Oligocene Tripolis and Pindos flysch sandstones from above the detachment reflect sedimentary source ages. Early Miocene apatite fissiontrack cooling ages characterize the flysch sandstones, and show that early Miocene exhumation affected rocks above the detachment. The thermotectonic evolution of the flysch of Tripolis and Pindos units within the rocks above the Potamos detachment on Kythera is reconstructed using zircon and apatite fission-track (FT) thermochronology. The apatite FT data provide evidence for a burial depth of at least 6km for the samples, which were reset. Burial was not deeper than 11km, since the zircon fission-track system in the same rocks was not reset. The exposed rocks of Tripolis and Pindos flysch on Kythera represent part of an accretionary wedge with a burial shortly after deposition in or near the subduction trench, and a cooling history due to exhumation of the flysch in the early Miocene. The subsequent Mid-Late Miocene exhumation of the PQU unit follows from beneath the (mostly carbonate) Tripolis and Pindos sedimentary rocks.

Radiolarian biostratigraphy and geochemistry of the Koziakas massif ophiolites (Greece)

AbstractThe Koziakas massif, located at the western boundary of the Thessaly plain, consists of a nappe pile, which includes from bottom to top: 1– the Paleocene-Eocene Pindos Flysch; 2– the Western Thessaly Units (WTU); 3– the Ophiolitic Nappe, which consists of four minor tectonic units: a) the ophiolite-bearing Koziakas Mélange; b) the Fourka Unit; c) a thin discontinuous level of amphibolites (Metamorphic sole); d) a “Peridotite Unit”.This work focuses on the study of both the radiolarian assemblages of cherts situated at the top of basalts and the geochemistry of the latter. Our data show that in the Fourka Unit the cherts overlying the various basalts have diverse ages: a) latest Anisian (associated to WPB-OIB), almost coeval to the trachyandesites effused onto the continental rifts to the west; b) Early Carnian-Middle Norian and Late Carnian-Early Norian (associated to WPB-OIB); c) Early Norian (associated to E-MORB). In the Koziakas Mélange the age is Early-Middle Bathonian (associated to WPB-OIB).These data confirm the geodynamic evolution hypothesized for all the other ophiolitic massifs of the southern portions of the Dinaric-Hellenic belt, which can be synthesized as follows: a) birth of the Vardar-“Maliac” ocean in the Middle Triassic, coeval to continental basins to the west (Pindos basin, etc.); b) ocean spreading until Late Jurassic with intraoceanic subduction at the beginning of Middle Jurassic, followed by intraoceanic obduction; c) closure of the ocean (latest Jurassic-earliest Cretaceous) and thrusting of the Ophiolitic Nappe onto the eastern continental margin of Adria (the Pelagonian); d) westward displacement of the Ophiolitic Nappe testified by the presence of ophiolitic detritus first in the WTU (latest Jurassic to Late Cretaceous) and then, to the west, in the Pindos Flysch (Paleocene-Eocene).

OPHIOLITES FROM THE GRAMMOS-ARRENES AREA, NORTHERN GREECE: GEOLOGICAL, PALEONTOLOGICAL AND GEOCHEMICAL DATA

The Grammos-Arrenes ophiolites crop out between the Pindos Flysch to the East and the Meso-Hellenic basin to the West and represent the northernmost exposure of the Pindos Ophiolite belt in Greece. Field work and sampling on key outcrops of the Sub-ophiolitic Melange provided new data on the oceanization age and on the geochemistry of the effusive products. The basalts samples show a N-MOR affinity and are associated with latest Bajocian-early Bathonian radiolarian cherts. Emplacement of the ophiolites onto the continental margin is preceded by mass flow deposition of ophiolitic material in the basins facing the advancing ophiolitic nappe. Ophiolite-bearing debris flow deposits and slide blocks are recognized in the Early Cretaceous deep water sediments of the Beotian Unit and in the upper portion of the Tertiary Pindos Flysch. The intercalations of ophiolitic material in the Beotian Flysch first, and in the Pindos Flysch, later, are interpreted as the forerunners of the Ophiolitic Nappe which derived from the Vardar Ocean to the east, and was emplaced westwards onto the Adria continental margin. The collected data allow consolidating the constraints for the timing and mechanism of ophiolite emplacement in the Pindos-Grammos area. In addition, taking into consideration the geometry of the tectonic stack in the Grammos-Arrenes area and the ages of the involved sedimentary deposits it is possible to reconstruct a geodynamic history comparable to that of the other zones studied along the Dinaric-Hellenic Chain.

THE OPHIOLITE-BEARING MÉLANGE IN THE EARLY TERTIARY PINDOS FLYSCH OF ETOLIA (CENTRAL GREECE)

In Etolia (Central Greece), west of the Parnassus/Vardoussia units, the Pindos succession crops out, with its higher formation: the Pindos Flysch. In its upper portion levels of debris flow deposits and slide blocks (olistostromes and olistoliths) contain ophiolitic material with fragments derived from the Parnassus/ Vardussia formations. This ophiolitic material consists of serpentinites, basalts of WPB, E- and N-MOR affinity, and radiolarian cherts of Middle-Late Triassic and Middle-Late Jurassic age. Petrologic and biostratigraphic analyses confirm that the melange has the same features of the sub-ophiolitic melanges present at the base of the ophiolitic masses in Greece. Linked to the flysch, with contacts of unclear nature, a rhyolites body of Middle Triassic age indicates the continental nature of the Pindos Basin. In fact, here, as all over the Albanian-Greek section of the Dinarides, no record of an oceanic area in the central portion of the Dinarides exists: the Parnassus and Vardoussia units were directly thrust onto the Pindos Basin. The intercalations of ophiolitic and continent-derived material in the flysch, are interpreted as the forerunners of the Ophiolitie Nappe which, coming from the Vardar Ocean located to the east, reached during the Eocene the Pindos Basin.

The contribution of clay minerals in the landslides occurrence within Pindos flysh formation

An engineering geological investigation of the "Potamouli" area located west of Grevena town, for a water dam foundation, has revealed some geotechnical problems related to landslide phenomena. Landslides are of limited extent in the reservoir area, but significant instabilities were identified within the broad catchment basin. The basin is built up mainly by the chaotic unit of Pindos flysch formation, which consists of a silty clayey matrix with heterogeneous inclusions of rock masses in diverse frequency and size. In order to investigate the major contributing factors to landslide occurrence, several physical properties were measured, with the results suggesting that the overall mechanical behaviour of the unit is determined by the clay matrix properties. The mineral composition of the less than two micron fraction of this material was determined by X-ray diffraction. The clay minerals present are illite and montmorillonite. The percentage of montmorillonite reaches the 10% of the matrix fraction and may exert great influence upon the Atterberg limits, swelling, water adsorption, and shrinkage of the matrix material. Montmorillonite absorbs water between its individual silicate layers with resulting high swelling and low frictional resistance becoming by itself a contributing factor to the failures. The presence of expandable clay minerals within the chaotic unit of the Pindos flysh, may indicate that the remove of loose soil cover from the slopes of the reservoir area during the construction of the dam, may be inadequate for preventing future landslides, and a sealing up process may be needed.

Sedimentology and tectonic setting of the Pindos Flysch of the Peloponnese, Greece

Abstract The Palaeogene Pindos Flysch of the Peloponnese shows important differences from the flysch of northern Greece. Stratigraphic sections and palaeocurrent indicators were measured in the Pindos Flysch Formation and the underlying Kataraktis Passage Member throughout the Peloponnese. The Kataraktis Passage Member records carbonate-dominated sedimentation from the Apulian continental margin to the west, with intercalated terrigenous sediment also derived from the west. Variations in thickness and turbidite facies show that the overlying Pindos Flysch Formation was deposited in channels with levees and in channel-termination lobes in the western Peloponnese and in a distal basin plain, locally ponded, in the east. At least in the central Peloponnese, facies variation, palaeocurrents and detrital petrology show that the Pindos Flysch was derived from the Apulian margin. The Pindos Flysch of northern Greece, of late Paleocene to Oligocene age, was deposited in a foreland basin and derived from the rising Pelagonian nappes to the east. A younger microcontinental collision south of the Gulf of Corinth line resulted in the Pindos Flysch of the Peloponnese being incorporated in the accretionary prism by Mid-Eocene time.

PROVENANCE OF PINDOS FLYSCH DEPOSITS IN METSOVO AND FOURNA AREAS USING SCANNING ELECTRON MICROSCOPY AND MICROANALYSIS

Pétrographie observation of sandstones that contain detrital grains and lithic fragments along with microanalytical data from certain minerals suggest that detrital material in Pindos flysch deposits, in Metsovo and Fourna areas, may have been sourced in the Pindos ophiolite and the Pelagonian metamorphic rocks; additionally some material from Fournas has probably been derived from the Koziakas ophiolite outcrop. The Loumnitsa Unit (Pindos ophiolite), has probably supplied the Pindos foreland with ma+erial from the erosion of amphibolites while the Dramala Unit was the most probable source of spinels and ultramafic material. Fragments of acid plutonio rocks have been observed, too, owing their origin from the plutonite of Vamounta-Kastoria (Pelagonian Zone). The area of Fourna has been also fed by the Koziakas ophiolites, as evidenced from the composition of chlorites and epidotes.

BEHAVIOR OF PINDOS FLYSCH DURING TUNNELLING THROUGH A THRUST ZONE. DEFORMATION AND ROCK BEHAVIOR. EXPIERENCE FROM THE ACHELOOS RIVER DIVERSION TUNNEL TO THESSALY.

The Acheloos diversion project consists of a series of reservoirs and a diversion tunnel. The tunnel has a designed internal diameter of 6m and a total length of ca. 17 400 m. Through the tunnel waters from the upper Achellos will be transferred to Thessaly. The project area belongs entirely to the Pindos zone. To the west (Mouzaki - Drakotrypa area) limestone, Jurassic chert and transitional strata (limestone and siltstone interchanges) overthrust sandstone and siltstone of the Pindos Flysch association (Paleogene). The thrust plane is well exposed and its geometrical features are clearly defined on the surface. Within silt- and sand- stones of the flysch, the developement of shear zones borders the thrust plane. Tunneling through limestone and chert advanced without specific problems. Tunneling through the flysch sequence slowed down the advancing rate. This was partially due to the composition and structure of the formation. The stand-up time was reduced due to compositional changes and the throughout development of shear zones. Heavy support measures were insalled and immediate monitoring began in the area where the thrust zone was developed. Data analysis and its results show that the rock formation remained into a dynamically active status. Four months after the excavation forces acting at the tunnel perimeter, exceeded the support measures bearing abilty causing tunnel radial convergence and the development of damages became visible. In this paper we describe tunneling conditions, the geology and the response of formations during excavation, as this was interpreted by monitoring data. We describe the damages caused as well as the counter measures applied in order to control and terminate the tunnel convergence.

Provenance of the Peloponnese (Greece) flysch based on heavy minerals

The heavy mineral distribution of the Palaeogene flysch deposits of the Ionian, Gavrovo–Tripolitza and Pindos zones of the Peloponnese has been systematically investigated. The Ionian zone is distinguished from the Gavrovo–Tripolitza zone by higher amounts of detrital chrome spinel. The Ionian and the western occurrences of the Gavrovo–Tripolitza flysch are comparable with the successions of the Greek mainland, whereas samples of the Gavrovo–Tripolitza flysch from central and eastern locations of the Peloponnese, which crop out in tectonic windows, are clearly distinct. On the basis of heavy mineral distribution, the Gavrovo–Tripolitza flysch of the central and eastern Peloponnese shows clear relationships to the metaflysch sediments exposed in the tectonic windows of Olympos and Ossa, in Thessaly, which have no relation to the Gavrovo flysch of the mainland. The Pindos flysch from the Peloponnese contains the same heavy mineral assemblages as the pre-Middle Eocene deposits of the mainland. Younger Pindos flysch sediments are not observed on the Peloponnese. The differences in heavy mineral distribution within the Gavrovo–Tripolitza flysch, between the western and eastern localities, can be explained by an intensive reworking of Pindos flysch during the tectonic progradation of the Pindos nappe onto its foreland basin.

On the provenance of flysch deposits in the External Hellenides of mainland Greece: results from heavy mineral studies

The terrigenous materials of the flysch deposits of the External Hellenides of mainland Greece have been characterized by their heavy mineral assemblages, based on 194 samples. Three major source types were distinguished. (1) A metamorphic source is shown by abundant garnet accompanied by traces of staurolite and chloritoid. In the source of the Pindos and Ionian zones, blueschist complexes were incorporated within the metamorphic terrains, demonstrated by the frequent occurrence of blue amphiboles. (2) The existence of ophiolitic sources is indicated by the occurrence chrome spinel. Pyroxenes, green amphiboles and partly epidote are related to volcanic/metavolcanic complexes. High ophiolitic detritus was especially found in Mid-Cretaceous turbiditic layers supplied from internal terrains. (3) Granitoid and gneiss source terrains are indicated, predominantly represented by zircon, tourmaline and apatite. This type of source is characteristic for Mid-Cretaceous turbidites sampled in western parts of the Pindos zone. In the terminal flysch deposits, granitoid detritus played only a subordinate role. An extensive recycling of Pindos Flysch material into the younger Western Hellenic Flysch can be excluded. Stratigraphic trends in the heavy mineral distribution of the terminal Pindos Flysch give insights into the changing tectonic situation of the source terrains. A regional east–west trend with changing ophiolitic detritus, observed in the Parnassos-Ghiona Flysch, points to a complex feeder system.

Die Flysch-Zonen Griechenlands V. Zur Stratigraphie des Flysches der Pindos-Zone im nördlichen Pindos-Gebirge zwischen der albanischen Grenze und der Querzone von Kastaniotikos (Griechenland)

Die Flysch-Zonen Griechenlands V. Zur Stratigraphie des Flysches der Pindos-Zone im nördlichen Pindos-Gebirge zwischen der albanischen Grenze und der Querzone von Kastaniotikos (Griechenland)

Tectono-stratigraphy and evolution of the Mesozoic Pindos ophiolite and related units, northwestern Greece

The northwest Pindos Mountains expose Mesozoic and Tertiary thrust sheets, which include the Jurassic Pindos ophiolite, composed of ultramafic and mafic oceanic crustal rocks. The tectono-stratigraphy of these units is: (i) mainly ultramafic ophiolitic thrust sheet and basal metamorphic sole (Dramala Complex and Loumnitsa Unit); (ii) Late Cretaceous platformal limestones (Orliakas Group); (iii) dismembered intrusive and extrusive ophiolitic rocks (Aspropotamos Complex): (iv) tectonic melange and olistostromes, dominated by Triassic-Jurassic volcanic and sedimtntary rocks (Avdella Melange); (v) coherent thrust sheets of Late Jurassic–Late Cretaceous deep-water sediments (Dio Dendra Group); (vi) Early Tertiary flysch (Pindos Flysch). Immobile trace-element studies indicate that Triassic and Jurassic extrusives of the volcanic-sedimentary melange formed mainly at within plate and/or mid-ocean ridge settings. By contrast, structurally overlying ophiolitic extrusives include boninitic volcanics and island arc tholeiites, of supra-subduction zone origin. Initial ophiolite displacement ( c . 165 Ma) is recorded in metamorphic sole formation, including basal peridotite mylonite, amphibolites and greenschists. The sole rocks have MORB and WPB chemical affinities. In our favoured model, the Pindos ophiolite formed above a Mid-Jurassic westerly-dipping intra-oceanic subduction zone, accompanied by accretion to form melange, followed by collision and emplacement with the Pelagonian margin. Final suturing of the Pindos ocean, however did not take place until Early Tertiary times.

Paleomagnetic results from the Pindos, Paxos, and Ionian zones of Greece

Maastrichtian to Miocene sediments were sampled at 12 sites in central Greece (Meso-Hellenic basin, Pindos zone and Western Thessaly unit) and four sites on Lefkas island (Paxos and Ionian zones). The samples were subjected in the laboratory to thermal and alternating field (AF) cleaning. As a result, characteristic remanent magnetizations (ChRMs) were obtained for 11 sites. In comparing these paleomagnetic directions with others already obtained for the external Hellenides, the following points are noteworthy. 1. (1)|In post-Alpine times a slight clockwise rotation seems to be common to the zones of the external Hellenides in Western Greece; 2. (2)|independent movement of the Pindos flysch and the Ionian Paleogene sediments is plausible as the sampled sites from the former exhibit large counter-clockwise declination rotation with respect to the latter; 3. (3)|the net rotation of the Mesozoic sediments of both Pindos and Ionian zones is similar. These observations may indicate that the two zones rotated independently as ‘blocks’ before the Miocene, for the detachment of the Paleogene from the Mesozoic sediments is opposed on geological grounds. Thus the similar declinations observed for the Mesozoic sediments of the Pindos and Ionian zones must be regarded as coincidence.

Origins and significance of rocks in an imbricate thrust zone beneath the Pindos ophiolite, northwestern Greece

Summary Major zones of imbrication under the Pindos ophiolite of northwestern Greece relate to the formation of frontal and oblique ramp structures. These are marked by a northwest-trending line of tectonic windows in the ophiolite and a northeast-trending anticlinal structure which folds thrust contacts. The simplified structural sequence from top to bottom is: (1) Ophiolite lithologies, mainly pillow basalts and basal serpentinite; (2) Metabasites and meta-sediments of the ophiolite dynamothermal aureole ranging up to lower amphibolite facies; (3) A complex sequence of basalt, gabbro, pelagic sediments, olistostromes, debris flows and breccias interpreted as a sea floor sequence (the Perivoli Complex); (4) Early Cretaceous calcareous flyschoid sediments; and (5) Tertiary Pindos Flysch and melange. All the greenschist facies and the higher grade metamorphic rocks are interpreted as part of the metamorphic aureole and not as Palaeozoic basement. The generalized sequence of major deformational episodes is: (A) Thrusting within the sea floor with concurrent metamorphism causing polyphase deformation and juxtaposition of the ophiolite, the dynamothermal aureole and the Perivoli Complex. (B) The main imbrication along NNW-trending, E-dipping planes, involving all the lithologies and associated with the formation of major frontal and oblique ramp structures. (A) occurred during the Middle Jurassic ‘displacement’ of the ophiolite sheet. ‘Emplacement’-related deformation may have occurred in (1), (2) and (3), but is difficult to isolate due to the intensity of episode (B) which occurred during westward overthrusting in the Late-Tertiary and may have been related to an E-dipping subduction zone.