Ionian Zone Research Articles

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.

New ammonite data about the earliest syn-rift deposits (Lower Jurassic) in the Ionian Zone of N-W Greece (Epirus)

New ammonite data about the earliest syn-rift deposits (Lower Jurassic) in the Ionian Zone of N-W Greece (Epirus)

Evaporites in Albania and their impact on the thrusting processes

The Upper Triassic evaporites are widespread in Albania, Greece, and Montenegro (mainly on External zones). They belong to the Alpine orogene system of the Periadriatic chains. The Upper Triassic age of the evaporites up to date had been determined by spore-pollen examinations only for the Ionian zone. For the Kruja and Korabi zones there are no determinations. All the evaporite outcrops in the Ionian zone (Dumrea’s, Glina’s Zavrohona’s, Delvina’s, Picar-Kardhiqi’s, Bashaj’s, Xara’s, Filat’s etc) result from eruption under the effect of thrust tectonics. The wells drilled both in Albania and Greece have shown a wide extension of the evaporites on the surface. The evaporite outcrops are absent in the Kruja zone in Albania. Evaporitic diapirs have extruded through the thrusting faults of the zones, belts and units. In some cases they have flowed nearly vertically in the center of the carbonate anticlinal structures. The External zones resulted from the orogenic activity over which evaporites have played a large role with the form of folds and thrust belts. Especially, they have helped the thrusting process of the structural belts and tectonic zones.

Geomechanical properties of sandy soil near Scanzano Jonico (Basilicata, Italy)

The soils of the Ionian coastal zone, except those in proximity to Taranto where overconsolidated clays outcrop, are not currently well known from the perspective of their physical characteristics and mechanical behaviour. This note report a series of data from laboratory and on site tests (SPT and CPT) that have made it possible to undertake interesting quantitative comparisons as well as verifying some correlations proposed in the literature. The results show how to deal with, at least for more obviously sandy soils, medium and/or high density sands, to which can be attributed friction angles even of the order of 40° and greater, while the soils nearer the surface show notable variability related to the presence of soils with finer grain size distribution.

Zyklische Massenstromsedimentation im obereozänen bis untermiozänen Flyschbecken der östlichen Ionischen Zone bei Ioannina (Epirus/NW-Griechenland)

Zyklische Massenstromsedimentation im obereozänen bis untermiozänen Flyschbecken der östlichen Ionischen Zone bei Ioannina (Epirus/NW-Griechenland)

Geological construction of southern part of Ionian zone based on interpretation of seismic data

The Ionian zone is the main object of seismic interpretation for a long time. Within this framework, we shall analyze the new seismic intrpretation methods used in oil and gas exploration in the western part of Ionian zone. The Ionian zone is very complex involving certain tectonic faults. In the central part, we can see the duplex tectonic style. Anticline belts from east to west can be interpreted.The Ionian zone comprises three anticline belts:Berati belt, Kurveleshi belt and Cika belt. By application of SeisWork2D in the eastern part of the belt, we have evidenced some perscpective structures, meanwhile in the western part, the seismic quality is very chaotic. Kurveleshi belt is constructed by structures of various forms and dimensions associated with developed tectonics up to thrusting. Cika anticline belt is constructed mainly by prolonged structures of considerable dimensions associated with evaporate outcrops as in Xara, Fterra, Cika etc.

QUANTITATIVE ANALYSIS OF DEFORMATION ALONG THE FAULT DAMAGE ZONE OF THE KLIMATIA THRUST (NW GREECE, IONIAN ZONE)

In this study, we present structural, fracture orientation and fracture density (FD) data in order toquantify the deformation pattern of a damage zone that form around the slip plane of a large scalethrust fault which is located on the Ionian zone (External Hellenides) in northwestern Greece. Structuralanalysis showed at least two major deformation stages as indicated by the presence of refolding,backthrusting and break-back faulting. The fracture orientation analysis revealed three mainfracture systems, a dominant conjugate fracture system which is perpendicular to the transport direction(NW-to NNW trending sets), a conjugate fracture system trending parallel to the transport direction(ENE-trending conjugate sets) and a third diagonal conjugate fracture system (WNW andNNE trending sets). Resulting fracture density-distance diagrams display a decrease of total fracturedensity away from the studied fault, which is largely heterogeneous and irregular on both footwalland hanging wall. The conjugate fracture system trending perpendicular to the transport directionhas the dominant contribution to the accumulation of total fracture density. Based on theseresults we suggest that the observed heterogeneous and irregular distribution of fracture densityfashioned during the second deformation stage and is attributed to the formation of backthrusts andbreak-back thrust faults.

Geomorphic evolution of the upper reaches of the drainage basin of Acheloos river

The scope of this study work is to give an insight into the dynamic processes which shape the relief in the drainage basin of the upper reaches the Acheloos river, so that the geomorphological and geodynamical evolution of the region in the past can be approached, together with a possible prediction. For this reason, the relationships between the relief and the endogenic and exogenic factors are sought. The investigated area is made up of geological formations that belong to the zones: "Ionian" (inner Ionian zone), "Gavrovo", "Pindos" and "Hyperpindos". There are also younger rocks (postalpine formations), together with some volcanic rocks. The main stream segment of Acheloos river was formed in the Upper-Middle Miocene, after the deposition of the flysch of "Gavrovo" and the tectonism of the zone. The structures were cut to a large extent by trace-slip faults, striking ENE-WSW, during the Middle-Upper Miocene. At the same time (Lower Miocene - Plio-Quaternary), in NW-Greece, is observed a horizontal clockwise rotation (45°). Finally, the region shows an expanding movement from North to South. Due to the above tectonic activity, the drainage basin shows a monoclinic structure with a westward displacement of the drainage pattern. The displacement increases from North to South. The displacement of the drainage pattern is also favoured by the presence of erodible rocks in the western part (flysch of "Gavrovo") and the general eastward dip of the strata. Neotectonic activity controls the river up to date, as it is inferred from the orientation of the stream segments, which follow the tectonic structure (lithological boundaries, faults, thrusts). The drainage pattern appears to be in an early mature stage. According to the quantitative geomorphological analysis data, the drainage pattern (mainly the west part of it) is in an unstable dynamic status. During Plio-Quaternary there were a few rejuvenating episodes, due to tectonic and climate changes. The present rejuvenated stage, which is more obvious in the southwestern part of the investigated area, is supported by morphotectonic data. Among them, the most remarkable are: a)the steep slopes (30-60 %), b)the negative deviation of "cummulative" area compared to ideal values, c)the slope flexions, which separate the new lower level from the old higher one.

Emersion generalisee intra-maastrichtienne de la plate-forme de Gavrovo-Tripolitza (Grece); effets sur les populations de foraminiferes Rhapydionininae

Abstract The reliability of biostratigraphic correlations in neritic carbonate platforms is often questioned because the benthic fauna on which biozonation is based are particularly sensitive to environmental change. It is crucial to know whether a population change corresponds strictly to a facies change. Conversely, there arise the questions of determining how populations are renewed over time and how new species appear even if facies associations remain unchanged. This is the case with the Gavrovo-Tripolitza zone of Greece, an isolated shallow carbonate platform surrounded by two oceanic domains (Pindos-Olonos Zone and Ionian Zone). The absence or scarcity of faunas generally used in Upper Cretaceous biostratigraphy has led to the use of local biozonation instead, based on faunas endemic to Adriatico-Aegean platforms. The final two biozones based on Rhapydioninidae foraminifera are: - CsB6 (Upper Campanian-Lower Maastrichtian): the "Murciella biozone" is the total range zone of all Rhaphydionininae except for Rhapydionina liburnica; - CsB7 (Upper Maastrichtian): the total range zone of R. Liburnica. The purpose of this paper is to test the biostratigraphic value of the benthic foraminifera by comparing the distribution of the biostratigraphic limits with the distribution of time-surfaces. These time-surfaces are established from sedimentological analysis and sequences stratigraphy. The Upper Cretaceous of the Gavrovo platform is formed by stacked shallowing-upward parasequences which are usually capped by an exposure surface. Most of them were exposed in supratidal environments and dolomitized to a greater or lesser extent. Some underwent continental diagenesis as recorded by karsts, microkarsts and karstic fillings (fig. 5), root traces, alveolar-septal structures, microcodiums, pseudomicrocodiums, pedogenetic pseudomicrokarsts and continental stromatolithic laminations. Although outcrops are great distances apart and located on different structural blocks, they record a major discontinuity within the Maastrichtian. It is characterized by continental exposure, a change in the main type of parasequences, and disruption of the parasequence stacking pattern as evidenced on Fischer plots. In each outcrop, limestones exhibiting continental diagenesis are cut by an erosional surface. This surface is proposed as a local maximum of regression and a transgressive surface. On a peculiar outcrop, the surface marks the inflection point between thinning-upward and thickening-upward parasequence trends on the Fischer plot. In proximal platforms, such a point can be interpreted as corresponding to a local maximum of regression and this surface is also a transgressive surface. The same features occurred in many other outcrops and show that the entire platform was subaerially exposed. Similar episodes of exposure associated with continental diagenesis are reported for Maastrichtian deposits of other Adriatico-Aegean platforms. Continental exposure and associated erosion is currently interpreted as a result of a fall in relative sea level caused either by uplift or by eustatic sea level fall. Successive shallowing up parasequences showing final exposure and continental diagenesis would imply an impossible yo-yo type subsidence. Accordingly, the proposed maximum of regression is thought to be eustatically controlled. Moreover, the maximum of regression caps CsB6 parasequences controlled by allocyclic mechanisms as indicated by similar stacking patterns in different and remote outcrops. This strongly suggests CsB6 sedimentation was eustatically controlled and the relevant maximum of regression is proposed as a time-surface. The distribution of foraminifer populations in the outcrops studied here indicates that the Rhapydionininae of biozone CsB6 do not occur above the maximum of regression. The regressive maximum clearly coincides with the disappearance of foraminifer species whereas the subsequent transgressive episode is characterized by the emergence of just one species. And yet, population renewal is not related to a fundamental change in the platform environment: very shallow water facies association below and above the maximum regression surface are identical. This supports the hypothesis that sea level variations were the cause of faunal extinction and renewal. It is evidenced too that the boundary between the two populations can be used as a time marker. In this case study, the biostratigraphy based on the use of benthic and shallow-water dependent foraminifera is genuinely chronostratigraphic.

Tectonic relationship between the Druja (Gavrovo) and the Ionian zones of the Albania thrust belt

The Kruja zone and the Ionian one are integral parts of the Albanian Thrust Belt, which lie directly in the northern continuation of the Western Hellenic Nappes up to their interruption against the thrust front. Flysch of the Oligocene and rarely carbonate deposits of Cretaceous-Eocene age consist the area along the boundary between the tow zones in question. Deposits of both tectonic zones are similar. But, despite the lithological similarities, presence of conglomerates in the Oligocene flysch and dolomites in the Cretaceous carbonates are the main characteristics of the Kruja zone. Whereas, pelagic carbonates in the Cretaceous section, as well as presence of detritic foraminifer limestone in the Oligocene flysch typify the Ionian zone.

Structural and neotectonic features of the periadratic depression (Albania) detected by seismic interpretation

The Periadriatic Depression includes the western Lowland of Albania from Vlora to Ulqini. The Periadriatic basin, formed after the main folding and thrusting of Ionian zone, is filled with molasses deposits. The molasse formation building this Depression is made up by Middle Miocene up to Pliocene sediments. The Periadriatic Depression extends on its eastern and southern bordes over folded and thrusted structures of the Ionian and Kruja Zones. The folding and thrusting of Periadriatic Depression is finally due to the Early Pleistocene compressional phase that is evidenced by some important structural unconformities. The Periadriatic Depression is built by some linear relatively narrow anticlines, superimposed over thrust or backthrust faults, and wide synclines. The Mio-Pliocene anticlinal folds generally do not outcrop with all their tectonic elements (flanks,periclines). The positive structures of western coastal part are well expressed on the relief; so, the anticlines here build hills while the synclines are buried under Holocene plains between them. The structural and neotectonic features are evidenced in the seismic lines

The so called "triassic breccias" of the Ionian zone in Greece and Albania: Their stratigraphie position and the ensuing tectonic implications

Field observations are reported which show that: 1) at least part of the so called "Triassic breccias" of the Ionian isopic zone actually represent a local variant of the basal breccias of a Middle-Upper Miocene marine terrigenous sequence; 2) other portions of the same Miocenic basal breccias have been often mistaken in the past for some other looking-like terrane of different age (from Jurassic to Quaternary!). Since some currently accepted inferences on the time-sequence of both sedimentary and tectonic events ensuing from the above misunderstandings become questionable, new field investigation should be extended to the entire Ionian zone with due regard to the above terranes.

Origin and migration mechanism of the main hydrocarbon seeps in western Greece

In this presentation a description of the main hydrocarbon indications of Western Greece is given, in relation to their origin and migration mechanism. Five groups of oil have been defined (Palacas et al.1986, Ν. Rigakis 1999) and their appearance on surface or in wells is explained. Doger shales are the source rocks of the first group of oil seeps in the central Ionian zone in Epirus (Botsara). Migration takes place through inverse or thrust faults. The second group is located at Trifos of Etoloakarnania, and Kyllini and West Katakolon well of NW Peloponissos. It is originated from Lower Cretaceous source rocks and migration happens through active diapiric movements of the Triassic evaporites. Triassic evaporites play important role in the maturation and migration and possible entrapment of this group of oil. The third group has genetic and migration relation with Triassic evaporites and their movements and is found at Delvinaki of Epirus and in the Well South Katakolon, offshore West Peloponissos. The fourth group that appears at Keri and Alikes of Zakynthos Island, it is possible to be originated from Middle- Upper Miocene post-tectonic sediments. The unconformity between Alpine and Post-Alpine sediments and some normal faults, is the possible pathway of migration mechanism. In the same team another oil show at Marathopolis, near Filiatra, is included with some doubts about its real origin. The fifth group is found at Paxos Island in the Preapulian zone. The oil is generated mainly from Middle-Upper Jurassic sediments, while older sediments of Lower Jurassic and Triassic are not excluded as possible source of the oil seeps. It is important to note that the contribution of the ground water movements is important in migration mechanism in some of the described cases. Finally, we strongly believe that the geological sections that are included in the text explain better our results and thoughts.

Migration and trapping of the Ionian series hydrocarbons (Epirus, NW Greece)

Surface oil shows in the Ionian zone of NW Greece are mainly linked to the organic matter rich Lower Posidonia beds of Toarcian age and shale fragments within the Triassic breccias. The calcareous formations of the Ionian series are characterized by insignificant primary porosity-permeability. Only fractured carbonates might comprise potential reservoir rocks capped on top by the detrital series. Other prospective traps, with the evaporites playing the role of cap-rocks, are related to the degree of basement involvement in the structural evolution of the Ionian basin.

Thrust dissection control of deep-water clastic dispersal patterns in the Klematia–Paramythia foreland basin, western Greece

The Klematia–Paramythia basin is an internal part of the middle Ionian zone of the Hellenide orogen in western Greece. It consists of Middle Eocene to Late Miocene turbidites, up to 3300 m thick, which were deposited in a series of submarine fans. Field studies suggest that the configuration and the depositional environments of the basin were affected by two tectonic phases. During the first tectonic phase, in Middle Eocene to Late Oligocene times, a foreland basin was formed west of the Pindos Thrust front. During the second tectonic phase, in the Early Miocene, the Ionian zone (a part of the foreland basin) was subdivided by internal thrusting into three sub-basins (internal, middle and external) and changed to a complex type foreland basin. Comparison of the type and facies associations of the turbidite deposits that accumulated within the basin suggests that these two tectonic phases had a significant effect on sedimentary dispersal patterns. During the first tectonic phase in the Klematia–Paramythia basin (when it was part of the foreland basin), fine-grained turbidites, up to 1050 m thick, accumulated on the distal part of a submarine fan. The lower part (900 m thick) of these deposits consists of thin to thick interbedded sandstone/mudstone beds which are interpreted as lobes and lobe-fringe (outer-fan) deposits. The upper parts (150 m thick) of these deposits are composed of very thin to thin siltstone/mudstone beds, representing a basin plain environment. During the second tectonic phase, sediments up to 2260 m thick were deposited in the Klematia–Paramythia basin. These deposits are interpreted as lobes and lobe-fringe (outer-fan) fine-grained turbidites in the central part of the basin, channel and interchannel deposits (inner-fan) in some areas of the periphery of the basin, and shelf deposits in the northern and southern terminations of the basin.

Fluid circulation in the Ionian fold and thrust belt (Albania): implications for hydrocarbon prospectivity

Within the Ionian zone, which belongs to the external Albanide fold and thrust belt, a surface reservoir analogue was studied with the aim of unravelling the processes which exert an effect on the dual porosity network. Matrix porosity preservation in the Cretaceous to Eocene carbonate turbidite beds relates to early cementation, where the presence of a mixture of micritic and mono-crystalline bioclasts (crinoids and rudists) controls the framework-stabilising development of cements. The presence of these cements explains why these lithologies have not been entirely compacted (as happened for the overlying micrite-dominated lithologies). The underlying bioclast-rich layers also do not possess any porosity since they were entirely cemented.Present-day oil production is mainly fracture-related. Several vein generations have been recognised as well as other tectonic features such as conjugate high-angle or tension joints and stylolites. With respect to the latter, bed parallel (i.e. compactional) and bed perpendicular (i.e. layer parallel shortening or tectonic) stylolites have been differentiated. The spatial relationships between these stylolites and the veins allow differentiation of pre-, syn- and post-kinematic fluid fluxes, which have been characterised based on their petrographical (i.e. cathodoluminescence), geochemical (trace and stable isotope) and fluid inclusion features. This exercise shows that the fluid flow system was rock buffered until the folding and thrusting period. From then onwards the fluid flow system reflects the interaction with fluids which reacted with evaporites which occur as decollement horizons as well as fluid flow systems in relation to the maturation of hydrocarbons. Finally after folding and faulting, the studied anticlinal structure was temporarily emergent during the Miocene. During this period sediment infilled karst cavities formed. Since the latter sediment infill is not compacted but porous, they contribute to the total oil-in place.

Calpionellid zonation at the Jurassic/Cretaceous boundary within the Vigla Limestone Formation (Ionian Zone, western Greece) and carbon isotope analysis

The calpionellid standard zones, Crassicollaria, Calpionella andCalpionellopsis , identified in the Tithonian–Berriasian carbonate sequence at Paramythia (Ionian Zone, western Greece), have been subdivided into eight subzones: the Tithonian Crassicollaria Zone into the Crassicollaria intermedia and Crassicollaria brevis Subzones, the early Berriasian Calpionella Zone into theCalpionella alpina , Remaniella and Calpionella elliptica Subzones, and the late BerriasianCalpionellopsis Zone into the Calpionellopsis simplex, Calpionellopsis oblonga andPraecalpionellites murgeanui Subzones. On the basis of this zonation the Jurassic/Cretaceous boundary (Tithonian/Berriasian boundary) is equated to the lower boundary of the Calpionella alpina Subzone. The carbon-stable isotope measurements performed on bulk samples from Paramythia indicated a decrease in δ13C values from the Tithonian to the Berriasian owing to (a) a decrease in transfer of organic matter into the sea caused by the lowering in Calcite Compensation Depth, (b) the presence of a deeper-water environment in the Ionian Basin and (c) a fall in the sea level and increased oxygenation of the water column. These changes, which favoured the deposition of carbonates, led to a decrease in burial rate of the organic matter and to the fall in the carbon-stable isotope values.

Thrust Tectonics and the Role of Evaporites in the Ionian Zone of the Albanides

This study focuses on the Alpine fold and thrust belt in the Ionian basin of Albania, where there are giant onshore oil fields. The evaporites have acted as a detachment layer but also have been cut by thrusts that carry evaporites to the surface in their hanging walls. Where the detachment is located at the top of the evaporites, they are dragged up in the footwall along thrusts, and faults develop at the base and the top of the evaporite. Simple shear deformation along the thrusts causes greater than 80% thinning of the evaporite, so that sheets of only 40-200 m thickness are preserved, whereas the original evaporite thickness probably was well in excess of 2000 m. Where ramps cut through the evaporite and cause repetition of the complete evaporite layer, the salt is remobilized into salt-filled compressional anticlines or escapes at the surface to produce smeared-out surface extrusions. The most spectacular example of this is the Dumrea structure, where the evaporites have developed into a complex shape from an overthrusted allochthonous sheet that has been extruded at the surface. The Dumrea structure is up to 5.6 km thick proved by drilling and has been displaced laterally by up to 25 km, and it has the effective geometry of a giant sheath fold.

The source rock horizons of the Ionian Basin (NW Greece)

The organic geochemical study of six geological sections and two wells in the Ionian Zone (NW Greece), allows us to distinguish five horizons of possible source rocks: The Vigla shales (Cenomanian–Turonian), the Upper Posidonia Beds (Callovian–Tithonian), the Lower Posidonia Beds (Toarcian–Aalenian), the marls at the base of the Ammonitico Rosso (Early Toarcian), and shale fragments incorporated within the Triassic breccias. These horizons have good hydrocarbon potential and an organic matter type I to II. In the deeper parts of the Botsara sub-basin, the oil window is located in the interval between 3700–5800 m depth. Consequently, the Triassic shales have already entered the gas window. The Lower and Upper Posidonia Beds, and the marls at the base of the Ammonitico Rosso are mature in terms of oil generation. The Vigla shales maturity corresponds to the early maturation stage. The timing of the principal oil-source horizons maturation is the Late Jurassic for the Triassic shale beds and the Serravalian for the Lower Posidonia Beds. The preservation of the organic matter in the Lower and Upper Posidonia Beds through Toarcian to Tithonian and in the marls at the base of the Ammonitico Rosso during Early Toarcian are directly related to the geometry of the syn-rift period of the Ionian Basin. The organic matter preservation in the Vigla shales is related to the sub-basins that were preserved by the continuation of halokinetic movements during the post-rift period. The geometry of the restricted sub-basins that were formed during the syn-rift and post-rift period of the Ionian Basin evolution favored water stagnation and the development of local euxinic conditions in the bottom waters; these conditions were accentuated during the anoxic events that are known to have affected the Tethys ocean during the Early Toarcian and Late Cenomanian. The organic rich shale fragments within the Triassic breccias were initially deposited as stratigraphic layers in sub-basins of the evaporitic basin. The establishment of evaporitic sedimentation in the entire basin favored the preservation of the organic matter. The processes that resulted in the formation of the evaporite dissolution collapse breccias caused also the fragmentation of the organic rich layers, which are present actually as organic rich shale fragments within the Triassic breccias.

Sedimentological study of the triassic solution-collapse Breccias of the Ionian zone (NW Greece)

The Triassic Breccias of the Ionian zone are typical evaporite dissolution collapse breccias. Several features indicate the pre-existence of evaporites, while alternation of dolomites and evaporites consist a very common association in the subsurface.