Ionian Zone Research Articles

Sedimentary Characteristics and Basin Evolution of a Compartmentalized Foreland Basin—Internal Ionian Zone, Western Greece

This study is based on the detailed sedimentological analysis of eleven sections and one well through the late Eocene–Oligocene flysch formation of the Internal Ionian Zone (IIZ) in Western Greece. The sections are spread from the northern parts of Epirus to the north and Aitolokarnania to the south. Sedimentological data combined with biostratigraphic analyses resulted in a five-stage evolutionary model for the basin. Unit I corresponds to the lower part of the examined sections, indicating the onset of clastic sedimentation. Regarding depositional environments, it is regarded as a basin plain where lobe distal fringe accumulations occur. Unit II consists almost exclusively of heterolithic facies, marking the advance of a lobe complex system. Massive sandstone facies dominate unit III and can be considered a more proximal submarine fan system. Unit IV reflects a calm period of the basin, where mud-dominated heterolithics and hemipelagic mudstones were deposited. Hemipelagic mudstone facies with intervals of heterolithics, conglomerates, and deformed and massive sandstone facies characterize unit V. The architecture resembles a slope system incised by canyons and channels. The sand-rich intervals in Units III and V could act as the most favorable reservoir levels. In contrast, the sand-rich intervals in Unit II are considered less promising due to their higher heterogeneity.

Contrasting Styles of Salt‐Tectonic Processes in the Ionian Zone (Greece and Albania): Integrating Surface Geology, Subsurface Data, and Experimental Models

AbstractThe Ionian Zone (IZ) is one of the key elements of the fold and thrust belt (FTB) of the Albanian and Hellenides orogen and contains large outcrops of Triassic evaporites. The IZ consists of various thrust sheets with a general westward vergence, stacking over the Apulian and Pre‐Apulian zones, and repeating a thick carbonate sequence of Upper Triassic to Eocene age. Thrusting becomes younger toward the west with a piggyback sequence, starting during the latest Oligocene Epoch in the Internal Ionian and ending in the Pliocene in the External Ionian. We have studied the IZ in southern Albania and northwestern Greece using field observations and borehole data and by fully interpreting a recently acquired 2D seismic data set. Our objectives are to establish the geometry and nature of the contacts associated with the major Triassic outcrops, to unravel precursor salt diapirs, and to assess their role during the Alpine contraction. Salt structures include gentle salt pillows, isolated salt plugs and diapirs, thrust welds, and salt walls. Combining these observations with experimental modeling results, we show how these structures control the geometry and kinematics of the Alpine thrusts or the location and kinematics of recent strike‐slip faults. Salt minibasins have also been identified, demonstrating salt mobility conditioned Mesozoic sedimentation in the Ionian Basin. The use of salt‐tectonics principles to evaluate the structural style and evolution of the IZ FTB also opens new directions for interpreting the subsurface structure and evolution of the region.

Regional Scale, Fault‐Related Fluid Circulation in the Ionian Zone of the External Hellenides Fold‐And‐Thrust Belt, Western Greece: Clues for Fluid Flow in Fractured Carbonate Reservoirs

AbstractWe combined field mapping, structural and microstructural analyses, stable‐clumped isotope geochemistry, and U‐Pb dating of calcite veins and syn‐tectonic slickenfibres, to assess the regional scale fault‐related fluid flow during the evolution of the External Hellenides fold‐and‐thrust belt. We show that fluid circulation during forebulge uplift was characterized by cold meteoric water‐derived fluids, from which calcite precipitated and sealed bed‐perpendicular joints. Fluid circulation during foreland flexuring and early layer‐parallel shortening was characterized by warm fluids buffered by the carbonate host rock, which circulated through normal faults and bed‐parallel veins. Mixing with meteoric‐derived fluids also occurred at this stage of tectonic evolution. Fluid circulation during the late stage of thrust wedge accretion and post‐orogenic extension at 1.6 ± 1 Ma was characterized by increasing dominance of cold meteoric water circulating in strike‐slip and normal faults. The ingress of meteoric‐derived fluids was controlled by throughgoing fault conduits, while host rock‐buffered fluids were confined in isolated structures such as minor faults and veins. We developed a conceptual model of fault‐related fluid circulation, which invokes a transition from an open fluid system during forebulge uplift, to a semi‐closed fluid system during foreland flexuring and early layer‐parallel shortening, and to an open system during late thrust wedge accretion and post‐orogenic extension. This type of fluid circulation may have impacted fluid migration/leakage, including hydrocarbons, into or outside potential reservoirs in the highly prospective Hellenides‐Albanides fold‐and‐thrust belt, a renovated frontier for hydrocarbon exploration in the Mediterranean area.

Implications of Salt Diapirism in Syn-Depositional Architecture of a Carbonate Margin-to-Edge Transition: An Example from Plataria Syncline, Ionian Zone, NW Greece

The present study examines the imprint of salt tectonics on carbonate depositional patterns of the Ionian zone platform edge to slope transition. The study area is part of an overturned rim syncline adjacent to a salt diapir. The Ionian zone is made up of three distinct stratigraphic sequences (pre-, syn- and post-rift sequences) represented by evaporites and shallow water carbonates at the base that pass gradually to a sequence consisting of pelagic limestones with shale intervals. In the study area, six cross sections were constructed, mainly covering the edge-to-slope overturned succession of Early Cretaceous to Eocene carbonates (post-rift stage) in the northern limb of the syncline. In the measured sections, abrupt changes in sediment texture resulted in the formation of distinct, thick-bedded carbonate layers, identified as packstones to grainstones–floatstones, with abundant fossil fragments, indicating deposition by debrites in a platform slope or slope-toe environment. Planar and ripple cross-lamination also suggest the involvement of turbidity currents in the depositional process. In the upper levels of the Lower Cretaceous carbonates, chert bodies with irregular shapes indicate soft sediment deformation due to instability of the slope triggered by salt intrusion. Internal unconformities identified in the field and in the available seismic data combined with the vertical to overturned dipping of the strata correspond to a basal megaflap configuration. Syn-sedimentary deformation resulted in the accumulation of debritic and turbiditic layers, while the compressional regime established in the area from the Late Cretaceous to Early Eocene enhanced the fracture porosity of carbonates, which could eventually affect the reservoir properties.

Petrography and mineralogy of the Oligocene flysch in Ionian Zone, Albania: Implications for the evolution of sediment provenance and paleoenvironment

Abstract In this study, the reconstruction of the formation condition in the Oligocene flysch (Berati and Zhitomi section), in the Berati anticline structure, north-eastern part of the Ionian tectonic zone (Albania), is elucidated using petrographic–mineralogical characteristics and grain size analysis. Outcrops from the Berati and Zhitomi and the drilled wells were selected for sampling based on previous stratigraphic and paleontological studies. The mineralogical study of the flysch deposits made it possible to evidence for the first time three mineralogical zones: (a) quartz–garnet (b) serpentine, epidote with mica, and (c) feldspar zone, and three these petrographic zones: (a) quartz, (b) quartz–serpentine, and (c) quartz with mica and feldspars. The reconstruction of the depositional environment is based on the petrographic study of rock types, their textural characteristics, and grain size statistics. The granulometry coefficients like mean, sorting, skewness, and kurtosis are calculated arithmetically and the C/M diagram as well. Referring to the mineralogical composition of the sandstones and siltstones, the obtained data were used for the correlation of the sections and the delineation of the leaching area and the direction of the sediment movement. The mineralogic and petrographic characteristics show that during the Oligocene, the region has been under continuous paleogeographic change and under intensive orogenic activity, which has influenced the character of the mineralogical–petrographic composition of these deposits. Based on the pebbles petrography present in the slump horizons and on heavy mineral assemblages, it was evidenced that the eastern tectonic zones of Kruja, Krasta, and Mirdita (Albania) were the main suppliers of sedimentary material. The Passega C/M diagram suggests suspension and saltation as the main mode of sediment transport prior to deposition.

Geotechnical and petrographic properties of carbonate sedimentary rocks from Sasaj region (Ionian Zone) and their use as aggregates for road pavement

This paper is a part of the master’s thesis with the title “Geotechnical and petrographic properties of carbonate sedimentary rocks from different zones of Albania regarding their use as aggregates for road pavement” where this topic presents a particular method of study of limestones and dolomite aggregates from the point of view of their petrographic characteristics, the petrography being an important working tool which proves to be indispensable alongside the classical geotechnical study currently used in Albania. Our work was born from the need to demonstrate that the studies carried out by engineering, geotechnics and geomechanics should not lack synthetic reports on the different types of aggregates used in Albania, especially those of carbonate origin. Moreover, our goal was to take a step forward to fill this gap by accurately correlating the general geological knowledge and the lithological and petrographic characteristics of carbonate rocks with the engineering properties of the aggregates produced from these types of rocks. It is well known that petrography is focusing on details invisible to the naked eye, and therefore, for rock materials selected for the production of aggregates, this microscopic analysis is also necessary, as well as other laboratory analyses, if necessary to verify the stability of these aggregates. Concretely, in this paper we will present a part of our results which show the methods which we used in the analysis of materials from samples of carbonate rocks coming from Sasaj region, one of the four carbonate rock formations that we studied in our master thesis, these formations belonging to four different geological tectonic zones of Albania: Mirdita, Albanian Alpes, Kruja and the Ionian zones. The complete material will be the subject of a more detailed paper for a high impact international journal.

Periadriatic Foredeep (onshore Albania) Is Developed as Dextral Pull-Apart Basin

The Periadriatic Foredeep onshore Albania is the only Foredeep basin located in the frontal part of the Albanides orogeny bordering eastward the Adriatic Foreland. The recent neotectonic investigations and previously published ones prove the formation of Periadriatic Foredeep as a dextral pull-apart basin in the Middle Miocene (Serravallian), subsequently to the main folding and thrusting of the Ionian Zone, through the strike-slip faulting mechanism. The two elements that commonly lead to the formation of the Periadriatic Foredeep Pull-apart Basin are the cross-basin strike-slip faults of Drini Bay-Lezha and Vlora-Bishqemi, and the oblique normal faults of Durresi-Frakulla and Preza-Rova-Bishqemi. The infill consists of the Serravallian to Pliocene molasses succession up to 6 km in thickness. The Periadriatic Foredeep Basin is located between the South Adriatic and Tirana Marginal Basins. The development of the Periadriatic Foredeep finally led to the different evolution of both the Periadriatic and Tirana depressions with different structures and mineral resources. The Periadriatic Depression structure is built by an NNW trending narrow anticline and wide syncline lines. From southwest to the northeast, these lines are distinguished: Frakulla-Durresi anticlinal line, Myzeqe syncline, Lushnja-Golem Kavaja anticlinal line, Erzeni i poshtem syncline, and Preza monocline. The Myzeqe and Erzeni i poshtem depocenters are separated by the intrabasinal Mliku-Shkoza high. The Divjaka gas field and Patosi, Marinza, and Kuçova oil fields are well known in the Periadriatic Depression. The Tirana Depression is developed from the Tirana marginal basin eastward bordering the Periadriatic Foredeep. It is characterized by the prevailing continental and shallow-marine Miocene sediments (with coal-bearing fields in Tortonian and Messinian deposits) that formed a wide northeast verging asymmetrical syncline due to the Preza-Rova-Bishqemi backthrust. The Tirana Depression overlies the Kruja Zone substratum to the north of Tirana, and partly, the Ionian Zone substratum to the south of Tirana along its western limb to the east of the Rova anticline backthrust. Deformation of orogenic crust at the Albanides-Adria collision zone during Tertiary occurred and occurs into both levels: i) a basal fold-and-thrust system in the Ionian Zone, that accommodated an increasing amount of SW directed shortening, and ii) a structurally higher system of thrust faulting affecting the overlying structure of the Periadriatic Depression, that underwent a strong structural rearrangement.

Sedimentary and Diagenetic Controls across the Cretaceous—Paleogene Transition: New Paleoenvironmental Insights of the External Ionian Zone from the Pelagic Carbonates of the Gardiki Section (Epirus, Western Greece)

Field investigation, biostratigraphic, paleoecological, and sedimentary microfacies analyses, as well as diagenetic processes characterization, were carried out in the Epirus region (Western Ionian Basin) to define the depositional environments and further decipher the diagenetic history of the Late Cretaceous–Early Paleocene carbonate succession in western continental Greece. Planktonic foraminiferal biostratigraphy of the studied carbonates revealed that the investigated part of the Gardiki section covers the Cretaceous–Paleogene (K-Pg) transition, partly reflecting the Senonian limestone and calciturbidites formations of the Ionian zone stratigraphy. Litho-and bio-facies analyses allowed for the recognition of three distinct depositional facies: (a) the latest Maastrichtian pelagic biomicrite mudstone with in situ planktonic foraminifera, radiolarians, and filaments, (b) a pelagic biomicrite packstone with abundant planktonic foraminifera at the K-Pg boundary, and (c) an early Paleocene pelagic biomicrite wackestone with veins, micritized radiolarians, and mixed planktonic fauna in terms of in situ and reworked (aberrant or broken) planktonic foraminifera. The documented sedimentary facies characterize a relatively low to medium energy deep environment, representing the transition from the deep basin to the deep shelf and the toe of the slope crossing the K-Pg boundary. Micropaleontological and paleoecological analyses of the samples demonstrate that primary productivity collapse is a key proximate cause of this extinction event. Additional petrographic analyses showed that the petrophysical behavior and reservoir characteristics of the study deposits are controlled by the depositional environment (marine, meteoric, and burial diagenetic) and further influenced by diagenetic processes such as micritization, compaction, cementation, dissolution, and fracturing.

Discovery of a new source-rock interval within the Pantokrator Formation, Ionian Zone, western Greece: Insights from sulfur speciation and kinetics analyses

The Ionian Zone in western Greece constitutes a Mesozoic sedimentary basin with petroleum potential. Numerous rock intervals with source, reservoir, and seal properties, along with several surface oil seeps have been identified. These rocks are linked to the northern portion of the Ionian Zone in nearby Albania, where similar rocks host oil and gas fields. This study describes a newly discovered source rock interval, the “Pantokrator Shales”, which lies within the Pantokrator Carbonates Fm, between the Rhaetian platform dolomite (“Pantokrator Dolomites” Fm.) and the lower Liassic platform limestone (“Pantokrator Limestones” Fm.) sequence. This interval is an important source rock for the petroleum system of the Ionian Zone in western Greece and Albania. The samples were acquired from outcrops and subsequently examined by programmed pyrolysis and organic petrography, as well as for sulfur speciation. The Pantokrator Shales Formation is comprised of ∼30 m of organic-rich shales alternating with less organic-rich light gray and thin-grained dolomitic sandstones and dolomite beds. The results of organic geochemical and organic petrographic analyses suggest high amounts (up to 38.68 wt% TOC) of Type I and mixed II/II-S organic matter with high generation potential (S1+S2 is up to 269.79 mg HC/g and HI of up to 790 mg HC/g TOC). Selected intervals analyzed have large amounts of labile organic sulfur. Pyrolysis Organic Sulfur (POS) ranges between 1.22 and 4.87 wt% on a whole-rock basis, with Sulfur Index (SI) values ranging from 116 to 174 (minimum SI for Types IS and IIS = 100), suggesting that the kerogen has already entered the oil window and generated liquid hydrocarbons in accordance with reflectance values measured on vitrinite (%VR: 0.60–0.65) and/or solid migrabitumens. Widespread conditions that favored the deposition and preservation of high amounts of oil-prone organic matter (including vulcanization processes of organic matter) existed locally in the basin during the Late Triassic to Early Liassic. This study showed that the stratigraphic position, the lateral and vertical extent, the organic matter quantity and quality, as well as the sulfur (S) content of the Pantokrator Shales, are comparable to intervals in nearby Albania, Sicily and the Italian peninsula. The high clastic input that was recorded may be associated with a regional shift in climatic conditions towards more seasonably controlled wetter conditions, as inferred from adjacent areas.

Rare earth element patterns in a rapidly changing karst environment

Samples of surface water, groundwater and rocks were collected along the Louros River karst system in Greece to study the evolution of the chemical composition of groundwater. It was found that the hydrochemistry is closely related to the lithology of the host rocks. Emphasis was placed on the study of REEs due to the presence of phosphate-rich rocks in the area. A distinctive feature that was also taken into account was the high velocities of surface and groundwater in this rapidly changing karst environment.The carbonate formations of the Ionian Zone determine the hydrogeology of the catchment, particularly the Senonian, Vigla and Pantokrator limestones, through which groundwater mainly moves at relatively high velocities, play a key role. From the northernmost areas at the upper part of the catchment to the southernmost areas at the river's mouth, a multitude of springs, along the river, mark the main base level, above which a common aquifer is formed on either riverbed, hydraulically and locally connecting those geological formations.The chemical composition of the water is mainly controlled by the dissolution of calcite, dolomite and gypsum, with Ca–HCO3 being the dominant water type. Elevated pH values (>7), increased concentrations of dissolved oxygen and low concentrations of Fe and Mn indicate a karst system with oxidising alkaline waters. Groundwater type changes when it encounters gypsum in the area, or when the process of dedolomitisation takes place and, together with the phosphate minerals contributes to the release of REEs into the water. ΣREEs range from 0.22 in anhydrite to 33.8 ppm in the sandstones. The REE concentrations in the 0.45 μm-filtered surface and groundwater samples range between 50 and 260 ng/L. REEs concentration in groundwater is controlled by pH.The European shale normalised REE profiles of the rock samples are enriched in LREEs compared to HREEs and show a slightly negative Ce anomaly, which is explained by an oxidising sedimentation environment. The positive Eu anomaly of the same samples was attributed to the presence of phosphate minerals. Positive anomalies in both Ce and Eu were observed in the corresponding profiles of surface and groundwater samples. The effect of carbonate species, especially HCO3−, on surface and groundwater resulted in their enrichment in HREEs. In general, an enrichment of HREEs in surface and groundwater was observed in proportion to the distance covered.

Triassic evaporites and the structural architecture of the External Hellenides and Albanides (SE Europe): controls on the petroleum and geoenergy systems of Greece and Albania

A combination of well data, seismic information on thrusting and tectonic shortening, plus analyses of the nature and depth of the Mesozoic units related to main detachment horizons (Triassic evaporites, flysch), are used to review, and further update the complex structural styles of the External Hellenides and Albanides Orogenic Belts, SE Europe. In the study area, the late Alpine orogenic evolution resulted in a structural architecture characterised by the successive westward thrusting of tectonic nappes (Gavrovo/Kruja, Ionian), with an imbricate tectonic style prevailing in all external zones. In the internal and central Ionian zone, imbricate thrusts and duplex structures are recorded, especially where about 24 km of stacked Mesozoic–Tertiary successions have been formed in Albania. Triassic evaporites, up to 3.5 km thick, acted as a detachment horizon for the internal deformation of the Ionian and Pre-Apulia zones (1.7–1.8 km thick in Greece), whereas the flysch unit of Upper Eocene–Oligocene (External Hellenides) and Oligocene–Aquitanian (Albanides) contributed to the deformation of the Ionian zone. In the Ionian zone, Triassic evaporites are laterally continuous and act as an effective seal unit when thrusted above Mesozoic carbonate/Tertiary units. Most of the oil and gas fields, oil shows and surface seeps have been developed in association with the relative more complex structure styles in the internal and the central Ionian zone of Albania and Greece. The Triassic evaporite detachment is detected at depths of 8–22 km in Albania, and about 5 km to 12–13 km in Greece. Thin and probably combination of thin- and thick-skinned deformation (SW Greece) of the Meso-Cenozoic succession above the Triassic evaporite and Permian sequences better depicts the complex structural architecture of the External Hellenides and Albanides, later affected by strike-slip tectonics and extensional deformation active since the Early Pliocene times. The main source rock levels, Lower Cretaceous shale/carbonate, Toarcian Posidonia and Triassic shales, are common in the Albanides and the Hellenides forelands. The thickness and Total Organic Carbon of these levels significantly increase in Albania, whereas trapping mechanism is almost the same and the Triassic evaporites play a significant role in both forelands. The hydrocarbon migration primarily followed developed thrust faults and important halokinesis, to charge fractured Cretaceous–Eocene carbonate reservoirs in the overthrust unit (Ionian zone), likely beneath the thrusted anticlinal belts. These sub-thrust structural models are related to the evaporites. Sub-thrust plays, referred to the autochthonous units (Apulia, Pre-Apulia/Paxos, Sazani zones), may also present reservoir potential in Albania and Western Greece. Upper Miocene and Pliocene deposits (sands) record reservoir potential in stratigraphic traps and good caprock characteristics in the Peri-Adriatic depression (Albania), whereas Messinian evaporites and clays may document seal potential for Upper Miocene sands in the southern areas of the Ionian Sea (Kyparissiakos Gulf, SW Kythira).

Discovery of a New Source-Rock Interval within the Pantokrator Formation, Ionian Zone, Epirus, Western Greece: Insights from Sulfur Speciation and Kinetics Analyses

Discovery of a New Source-Rock Interval within the Pantokrator Formation, Ionian Zone, Epirus, Western Greece: Insights from Sulfur Speciation and Kinetics Analyses

Evolution of Sedimentary Basins as Recorded in Silica Concretions: An Example from the Ionian Zone, Western Greece

Chert concretions in thick limestone successions preserve a more complete paragenetic sequence of diagenetic minerals than their host limestone and interbedded shale. The goal of this study was to test the possible presence of a high-temperature mineralising system in the Ionian basin of western Greece. Upper Cretaceous chert nodules were sampled at Araxos, where rocks are highly faulted and uplifted by salt diapirism, and on Kastos Island, on the flanks of a regional anticline. Chert concretions have microporosity produced by recrystallisation of opal to quartz and fractures produced in the brittle chert during basin inversion. Diagenetic mineral textures were interpreted from backscattered electron images, and minerals were identified from their chemistry. Diagenetic minerals in pores and veins include sedimentary apatite (francolite), dolomite, Fe-chlorite, Fe oxide-hydroxide mixtures, sphalerite, barite and calcite. Sphalerite is restricted to Araxos, suggesting that inferred basinal fluids were hotter and more saline than at Kastos. At Araxos, the Fe oxide-hydroxide also includes minor Cu, Zn, and Ni. Whether the transported metals were derived from sub-salt clastic rocks and basement, or from enriched Mesozoic black shales, is unclear. The effectiveness of this novel approach to understanding fluid flow history in thick limestone successions is validated.

Seismotectonics of Vlora-Elbasani-Dibra Transversal Fault Zone (Albania): A Review

The Vlora-Elbasani-Dibra transversal fault zone crosses from south-west to northeast the Albanides collision zone starting from Vlora area to the Dumre diapir and continuing from Elbasani Quaternary graben to Dibra area, within the internal Albanides extensional zone. The Vlora-Elbasani-Dibra seismogenic fault zone is expressed by an alignment of important historical and instrumental seismicity with 15 Ms > 6 earthquakes. The Vlora-Berati-Elbasani segment of this fault zone during the year 1851 has been activated along all is length. The geological and neotectonic investigations and the focal mechanism solutions of earthquakes that occurred along the Vlora-Elbasani-Dibra fault zone prove its division into two distinct fault zones: a) the Mali i Kanalit Block - Dumre diapir strike-slip fault zone NNE trending in transpression, and b) the Elbasan-Dibra normal fault zone NE trending in transtension. The Mali i Kanalit Block-Dumre diapir strike-slip zone NNE trending in transpression offsets dextrally and to SW the folds and thrusts of the Çika, Kurveleshi and Berati anticlinal belts of Ionian zone. The Neogene (mainly since Middle Miocene) offset of the Çika, Kurveleshi and Berati anticlinal belts from generally NW-SE trending to near N-S one has led to thrust’s steepening and turning into high-angle strike-slip faults due to NE-SW oblique compression from the Albanides collision zone. The Othoni Island-Dhermi strike-slip fault offsets the dextrally dragged Devolli (to the east of Dumre diapir), Osumi (near to Berati town), and Vjosa (west of Shkoza village) rivers’ valleys formed from the Middle Pleistocene (180,000 years) to historic times. The Othoni Island-Dhermi dextral strike-slip fault, that reaches the maximum velocity of greater than 5 mm/year to the south of it, is the only leading fault that shaped the Mali i Kanalit Block-Dumre diapir dextral strike-slip fault zone. Focal mechanism solutions of earthquakes that occurred on the Mali i Kanalit Block - Dumre diapir dextral strike-slip zone show their generation from strike-slip faults in transpressional motions. Focal mechanism solutions of earthquakes that occurred on the Elbasan-Dibra were generated from normal faults with dextral strike-slip movements.

Sedimentary Facies Analysis, Reservoir Characteristics and Paleogeography Significance of the Early Jurassic to Eocene Carbonates in Epirus (Ionian Zone, Western Greece)

Sedimentological, micropalaeontological, and marine geological results from the Early Jurassic to Eocene carbonate formations of the Ionian zone, from six localities of Epirus, provide new insights into the basin palaeogeographic evolution and better correlation with coeval analogous tectono-stratigraphic successions along the southern margin of the Neo-Tethys Ocean. Facies analysis allowed the recognition of several microfacies types and their depositional characteristics. During the Early Jurassic, autochthonous carbonates (Pantokrator Limestones) were deposited in shallow-water environment. The overlying (hemi)pelagic Siniais or their lateral equivalent Louros Limestones were deposited to the basin borders and mark the general deepening of the Ionian domain. During Toarcian to Tithonian, the Ionian Basin was characterized by an internal differentiation in small sub-basins with half-graben geometry presenting abrupt thickness and facies changes. The deeper parts were characterized by continuous sedimentation, while the elevated parts were marked by unconformities. The Early Cretaceous marks the homogenization of sedimentation by the deposition of the pelagic Vigla Limestones all over the Ionian zone. The transition from the Early to Late Cretaceous records a significant carbonate diversification in terms of biota assemblages, and related mineralogy due to intense tectonic activity in the region. From Late Cretaceous to Paleogene, allochthonous carbonates were transported to the outer shelf by turbidity currents (calciturbidites) and/or debris flows (limestones with breccia) formed by the gravitational collapse of the platform margin. Additional porosity and bulk density measurements showed that petrophysical behavior of these carbonates are controlled by the depositional environment and further influenced by diagenetic processes. The partly dolomitized neritic Jurassic carbonates, but mainly the Senonian calciturbidites and the microbrecciated Paleocene/Eocene limestones display the higher average porosity values, and therefore present enhanced carbonate reservoir quality.

Early-orogenic deformation in the Ionian zone of the Hellenides: Effects of slab retreat and arching on syn-orogenic stress evolution

In this work we report on early-orogenic fracture patterns affecting a Cretaceous to Eocene sedimentary succession exposed in western Greece. These rocks belong to the Cenozoic External Hellenides, which form the western portion of the Aegean orocline. The analysis of fracture type, orientation, and crosscutting relationships provides constraints on the stress and strain patterns during the early stages of orocline formation. The fracture patterns in the study area includes early-orogenic extensional fractures arranged into two mutually orthogonal sets. These developed during progressive burial in the forebulge-foredeep system, ahead of the advancing compressive front. Tectonic solution seams at a high angle to bedding postdate these extensional structures. Solution seams are arranged in different sets, oblique to each other, and developed in the early stages of thrusting and folding. Extensional structures and solution seams are oblique to each other. Their orientation and crosscutting relationships provide evidence for clockwise vertical axis rotation of stress directions with time. This is consistent with the progressive arching of the forebulge-thrust belt system during progressive slab retreat.

Mineralogy of siliceous concretions, cretaceous of ionian zone, western Greece: Implication for diagenesis and porosity

Siliceous (chert) concretions are a prominent component of Cretaceous limestones in the Ionian zone of western Greece. This study investigates the diagenetic evolution of such cherts from two localities: largely undeformed strata on Kastos Island and highly faulted strata at Araxos. In both areas, lower Cretaceous limestones contain abundant small chert nodules, whereas in the upper Cretaceous nodules are larger but less abundant. Seventy seven powdered samples, from 67 representative field samples, were analyzed by X-ray Powder diffraction (XRPD). The analyzed samples came from both nodular and siliceous beds and showed that quartz is the dominant mineral, with rare to common residual calcite. The presence of moganite and opal-A minerals suggests that quartz recrystallized from original amorphous silica. A few samples from Araxos contain traces of halite and anhydrite. The variability in the calcite content and the presence/absence of halite and anhydrite in the different studied areas are related with the different tectonic activity in these areas, with more intense tectonic activity in NW Peloponnesus than in Kastos Island. Size of nodules is related to variation in primary porosity of the host rocks. Finally, the presence of dolomite was related with the pre-existing underlying dolomites of Early Cretaceous age in Ionian basin, whereas the presence of maghemite is due to the presence of iron minerals in water solutions. • Zoned chert nodules and beds in Cretaceous calcturbidites and landslide deposits. • Moganite and opal-A minerals recrystallized from original amorphous silica. • Size of chert concretions related to porosity of host limestones. • Dolomite in cherts only where underlying dolostone. • Halite and anhydrite in cherts due to Paleogene deformation of Triassic evaporites .

The study of lepidocyclina (eulepidina) (foraminifera) from middle Oligocene to lower Miocene of South Albania

There are studied too many samples from Ionian Zone (geological outcrops and drilling wells) and Koma depression containing Larger Foraminifers, Lepidocyclina (Eulepidina) subgenus. For their study, determination to species level, biometrie and counting measurements known in literature are used. According to proposal (for Mediterranean region) we suggest that in south Albania also can be separated the following species and subspecies: - Lepidocyclina-(Eulepidina) formosoides DOUVILLE R. - Lepidocyclina-(Eulepidina) dilatata (MICHELOTTI) - Lepidocyclina-(Eulepidina) dilatata (MICHELOTTI) var concentrica SILVESTRI For the specimens of microsphaeric generation (B-Form, diameter more than 5 centimeter) maintained the typological concept of classification and were attributed to the species Lepidocyclina (Eulepidina) elephantine LEMOINE and DOUVILLE (1904). They are given briefly the deposition conditions of the shells of this subgenus in flysch (Ionian Zone and mollasic deposits (Korria depression) Middle Oligocene- Lower Miocene age. The paper has been accompanied by means 3 plates.

Karst and geotops of karst origin in Albania

Albania is one of the most karst-developed countries in Europe. Karst phenomena are related to soluted carbonate formations which cover of about 7300 km2 of Albanian territory and with sulfate evaporates rocks, which outcrop of about 500 km2. Typically alpine relief of average altitude 708 m above the sea level and high horizontal splitting are favorable for karst development. Karst and geological sites of karst origin are widespread mainly in Albanian Alps and in Ionian zone. In Albanides there are determined surfaces and underground karst forms which belong to the Neo-Pliocene-Quaternary age and deep karst forms belonging to the paleokarst in old formations. The most widespread karst forms in carbonate rocks there are valleys, caves, cones etc., while into salt rocks there are formed many karstic lakes and depressions. Up to now there are determined about 80 karstic caves, nice karst fields, valleys, plains, which represent geological sites of karst origin.

Messinian biostratigraphy based on foraminifera and ostracodes in Ionian zone of Albania

Messinian biostratigraphy based on foraminifera and Ostracodes was studied in several surface sections within Peqin-Durres region. The sections are located in the eastern and northwestern part of the Peri-Adriatic Foredeep (PAF) of Albania (FigJ ). The Thartor section is located more or less in the center of the region studied. Its Messinian sediments in particular late Messinian one are well exposed and just in this place they represent the boundary of great differences between these sediments and those that could be occurred towards east or towards south. Firstly, here well distinguished the preevaporitic sequence which very rapidly wedge-out towards southeast. Secondly, here is the latest southeast boundary of gypsum blocks occurrence. Moreover in this section the lack of "lago-mare" biofacies is apparently owing to its erosion. Towards northern and western sections the lower boundary of "lago-mare" biofacies is well determined lithologically and faunistically. Towards southeast and eastern sections this boundary determined also by first occurrence of Cyprideis, Candona etc., as above but it seems to be not synchronous from section to section. In this aspect this "lago-mare" biofacies is more similar with a Paratethyan biofacies. Within the gypsum bearing region "lago-mare" biofacies is focused in the latest Messinian only, in this aspect it could be called "Tethyan lago-mare' biofacies.