Kruja Zone Research Articles

Carbonate texture identification using multi-layer perceptron neural network

Abstract This study proposes an approach to identifying carbonate rocks depositional texture utilizing more than 1250 thin-section photos as a data set from shallow-water carbonates of the Kruja zone (Albania). The proposed technique uses a numerical methodology based on digitized images of thin sections. According to the Dunham classification, it permits the user to recognize the carbonate texture automatically. The carbonate rock should not be affected by post-depositional processes. This technique uses as input gray-scale digital images taken from thin sections. Image processing can extract (as output) a set of 22 numerical parameters measured in the entire image, including white areas representing calcite cement. A multi-layer perceptron (MLP) neural network inputs these numerical parameters and produces, as output, the estimated depositional texture. We utilized 654 images of thin sections to evaluate this technique to train the neural network. We used 348 pictures taken from the same data set and 250 from the Burizana section (Kruja zone, Albania) to test the technique. The proposed method has shown 90.5 and 91.3% accuracy in identifying the automatically depositional texture using digitized images on the 348 and 250 test sets. Based on the good results obtained, this technique can be extending not only in identifying carbonate rocks texture but in every type of rock, getting fast and correct results. Python was used as a computer programming language for image processing and displaying images.

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.

Study of Heavy Minerals from the Vjosa and Mati river delta sediments in Albania

This research is focused on the determination of the heavy minerals (HM) load of the Vjosa and Mati river delta deposits along the Albanian coastline and it is based on X-ray Diffractometry. The Albanian coastline consists of sandy beaches at the north (Adriatic coastline) and rocky escarpments at the south (Ionian coastline). Several layers of heavy mineral deposits, up to 50 cm thick, with heavy mineral fraction up to 95% and 88% of total sample for Vjosa and Mati sediments respectively, are identified. The layers enriched in heavy minerals from Vjosa delta deposits are almost black in colour, while at Mati delta these layers are dark green coloured. Separation of the heavy from the light fraction was performed, in order to compare the different fractions between the two studied delta areas. The accumulation of HM occurs mainly in the fraction of 125-250 µm in the sediments of both deltas. The HM dominate in the magnetic field of 0.4-0.8 A/m. XRD analysis results show a great variety of minerals present in the delta samples which can be attributed to the wide variety of geological zones and lithologies that are intersected by the Vjosa and Mati rivers, respectively. In the 63-425 μm fraction rich in heavy minerals of both delta systems considerable amounts of magnetite (up to 39.4% in Vjosa samples), chromite (up to 20.2% in Vjosa samples), garnet (up to 13.6% in Vjosa samples), ilmenite (up to 8.3% in Mati samples), rutile (up to 4.7% in Mati samples), hematite (up to 2.2% in Mati samples), and zircon (up to 2.1% in Vjosa samples) are observed. Rock forming minerals such as pyroxene, amphibole, and epidote compose significant percentages of this fraction. In addition, the presence of gold grains in Vjosa delta sediments is remarkable. Both catchment areas consist to a great extent of similar formations such as the Mirdita Ophiolite Zone and the Pindos Ophiolite complex, providing thus a similar HM fingerprint at both delta areas. Minerals that occur in higher abundances reflect the extensive presence in the drained areas of related parent rocks which are rich in these minerals and which are often more vulnerable to weathering. The samples of Vjosa river delta show high percentage of carbonate constituents, which is related to the presence of carbonate rocks of the Ionian and Kruja tectonic zones within which the hydrographic network of the Vjosa River has been developed. The samples of Mati river delta show lower abundance of carbonate minerals, reflecting the limited presence of carbonate rocks at the Kruja Zone, which occur in the catchment area of the river near its mouth.

Microfacies Analysis and Diagenetic Settings of Upper Cretaceous Shallow Water Carbonates from the Borizana Section (Kruja Zone, Albania)

This paper deals with the preliminary results of a detailed study based on the microfacies analysis and diagenetic settings of the Upper Cretaceous shallow water carbonate deposits from Borizana section, Kruja zone, Albania. In the Makareshi structure, the Upper Cretaceous deposits, in the mainly consists of limestones, dolomitic limestones and different levels of dolomite intercalations. The study was carried out after a systematic sampling of a total of 230 rock samples and then by studying selected thin sections from individual beds and from different parts of the same bed. 250 thin sections were studied from a 1000m thick section in order to analyse its sedimentology, microfacies assemblages and diagenetic featuress. Different types of microfacies mainly represented by laminated, peloidal and bioclastic grainstones along with presence of dolomitized microfacies at some levels were determined. Also different types of cement and diagenetic features such as compaction, dolomitization and neomorphism were also observed in Borizana section. All these microfacies associations and their diagenetic features indicate that this formation has been deposited in a restricted platform interior facies belt (FZ8, FZ9). DOI: 10.5901/ajis.2015.v4n2p95

Foraminiferan-calcimicrobial benthic communities from Upper Cretaceous shallow-water carbonates of Albania (Kruja Zone)

From the Kruja Zone of Albania, shallow-water carbonates assigned to the lower Campanian are described and grouped into six microfacies types of shallow subtidal to intertidal depositional settings. The limestones display internal layering suggestive of microbial fabrics with abundance of nubeculariid foraminifera, incertae sedis Thaumatoporella Pia, and subordinate calcimicrobes of possible cyanobacterial origin: Gahkumella Zaninetti, Girvanella sp., and Decastronema kotori (Radoičić). The nubeculariid morphotypes with ornamented tests and microbial coatings reveal some kind of mutualistic relationship comparable to Late Palaeozoic–Mesozoic Tubiphytes Maslov and Crescentiella Senowbari-Daryan et al. The present study expands our knowledge on the micropalaeontological characteristics of the Late Cretaceous “Decastronema–Thaumatoporella association” widespread in carbonate platforms of the peri-Mediterranean region. Our findings indicate that nubeculariids may have played an important binding role in Late Cretaceous peritidal laminated limestones.

AN OVERVIEW OF THE PETROLEUM SYSTEMS IN THE IONIAN ZONE, ONSHORE NW GREECE AND ALBANIA

The Ionian and Gavrovo Zones in the external Hellenide fold‐and‐thrust belt of western Greece are a southern extension of the proven Albanian oil and gas province. Two petroleum systems have been identified here: a Mesozoic mainly oil‐prone system, and a Cenozoic system with gas potential. Potential Mesozoic source rocks include organic‐rich shales within Triassic evaporites and dissolution‐collapse breccias; marls at the base of the Early Jurassic (lower Toarcian) Ammonitico Rosso; the Lower and Upper Posidonia beds (Toarcian–Aalenian and Callovian–Tithonian respectively); and the Late Cretaceous (Cenomanian–Turonian) Vigla Shales, part of the Vigla Limestone Formation. These potential source rocks contain Types I‐II kerogen and are mature for oil generation if sufficiently deeply buried. The Vigla Shales have TOC up to 2.5% and good to excellent hydrocarbon generation potential with kerogen Type II. Potential Cenozoic gas‐prone source rocks with Type III kerogen comprise organic‐rich intervals in Eocene–Oligocene and Aquitanian–Burdigalian submarine fan deposits, which may generate biogenic gas. The complex regional deformation history of the external Hellenide foldbelt, with periods of both crustal extension and shortening, has resulted in the development of structural traps. Mesozoic extensional structures have been overprinted by later Hellenide thrusts, and favourable trap locations may occur along thrust back‐limbs and in the crests of anticlines. Trapping geometries may also be provided by lateral discontinuities in the basal detachment in the thin‐skinned fold‐and‐thrust belt, or associated with strike‐slip fault zones. Regional‐scale seals are provided by Triassic evaporites, and Eocene‐Oligocene and Neogene shales.Onshore oil‐ and gasfields in Albania are located in the Peri‐Adriatic Depression and Ionian Zone. Numerous oil seeps have been recorded in the Kruja Zone but no commercial hydrocarbon accumulations. Source rocks in the Ionian Zone comprise Upper Triassic – Lower Jurassic carbonates and shales of Middle Jurassic, Late Jurassic and Early Cretaceous ages. Reservoir rocks in both oil‐ and gas‐fields in general consist of silicilastics in the Peri‐Adriatic Depression succession and the underlying Cretaceous–Eocene carbonates with minimal primary porosity improved by fracturing in the Albanian Ionian Zone. Oil accumulations in thrust‐related structures are sealed by the overlying Oligocene flysch whereas seals for gas accumulations are provided by Upper Miocene–Pliocene shales. Thin‐kinned thrusting along flysch décollements, resulting in stacked carbonate sequences, has clearly been demonstrated on seismic profiles and in well data, possibly enhanced by evaporitic horizons.Offshore Albania in the South Adriatic basin, exploration targets in the SW include possible compressional structures and topographic highs proximal to the relatively unstructured boundary of the Apulian platform. Further to the north, there is potential for oil accumulations both in the overpressured siliciclastic section and in the underlying deeply buried platform carbonates. Biogenic gas potential is related to structures in the overpressured Neogene (Miocene–Pliocene) succession.

The structural style and hydrocarbon exploration of the subthrust in the Berati Anticlinal Belt, Albania

The Albania thrust belt consists of both internal and external tectonic zones, which are westward overthrusts with large amplitude (50–100 km), above the Apulian Patform and the South Adriatic Basin. The External Albanides are subdivided into distinct tectonic-stratigraphic units: the Kruja zone (shallow carbonate water) in the east and the Ionian zone in the west, which is represented by pelagic limestone. The Ionian zone, located between the Sazan (Pre-Apuliane) and Kruja zones, consists of three anticlinal belts: the Berati, Kurveleshi and Cika anticlinal belts. Their western margin is bordered on overthrust faults, which have produced large westward overthrusts on each of them, with amplitudes of 10–30 kms, and are utilized through a large diapir masses. Therefore, they mask perspective plays in subthrusts. The Berati anticlinal belt is the most eastern in the Ionian zone and lies mostly in the Albanian territory and partly in the Greek territory. It has a length of about 225 kms and a width 12–22 kms, and is differentiated into two sectors: the southern sector (south of the Qafa Kicoku) and the northern sector (north of the Qafa Kicoku). Understanding the evolution of evaporite tectonics is important in determining the principal features of the structural model on the Berati anticlinal belt. The changes in the lithostatic pressure on the space have a greater role in the development of evaporite tectonics, which are conditioned by the deposition thickness of the cover sediments above the evaporites and the presence of weak tectonic loops. These loops belong to the intersecting places of transverse and longitudinal fault generated since the rifting phase (T3-Cr1). Such intersecting places are the Dumrea (Albania) and Zavrohon (Greece) on the surface. We stress that evaporites are also extended over regional thrust faults of the Berati belt, helping its overthrusting westward about 20–30 km (depicted by seismic and deep wells data). The tectonic evaporite effect differs from the expansion of the Berat thrust belt. Thus, in its southern part, as a result of a diapirism that has not emerged on the surface, it is helping orogenies in developing large fan-type anticline structures (Golika, Nemercka, Mitsikeli anticlines, etc.), that have backthrusts in their eastern flank. Moreover, we encountered the presence of a carbonate massive in the middle of the Epiro-Akarnani syncline (e.g. Timfeu massive in Greece), caused by the “blind” evaporite body effect. The northern sector (north of Qafa e Kicoku), is characterized by a smaller evaporite effect, which is reflected in increasing density of the anticlinal structures on the surface units and their normal passing to each other. The Dumrea diapir is a considerable ellipsoid-shape evaporite mass outcropping with a surface area of about 210 km2 and axes 20 × 10 km. It is an ordinary diapir with a westward overthrust (20–30 km). Most oil fields in Albania are in carbonate sections (Cr2-Pg2) in the anticline structures delivered to the thrust of adjacent units. There is another new prospect of the high perspective: The carbonate structures under overthrust of different units (subthrust complex) of the Ionian zone. The subthrust in the Ionian zone is divided into three types: 1. The subthrust beneath overthrust of thrust belts. These overthrusts are related to the evaporite detachment horizon, and they mask folded structures of subthrust. 2. The subthrusts beneath the overthrusts of the anticline units. These overthrusts have a local character and they are more developed in the Kurveleshi thrust belt. 3. The subthrusts beneath the overthrusts of the tectonic zones of the orogenetic front (Ionian and Kruja Zones) above the western autochthonous (Apulian Platform and South Adriatic Basin). These structures display duplex and triplex style. Currently, the more interesting opportunity lies in the subthrust beneath the Berati thrust belt. This has a higher perspective than the other subthrusts beneath the Kurvelesh and Cika anticlinal belts. Actually, the Berati subthrust is in the processes of being the subject of a seismic survey and exploration drilling. The discovery of a new oil field in the subthrust of the Berati anticlinal belt, with drilling of the Shpiragu-2 well, which in the first test gave 800–1300 barrels (light oil with density 35–37° API) and 2–5 mmcfd gas per day, is of great importance for the entire tectonic ensemble of the Dinaric-Albanid-Hellenic. The presence of prospective structures such as the Dumrea anticline in the north and its continuation southward (the Shpiragu oil field, Molishti anticline, etc.), beneath the thrust belt, as shown by both drilling and seismic data, together with the presence of the surface structures (e.g. the Kasidhiaris, Kurenton and Thesprotikon anticlines) in Greece, shows the regional scale potential of petroleum plays. These prospects for new oil and gas discoveries constitute the object of this important paper, offering completely new ideas.

Late Cretaceous – Eocene interval of the Apulian passive margin in Albania (Kruje-Dajt and Makareshi massifs, Kruja Zone): facies, micro-organisms and sedimentary cycles of a shallow-water carbonate platform

Abstract Two sections, respectively in the Kruje-Dajt and Makareshi massifs of the Kruja Zone carbonate platform (located in the Apulian passive margin of Albania), and representing a period which extends from the Late Cretaceous to the Eocene, have been studied from several points of view : biostratigraphy, lithology and sequence stratigraphy. The proposed biozonation for the Late Cretaceous which has been established with benthic foraminifera (CsB4, CsB5, CsB6 and CsB7) improves substantially the stratigraphy for this period in this region. Eleven different facies (F1 to F11) characterise the Upper Cretaceous-Paleocene-Eocene carbonate sediments, and are distinguished for the first time. Fourteen sequences in the Kruje-Dajt massif and seven sequences in the Makareshi massif are recognized, using sedimentological criteria and clearly distinguished according to an established model for calcareous facies of this platform. Intense early dolomitization (sebkha type) is generally superimposed to the facies. The two sections represent a mostly homogeneous environment, evolving from the infra to supratidal environments. However, small variations of subenvironments are observed and linked to local and temporary variations of the platform. They are attributed to frequent eustatic fluctuations, and in two cases at least to instabilities of the platform which had cause emergencies and temporal discontinuities at the end of Cretaceous and early Eocene times (ca 20 and 5 m.y.).

Rift-Drift, Seafloor Spreading, and Subduction Tectonics of Albanian Ophiolites

Albanian ophiolites in the Dinaride-Albanide-Hellenide mountain system in the Balkan Peninsula represent oceanic remnants of the Mesozoic Pindos-Mirdita basin and structurally overlie the peripheral tectonic units, composed mainly of volcanosedimentary rift assemblages and conjugate passive margin sequences. These tectonic units and the ophiolites collectively record the rift-drift, seafloor spreading, and subduction evolution of the Pindos-Mirdita basin, which developed as a Tethyan seaway between the Apulian and Korabi-Pelagonian microcontinents. The peripheral tectonic units on the west include, from west to east, the Apulian platform (Sazani, Ionian, and Kruja zones), Apulian passive margin sequences (Krasta-Cukali Zone), volcanosedimentary unit (Triassic-Upper Jurassic), subophiolitic mélange, and metamorphic assemblages; the Korabi-Pelagonian platform and its passive margin sequences bound the ophiolites on the east. Metamorphic assemblages include amphibolite, micaschist, and marble that generally display inverted field gradients, analogous to metamorphic soles beneath other ophiolites in the eastern Mediterranean region. Some metamorphic assemblages with cooling ages >169 Ma in southern Albania may represent, instead, dynamothermally metamorphosed volcanosedimentary rocks developed during advanced stages of continental rifting, prior to the onset of seafloor spreading. The subophiolitic mélange contains blocks and clasts of material derived from ophiolites, metamorphic units, platform carbonates, and passive margin sequences, and represents a subduction-accretion complex formed during initial displacement and tectonic emplacement of the ophiolites. The supra-opholitic mélange and the overlying flysch deposits (Tithonian-Valanginian) and neritic limestones (Barramian-Upper Cretaceous) unconformably rest on the ophiolites and the platform carbonates, and constrain the timing of ophiolite emplacement onto the Korabi-Pelagonian continental margin as the latest Jurassic-Early Cretaceous. The Pindos-Mirdita basin initially developed as a broad transtentional, intra-continental rift system with highly oblique, ultraslow rifting and spreading. Ophiolites in the Mirdita region show a transition from MORB to IAT and boninitic affinities from west to east and structurally upwards, indicating magma genesis from highly depleted, refractory mantle sources increasingly affected by subduction-derived fluids. These spatial, temporal, and chemostratigraphic relations point to a suprasubduction zone origin of the eastern ophiolites above a west-dipping, intra-oceanic subduction zone, whose rollback resulted in lithospheric extension and the formation of a boninitic "proto-arc" in the upper plate. This subduction-accretion system was terminated by collision of the Korabi-Pelagonian margin with the trench that facilitated eastward emplacement of the ophiolites. Subsequent oblique collision of Apulia with Eurasia during the Maastrichtian-Paleogene transported the Albanian ophiolites westward onto the Apulian margin. The bidivergent emplacement tectonics of the Albanian ophiolites is hence a result of two separate collisional events at different times.

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.

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

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.

Vlora-Elbasani-Dibra (Albania) transversal fault zone and its seismic activity

The transversal fault zone Vlora-Elbasan-Dibra (VED)with Northeastern strike dislocated the structure ofAlbanides along all their width. This transversalfault is distinguished by the flexure of Lushnja, thediapire dome of Dumrea, the transversal Quaternarydepression of Elbasani, the belt of transversalstructure of Labinoti, and then it continues towardsNortheast with transversal horst of Golloborda andgoes toward FYROM in NE direction. In the Southwesternpart of this transversal fault, near Fieri town, themolasse subsided toward North. The structures ofIonian and Kruja zone, near this transversal fault,also subsided and uplifted more toward North. Throughmarine investigation a transversal fault with ENEstrike direction was discovered near the Northern partof Sazani Island (Aliaj et al., 1996). We think itmay belong to the big transversal fault zone VED.The transversal fault zone VED is clearlyoutlined by the location of strong and weakearthquakes, migration of foci along this fault, themacroseismic field and focal mechanisms. Generally,along this transversal fault it is the transtensionalstrike-slip dextral motion that dominates.In our studies the transversal fault zoneVlora-Elbasani-Dibra was considered to be the mostpotential transversal seismogenetic belt in Albaniaand nearby. It has played, and is still playing,an important role in seismotectonics in Albania andits surrounding regions.

Geological sites of the External zones of Albania

Many interesting geological phenomena occur within the External zones of Albania, such as stratigraphic sections of sedimentary rocks, sedimentation breaks, folds, diapir and thrust tectonics, etc. The lithostratigraphic sections of Mali Gjere (Ionian Zone), Karaborun (Sazani Zone), Spiten (Krasta Subzone) and Komani (Cukali Subzone) are sites of special scientific and educational importance. Outcrops of "ammonitico rosso", Posidonia beds, finely stratified and laminated limestones rich in macrofauna, etc. are very typical. The outcrops of carbonateradiolarite rocks at Komani demonstrate important stratigraphic and tectonic features. Sedimentation breaks with bauxite ores are observed in the carbonate rocks of the Kruja Zone. Many deposits and findings of phosphorites, oil and gas, salts, bitumen and bitumen-bearing rocks, dolomites, etc. are prospected in these zones. Pure underground springs of karst origin and karst caves are other very interesting sites. Many beautiful tourist landscapes, archaeological and architectural monuments are also situated within the External tectonic zones.

Relations between Tectonic Zones of the Albanides on the Basis of Results of Geophysical Studies

The Ablanides are located between the Dinarides of Yugoslavia and the Hellenides of Greece, which together form the southern branch of the Mediterranean Alpine Belt. Our analysis of the Albanides and their extension into the Adriatic Sea integrates surface geological observations, well data, and results of seismological, reflection-seismic, gravity, magnetic, and geoelectric surveys. Evolution of the Albandies began with the Triassic subsidence of their Hercynian substratum under a tensional regime, culminating in crustal separation and opening of the Hellenic-Dinaride oceanic basin. The internal Albanides (IA) formed part of the oceanic Hellenic-Dinaride Basin, whereas the external Albanides (EA) developed out of the westward adjacent passive margin and continental shelf of the Adriatic plate. This was accompanied by the development of a synorogenic foredeep basin. During the tectonic, tarditectonic, and neotectonic phases, progressive westward shift of the foredeep basin axis to its present location in the Adriatic. The EA evolved out of a shelf and continental margin sedimentary prism and a superimposed foredeep wedge, which together form the Alpine-deformed hydrocarbon-bearing Albanian Sedimentary Basin. Reflection-seismic and gravity surveys done in the EA and the Adriatic Sea define distinct structural belts related to different tectonic zones of the Albanian Sedimentary Basin. The most importantmore » oil and gas accumulations are found in the Jonian zone and in the Periadriatic depression. The carbonate-dominated Late Triassic to Late Cretaceous series of the lonian, Kruja, and Krasta-Cukali zones contains several rich source rock intervals. In the lonian zone, Late Cretaceous, Paleocene, and Eocene carbonates and oligocene-Miocene flysch-type sandstones form the reservoirs of the main oil and gas accumulations. The Tortonian-Pliocene Molasse-type clastics of the Periadriatic depression also contain source rocks and stratigraphically trapped gas accumulations.« less