Mirdita Zone ophiolites and associated sediments in Albania reveal Neotethys Ocean origin

The Mirdita Ophiolite Zone in Albania is associated with widespread mélanges containing components of up to nappe-size. We dated matrix and components of the mélange by radiolarians, conodonts, and other taxa. The components consist of radiolarites, pelagic limestones and shallow-water limestones, all of Triassic age, as well as ophiolites. Triassic radiolarite as a primary cover of ophiolite material proves Middle Triassic onset of Mirdita ocean-floor formation. The mélange contains a turbiditic radiolarite-rich matrix (“radiolaritic flysch”), dated as Late Bajocian to Early Oxfordian. It formed as a synorogenic sediment during west-directed thrusting of ophiolite and sediment-cover nappes representing ocean floor and underplated fragments of the western continental margin. The tectonic structures formed during these orogenic events (“Younger Kimmeridian or Eohellenic Orogeny”) are sealed by Late Jurassic platform carbonates. The geological history conforms with that of the Inner Dinarides and adjoining areas; we therefore correlate the Mirdita-Pindos Ophiolite Zone with the Vardar Zone and explain its present position by far-distance west-directed thrusting.     

Diagenesis and fracturing of Paleocene–Eocene carbonate turbidite systems in the Ionian Basin: The example of the Kelçyra area (Albania)

The Kelçyra area is emplaced in a foreland fold-and-thrust belt (FFTB), characterized by a westward thrusting with the Triassic evaporites as the major décollement level. Several secondary features related with this evolution, like backthrusting, folding, duplex structures, evaporite diapirism are present. During the FFTB evolution, the study area has been subjected to several fracturing events with associated stages of fluid migration. During the pre-deformational stage, complex textures such as crack-and-seal features most likely reflect expulsion of overpressured fluids. These fluids were dominantly host-rock buffered. Within the post-deformational stage, a meteoric fluid caused cementation and development of a karst network during a period of emergence after the thrust emplacement. Subsequently, Mg calcite reprecipitated in the more stable carbonate phase calcite and dolomite, which filled part of the karts network. The latter is finally dedolomitized and locally partially dissolved by a second meteoric fluid flow, which greatly increased the secondary porosity.     

Petrology and PGE Abundances of High‐Cr and High‐Al Podiform Chromitites and Peridotites from the Bulqiza Ultramafic Massif,Eastern Mirdita Ophiolite,Albania

The Bulqiza ultramafic massif, which is part of the eastern Mirdita ophiolite of northern Albania, is world renowned for its high-Cr chromitite deposits. High-Cr chromitites hosted in the mantle section are the crystallized products of boninitic melts in a supra-subduction zone (SSZ). However, economically important high-Al chromitites are also present in massive dunite of the mantle-crust transition zone (MTZ). Chromian-spinel in the high-Al chromitites and dunites of the MTZ have much lower Cr# values (100Cr/(Cr+Al)) (47.7–55.1 and 46.5–51.7, respectively) than those in the high-Cr chromitites (78.2–80.4), harzburgites (72.6–77.9) and mantle dunites (79.4–84.3). The chemical differences in these two types of chromitites are reflected in the behaviors of their platinum-group elements (PGE). The high-Cr chromitites are rich in IPGE relative to PPGE with 0.10–0.45 PPGE/IPGE ratios, whereas the high-Al chromitites have relatively higher PPGE/IPGE ratios between 1.20 and 7.80. The calculated melts in equilibrium with the high-Cr chromitites are boninitic-like, and those associated with the high-Al chromitites are MORB-like but with hydrous, oxidized and TiO2-poor features. We propose that the coexistence of both types of chromitites in the Bulqiza ultramafic massif may indicates a change in magma composition from MORB-like to boninitic-like in a proto-forearc setting during subduction initiation.     

The Holocene tephrostratigraphic record of Lake Shkodra (Albania and Montenegro)

Two cores were recovered in the southeastern part of Lake Shkodra (Montenegro and Albania) and sampled for identification of tephra layers. The first core (SK13, 7.8 m long) was recovered from a water depth of 7 m, while the second core (SK19, 5.8 m long) was recovered close to the present‐day shoreline (water depth of 2 m). Magnetic susceptibility investigations show generally low values with some peaks that in some cases are related to tephra layers. Naked‐eye inspection of the cores allowed the identification of four tephra layers in core SK13 and five tephra layers in core SK19. Major element analyses on glass shards and mineral phases allowed correlation of the tephra layers between the two cores, and their attribution to six different Holocene explosive eruptions of southern Italy volcanoes. Two tephra layers have under‐saturated composition of glass shards (foiditic and phonolitic) and were correlated to the AD 472 and the Avellino (ca. 3.9 cal. ka BP) eruptions of Somma‐Vesuvius. One tephra layer has benmoreitic composition and was correlated to the FL eruption of Mount Etna (ca. 3.4 cal. ka BP). The other three tephra layers have trachytic composition and were correlated to Astroni (ca. 4.2 cal. ka BP), Agnano Monte Spina (ca. 4.5 cal. ka BP) and Agnano Pomici Principali (ca. 12.3 cal. ka BP) eruptions of Campi Flegrei. The ages of tephra layers are in broad agreement with eight ¹⁴C accelerator mass spectrometric measurements carried out on plant remains and charcoal from the lake sediments at different depths along the two cores. The recognition of distal tephra layers from Italian volcanoes allowed the physical link of the Holocene archive of Lake Shkodra to other archives located in the central Mediterranean area and the Balkans (i.e. Lake Ohrid). Five of the recognised tephra layers were recognised for the first time in the Balkans area, and this has relevance for volcanic hazard assessment and for ash dispersal forecasting in case of renewed explosive activity from some of the southern Italy volcanoes. Copyright © 2009 John Wiley & Sons, Ltd.     

Tracer methods used to verify the hypothesis of Cvijić about the underground connection between Prespa and Ohrid Lake

Prespa Lake and Ohrid Lake constitute a hydraulic system shared between Albania, FYR of Macedonia and Greece. Karst rocks separate both lakes. The elevation of Prespa Lake is about 150 m higher than that of Ohrid Lake. Considering these facts, Cvijić formulated in 1906 the hypothesis that Prespa Lake recharges the St. Naum and Tushemisht springs at Ohrid lakeside. Environmental isotopes demonstrated that Prespa Lake recharges about 37–42 and 52–54% of water emerging in St. Naum, and Tushemisht springs, respectively. An artificial tracer experiment carried out in 2002 physically demonstrated the underground connection between both lakes. This experiment confirmed the supposed underground connection and brought important information about the groundwater velocity, transit time, and karst water conduits development.     

The Late Holocene to Pleistocene tephrostratigraphic record of Lake Ohrid (Albania)

We present in this work a tephrostratigraphic record from a sediment piston core (JO 2004) from Lake Ohrid. Five tephra layers were recognised, all from explosive eruptions of southern Italy volcanoes. A multidisciplinary study was carried out, including stratigraphy, AMS ¹⁴C chronology and geochemistry. The five tephra layers were correlated with terrestrial proximal counterparts and with both marine and lacustrine tephra layers already known in the central Mediterranean area. The oldest is from Pantelleria Island (P11, 131 ka BP). Other three tephra layers are from Campanian volcanoes: X6, Campanian Ignimbrite-Y5 and SMP1-Y3 (107, 39 and 31 ka BP respectively). The youngest tephra layer corresponds to the FL eruption from Etna Volcano (3.4 ka BP). In three cases these recognitions confirm previous findings in the Balkans, while two of them were for the first time recognised in the area, with a significant enlargement of the previous assessed dispersal areas.     

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.     

The last 40 ka tephrostratigraphic record of Lake Ohrid,Albania and Macedonia: a very distal archive for ash dispersal from Italian volcanoes

A 1075 cm long core (Lz1120) was recovered in the south-eastern part of the Lake Ohrid (Republics of Macedonia and Albania) and sampled for identification of tephra layers. Magnetic susceptibility investigations show rather high magnetic values throughout the core, with peaks unrelated to the occurrence of tephra layers but instead to the relative abundance of detrital magnetic minerals in the sediment. Naked-eye inspection of the core allowed us to identify of two tephra layers, at 896–897 cm and 1070–1075 cm. Laboratory inspection of the grain-size fraction > 125 μm allowed for the identification of a third cryptotephra at 310–315 cm. Major element analyses on glass shards of the tephra layers at 896–897 cm and 1070–1075 cm show a trachytic composition, and indicate a correlation with the regionally dispersed Y-3 and Y-5 tephra layers, dated at ca 30 and 39 cal ka BP. The cryptotephra at 310–315 cm has a mugearitic–benmoreitic composition, and was correlated with the FL eruption of Mt. Etna, dated at 3370 ± 70 cal yr BP. These ages are in agreement with five ¹⁴C AMS measurements carried out on plant remains and macrofossils from the lake sediments at different depths along the core.     

Recent geomorphological evolution of the deltas of the rivers Seman and Vjosa,Albania

Rising in the Neogene hills of the Mallakaster, the rivers Seman and Vjosa have built up two large joint deltas on the Albanian Adriatic shore. This shoreline is characterized by a low sandy coast with bars and spits. Changes in the river courses and migration of the mouths of the deltas were rapid and numerous from the Holocene period until the beginning of drainage works in the 1950s. The drainage basins of the two rivers are developed in soft clastic rocks (flysch and molasse) in the proportion of 71·4 per cent for the Seman and 44·8 per cent for the Vjosa. Both rivers carry abundant sediment loads, amounting to 6·7 × 10⁶ tonnes per year for the Vjosa and 13·2 × 10⁶ tonnes per year for the Seman. This is the reason why the alluvial deposits of the Seman have built up two‐thirds of the alluvial plain. The use of a SPOT image dated 25 May 1995 (HRV 3 081‐268) enabled us to view the effects of coastal and fluvial dynamics, the role of neotectonics as well as the predominance of the plume of suspended sediment of the Seman river. Using this image, a geomorphological map was drawn, which identifies the palaeochannels of the Seman and the Vjosa. In order to date those palaeochannels we have made an archaeological inventory from oral and written published information. The location of the sites we studied was checked systematically in the field. The mediaeval and Ottoman archives kept in Tirana also provided substantial information, as well as the reconstitution of the evolution of the shoreline between 1870 and 1990, carried out using an inventory of topographic maps. This work allowed us to reconstitute the progression of the deltas of the Seman and the Vjosa since antiquity. We may then infer that from antiquity up to the Middle Ages, the deltas of the Seman and the Vjosa both progressed very moderately and in a comparable way. However, at the end of the 15th century the Seman underwent a major change in its course, through a southward migration of the river. The natural processes of alluviation and changes in the river courses seem to have been accelerated as agricultural exploitation of the Neogene hills that form most of the drainage basin of the Seman increased. This exploitation is linked with the massive exportation of cereal from the port of Skela e Pirgut, which started in the 14th century. It appears that the 20th century has been the period of the largest progression of the deltas during historical times. The speed of progression increased as early as the beginning of the century, as a result of the rapid growth of the rural population densities. Soil erosion from arable fields increased catchment sediment yields to promote rapid changes in the river courses. This resulted in abandonment of deltaic mouths, a phenomenon leading to a straightening of the coast. Thus to the south of the present mouth of the Seman the coast receded by 7 to 30 m per year between 1968 and 1990 as a result of the abandonment of a mouth. Copyright © 2001 John Wiley & Sons, Ltd.