Alpine Formations Research Articles

Reconstructing Impact of the 1867 Ionian Sea (Western Greece) Earthquake by Focusing on New Contemporary and Modern Sources for Building Damage, Environmental and Health Effects

The 4 February 1867 Cephalonia (Western Greece) earthquake is the largest in the Ionian Islands and one of the largest in the Eastern Mediterranean. However, it remained one of the least studied historical events. For reconstructing this earthquake, we reevaluated existing knowledge and used new contemporary and modern sources, including scientific and local writers’ reports and books, local and national journals, newspapers, and ecclesiastical chronicles. The extracted information covered the earthquake parameters, population impact, building damage, and earthquake environmental effects (EEEs). The earthquake parameters included the origin time and duration of the main shock, epicenter location, precursors, aftershocks, and characteristics of the earthquake ground motion. The population impact involved direct and indirect health effects and population change. Building data highlighted the dominant building types and the types, grades, and distribution of damage. The EEEs included ground cracks, landslides, liquefaction, hydrological anomalies, and mild sea disturbances. Field surveys were also conducted for validation. The quantitative and qualitative information enabled the application of seismic intensity scales (EMS-98, ESI-07). The study concluded that since the affected areas were mainly composed of post-alpine deposits and secondarily of clay–clastic alpine formations with poor geotechnical properties, they were highly susceptible to failure. Effects and maximum intensities occurred in highly susceptible areas with a rich inventory.

Recent geodynamics, active faults and earthquake focal mechanisms of the zone of pseudosubduction interaction between the Northern and Southern Caucasus microplates in the southern slope of the Greater Caucasus (Azerbaijan)

Our study was focused on the active tectonics of the southern slope of the Greater Caucasus within Azerbaijan. The study area is the zone of under-thrusting (pseudosubduction) interaction between Southern and Northern Caucasus continental microplates, which caused the tectonic stratification of the Alpine formations into various allochthonous and parauthochthonous thrust slices of southern vergency between the Middle Bajocian and Quaternary periods. These slices are grouped into the nappe complexes that form the modern structure of the trough in the study area. The large linearly stretched tectonic units (megazones) correspond to the axis of the Alpine marginal sea basin, the consolidated crust of which is subjected to destruction and thinning. The trough’s Alpine cover was compressed in the underthrust zone and pushed southwards. As a result, an accretionary prism formed allochthonously overlapping the northern side of the Southern Caucasus microplate by the system of gently dipping overthrusts. During the continental stage of Alpine tectogenesis (starting from the end of Miocene), intensive lateral compression process was caused by intrusion of the frontal wedge of the Arabian indenter into the buffer structures of the southern frame of Eurasia. This is evidenced by the GPS monitoring data on modern geodynamic activity, which demonstrates the Southern Caucasus block’s intensive (up to 29 mm/year) intrusion in the northern rhumbs as compared to the relative stability of the Northern Caucasus microplate (0–6 mm/year). This, in turn, is a reflection of the ongoing pseudosubduction regime (continental subduction or S-subduction) at the band of collision junction of these microplates. It is suggested that this process caused historically observed seismic activity in the study area, wherein the earthquakes occurred mainly in the southern slope’s accretionary prism area and the adjacent strip of the Southern Caucasus microplate. In this article, we analyze and correlate the whole range of seismic events that occurred in the study area until 2017 and the focal mechanisms of the recently recorded earthquakes (2012–2016). It is established that earthquake foci are confined either to the intersection nodes of variously trending ruptures with the faults of different directions or to the planes of deep tectonic ruptures and lateral displacements along the unstable contacts between the material complexes with different competence. The focal mechanisms of seismic events reveal various, mostly near-vertical, planes of normal and strike-slip faults. However, the earthquake foci are generally confined to the intersection nodes between the Caucasus and anti-Caucasus-striking rupture dislocations. The results of our studies are interesting in terms of their real-time application for drawing a regional summary of causes for both geodynamic and seismic activity of the Greater Caucasus system and the adjacent areas of Alpine-Himalayan fold belt.

CLASSIFICATION OF BUILDING STONES OF THE FRANGOKASTELLO CASTLE, SFAKIA, CRETE

Frangokastello is a medieval castle which was built by the Venetians in 1371-74 in a narrow coastal zone at the southeastern part of the White Mountains, approximately 12 km east of Chora Sfakion. The region around Frangokastello characterized by a strong morphological relief, which was formed by activity of normal faults striking E-W, NNESSW and NNW-SSE. The region of interest has covered at the surface from sequences mainly marine sediments of Τortonian, Low Pliocene and Lower Pleistocene. From the Middle Pleistocene multiple alluvial fans have been cover the alpine basement of the region which consists from metamorphic rocks of the Plattenkalk Group, Trypali Unit and Phyllite Quartzite Series as well the youngest in age formations. Rounded and angular fragments of rock materials from alpine and post alpine formations transported and deposited within the various parts of alluvial fan which had deposited over the Frangokastello formation, constituted the building stones for the construction of the castle. The microclimate of the region and the intense tectonic activity associated with relatively high rates of uplift of the tectonic segments in the region, has critically affect not only the static of the castle but also the resistance from the weathering of building stones after physical dismantling large parts of the binding cement and surface from outer wall. On the basis of the above, the objective of this work is initially the collection of bibliographic data related to the stratigraphy and tectonics of the region. The results obtained, combined with the results from counting and statistical processing of various lithological types of building materials of the castle can be considered input data to form static models, in the framework of proposals for maintenance and restoration of the monument.

The Morphotectonic units of Ikaria island – Contribution in the natural hazards research

Present morphological and tectonic image of Ikaria island is the complex result of both the tem-poral evolution of the island, as part of the geodynamical evolution of the Hellenic Arc, especially that of the last stages (from the upper Miocene and after), and the exogenous factors. Also human impact functions as an additional parameter for the formation of Ikaria geoenvironment.According to field data and their analysis, computing and estimation which took part with the use of modern technologies (use of GIS, analysis of geographical and descriptive databases) the mor-photectonic units of Ikaria Island were defined. The definition of the morphotectonic units was based on their special features and more precisely on the lithological differentiation (granite, metamorphic rocks and post alpine formations) as well as the complex ductile and brittle structures (large scale ductile shear-zones and brittle detachment faults, normal faults, strike-slip transfer faults and join sets) and the morphological features (slope distribution, asymmetry of the drainage system, planation surfaces, morphological discontinuities etc).The synthesis of the special features of each morphotectonic unit in combination with the human impact (fires, overgrazing etc), defines the kind, the intensity and the geographical localization of the natural hazards which occur in various sites of the island, such as landslides, erosion, floods, seismic activity, relief changes, coastline changes etc.

TECTONIC SETTING AND DEFORMATION OF THE KALLIDROMO MT, CENTRAL GREECE

Kallidromo Mt. consists of alpine formations which in places are unconformably covered by Neogene and Quaternary sediments. The ophiolites are overthrusted on the massive Mesozoic platform carbonate sequence, which forms the basement unit. The base of the tectonic nappe is characterized by a tectonic melange that consists of sandstones, clay stones, limestones, cherts and basaltic rocks that are mainly observed in pillow forms. Two distinct compressional deformation phases (D1, D2) are traced. Deformation D1 whereas the fold axes, the predominant schistocity planes and shear zones clearly follow a N295o (±10o )-115o (±10o ) trend that relates to the Upper Jurrasic-Lower Cretaceous ophiolitic emplacement of the Eo-alpine orogeny and is the predominant feature over the entire study area. Deformation D2 relates to the Cretaceous-Eocene alpine orogeny, follows a N020o (±15o )-N200o (±15o ) trend and has a much weaker and secondary imprint in the study area. The tectonic study of the alpine and post-alpine formations shows a complex deformation pattern with a variety of quantitative and qualitative characteristics. These variations can be correlated with different phases and stages of deformation (compressional to extensional) from the timing of the tectonic emplacement of the ophiolites inUpperJurrasic-Lower Cretaceous up to the present-day field.

New Data on the Upper Miocene Presence in the Aegean Region: The Geological Evolution of Spetses Island, Peloponnesus, Greece

Based on detailed geological and geomorphological mapping, sampling and micro-palaeontological determinations, both of the alpine and neogene formations, new data have been derived for Spetses Island (SW Aegean). The applied methodology provided results on the paleogeographic evolution for Spetses Island and the nearby land of Argolida peninsula as well. Based mainly on characteristic nannofossils, a Miocene age of the post-alpine formations is determined. It is the first time that miocene formations have been identified, not only in Spetses Island and Argolida, but in the whole area of Peloponnesus, where only Plio-pleistocene deposits have been described. This work also leads to the conclusion that Spetses Island is attached to the Argolida peninsula, forming an independent paleogeographic unit since Upper Miocene.

MAGNUS--A Seismological Broadband Experiment to Resolve Crustal and Upper Mantle Structure beneath the Southern Scandes Mountains in Norway

The 4-D evolution of topography is a complex scientific topic in geosciences that requires interdisciplinary efforts. In Europe, increased attention toward this research topic was originally coordinated by the TOPO-EUROPE initiative (Cloetingh et al. 2007), which has led to a continent-wide research program under the auspices of the European Science Foundation. One project within that framework is titled “TopoScandiaDeep— the Scandinavian Mountains: Deep Processes,” which aims at developing a self-consistent geophysical model for the lithosphere-asthenosphere system under southern Norway and at understanding the mechanisms that led to mountain-building far away from the plate boundary. A major component of the project is the analysis of recently acquired, passive seismological data from the MAGNUS ( MA ntle investi G ations of N orwegian U plift S tructures) experiment. The temporary network covered the high topography of southern Norway, which is, in the absence of compressional tectonics, a typical example of a particular geoscientific problem that is still not entirely understood—the origin of high topography along passive continental margins ( e.g. , Japsen and Chalmers 2000). Along the Northeast-Atlantic continental margin, at the western rim of the Fennoscandian shield, this topography is expressed through the Scandes mountain range, the second largest mountain range in Europe (Figure 1). It extends over a total length of more than 2,000 km along the entire Norwegian coast and has a peak topography of up to 2,500 m. With a few exceptions, such as the alpine formation in Sunnmore (central Norway), the topography is rather smooth, to a large extent dominated by subplanar (paleic) surfaces at elevations above 500 m. Contrary to the central European Alps, whose orogeny is in principle well understood as a classic collision belt, the evolution of the Scandes and its high topography remains an unsolved and highly debated issue. In particular the vicinity of …

The Itea–Amfissa detachment: a pre-Corinth rift Miocene extensional structure in central Greece

Abstract The Itea–Amfissa valley, separating Giona Mountain to the west from Parnassos Mountain to the east, is related to an extensional detachment observed along the eastern slopes of Giona. The detachment is traced for 30 km north of the Corinth Gulf and dips 25°–40° to the east, showing an east–west extension parallel to the Hellenic arc. The lower nappes of Pindos, Penteoria, Vardoussia and mainly the basal thrust of the Parnassos unit form part of the footwall, whereas the upper thrusts of the Parnassos unit and the Western Thessaly–Beotia nappe form part of the hanging wall. The eastern slopes of Giona are controlled by the detachment and several hundred metres of syn-tectonic breccia-conglomerates are observed at the top of the hanging wall rocks and are back-tilt towards the detachment plane. Two conglomeratic sequences are distinguished: the lower one consists of argillaceous matrix and abundant ophiolite detritus whereas the upper one bears carbonate matrix with carbonate detritus together with large olistholites of Mesozoic limestones. Based on calcareous nannofossils a middle Miocene age has been determined for the lower formation and a middle–upper Miocene age is probable for the upper. Planation surfaces cut on top of the sediments rise from south to north starting from sea level at Galaxidi to about 1400 m at Prosilio. The throw of the detachment is about 2.5–4.2 km measured mainly from the structural omission of the Alpine tectono-stratigraphic units. A contrast between the footwall and the hanging wall structure is described, with monoclinic sequence of the Parnassos nappe dipping to the west in the footwall but a complex synsedimentary horst and graben structure of sliding blocks of Alpine formations within the Miocene clastic sequences in the hanging wall. The detachment has been deformed by the east–west-trending steep normal faults that have created the Corinth rift during late Pliocene–Quaternary time showing a north–south extension. The Itea–Amfissa detachment forms the northern tip of the broader East Peloponnesus detachment, observed south of the Corinth rift structure from Feneos to Kyparissi. Similar geodynamic phenomena with large olistholites and breccia conglomerates are known from the Serravalian of Crete, related to the activity of the Cretan detachment.

THE ROLE OF THE TECTONICS AND HYDROGEOLOGY AT THE TSAKONA (ARKADIA, PELOPONNESE, GREECE ) LANDSLIDE

The present paper aims to the understanding of the causes of the large-scale landslide that occurred at Tsakona area (SW Arcadia, Peloponnesus) during February 2003. This is the largest landslide that have ever effected the Greek National highway network as it entirely rubed out the new Megalopolis-Kalamata highway at a length of 200m. It took place at the western slopes of Drosovouni Mt., which exhibits an elogated shape of NE-SW direction. At the broader area of the slide three alpine formations of the Pindos unit occur which from lower to upper are: (i) the Jurassic radiolarites, (ii) the so called 1s t flysch and (iii) the Upper-Cretaceous pelagic limestones. The initial sliding took place inside the first two formations and the landslide moved more than 1,000 meters downward along the mountain slope at an E-W direction while its headscarp was near the tectonic contact between these formations and the upperlying pelagic limestones.In order to understand the causes of the landslide we carried out a detailed geological, morphotectonic, microtectonic and neotectonic study of the broader area. Additionally we constructed the structural contour map between the limestones nappe and the underlying formations. From all the aforementioned we suggested that the landslide occurred in a tectonically active area where the neotectonic deformation. Based on the above-mentioned studies, we have to mention the followings: The landslides occur in a site that the tectonic deformation is very intense. There were old landslides before the activation of the last one and before the study and construction of the highway. The constructors as well as the people that studied the area did not take into account the already existed landslides. It has to be mentioned that hydrogeological regime of the area is of great importance, as to the opposite slopes of the landslide in which occur the same formations like in the landslide area there is no landslide activity at least the last 100 years as indicated by the existing railway, due to the no occurrence of limestones above the radiolarites. From all the above mentioned it is clear that the tectonics - neotectonics affected the major area are the main factors involved to the initiation of the landslide, and the crossing of the landslide by the highway contributed to the reactivation together with the rains.

In the wake of a counterclockwise rotating Adriatic microplate: Neogene paleomagnetic results from northern Croatia

In northern Croatia, the Neogene sediments cover complicated basement rocks which consist of Alpine and Dinaridic elements in the Zagorje area, and Variscan – Alpine formations of the Tisia (Tisza) megatectonic unit in the Slavonian Mountains (Mts.). The Neogene sediments were deposited in two separate basins before the Karpatian, but sedimentation became uniform from the Karpatian onwards (~17.5 Ma). Of the 24 localities that we have studied so far paleomagnetically from northern Croatia, 16 localities are of Karpatian or younger age, while the rest are pre-Karpatian.

Geological Structure and Evolution of Kefallonia and Ithaki islands

This paper deals with the geological formations and the fades of the sediments that appear in Kefallonia and Ithaki islands. Kefallonia is built by formations that belong to the units of Paxos and Ionian while Ithaki is mainly dominated by carbonate sediments of Ionian unit. Furthermore, younger formations lay uncomformably upon the previous alpine formations while both in Kefallonia and Ithaki islands a lower marine and an upper continental sequence are observed. The structure of Kefalonia and Ithaki islands is the result of a string of successive tectonic compressional episodes, among which extensional episodes that hosted gravitational movements have taken place. These tectonic compressional episodes are characterised by reverse faults, thrusts and folds while structures due to gravity correspond to faults with normal or oblique-normal offset. Strike slip faults are also present. On both sides of fault surfaces, block movements are responsible for shoreline uplift or submergence, remarkable incision on upthrown blocks, deflection of drainage network, and so on. Each block is particularly described below. Based on the geometric and kinematic data of tectonic discontinuities, the main stages of Kefallonia and Ithaki islands tectonic evolution are presented from the Up.Miocene - L.Pliocene until the Present.

Geological and tectonic structure of the area between Aigaleo and Parnitha Mt. (Attica, Greece) and their importance to antiseismic planning

The September 7,1999 earthquake sequence hit the northwestern part of the basin of Athens (area between Aigaleo and Parnis Mt.), causing a large number of deaths and injuries, as well as extensive damage to structures. The major area represents a small basin which is covered by thick post-alpine formations, which are extended talus cones and, to a lesser extent, neogene lacustrine and fluvial deposits. The latter have been blanketed by the talus and the alluvial deposits at the north of the area. The basin is flanked by a hill range, where the non-metamorphic alpine carbonates of the "Sub-Pelagonian" Unit and an allocthonous tectonic melange that belongs to the "Athenian nappe" outcrop. The talus cones, with a thickness that ranges from a few m. to 100 m., contain frequent lateral transitions alternations of cohesive or semi-cohesive scree and loose deposits -sand, pebbles, gravel, clay, etc. The alluvial deposits consist of clay, red soils and conglomerates is clay matrix and have a thickness between a few m. and 20-30 m. The rieogene deposits comprise relatively compacted phacies of marls, marly limestones, clays and conglomerates. The alpine formations of both the autochton and the allocthon consist largely of carbonate rocks (limestones and marbles) and, to a lesser extend, of clastic deposits (sandstones, shales, schists, and graywackes). The main tectonic feature in the area is the contact between the two alpine units, located at the eastern margin. Besides this tectonic discontinuity, numerous other faults were located, either at the basin flanks, or within the postalpine formations. All these faults determined by a large number of boreholes. They are neotectonic structures that belong to two sets, one with NNW-SSE strike and 60°-80° WSWward or ESE-ward dips, and a second one with ESE-WNW strike and 60°-80° northerly or southerly dips. In fact, these faults are directly related to the creation and evolution of the small neogene basin, which is now buried under the talus scree and the alluvial deposits. It is a complex structure, since it incorporates smaller-scale horsts and grabens. The whole picture is in good accordance with the one we get from the greater area. The damage is located within a broad, NNE-SSW trending zone that covers the central and eastern parts of the area. The correlation of this picture with the geological and structural data from the studied area showed that the most serious damage took place on loose foundation formations, which were either the unconsolidated members of the talus cones, or the alluvial deposits. However, this was not the only factor that affected the damage distribution, since the heaviest damage was located (i) along the trace of the tectonic contact between the two alpine units, (ii) at the areas with higher fault density, usually close to the basin margins, but also locally within the basin. These faults were not reactivated in the September earthquake, but "channeled" the seismic energy into specific zones, which also holds, at a larger scale, for the greater meizoseismal area. Hanging wall effects, effects of sedimentary basins, basin edge effects and focusing effects are also probably to have played a significant part, at the locations where the fault geometry and the basin structure performed as reflectors, magnifying the effects of shaking and thus maximizing the strong ground motion values. Besides, the fact that the heaviest damage is located at the central and eastern part of the basin, where the fault fabric is denser and the faults better expressed, is not accidental.

Brazilian Páramos I. An introduction to the physical environment and vegetation of the campos de altitude

Summary Aim The campos de altitude are a series of cool‐humid, grass‐dominated formations restricted to the highest summits of the southeastern Brazilian Highlands. Relatively little is known of the ecology, biogeography, or developmental history of this archipelago of mountaintop formations. This contribution presents an overview of our present state of knowledge with respect to the past and present physical environment and vegetation of the campos de altitude. The aim is (1) to introduce an international audience to the natural history of these diminutive yet important ecosystems, and (2) to provide the background for a series of forthcoming contributions that will treat the ecology of the campos de altitude and explore physical and biotic relationships between these ‘Brazilian páramos’ and similar formations in the high mountains of equatorial South and Central America. Location Beginning at altitudes of 1800–2000 m, the campos de altitude are found atop the highest summits of the main ranges of the southeastern Brazilian Highlands, between the states of Santa Catarina and Minas Gerais/Espírito Santo. Methods Drawing upon both original data and previously published results, this contribution reviews what we presently know about the physical environment and vegetation of the campos de altitude, in the context of geographic setting, geology, palaeoclimatology and palaeobotany, modern climate, modern vegetation, and conservation. Results and main conclusions Uplift of the southeastern Brazilian ranges to altitudes high enough to support orographic grasslands may have occurred as early as the middle‐ to late‐Tertiary; pollen records show that campos de altitude have been extant on southeastern summits at least since the Late Pleistocene. The present‐day climate of the campos de altitude is cool and (per)humid, but patterns of rainfall, temperature, and frost are distinctly seasonal. Although the flora of the campos de altitude is highly diverse and characterized by a high degree of endemism, the campos de altitude maintain strong floristic similarities to equatorial alpine formations of the Andean and Central American Cordillera; these similarities also extend to climate, soils, and vegetation physiognomy. Anthropogenic fires and grazing are widespread in the campos de altitude and probably contribute significantly to the modern structure of vegetation communities.

Environment and Floristics of Ten Australian Alpine Vegetation Formations

Data on floristics, structure and environment were collected from quadrats throughout the geographic range of alpine vegetation in Australia. These data were used to explore the floristic and environmental relationships of ten alpine vegetation formations: bolster heath, coniferous heath, heath, alpine sedgeland, fjaeldmark, tall alpine herbfield, short alpine herbfield, grassland, bog and fen. Alpine sedgeland and coniferous heath, and tall alpine herbfield and grassland, proved to be closely similar in their floristics. Grassland and coniferous heath were most separated in ordination space. The environmental variables with the largest numbers of significant differences between formations were extractable phosphorus, summer temperatures, winter temperatures and topography. However, many other edaphic, climatic, topographic and biotic variables were important in discriminating between formations. The results of the formation-environment analyses were largely consistent with the relationships suggested in the previous literature. However, some environmental differences between formations that were observed or posited from local studies did not prove to be exportable to the alpine zone as a whole. Edaphic and topographic variables appear to be more important in discriminating the environments of alpine formations than the environments of alpine floristic communities.

Structures affecting the coast around Lulworth Cove, Dorset and syn-sedimentary Wealden faulting

Pre-Albian northwest-southeast faults have been inferred along the coast between Durdle Door and Worbarrow Tout. From the westward increase in the thickness of Wealden units between Mupe Bay and Lulworth Cove followed by dramatic thinning across the cove it is suggested that these faults were syn-sedimentary growth faults during the early Cretaceous. Also the Wealden is shown to contain two main quartz grit bands, only the lower of which is seen in Lulworth Cove due to increasing westwards Albian erosion which mainly explains the westwards thinning of the Wealden. These faults may have continued to be active throughout the rest of the Cretaceous. During the later Alpine formation of the Purbeck monocline, southward dipping thrusts also developed. Their alignment may have been controlled by the reactivated northwest-southeast faults. To the west of Lulworth Cove much of the succession between the Portland Stone and the Chalk is cut out by these east-west thrusts.

Siphulella, a New Lichen Genus from Southwest Tasmania

The lichen genus Siphulella (Lichenised Ascomycotina, Helotiales, Baeomycetaceae) is described, based on the single species Siphulella coralloidea Kantvilas, Elix & James sp. nov. The genus is characterised by a dimorphic thallus, apothecia borne on podetia, eight-spored asci of the Baeomyces-type, and simple, hyaline ascospores. Its chemistry consists ofsiphulellic acid, a unique previously unknown 3-orcinol depsidone structurally related to psoromic acid. Siphulella is endemic to Tasmania where it occurs on soil, peat, and stones in treeless vegetation in high rainfall areas. Its relationships with the other genera of the Baeomycetaceae are discussed briefly. The present paper deals with a remarkable new macrolichen genus which appears to be endemic to southwest Tasmania. This is a wilderness region within the Tasmanian Wilderness World Heritage Area and is characterised by a rugged topography, high rainfall (to 3,400 mm per annum), and a pre- dominantly metamorphic, pre-Carboniferous ge- ology. Its vegetation consists of extensive areas of buttongrass moorland (dominated by a sedge, Gym- noschoenus sphaerocephalus) and cool temperate rainforest, as well as alpine formations and eucalypt forest, and includes a large proportion of Tasma- nia's endemic vascular flora. Recent investigations (e.g., Kantvilas & Jarman 1988, 1991) indicate that the cryptogamic flora of the region is also rich and distinctive and several interesting species are either confined to or attain their peak of development there (e.g., see Coppins & Kantvilas 1990; Galloway & James 1987; Henssen & Kantvilas 1985; Kantvilas 1987, 1990; Kantvilas & Elix 1987). The present new genus appears to be another such taxon.

Petrological evidence of a typical oceanic crust in the western Mediterranean Sea

During the “Cyaligure” submersible diving campaign, volcanic lavas have been sampled on a linear magnetic anomaly located off southwest Corsica. Their petrology reveals that they are metamorphic basalts, probably of tholeiitic origin. Some characteristics such as the paragenesis of the metamorphic minerals (chlorites, albite, epidote, actinolite) reveal a “greenschist” metamorphism facies. This rock would thus suggest an oceanic setting with a high thermal gradient at shallow depths. Thus, this basalt sampled in a well-defined morphostructural environment, located far from the alpine formations of Corsica, would represent the first petrological evidence of a typical oceanic crust in the Mediterranean Sea.

Transcontinental crustal sections of the U.S.S.R. and adjacent areas

Transcontinental sections of the earth's crust and Upper Mantle from the Kuril Islands to the Carpathians, and along other principal directions, in all about 15 000 km long, show the following features:(1) The depth of an asthenosphere horizon agrees well with the position of a high-conductivity layer in the Upper Mantle.(2) Hypocenters of earthquakes are located in fault zones. In the zone of the Kuril Island arc, they plunge into the Upper Mantle to depths of hundreds of kilometers, dipping towards the continent.(3) Boundary velocities along the Mohorovičić discontinuity are not dependent on its depth, for they are always in the range 8.0–8.2 km/s; velocities within the crust are correlated with the depths of layers; in the roots of high mountains a layer of 7.5–7.8 km/s has been distinguished near the base of the crust.(3) The crustal thickness in folded areas is in a certain accordance with the altitude of the surface of the earth's solid cover, with Bouguer anomalies and amplitudes of neotectonic movements. It varies from 8 km in margin areas of the Pacific Ocean basin to 60 km in the Tien Shan. Average crustal thicknesses within the platforms are in the region of 40 km, increasing to 50 km in the southern outlying areas of the East-European platform and to 46 km in areas of recent tectonic activity within the Turanian and Siberian Platforms.(4) In deep depressions, internal and outlying seas, the crustal thickness is reduced, and 'granite' layer (6.0–6.5 km/s) is absent. Mesozoic formations of the Far East and adjacent zones of transition from the Pacific Ocean to the continent are distinguished by reduced thicknesses. In Alpine formations the 'basalt' layer dominates over the 'granite' layer.(5) Subhorizontal crustal stratification complicated by deep faults has been found everywhere. Plicate geosynclinal folding is not reflected in deep crustal structures.(6) Temperature of the platform folded basement is mainly related to thickness and composition of the sediments.The transcontinental sections provide a clearer idea of the relationship between anomalous geophysical fields and deep and shallow crustal structures than is given in corresponding maps.