Search results for "TECTONICS"
showing 10 items of 385 documents
Helium isotopes and tectonics in southern Italy
1989
Geodynamic evolution of southern Italy can be understood within the framework of the Mediterranean-Alpine System. Subduction of a plate along the Sicily-Calabrian forearc under the Tyrrhenian Sea has been suggested by many geophysicists, although it is not yet confirmed and remains somewhat controversial. Helium isotope ratios provide useful information on the geotectonic structure of the region. The authors report here the {sup 3}H/{sup 4}He ratios of terrestrial gas samples from southern Italy. The observed {sup 3}He/{sup 4}He ratios are relatively high in the Eolian volcanic arc region and low in the other areas. Dichotomous explanations are presented. Firstly, volcanic arc-forearc hypot…
Mesozoic tectono-sedimentary evolution of Rocca Busambra in western Sicily
2008
The Rocca Busambra ridge in western Sicily is a shallow to pelagic Meso-Cenozoic carbonate structural unit of the Sicilian fold and thrust belt with a variety of tectono-sedimentary features. Palaeofaults, unconformities (buttress unconformity, onlap, downlap), a network of neptunian dykes with several infilling generations, several large hiatuses, different facies and lateral facies changes, and erosional submarine and subaerial surfaces are observed. Detailed fieldwork and structural analyses have indicated the occurrence of fault planes with different orientations. These data, combined with facies studies and physical-stratigraphy analyses, allow for the distinction of different depositi…
Tectonic evolution of the Sierra Maestra Mountains, SE Cuba, during Tertiary times: From arc-continent collision to transform motion
2008
Abstract A structural study was carried out along the southern Sierra Maestra mountain range, SE Cuba. This was aimed to monitor the effects of Paleogene island arc formation and collision due to convergence of the Caribbean and North American plates and subsequent Neogene disruption of the arc by initiation of the North Caribbean Transform Fault. In the Sierra Maestra two different and unrelated volcanic arcs are exposed, one of Cretaceous age (pre-Maastrichtian) and the other of Paleogene age, the latter forming the main expression of the mountain range. The volcanic arcs are overlain by Middle–Upper Eocene siliciclastic, carbonate and terrigenous rocks. Six distinct phases of deformation…
SIGNIFICANCE FOR INTERNATIONAL CORRELATION OF THE PERAPERTÚ FORMATION IN NORTHERN PALENCIA, CANTABRIAN MOUNTAINS. TECTONIC/STRATIGRAPHIC CONTEXT AND …
2021
Small ammonoid assemblages are recorded from the Perapertú Formation in northern Palencia. This is a mudstone unit with local platform limestones characterised by carbonate debris flows on the limestone margins. This unit, of Late Bashkirian to Early Moscovian age, participates in a series of southwards verging thrust slicesNorth of a major fault zone which originated as the head (leading edge) of a large thrust sheet with an internal deformation consisting of thrust slices and at least one nappe structure. Opposed vergencies at the head of this major thrust sheet (Carrionas Thrust Front) and the Ruesga Fault which locally modifies its trace, mark the position where the northern branch of t…
Etna and the perception of volcanic risk
2013
Sicily’s uneven geological structure is positioned within a system of tectonic plates, and its very active volcano has always made it prone to disasters. Many Sicilian cities have in fact been destroyed by natural events many times over the centuries. This can certainly be understood negatively as the destruction of entire towns, the emission of volcanic ash, and the mutation of landscapes by a terrifying force have instilled fearful memories in local populations. But from another point of view one must consider the positive elements of Etna. Its beautiful landscapes were a major attraction on the Grand Tour, and its inhabitants have long associated the volcano with the concept of rebirth a…
Sedimentary basins evolution and olistoliths formation: The case of Carpathian and Sicilian regions
2012
Abstract Comparative research carried out within two different basins, one in the Carpathians of Poland (Late Jurassic to Early Miocene) and another in the Apenninic-Maghrebian mountain chain of Sicily (Triassic-Miocene), indicate significant similarity not only in their evolution but also in the sedimentary features of horizons with olistoliths. The olistolith-bearing units are genetically related to stages of tectonic evolution and are independent of the size of the basins and of duration of these stages. However, the observed differences in composition and size of olistoliths suggested, among the others relationship with the size of source areas and thickness of their sedimentary cover.
Tectono-stratigraphic evolution of a basin generated by transpression: the case of the Early Pliocene Lascari Basin (northern Sicily)
2011
Integrated stratigraphy and structural analysis carried out in the Madonie Mts. (Northern Sicily) is aimed to the description of a syn-sedimentary tectonic event, recorded in a small infra-pliocene basin restricted to the Lascari Syncline core. The onset and evolution of the basin was driven by transpressive tectonics, generating a lens-shaped, deep and narrow tectonic depression, bounded by steep and high, tectonically controlled slopes, also reflected in the present-day topography of the area. During the genesis of the basin, the tectonic control interferes with a dramatic sea level oscillation during the Messinian-Early Pliocene time interval. In this paper, the syn-tectonic deposits of …
Friction of Shear-Fracture Zones
2017
A shear fracture of brittle solids under compression undergoes a substantial evolution from the initial microcracking to a fully formed powder-filled shear zone. Experiments covering the entire process are relatively easy to conduct, but they are very difficult to investigate in detail. Numerically, the large strain limit has remained a challenge. An efficient simulation model and a custom-made experimental device are employed to test to what extent a shear fracture alone is sufficient to drive material to spontaneous selflubrication. A “weak shear zone” is an important concept in geology, and a large number of explanations, specific for tectonic conditions, have been proposed. We demonstra…
Geophysical study of an landslide in northern Sicily
2002
The San Fratello area in the Nebrodi Mountains (northern Sicily) is a region of high instability. It has suffered many devastating occurrences, which have hit and destroyed the village of San Fratello. At present the area is still subject to a high landslide risk. A series of geophysical surveys have been carried out with the aim of determining the thickness and dimensions of the landslide body as well as some tectonic features, in order to gain insight into the evolution of the landslide. The following geophysical techniques have been used: borehole seismic tomography, i.e. down-hole tomographic seismic soundings (DH TSS), time-domain electromagnetic (TDEM) soundings and georadar profiling…
Geomorphological and geophysical investigations to study the landslide affecting the archaeological site of abakainon
2016
In recent years, a detailed archeoseismological investigation has been carried out in the necropolis of Abakainon in order to identify traces of an ancient earthquake. Although the identification of seismic damage was undoubtedly attributed to the 1st century AD earthquake, it was hypothesised that the level of damaging observed in the necropolis, as well as the counter slope tilting of the tomb basements may have also caused by a seismo-induced landslide, which produced locally an amplification of the seismic shaking. In order to identify the landslide, on which the Greek site lies, detailed geomorphological and geophysical surveys have been carried out. The research was directed to the ac…