34 research outputs found
Regional-scale seafloor mapping and geohazard assessment. The experience from the Italian project MaGIC (Marine Geohazards along the Italian Coasts)
No full textRecent developments in seafloor imaging and mapping techniques greatly improved our capability of identifying marine geohazards affecting continental margins. Geomorphic features can be detected in great detail by high-resolution multibeam imaging and regarded as geohazard indicators; the most common include slide scars and deposits, canyon headscarps and steep erosional flanks, fault-related seafloor unevenness, mud volcanoes, pockmarks, gravity flow deposits, erosional scours and bedforms indicating sediment mobility at diverse temporal/spatial scale. These processes are widespread on Italian continental margins and are potential indicators of geohazard for human settlements and infrastructures in the offshore and coastal zones. The national Project MaGIC (Marine Geohazards along the Italian Coasts) aims at documenting potential geohazards based on the acquisition of high-resolution multibeam bathymetry and on the production of maps of the geohazard-related geomorphic features for most of the Italian continental margins. With reference to this issue, we discuss some of the most frequent problems dealing with reconnaissance, interpretation and cartographic representation of geohazard-related geomorphic features at a regional scale
The Italian MaGIC Project: A first-order geohazard assessment by means of regional seafloor mapping
No full textOver the past decades interest for marine geohazard assessment has rapidly grown up, driven by the increasing exploitation of natural resources, the emplacement of bottom-lying structures (cables and pipelines) and by the development of coastal areas, whose infrastructures increasingly protrude to the sea. At the same time, recent advances in seafloor mapping techniques have greatly improved our knowledge of geomorphic features that can be regarded as geohazard indicators, such as volcanic vents, slide scars, canyon headscarps, and fault-related seafloor unevenness. The national Project MaGIC (Marine Geohazards along the Italian Coast) is aimed at depicting potential geohazards based on the acquisition of highresolution bathymetry and on the production of maps of the geohazard -related geomorphic features for most of the Italian continental margins
Depositional and erosional bedforms in Late Pleistocene-Holocene pro-delta deposits of the Gulf of Patti (southern Tyrrhenian margin, Italy)
No full textMultibeambathymetry, high-resolution seismic profiles and seafloor samples have been analyzed to characterize
depositional and erosional dynamics recorded pro-deltaic deposits and outer shelf sediments along of a sector of
the NE Sicilianmargin (southern Tyrrhenian Sea). The deltaic deposits cover an area of ca. 15 km2 in front of the
Mazzarrà River, and are morphologically characterized by waveforms trending overall along strike and incised
cross-strike gullies of variable length. The gullies are shallow and characterized by small, coaxial erosive scours
in the inner-middle shelf, whereas they become larger and deeper in the outer shelf-upper slope, in relation to
the marked increase of slope gradients at the shelf break. Here, the wider gullies are characterized by a frame
of crescent-shaped bedforms interpreted as cyclic steps, indicating the occurrence of sedimentary gravity flows
in supercritical regime. Prodelta waveforms are widespread between −50 and −120 m, with wave lengths of
34–110 m and wave heights of 0.5–3 m. Morphometric characterization and spatial distribution of the waveforms
suggests a main role in their genesis played by hyperpycnal flows, althoughwe cannot discard the possible
effect of internal waves or slow deformation processes (i.e., creep).
Depositional and erosional features similar to those observed on the seafloor are evident in the subsurface stratigraphy,
revealing the onset and growth of theMazzarrà Delta since the Last GlacialMaximum. The post-glacial
sea level rise caused lateral shifts of the Mazzarrà Rivermouth controllingmigration of depositional lobes and intensity
of seafloor incision and sediment reworking, ultimately resulting in the observedwavy bedforms extending
from the inner shelf to the upper slope
Middle-Upper Pleistocene record of 100-ka depositional cycles on the Southern Tuscany continental margin (Tyrrhenian Sea, Italy). Sequence architecture and margin growth pattern
No full textFive unconformity-bounded depositional sequences have been seismically defined on the Tyrrhenian margin offshore Southern Tuscany, Italy. The set of sequences encompasses a ~ 500. ka interval, each sequence recording a ~ 100-ka orbitally-driven climate-eustatic cycle. Similarly to most of Quaternary continental margins, sequences on the Southern Tuscany margin show an overall regressive motif reflecting shelf sediment progradation basically during the prolonged phases of sea level fall that characterise the Middle-Upper Pleistocene 100-ka cyclicity. On seismic profiles, however, progradational units within each sequence display a variable clinoform geometry, interpreted as a record of the alternation of highstand, falling and lowstand intervals within 100-ka. cycles. The observed geometric variability is thus used as a key for separating systems tracts otherwise merging into a general progradational/regressive sedimentary body composing the bulk of each sequence. On a longer term, the interplay between sea level changes modulated by 100-ka. cycles and regional subsidence controls the stratigraphic architecture and the growth pattern of the continental margin. This effect is documented by the overall aggradational/retrogradational stacking pattern of sequences, superimposed on shelf margin progradation and reflecting the renewal of accommodation space landward of the shelf margin and its exploitation at each cycle. © 2012 Elsevier B.V
High-resolution morpho-bathymetric imaging of the Messina Strait (Southern Italy). New insights on the 1908 earthquake and tsunami
No full textThe 28 December, 1908 Reggio Calabria and Messina earthquake (named after the two most damaged cities on the coasts of Messina Strait) was one of the strongest (MW 7.1) ever to occur in Italy, and was also followed by a tsunami that severely impacted the coasts of the Strait. Although there is general agreement that its epicentre is located offshore in the Messina Strait, the source fault has never been detected; a century-long question is therefore pending on the source of both the 1908 earthquake and tsunami. Within the ongoing debate on this subject, little attention has been given, so far, to morphological insights from high resolution bathymetric (multibeam) data, particularly as regarding the evidence of faults affecting the seafloor and the question of whether a submarine landslide may had been the cause of the tsunami. We aim to address this issue by presenting the results of a morpho-bathymetric study in the Messina Strait and surroundings, investigated by means of high-resolution swath bathymetry. The primary morpho-structural feature in this area is the axial channel of the Messina Canyon, towards which flow several tributary canyons that incise the steep continental slope on the Calabrian and Sicilian margins. These canyons carve deeply into a very narrow (almost lacking) continental shelf and merge laterally forming a continuous erosional margin rimming the Messina Strait. This giant, composite canyon environment is the locus of intense erosional and depositional processes that superimpose on active tectonic deformation, resulting in a complex geomorphology that hinders the distinction between tectonic and sedimentary features. Seafloor ruptures that may be linked to fault systems compatible with the source of the 1908 earthquake and tsunami could not be identified based from our morpho-bathymetric analysis; however, we provide evidence of several geomorphic features indicative of tectonic deformation in the Messina Strait, define the presence and distribution of submarine landslides, and evaluate their possible role as tsunami sources. © 2013 Elsevier B.V
Il mito di Tristano nella "morte a Venezia" di Thomas Mann
No full textPresentazione critica del libro di Sara Zurletti "Amore luminoso, ridente morte. Il mito di Tristano nella Morte a Venezia di Thomas Mann", Roma, Castelvecchi, 2016. Altro presentatore: Paolo Isotta. Conduzione di Natalino Irti
Bedforms feeding and bedforms fed by canyon activity around Punta Alice Promontory (Calabria Ionian Margin, Italy)
No full textSubmarine canyons along the Ionian Calabria margin indent large shelf sectors as the
coalescing of smaller failure scarps progresses under the control of tectonic deformation
and high sedimentation rates, promoted by regional uplift and rejuvenation of the drainage
basin. The Punta Alice Canyon and the Cirò Canyon show such complex canyon heads,
almost completely eroding the shelf and thus affecting sediment pathways along and across
strike. Wavy bedforms of variable shape and size are observed both outside and inside the
two canyon systems, providing an indication of how sediment is sourced and transported.
We analyse the distribution of bedforms in order to define how both open shelf currents and
confined sediment fluxes contribute to their formation outside and inside canyons. We also
remark on the importance of the orientation of canyon heads and channels relative to flow
direction of currents, and of slope failure as a sediment source
Coastal and Submarine Landslides in the Tectonically-Active Tyrrhenian Calabrian Margin (Southern Italy): Examples and Geohazard Implications
No full textHigh-resolution multibeam bathymetry is used as basis for detecting instability processes on the Tyrrhenian margin offshore Calabria (Italy). Among the many evidence at different spatial scale, we focus on selected cases that may represent a potential geohazard because of their scale, shallow/proximal location and state of activity. These include failures along coastal cliffs and canyon headwalls indenting narrow shelves. Coastal rocky failures impacting shallow water offshore Scilla and Palmi retain significant tsunamigenic potential, as proved by the 1783 Scilla event. Slide scars at canyon headwalls offshore Bagnara Calabra and Gioia Tauro indicate retrogressive failure active at water depth <10 m, just few hundreds of meters from the coast and the settlements and infrastructures there present. Geohazard related to these features is therefore relevant as testified by the failure induced during construction of the Gioia Tauro harbour in 1977
MARTIN LISTER’S 1678 <em>AMMONIS CORNU</em> AND THE MISREADING OF <em>HILDOCERAS BIFRONS</em> (BRUGUIÈRE, 1789). AN HISTORICAL INSIGHT ON THE RELEVANCE OF ARTWORK AND DETAILS IN TAXONOMY
No full textHildoceras bifrons (Bruguière, 1789) is a cosmopolite ammonite species from the Lower Jurassic of the Boreal and Mediterranean (Tethys) palaeogeographical provinces. Inter-demic and phylogenetic variability are noticeable, also affecting the most distinctive morphological trait: the spiral groove along the whorl flank. Since the XIX century, however, a number of morphotypes assigned to Hildoceras bifrons (many of which from the Apennines and other Italian localities) lacked a neat spiral groove, replaced by a shallow, variably evident and discontinuous inflection. Buckman (1918) provided a photographic illustration of a specimen he interpreted as corresponding to the holotype, until then represented by a drawing described by Lister (1678) as Ammonis cornu. Buckman’s illustration assessed the well-carved spiral groove as a distinctive feature of the holotype and a trademark of the species. Nevertheless, several authors insisted on referring faintly grooved specimens to Hildoceras bifrons, an attitude thus envisaged as due to their negligence or inaccuracy. In contrast with this view, it is herein argued that, on one hand, the specimen illustrated by Buckman, in quality of holotype or neotype, differs from Lister’s drawing to a point that it may not be the same specimen; on the other hand, Lister’s drawing (never formally invalidated as holotype) could have been legitimately considered representative also of those faintly grooved Hildoceras now assigned to Hildoceras lusitanicum Meister, 1913. This alternative view clarifies the taxonomic approach held by many authors, proving the coherency of their taxonomic work rather than their attitude at a superficial evaluation of diagnostic traits
Preliminary interpretation of high resolution 3D seismic data from offshore Mt. Etna, Italy
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