Ennio Marsella

Large-scale longitudinal extension in the southern Apennines contractional belt, Italy

During late Cenozoic thrusting, the interior of the peri-Tyrrhenian orogenic belt in the southern Apennines underwent two episodes of nearly orthogonal extension. Early extension was oriented subparallel to the axis of the tectonic belt and formed in response to progressive thrust-belt arcuation. The length of the tectonic belt increased by ∼50%, and the longitudinal strain was accommodated by low-angle normal faults concentrated in tectonic domains recording up to 150%-200% extension. Younger extension, oriented at a high angle to the orogen, was accompanied by Pliocene-Pleistocene uplift and by southeasterly migration of Tyrrhenian Sea rifting.

Rifted margin formation in the south Tyrrhenian Sea: A high‐resolution seismic profile across the north Sicily passive continental margin

A new, 150 km long seismic line across the continental margin of north Sicily has been acquired and interpreted. The overall structure of the margin is controlled by extension, which caused crustal thinning and widespread normal faulting. Two main thinned zones are observed in the south in correspondence with the Cefalu basin and farther to the north at the continent-ocean transition. Zones of thinned crust coincide with zones of intense normal faulting. Extension began in late Tortonian times and caused the opening of the Cefalu basin controlled by a northward dipping listric fault. Messinian stretching affected most of the future margin and provoked a widening of the Cefalu basin and normal faulting in the north. Following a phase of relative quiescence in the early Pliocene, renewed extension determined further opening of the Cefalu basin and subordinate normal faulting in the north. Here, however, the record is unclear because of the emplacement of the calc-alkaline Sisifo volcano with associated volcanoclastic deposits. Breakup took place in the late Pliocene and was followed by the deposition of postrift Pleistocene sediments. At the lithospheric scale the sites of extension/thinning did not migrate during rifting. On the smaller scale, on the contrary, the Cefalu basin displays a remarkably systematic pattern of migration toward the foot-wall of the listric fault, which controlled the opening of the basin. The spacing of 4–6 km between faults is also quite systematic. Elongation experienced by the continental part of the margin (presently ∼97 km) has been derived by comparing the present-day and the preextensional lengths and is ∼10 km. The corresponding strain rate is 5×10−16 s−1.

Tectonic history of the Lagonegro Domain and Southern Apennine thrust belt evolution

Abstract The tectonic history of the Lagonegro Domain in Southern Italy is an intriguing topic for the Mesozoic Mediterranean paleogeography and is important for reconstructions of the Tethys. Previous interpretations postulate the paleogeographic position of a deep Lagonegro-Molise-(Sicilide) basinal domain between the external Apulia carbonate platform to the east, and the internal Apenninic carbonate platform (i.e. the Alburno-Cervati-Maddalena Mountains) to the west. A second and separate deep basin more to the west was the home of the Liguride units which cover extensive areas of the Southern Apennines. Following an extensive review of previously published concepts and on the base of the structural interpretation of the Southern Apennines thrust belt using additional subsurface data and extensive field mapping, the authors now suggest that all deep basinal units of the Southern Apennines, i.e. the Ligurides, the Lagonegro units and the Molise-Sicilide units, derive from internal areas located to the west with respect to a coeval wide carbonate platform-slope-shallow-basin complex which, in its pre-Middle Miocene reconstruction, extended from Apulia well beyond the present-day Tyrrhenian coast of Southern Italy. The basinal units were first assembled as an accretionary wedge and overthrusted during the Late Miocene over the carbonate platform-slope-shallow-basin complex. The Liguride-Lagonegro-Molise-(Sicilide) accretionary wedge was later cut by an envelopment thrust which overthrust the previously underlying platform complex over the previously emplaced complex accretionary wedge. Our hypothesis in part revives an old concept proposed by Selli (1962) and requires further testing and research. We conclude that paleogeographic reconstructions of the Southern Apennines and the Mediterranean Tethys are still in a state of flux.

Utility of benthic foraminifera for biomonitoring of contamination in marine sediments: A case study from the Naples harbour (Southern Italy)

We propose a detailed investigation on the distribution patterns of the benthic foraminiferal assemblage and their predominant species in the highly contaminated marine sediments of the Naples harbour. Combined use of multivariate canonical, cluster and principal component analysis in a proper geostatistic framework provided an appropriate approach to explore the role played by a number of contaminants (heavy metals, polycyclic aromatic hydrocarbons, volatile organic compounds, heavy hydrocarbons, PCBs) and different physical parameters (grain size, pH, redox potential, total organic carbon) on the spatial distribution of the benthic foraminiferal assemblage and its single species. Obtained results provide evidence for a high and systematic non-linear response of the biota to the effects of contamination of the different classes of pollutants. The reduced number of specimens per sample, their small dimensions and low diversity, testify the negative effects of a highly contaminated environment. For this reason, it appears very difficult to clearly identify a differential sensitivity of different benthic species to single classes of contaminants. In particular, in addition to a number of case studies which invoked a key role of the heavy metals in the control of the distribution patterns of the benthic foraminifera in the marine environment, the results presented here underline an important effect of some classes of organic compounds (particularly the volatile organic compounds) on the distribution patterns of the benthic assemblage. However, the obtained results demonstrate that any kind of oversimplification would unquestionably cancel the strong complexity of the biotic response to combined effects of different coexisting contaminants.

Marine Geology and Morphobathymetry in the Bay of Naples (South-Eastern Tyrrhenian Sea, Italy)

Recent multibeam bathymetry (Elac, Bottomchart MK2) and high resolution seismics (Subbottom Chirp and 1–4 kJ Sparker source), acquired in the frame of an on-going programme of sea-floor mapping of Naples and Salerno Bays (south-eastern Tyrrhenian margin, Italy) and financed by the National Geological Survey of Italy, allows to put new insights into the recent evolution of the bay. The morphology and stratigraphy of the continental shelf and slope appear strongly controlled by the interplay of volcanism and canyoning that acted along the Magnaghi and Dohrn axes. Detailed bathymetry reveals the complexity of the drainage pattern which consists of a previously unknown, dense network of minor tributary channels. At places, the Dohrn and Magnaghi canyon walls are intensively affected by slope instability, as evidenced by numerous submarine slides and scars involving large volumes of sediments. Previously unreported mound-shaped morphological highs (“Bacarozzi” Facies), Holocene reworked sediments and sea-bottom creep appear on acoustic Chirp profiles in the inner sectors of the bay and seem to be related to volcano-sedimentary processes. On the contrary, sedimentation over the shelf at the southern edge of the bay (Sorrento-Capri) seems less influenced by volcanic activity and seabed features include Late Pleistocene regressive sand bodies and Holocene patch reefs, coastal dunes and depositional terraces.

Heavy metals in benthic foraminifera from the highly polluted sediments of the Naples harbour (Southern Tyrrhenian Sea, Italy)

A systematic investigation evaluated the concentrations of a selected number of trace elements (Cd, Co, Cu, Li, Ni, Pb, V and Zn) in carbonates of the benthic foraminifera Ammonia tepida collected from surface sediments of the highly polluted harbour of Naples. Application of cleaning procedures, combined with Scanning Electron Microscopy investigation (SEM) of the analysed shells allowed reliable quantification of the elements in the carbonate lattice. Adoption of biogenic carbonate/seawater distribution coefficients reported in the literature provided the ranges of variability of total dissolved trace elements in the studied marine environment. Very high concentrations of Zn, Cd, and Cu calculated in seawater (from 100 to 10,000 times higher than those reported for uncontaminated Mediterranean seawaters) testify to intense effects of anthropogenic impact on the harbour mainly related to the industrial and commercial activities carried out in the neighbouring area. The ensemble of the obtained results emphasizes the high potential of measurements of trace elements in the biogenic carbonates of benthic foraminifera as tracers of anthopogenic pollution of seawater and reliable proxies of potentially bioavailable forms (as free ions and/or more labile organic complexes) of seawater dissolved metals.

Quaternary structural evolution of terracina and gaeta basins (Eastern Tyrrhenian margin, Italy)

In the Terracina and Gaeta basins Quaternary sediments are displaced by normal faults, which affect also the Meso-Cenozoic tectonic units of the acoustic basement. The extensional tectonics is characterized by normal faults systems trending NE-SW and E-W. In the Terracina basin, roughly N-S oriented, half-graben structures are downthrown seaward through normal faults; the Gaeta extensional basin, E-W oriented, has two main depocenters and is bounded to the north and to the south by E-W trending normal faults and to the east by a NW-SE trending normal fault.RiassuntoI bacini di Terracina e Gaeta mostrano un significativo controllo tettonico sulla sedimentazione quaternaria, causato dalla presenza di faglie normali: esse dislocano le unità tettoniche meso-cenozoiche che rappresentano il basamento acustico. Sistemi di faglie normali ad andamento NE-SW e E-W determinano nel bacino di Terracina una struttura di tipo semi-graben orientata N-S e ribassata verso mare da faglie dirette. Il bacino di Gaeta rappresenta un bacino estensionale ad andamento E-W, articolato in due principali depocentri e delimitato verso nord e verso sud da faglie normali ad andamento E-W e verso est da una faglia diretta ad andamento NW-SE.

Seismic Tomography Experiment at Italy's Stromboli Volcano

Stromboli Island, located in the southern Tyrrhenian Sea, is the emerged part (about 900 meters above sea level) of an approximately 3-kilometer-high stratovolcano. Its persistent Strombolian activity, documented for more than 2000 years, is sometimes interrupted by lava effusions or major explosions. Despite the number of recently published geophysical studies aimed at clarifying the volcanos eruption dynamics, the spatial extent and geometrical characteristics of its plumbing system remain poorly understood. In fact, knowledge of the inner structure and the zones of magma storage is limited to the upper few hundred meters of the volcanic edifice [Chouet et al., 2003; Mattia et al., 2004], and P and S wave velocity models are available only in restricted areas [Petrosino et al., 2002].

Heavy metals in top core sediments from the southern Campania shelf (Italy): Hints to define large-scale geochemical backgrounds

The results of a geochemical survey carried out on the southern Campania shelf (southern Italy) are illustrated, offering a tempting opportunity to discuss the statement and definition of regional geochemical backgrounds for selected heavy metals. A total of 104 top core sediments, collected on average 1.5 km from one another and covering a shelf area of about 1300 km2, were analysed for grain size, organic carbon content (OC), and heavy-metal (As, Al, Fe, Cd, V, Cr, Zn, Cu, Ni, Hg, and Pb) concentrations. The characteristics of the area, scarcely influenced by industrial activities, and the extensive data set, make this study suitable for an appropriate multivariate and spatial geostatistical methodologies used for i) a reliable definition of large-scale marine sediments’ geochemical backgrounds and ii) an accurate discrimination of different geological controls on trace-element distribution patterns. Enrichment factors estimated with respect to both the average shale composition and the weighted average metal concentrations measured in inland soils rule out significant anthropogenic inputs. A spatial-geostatistics approach (kriging of spatial component based on an accurate implementation of variographic surveying) was applied, and this is proposed as an appropriate quantitative methodology to define the geochemical backgrounds for the different heavy metals. Two nested spatial structures were identified for some of the heavy metals, thus allowing clear identification of local and regional geochemical controls related to the different spatial variability of grain size.

Application of X-Band Wave Radar for Coastal Dynamic Analysis: Case Test of Bagnara Calabra (South Tyrrhenian Sea, Italy)

Sea state knowledge has a key role in evaluation of coastal erosion, the assessment of vulnerability and potential in coastal zone utilization, and development of numerical models to predict its evolution. X-band radar measurements were conducted to observe the spatial and temporal variation of the sea-state parameters along a 3 km long sandy-gravelly pocket beaches forming a littoral cell on Bagnara Calabra. We produced a sequence of 1000 images of the sea state extending offshore up to 1 mile. The survey has allowed monitoring the coastline, the directional wave spectra, the sea surface current fields, and the significant wave heights and detecting strong rip currents which cause scours around the open inlets and affect the stability of the submerged reef-type breakwaters. The possibility to validate the data acquired with other datasets (e.g., LaMMA Consortium) demonstrates the potential of the X-band radar technology as a monitoring tool to advance the understanding of the linkages between sea conditions, nearshore sediment dynamics, and coastal change. This work proves the possibility to obtain relevant information (e.g., wave number, period, and direction) for evaluation of local erosion phenomena and of morphological changes in the nearshore and surf zone.