Submarine mass movements around the Iberian Peninsula. The building of continental margins through hazardous processes

Submarine mass movements, such as those which occur in all environments in every ocean of the world, are widely distributed across the Iberian continental margins. A lack of consistent data from various areas around the Iberian Peninsula makes it difficult to precisely understand their role in the sedimentary record. However, all the studies carried out over the past two decades reveal that they are a recurrent and widespread sedimentary process that may represent a significant geohazard. The majority of submarine mass movements observed in both the Mediterranean and Atlantic margins of the Iberian Peninsula have been generically identified as Mass Transport Deposits, but debris flows, slides, slumps and turbidites are common. Only a few remarkable examples involve huge volumes of sediment covering large areas (such as ~500 km3 and ~6x104 km2 ), but more moderate deposits (<200 km2 ) are frequently found on the seafloor or embedded in the sedimentary sequences, building margins and basins

First evidence of contourite drifts in the north-western sicilian active continental margin (Southern tyrrhenian sea)

We present the results of an integrated geomorphological and seismo-stratigraphic study based on high resolution marine data acquired in the north-western Sicilian continental margin. We document for the first time five contourite drifts (marked as EM1a, EM2b, EM2, EM3a, and EM3b), located in the continental slope at depths between ca. 400 and 1500 m. EM1a,b have been interpreted as elongated mounded drifts. EM1a,b are ca. 3 km long, 1.3 km wide, and have a maximum thickness of 36 m in their center that thins northwards, while EM1b is smaller with a thickness up to 24 m. They are internally characterized by mounded seismic packages dominated by continuous and parallel reflectors. EM2 is located in the upper slope at a depth of ca. 1470 m, and it is ca. 9.3 km long, more than 3.9 km wide, and has a maximum thickness of ca. 65 m. It consists of an internal aggradational stacking pattern with elongated mounded packages of continuous, moderate to high amplitude seismic reflectors. EM2 is internally composed by a mix of contourite deposits (Holocene) interbedded with turbiditic and/or mass flow deposits. EM1a,b and EM2 are deposited at the top of an erosional truncation aged at 11.5 ka, so they mostly formed during the Holocene. EM3a,b are ca. 16 km long, more than 6.7 km wide, and have a thickness up to 350 m. Both EM2 and EM3a,b have been interpreted as sheeted drift due to their morphology and seismic features. The spatial distribution of the contourite drifts suggests that the drifts are likely generated by the interaction of the LIW, and deep Tyrrhenian water (TDW) on the seafloor, playing an important role in the shaping this continental margin since the late Pleistocene-Holocene. The results may help to understand the deep oceanic processes affecting the north-western Sicilian continental margin

Post glacial sediment partitioning on a tectonically controlled, narrow shelf (Calabro-Tyrrhenian margin, Italy). Issues in defining S2S budget

The re-analysis of high-resolution seismic profiles collected along the narrow (2–9 km) shelf facing ∼90 km of the Calabro-Tyrrhenian coastline has enabled the reconstruction of its sequence-stratigraphic architecture, along with the quantification of sediment volumes accommodated during the last post-glacial sea level rise and highstand. The shelf volumes are compared with the gross volumes supplied by the short and steep rivers draining the uplifted hinterland area, obtained from morphometric analysis and inferred denudation rates (derived from uplift rates) of the drainage basins. The study area is divided in two main sectors based on the different morpho-stratigraphic setting and fluvial network controlling sediment distribution on the shelf. The Coastal Range sector is characterized by closely spaced mountainous rivers and narrow coastal plains; on the shelf, the post-LGM deposits show a main depocenter (up to 60 m thick) elongated ∼27 km parallel to the coastline. This shelf sector hosts up to 80% of the sediment sourced from rivers, with a small percentage of sediment loss, mainly related to off-shelf export along a network of shelf-indenting submarine canyons. Sediment deficit due to river aggradation is considered negligible based on the narrow and V-shaped thalwegs typical of the rivers in this sector. The Santa Eufemia sector is characterized by larger rivers and a wider coastal plain, with a major depocenter (up to 50 m thick) confined off the Amato River. In this sector, the entire post-LGM sequence accounts only for about 30% of the sediment supplied by rivers (60% considering only the HST), indicating that, in addition to sediment exported off-shelf, a significant part is trapped by river aggradation within the coastal plain. The volumetric comparison has also evidenced local but significant discrepancies in sedimentary budget between adjacent sub-sectors, likely related to the effect of northward-directed shelf currents on sediment distribution along the shelf

A review of Rhodolith/Maerl beds of the italian seas

Coralline algal beds are comprised of biogenic calcareous formations considered a habitat of high conservation interest, hosting a high great biodiversity. To assess the status of this habitat in the Italian seas, we report results from a systematic analysis of the available scientific literature. Italian rhodolith/maerl beds are reported on 31 Italian sites mostly located around islands, shoals, banks, terraces, and gentley sloping shelves, from 9 m to 130 m water depth (with a mean depth of about 56 m). The dominant species occurring in the Italian submarine sites are Phymatolithon calcareum and Lithothamnion corallioides, with a rich associated fauna including sponges, bryozoans, hydrozoans, polichaetes, molluscs, amphipods, gastropods, echinoderms. Despite the high biodiversity characterizing the Italian rhodolith/maerl beds, only seven submarine sites hosting this sensitive habitat are part of Marine Protected Areas (MPAs). This evidence highlights the need for actions focused on the implementation of effective management and proper conservation measures to preserve such precious habitats. Protection of this habitat cannot be effectively provided without access to multidisciplinary data (e.g., geospatial, biological, geophysical, geomorphological data) capable of assessing its spatial distribution and biological characteristics over wide areas. An increased research effort to improve the production of fine-scale distribution maps and monitoring activities is therefore needed

Morphology of the submerged Ferdinandea Island, the ‘Neverland’ of the Sicily Channel (central Mediterranean Sea)

We present the bathy-morphological map at a scale of 1: 50,000 of the area around the submerged Ferdinandea Island, the ‘Neverland’ of the Sicily Channel (central Mediterranean Sea). We investigate an area of 100 km2, between 10 and 350 m, which is part of a triangular morphological high, 360 km2 wide, representing the SE-wards prolongation of the Adventure Bank. The study is based on the morphometric analysis based on high resolution multibeam, and sub-bottom CHIRP profiles collected in 2015. The area around the remains of Ferdinandea Island is morphologically shaped by the interplay between volcanic, tectonic, fluid seepage, and oceanographic processes. Since the study area is considered a hot spot of biodiversity affected by maritime traffic (especially in Ferdinandea Channel) and hosting communication pipelines, this map provides insights both for habitat mapping purposes and preliminary marine geohazard assessment due to the occurrence of historically active submarine volcanoes, pockmarks, and mass transport deposits

The interplay between sedimentary supply, sea-level rise and tectonics from the last glacial maximum onwards: insights from the Sant’Eufemia continental shelf (Offshore Calabria, Italy)

New high-resolution, multichannel seismic data, acquired in the Sant’Eufemia Gulf, provide constrains on the architecture of submarine depositional features (e.g. prograding wedges) formed since the last glacial maximum (LGM). Sedimentological and quantitative micropaleontological analyses of gravity cores integrated with calibrated radiocarbon age of samples allow us to calibrate the seismic profiles, constrain the sedimentation rate and reconstruct the paleoenvironmental evolution of the study area since the earliest Bølling-Allerød. Five sediment grain size intervals and benthic foraminifera assemblages outline the evolution of the sea-bottom environment. Basal coarse sand grains along with shallow water and epiphytic benthic foraminifera (e.g. genus Asterigerinata, Elphidium) point to an infralittoral environment. After that, we record a progressive grain size reduction culminating at the top core, where dominant silt, clay and benthic foraminifera assemblages point to a muddy bottom circalittoral environment. A reduced organic matter flux is observed in benthic foraminifera after 5.5 ka, supporting the evidence from calcareous plankton. Sedimentation rates vary from 4.9 to 12.9 cm/ kyr. The prograding wedges formed at distinct water depths at which the sea level was stationed or lowered during the relative sea-level rise from the LGM to the basal Holocene. The erosional surfaces and marine terraces result from wave action above the depth of closure. Therefore, the above features are suitable for reconstructing a relative sea-level curve. The error bar includes uncertainties due to the a) seismic velocities used for the time-to-depth conversion of profiles, b) water depth related to the formation of depositional and erosional features, and c) tectonics. The reconstructed sea-level rise curve shows a step-like trend, starting from the Heinrich stadial 1, followed by sea level rise during the warm and ice-melting period of Bølling- Allerød, with a peak of the rising rate during the Melt Water Pulse 1-A. Subsequently, it shows evidence of sea level still standing during the cold stadial Younger Dryas, followed by a rapid increase in sea level during the Melt Water Pulse 1-B. The obtained curve of relative sea-level rise was compared with the a) eustatic sealevel curve proposed by Lambeck et al. (2014) corrected for the Glacial Isostatic Adjustment (GIA), b) relative sea-level curve by Lambeck et al. (2011) for Briatico, seven eustatic sea level curves plus one calculated in the Mediterranean, all corrected for the GIA. The best overlap was obtained with the high-mantle-viscosity from the GIA correction model of the Australian National University (ANU14-HV). It is noteworthy that the eustatic sea-level curve proposed by Lambeck et al. (2014) overlaps our relative sea-level curve throughout the analyzed time interval

Basin-scale interaction between post-LGM faulting and morpho-sedimentary processes in the S. Eufemia Gulf (Southern Tyrrhenian Sea)

The integrated interpretation of high-resolution multibeam bathymetry, seismic profiles and backscatter data in the S. Eufemia Gulf (SEG; Calabro-Tyrrhenian continental margin, south-eastern Tyrrhenian Sea) documents the relationship between postglacial fault activity and morpho-sedimentary processes. Three systems of active normal faults that affect the seafloor or the shallow subsurface, have been identified: 1) the S. Eufemia fault system located on the continental shelf with fault planes mainly oriented N26E-N40E; 2) the offshore fault system that lies on the continental slope off Capo Suvero with fault planes mainly oriented N28E-N60E; 3) the Angitola Canyon fault system located on the seafloor adjacent to the canyon having fault planes oriented N60EN85E. The faults produce a belt of linear escarpments with vertical displacement varying from a few decimeters to about 12 m. One of the most prominent active structures is the fault F1 with the highest fault length (about 9.5 km). Two main segments of this fault are identified: a segment characterised by seafloor deformation with metric slip affecting Holocene deposits; a segment characterised by folding of the seafloor. A combined tectonostratigraphic model of an extensional fault propagation fold is proposed here to explain such different deformation.In addition to the seabed escarpments produced by fault deformation, in the SEG, a strong control of fault activity on recent sedimentary processes is clearly observed. For example, canyons and channels frequently change their course in response to their interaction with main tectonic structures. Moreover, the upper branch of the Angitola Canyon shows straight flanks determined by fault scarps. Tectonics also determined different sediment accumulation rates and types of sedimentation (e.g., the accumulation of hanging wall turbidite deposits and the development of contourite deposits around the Maida Ridge). Furthermore, the distribution of landslides is often connected to main fault scarps and fluids are locally confined in the hanging wall side of faults and can escape at the seabed, generating pockmarks aligned along their footwall

An Integrated Multiscale Method for the Characterisation of Active Faults in Offshore Areas. The Case of Sant\u2019Eufemia Gulf (Offshore Calabria, Italy)

Diagnostic morphological features (e.g., rectilinear seafloor scarps) and lateral offsets of the Upper Quaternary deposits are used to infer active faults in offshore areas. Although they deform a significant seafloor region, the active faults are not necessarily capable of producing large earthquakes as they correspond to shallow structures formed in response to local stresses. We present a multiscale approach to reconstruct the structural pattern in offshore areas and distinguish between shallow, non-seismogenic, active faults, and deep blind faults, potentially associated with large seismic moment release. The approach is based on the interpretation of marine seismic reflection data and quantitative morphometric analysis of multibeam bathymetry, and tested on the Sant\u2019Eufemia Gulf (southeastern Tyrrhenian Sea). Data highlights the occurrence of three major tectonic events since the Late Miocene. The first extensional or transtensional phase occurred during the Late Miocene. Since the Early Pliocene, a right-lateral transpressional tectonic event caused the positive inversion of deep (&gt;3&nbsp;km) tectonic features, and the formation of NE-SW faults in the central sector of the gulf. Also, NNE-SSW to NE-SW trending anticlines (e.g., Maida Ridge) developed in the eastern part of the area. Since the Early Pleistocene (Calabrian), shallow (&lt;1.5&nbsp;km) NNE-SSW oriented structures formed in a left-lateral transtensional regime. The new results integrated with previous literature indicates that the Late Miocene to Recent transpressional/transtensional structures developed in an 3cE-W oriented main displacement zone that extends from the Sant\u2019Eufemia Gulf to the Squillace Basin (Ionian offshore), and likely represents the upper plate response to a tear fault of the lower plate. The quantitative morphometric analysis of the study area and the bathymetric analysis of the Angitola Canyon indicate that NNE-SSW to NE-SW trending anticlines were negatively reactivated during the last tectonic phase. We also suggest that the deep structure below the Maida Ridge may correspond to the seismogenic source of the large magnitude earthquake that struck the western Calabrian region in 1905. The multiscale approach contributes to understanding the tectonic imprint of active faults from different hierarchical orders and the geometry of seismogenic faults developed in a lithospheric strike-slip zone orthogonal to the Calabrian Arc

Mid-to-late Holocene upper slope contourite deposits off Capo Vaticano (Mediterranean Sea): High-resolution record of contourite cyclicity, bottom current variability and sandy facies

none13noThe upper continental slope offshore Capo Vaticano (southern Tyrrhenian Sea) is characterized by a contourite depositional system with well-developed elongated sediment drifts. This system is related to a northward paleo-bottom current, similar to the present-day modified-Levantine Intermediate Water (modified-LIW) flowing from the Messina Strait. In this work, we show results from an integrated analysis of descriptive oceanography, high-resolution seismic profiles and core data (i.e., grain size, foraminiferal assemblages, tephrostratigraphy and AMS radiocarbon dating) collected from the crest and moat sectors of drift deposits. The studied succession formed since the mid Holocene, under the action of the modified-LIW and the stratigraphic architecture indicates an upslope migration of the moat and rather stable position of the crest sector. Grain-size features recorded from two sediment cores indicate the occurrence of a succession of complete bi-gradational sand-rich contourite sequences. Sandy facies were observed both as lag deposits formed in active moat channel and as coarser intervals of bi-gradational sequences forming drift deposits close to its crest. Their occurrence would highlight that upper slope environments impacted by intermediate water masses and proximal to sandy sources may represent favorable settings for accumulation of sandy sediment. The moat sector is characterized by a more complex stratigraphic record, where either moat sedimentation or lateral deposition of finer sediment occur, suggesting that further investigation is required to better understand this complex element of contourite systems. Based on available age information, some of the bi-gradational sequences probably formed during the Dark Age Cold Period, providing example of a small-scale cyclicity of contourite deposition, likely related to short-term (possibly multicentennial scale) fluctuations of the paleo modified-LIW. According to age constraints and analysis of foraminiferal assemblages, these fluctuations were likely governed by climate variations, with a weaker activity during warmer periods and faster currents during colder events.openMartorelli E., Bosman A., Casalbore D., Chiocci F., Conte A.M., Di Bella L., Ercilla G., Falcini F., Falco P., Frezza V., Gaglianone G., Giaccio B., Mancini M.Martorelli, E.; Bosman, A.; Casalbore, D.; Chiocci, F.; Conte, A. M.; Di Bella, L.; Ercilla, G.; Falcini, F.; Falco, P.; Frezza, V.; Gaglianone, G.; Giaccio, B.; Mancini, M