Search

The magnitude and rate of Late Pleistocene–Holocene vertical tectonic movements offshore of the Capo Vaticano Promontory (western Calabria, southern Italy) have been measured on the basis of the present-day depth variations of the edges of submerged depositional terraces (and associated abrasion platforms) that formed below the storm-wave base, during the sea level stillstand of the Last Glacial Maximum (LGM). These depositional features, represented by submerged prograding wedges and an associated terrace-shaped upper boundary, have been identified in high-resolution seismic reflection profiles acquired along the continental shelf and the upper slope of the promontory, and are referred to in this study as “Lowstand Infralittoral Prograding Wedges (LIPWs)”. Our new data and methods provide evidence that LIPWs can be used as geomorphological indicators of vertical movements in offshore settings with well controlled uncertainty. Removal of the non-tectonic component of vertical changes using an ice-volume equivalent eustatic sea level compilation indicates ∼11 (±3.2) m of uplift and ∼25 (±3.2) m of subsidence, from southwest to northeast, along the promontory, over a distance of ∼22 km, during the post-LGM. The resulting uplift and subsidence rates (including both regional and local components) for the last 20.350 (±1.35) years are 0.54 (±0.2) mm/y and 1.23 (±0.25) mm/y, respectively. These results are consistent with longer-term estimates based on uplifted 215–82 ka old coastal terraces and Late Holocene shorelines. This integration of offshore and coastal markers indicates a pattern of vertical movements characterized by a marked asymmetry associated with a northeast down tilt of the Capo Vaticano Promontory. The calculated tilt rate increases by one order of magnitude during the post-LGM in respect to the time interval from 215 to 82 BP. Displacement associated with the NW–SE striking normal fault that bound the Capo Vaticano Promontory to the Gioia Tauro Basin ended in the (?) Pleistocene, and thus does not contribute to the tilt of the promontory at least during the last 215 ka. [ABSTRACT FROM AUTHOR]

Resurgence uplift is the rising of the caldera floor, mainly due to pressure or volume changes in the magma reservoir. Identifying resurgence structures and understanding their relationship to the magmatic reservoir is challenging. We investigate the resurgence structures of the Neapolitan Yellow Tuff caldera (Italy) by integrating bathymetric data, high-resolution seismic profiles and Differential Synthetic-Aperture Radar Interferometry data. Our results show that the resurgent area is manifested as 1) a central dome constituted by two main blocks bounded by NNE-SSW trending faults, 2) an apical graben developed on top of the most uplifted block, 3) a peripheral zone including several uplifted and tilted blocks, bounded by inward-dipping faults. The onset of the uplift of the central dome occurred through re-activation, in reverse motion, of normal faults formed during the caldera collapse, and located in the peripheral zone. During periods of unrests, the blocks of the central dome move independently at different velocities, and the peripheral zone accommodates the deformation. The restless behaviour of the caldera is the result of a shallow magmatic reservoir located at 3.5 ± 0.7 km and characterised by a width that roughly corresponds to the extension of the overlaying resurgent area. Defining the caldera-forming fault system and identifying the area involved by the resurgence is crucial for estimating depth and width of the magma reservoir, and predicting the caldera behaviour during periods of unrest by localising possible vents and sectors that will deform. This knowledge contributes to the evaluation of the volcanic hazard. • The NYT caldera resurgence consists of a central dome constituted by two main blocks. • The onset of the uplift of the central dome occurred through reverse faults. • The reverse faults bound several uplifted and tilted blocks in a peripheral zone. • The peripheral zone accommodates the deformation during periods of unrests. • The shallow magmatic reservoir is located at the minimum depth of ~3.5 ± 0.7 km. [ABSTRACT FROM AUTHOR]

Ischia Island is an active volcano representing the emerged sector of an E -W trending volcanic ridge largely extending undersea. Its collapsing behaviour, mainly in the form of fast-moving, terrestrial and submarine debris avalanches, has been recognized during the Holocene, but much less is known about previous gravity-driven processes. Using high-resolution multibeam bathymetric data and seismic reflection profiles, we provide evidence that the Island's southwestern flank has been involved in a slow-moving, deep-seated slope deformation that has displaced large volumes of its apron since the Late Pleistocene and until very recent or contemporary times. A long tongue of deformed seafloor, spreading up to 45 km from the Island over an area of 330 km2, between 500 and 1300 m water depths, has been detected along its southwestern slope. Different types of mass movements, genetically associated with each other, characterize this landslide: 1) a basal slump anticline, corresponding to a bulge on the bathymetry detaching at about 400 m sub-bottom depth; 2) an intermediate-mass movement chiefly consisting of debris avalanches and debris/turbiditic flows; 3) an upper mass movement consisting of hundred-metre size slumps detaching at relatively shallow depths. Conservative estimates indicate that at least 50 km3 of volcano-clastic and hemipelagic deposits have been mobilized, most of which comprise the basal slump anticline. This submarine landslide can be explained as a gravity failure of the continental slope unrelated to volcanism or rather as a process related to the dynamics of the volcanic edifice, which would imply volcano-spreading. • Oceanic and continental volcanic edifices may undergo slow collapse, named spreading • Ischia is an active volcano suspected to undergo long-term subsidence along with seismicity • Its southern, undersea section is affected by fast and long-term landslide phenomena • This long-term gravity instability can be viewed within the concept of volcano-spreading. [ABSTRACT FROM AUTHOR]

Abstract Neptunian dykes are widely reported along the Tethyan carbonate platforms and are commonly considered as subsurface baffles or barriers to fluid flow. However, the fluid storage and migration properties of sheared Neptunian dykes are poorly known. For this reason, we investigate the inner structure and fluid flow properties of two Neptunian dykes, which can be characterized by different architectures if involved or not in brittle shearing processes. The dykes strike ca. WNW-ESE and crosscutting the tight Jurassic limestones exposed at Maranfusa Mt., NW Sicily, Italy. The unsheared and sheared Neptunian dykes are almost sub-vertical and at high-angle with respect to the horizontal plane, respectively. The first one includes a homogeneous pelagic limestone infill whereas the second one includes a heterogeneous, marl-rich pelagic limestone infill and also thin veneers of tectonic breccias vertically persistent throughout the investigated outcrop. The sheared Neptunian dyke shows evidences of transtensional faulting, which likely occurred during the early Jurassic up to middle Cretaceous times, with throw up to 2 m. The amount of fracture porosity and equivalent permeability are computed by integrating geological and structural field data with petrographic data obtained from selected samples and Discrete Fracture Network modelling of geocellular volumes representative of the study outcrops. Results are consistent with the sheared Neptunian dyke forming a combined barrier-conduit permeability structure, in which the low-permeability and low–porosity cataclastic core is flanked by a fractured damage zone that enhance the dyke-parallel fluid flow in the subsurface. Accordingly, the amount of fluid storage in the fractured damage zone is sensitively higher than in the surrounding limestone host rock. Data we present highlight that the m-offset, sheared Neptunian dyke, due to its inherited sedimentary infill, is characterized by a permeability structure that it is often associated to large fault zones made up of cataclastic fault cores that impede the cross-fault fluid flow. Highlights • Dyke forms isolated fluid baffle/barrier inhibiting the cross-dyke fluid flow. • Dyke in brittle deformation acquire structural architecture typical of faults. • Sheared dyke acquires permeability structure typical of larger faults. [ABSTRACT FROM AUTHOR]

Ice-sheet and sea-level fluctuations during the Early and Middle Pleistocene are as yet poorly understood. A stalactite from a karst cave in North West Sicily (Italy) provides the first evidence of four marine inundations that correspond to relative sea-level highstands at the time of the Middle Pleistocene Transition. The speleothem is located ∼97 m above mean sea level as result of Quaternary uplift. Its section reveals three marine hiatuses and a coral overgrowth that fixes the age of final marine ingression at 1.124 ± 0.2, thus making this speleothem the oldest stalactite with marine hiatuses ever studied to date. Scleractinian coral species witness light-limited conditions and water depth of 20–50 m. Integrating the coral-constrained depth with the geologically constrained uplift rate and an ensemble of RSL scenarios, we find that the age of the last marine ingression most likely coincides with Marine Isotope Stage 35 on the basis of a probabilistic assessment. Our findings are consistent with a significant Antarctic ice-sheet retreat. [ABSTRACT FROM AUTHOR]

Mapping and luminescence aging of raised marine terraces and aeolian ridges along an ∼90 km coastal stretch in southwestern Sicily provide the first quantitative assessment of vertical tectonic deformation in this region, which spans the frontal part of an active thrust belt. We recognized a staircase of eleven terraces and nine related aeolian ridges. The elevation profile of terraces parallel to the coast shows a >90 km long bell-shaped pattern, onto which shorter-wavelength (∼10 km long) undulations are superimposed. Luminescence ages from terraced beach deposits and aeolian sediments constrain the position of paleoshorelines formed during MIS 5e, 7a and 7c, with a maximum uplift rate of ∼0.75 mm/a, and indicate a late Middle-Late Pleistocene (80–400 ka) age for the sequence of terraces. The elevation of Lower Pleistocene morpho-depositional markers points that uplift may have occurred at similar rates at the beginning of the Early Pleistocene, but almost zeroed between ∼1.5 and 0.4 Ma before the recent renewal. The uneven elevation of Middle-Upper Pleistocene paleoshorelines observed moving along the coast documents that uplift embeds both a regional and a local component. The regional, symmetric bell-shaped uplift is related to involvement in the thrust belt of thicker crustal portions of the northern African continental margin. The short-wavelength undulations represent the local component and correspond to actively growing bedrock folds. The present study contributes to unravel the different spatial and temporal scales of deformation processes at a collisional margin. • We mapped eleven raised terraces and nine aeolian ridges in southwestern Sicily. • Luminescence ages indicate terraces and dunes formed in the last ∼400 ka. • Terraces display a ∼100 km long bell-shaped elevation profile with minor undulations. • Uplift rates up to ∼0.75 mm/a reflect both frontal thrust belt motion and fold growth. • Rapid Earliest and Middle-Late Pleistocene uplift separated by tectonic quiescence. [ABSTRACT FROM AUTHOR]