Francesco Fanucci

Late Quaternary deposits from the Ligurian continental shelf (NW Mediterranean): A response to problems of coastal erosion

The Ligurian continental shelf is a terrigenous platform characterized by variable extension and subsidence of the continental margin and thick accumulation of sediments originated by repeated sea-level oscillations. Its genesis and evolution occurred during the Plio-Quaternary, even if early erosive modelling in some sectors has been dated to the Late Miocene. The present morphology of the shelf is the result of transgressive–regressive Quaternary cycles. Using a high-resolution seismic grid of more than 1000 km, we have been able to define the seismostratigraphic characteristics of the Ligurian Sea shelf. On the basis of our studies, it has been possible to describe in detail the seismostratigraphy of the Late Quaternary and Holocene sediments that cover the shelf to various depths, in terms of sedimentary sources, for the purpose of distinguishing ‘relic’ deposits suitable for nourishing beaches undergoing erosion. From this detailed study of the evolution of the most superficial deposits, it is possible to distinguish between different sedimentary bodies deposited during a transgressive phase and located at a water depth ranging between 20 and 70 m; they are represented by relic sands cropping out at the sea bottom due to a relatively thin Holocene drape and could be explored for beach nourishment programmes.

Basal and Frontal Accretion Processes versus BSR Characteristics along the Chilean Margin

Multichannel seismic reflection data recorded between Itata () and Coyhaique offshores () were processed to obtain seismic images. Analysis of the seismic profiles revealed that weak and discontinuous bottom simulating reflectors were associated to basal accretion processes, while strong and continuous bottom simulating reflectors were associated to frontal accretion processes. This can be explained considering that during basal accretion processes, extensional tectonic movements due to uplifting can favour fluid escapes giving origin to weaker and most discontinuous bottom simulating reflectors. During frontal accretion processes (folding and thrusting), high fluid circulation and stable tectonic conditions however can be responsible of stronger and most continuous bottom simulating reflectors. Along the Arauco-Valdivia offshores, steep accretionary prisms, normal faults, slope basins, and thicker underplated sediment bed were associated to basal accretion, while along the Itata, Chiloe and Coyhaique offshores, small accretionary prisms, folding, and thinner underplated sediment bed were associated to frontal accretion.

Slope instability and erosional features of the Ligurian Margin

Abstract from 88th Congress of the Italian Geological Society, 2016-09-07 - 2016-09-09, NaplesAbstract from 88th Congress of the Italian Geological Society, 2016-09-07, 2016-09-09, Naplesbook Edited by D. Calcaterra, S. Mazzoli, F.M. Petti, B. Carmina & A. Zuccari doi: 10.3301/ROL.2016.79

Tectonic Processes and BSR Features along Chilean Margin

From seismic interpretation we can argue that basal and frontal accretions are the main processes that model this part of the Chilean margin. Frontal accretion areas are characterized by a smoothed oceanic crust top, anticline reliefs, high offset thrusts and positive flowers structures; while, basal accretion areas, are characterized by an irregular oceanic crust top, uplifted slope, low offset thrusts, normal faults affecting the upper prism sediments, negative flower structures and re-activated thrusts. In particular the BSR is strong and continuous, within prism sediments, where the frontal accretion processes are acting, while it is weak and discontinuous where the active process is the basal accretion. We can suppose that the uplifting by basal accretion generates extensional tectonic movements. This can favour fluid escape and, consequently, a change of temperature. A consequence of this change is that the BSR disappears or becomes weaker. It is possible to extrapolate that strong and continuous BSRs can be developed in presence of frontal accretion processes, because it is most probable that high-fluid flux can occur in compressive conditions, while weak and discontinuous BSR can be associated to basal accretion, because off-crapped sediments can uplift the entire accretionary prism favouring fluid escapes.

Characteristic of Gas Hydrates Reservoir from Seismic Analysis of Multichannel Seismic Profiles Offshore South Chile

We used a procedure already tested in order to characterize the gas hydrate and free gas reservoir along South Chile. We used the multichannel seismic data to obtain an accurate velocity model by using the Pre stack Depth Migration. The velocity model can