Seismic structure of the Central Tyrrhenian basin: Geophysical constraints on the nature of the main crustal domains

Abstract

[1] In this work we investigate the crustal and tectonic structures of the Central Tyrrhenian back-arc basin combining refraction and wide-angle reflection seismic (WAS), gravity, and multichannel seismic (MCS) reflection data, acquired during the MEDOC (MEDiterráneo OCcidental)-2010 survey along a transect crossing the entire basin from Sardinia to Campania at 40°N. The results presented include a~450 km long 2-D P wave velocity model, obtained by the traveltime inversion of the WAS data, a coincident density model, and a MCS poststack time-migrated profile. We interpret three basement domains with different petrological affinity along the transect based on the comparison of velocity and velocity-derived density models with existing compilations for continental crust, oceanic crust, and exhumed mantle. The first domain includes the continental crust of Sardinia and the conjugate Campania margin. In the Sardinia margin, extension has thinned the crust from~20 km under the coastline to~13 km~60 km seaward. Similarly, the Campania margin is also affected by strong extensional deformation. The second domain, under the Cornaglia Terrace and its conjugate Campania Terrace, appears to be oceanic in nature. However, it shows differences with respect to the reference Atlantic oceanic crust and agrees with that generated in back-arc oceanic settings. The velocities-depth relationships and lack of Moho reflections in seismic records of the third domain (i.e., the Magnaghi and Vavilov basins) support a basement fundamentally made of mantle rocks. The large seamounts of the third domain (e.g., Vavilov) are underlain by 10-20 km wide, relatively low-velocity anomalies interpreted as magmatic bodies locally intruding the mantle.

Seismic Evidence for Tectonically Dominated Seafloor Spreading in the Southwest Sub‐basin of the South China Sea

“…The velocities from 6.8-7.2 km/s to 8.0 km/s are too low for unaltered mantle and may result from serpentinization of the upper mantle (e.g., in fracture zones, Detrick et al, 1993, the COT of nonvolcanic rifted margins, Davy et al, 2016, and slow or ultraslow spreading oceanic basins; e.g., the Labrador Sea; Delescluse et al, 2015;Osler & Louden, 1992 or magma intrusion (e.g., in NW Indian Ocean; Gupta et al, 2010). In our final model (Figure 3b), velocities at depths >3 km below the top basement sit outside the envelopes for Pacific and magmatic oceanic crust newly compiled by Grevemeyer et al (2018;Figure 9a well with the velocity profiles in the models of thin oceanic crust overlying serpentinized mantle in the North Atlantic Ocean (Figure 9b; Davy et al, 2016;Funck et al, 2003;Hopper et al, 2004;Whitmarsh et al, 1996) and the exhumed mantle zone in West Iberia (Figure 9b; Dean et al, 2000;Sallarès et al, 2013) and the Central Tyrrhenian Basin (Figure 9c; Prada et al, 2014). Serpentinization of the upper mantle is facilitated when the crust is thin and fractured to allow seawater to flow in (Minshull et al, 1998;Sauter et al, 2013;Shillington et al, 2006).…”

Seismic Oceanography in the Tyrrhenian Sea: Thermohaline Staircases, Eddies, and Internal Waves

“…The seismic data were acquired as part of the MEDOC‐2010 survey (Ranero & The MEDOC Team, ), completed in April–May 2010, with the Spanish vessel R/V Sarmiento de Gamboa. It was a project designed to address the geological formation of rifted tectonic margins by utilizing both refraction and reflection seismology (e.g., Moeller et al, ; Prada et al, ). Seismic acquisition parameters are shown in Table S1 in Supporting Information S1.…”

Evolution of the Sea of Japan back-arc and some unsolved issues

“…Anomalous or thick ocean crust has also been found in back-arc basins in the Tyrrhenian Sea, Mediterranean region (Prada et al, 2014) and the South China Sea (Wang et al, 2006). As a result of tectonic inversion, Japan provides an opportunity to investigate the geochemistry of a magma-rich back-arc, and its ocean basement, in particular.…”