Marco Cuffaro

The tectonic puzzle of the Messina area (Southern Italy): Insights from new seismic reflection data

The Messina Strait, that separates peninsular Italy from Sicily, is one of the most seismically active areas of the Mediterranean. The structure and seismotectonic setting of the region are poorly understood, although the area is highly populated and important infrastructures are planned there. New seismic reflection data have identified a number of faults, as well as a crustal scale NE-trending anticline few km north of the strait. These features are interpreted as due to active right-lateral transpression along the north-eastern Sicilian offshore, coexisting with extensional and right-lateral transtensional tectonics in the southern Messina Strait. This complex tectonic network appears to be controlled by independent and overlapping tectonic settings, due to the presence of a diffuse transfer zone between the SE-ward retreating Calabria subduction zone relative to slab advance in the western Sicilian side.

Post-Mesozoic Rapid Increase of Seawater Mg/Ca due to Enhanced Mantle-Seawater Interaction

The seawater Mg/Ca ratio increased significantly from ~ 80 Ma to present, as suggested by studies of carbonate veins in oceanic basalts and of fluid inclusions in halite. We show here that reactions of mantle-derived peridotites with seawater along slow spreading mid-ocean ridges contributed to the post-Cretaceous Mg/Ca increase. These reactions can release to modern seawater up to 20% of the yearly Mg river input. However, no significant peridotite-seawater interaction and Mg-release to the ocean occur in fast spreading, East Pacific Rise-type ridges. The Mesozoic Pangean superocean implies a hot fast spreading ridge system. This prevented peridotite-seawater interaction and Mg release to the Mesozoic ocean, but favored hydrothermal Mg capture and Ca release by the basaltic crust, resulting in a low seawater Mg/Ca ratio. Continent dispersal and development of slow spreading ridges allowed Mg release to the ocean by peridotite-seawater reactions, contributing to the increase of the Mg/Ca ratio of post-Mesozoic seawater.

Evaluating the Role of Seagrass in Cenozoic CO2 Variations

Marine seagrass angiosperms play an important role in carbon sequestration, removing carbon dioxide from the atmosphere and binding it as organic matter. Carbon is stored in the plants themselves, but also in the sediments both in inorganic and organic forms. The inorganic component is represented by carbonates produced by calcareous organisms living as epiphytes on seagrass leaves and rhizomes. In this paper, we find that the rate of seagrass epiphyte production (leaves and rhizomes), averages 400 g m-2 yr-1, as result of seagrass sampling at seven localities along the Mediterranean coasts, and related laboratory analysis. Seagrasses have appeared in the Late Cretaceous, becoming a place of remarkable carbonate production and C sequestration during the whole Cenozoic era. Here, we explore the potential contribution of seagrass as C sink on the atmospheric CO2 decrease by measuring changes in seagrass extent, which is directly associated with variations in the global coastal length associated with plate tectonics. We claim that global seagrass distribution significantly affected the atmospheric composition, particularly at the Eocene-Oligocene boundary, when the CO2 concentration fell to 400 ppm, i.e. the approximate value of current atmospheric CO2.

A Model of Plate Motions

The wide use of space geodesy techniques devoted to geophysical and geodynamical purposes has recently evidenced some limitations due to the intrinsic Terrestrial Reference Frame (TRF) definition. Current TRFs are defined under hypotheses suited to overcome the rank deficiency of the observations with respect to the parameters that have to be estimated, i.e. coordinates and velocities (Dermanis, 2001; Dermanis, 2002). From a geodetic point of view, one possibility implies the application of the no-net-rotation condition (NNR). One of the main geophysical consequences due to the application of this condition is that it allows only accurate estimations of relative motions, whilst other motions of geodynamical interest, for instance with respect to the inner layers of the Earth body, are not determinable.

Transfer zones in an oblique back‐arc basin setting: Insights from the Latium‐Campania segmented margin (Tyrrhenian Sea)

New multichannel seismic reflection profiles were acquired to unravel the structure of a portion of the eastern margin of the Tyrrhenian basin. This extensional feature is part of an Oligocene to Present back-arc basin in the hangingwall of the west directed Apennines subduction system. The basin provides excellent conditions to investigate the early stage processes leading to the development of rifted passive margins and to the emplacement of oceanic crust in an oblique setting. The interpreted post-stack-migrated seismic profiles highlight the geometry and kinematics of the Pontine escarpment that connects the Latium-Campania continental margin to the Vavilov basin. The latter is the main feature of the area, related to the early Pliocene extension of the Tyrrhenian Sea. Several morphological variations are pointed out along strike, mirroring different structural settings of the margin itself: a steeper margin to the north corresponds to high-angle possibly transtensional faults, whereas a smooth slope in the southern portion corresponds to several more distributed listric faults. This work contributes to the understanding of the interplay between extensional and transtensional tectonics along the margins of an oblique back-arc basin.

Response: Commentary: Evaluating the Role of Seagrass in Cenozoic CO2 Variations

Dipartimento Scienze della Terra, Università Roma La Sapienza, Rome, Italy, 2 Istituto di Geologia Ambientale e Geoingegneria (CNR), Sez. Sapienza, Dipartimento Scienze della Terra, Università Roma La Sapienza, Rome, Italy, Càtedra Guillem Colom Casasnovas, Universitat de les Illes Balears, Palma de Mallorca, Spain, 4 Laboratorio de Zoología, Departament de Biologia, Universitat de les Illes Balears, Palma de Mallorca, Spain