On the geodynamics of the northern Adriatic plate

Abstract

The northern Adriatic plate underwent Permian-Mesozoic rifting and was later shortened by three orogenic belts (i.e., Apennines, Alps and Dinarides) developed along three independent subduction zones. The inherited Mesozoic horst and graben grain determined structural undulations of the three thrust belts. Salients developed in grabens or more shaly basins, whereas recesses formed regularly around horsts. A new interpretation of seismic reflection profiles, subsidence rates from stratigraphic analysis, and GPS data prove that the three orogens surrounding the northern Adriatic plate are still active. The NE-ward migration of the Apennines subduction hinge determines the present-day faster subsidence rate in the western side of the northern Adriatic (> 1 mm/year). This is recorded also by the SW-ward dip of the foreland regional monocline, and the SW-ward increase of the depth of the Tyrrhenian sedimentary layer, as well as the increase in thickness of the Pliocene and Pleistocene sediments. These data indicate the dominant influence of the Apennines subduction, which controls the asymmetric subsidence in the northern Adriatic realm. The Dinarides front has been tilted by the Apennines subduction hinge, as shown by the eroded Dalmatian anticlines subsiding in the eastern Adriatic Sea. GPS data suggest that southward tilting of the western and central Southern Alps, whereas the eastern Southern Alps are uplifting. The obtained strain rates are on average within 20 nstrain/year. The horizontal shortening obtained from GPS velocities at the front of the three belts surrounding the northern Adriatic plate are about 2-3 mm/year (Northern Apennines), 1-2 mm/year (Southern Alps), and < 1 mm/year (Dinarides). The shortening directions tend to be perpendicular to the thrust belt fronts. The areas where the strain rate sharply decreases along a tectonic feature (e.g., the Ferrara salient, the Venetian foothills front) are proposed to be occupied by locked structures where stress is accumulating in the brittle layer and thus seismically prone. Finally, we speculate that, since the effects of three independent subduction zones coexist and overlap in the same area, plate boundaries are passive features

Coexisting tectonic settings: the example of the southern Tyrrhenian Sea

“…The concurrence of more than one geodynamic setting in the same area could suggest the idea that plate boundaries may be passive features, and they could not substantially drive plate tectonics (Doglioni et al 2007;Cuffaro et al 2010). Fig.…”

Present-day surface deformationof the Alpine Region inferred from geodetic techniques

“…We do not detect a significant subsidence in the western part of the Po Basin; this may be a consequence of the poor distribution of our CO-GNSS stations in that region. Results of previous studies like Cuffaro et al (2010) or Serpelloni et al (2013) suggest subsidence rates up to -11 mm/a near Modena, Italy (11°E, 44.6°N). However, we do not detect these extreme vales.…”

“…South of the Alps are the Po and the Venetian-Friulian Basins. As mentioned, these three basins: Pannonian, Po and Venetian-Friulian Basins, are still foreland active basins; i.e., they continue subsiding and receiving sediments (e.g., Cuffaro et al, 2010;Serpelloni et al, 2006;. The Po Basin is also part of the northern foreland basin of the Apennines (e.g., Laubscher, 1988;Argnani, 15 2009).…”

“…The polarity of subduction changes from one area to the other: while the European 5 lithosphere is subducted beneath the Alps, the African lithosphere is subducted beneath the Apennines and the Dinarides-Hellenides (Argnani, 2009). In this way, Alps, Apennines, and Dinarides-Hellenides are still active orogens, although at different rates (D'Agostino et al, 2005;Devoti et al 2008;Cuffaro et al, 2010;Cheloni et al, 2014). Each subduction is associated with the usual vertical motions; i.e., subsidence in the foreland basin and uplift in the mountain belt.…”

Geology of the Brenner Pass-Fortezza transect, Italian Eastern Alps

“…The retro-wedge crystalline basement of the Adria-vergent Southern Alps (Castellarin et al, 2006;Cuffaro, Riguzzi, Scrocca, Antonioli, Carminati, Livani, & Doglioni, 2010;Spiess et al, 2010) is represented in the mapped area by the Permian Bressanone Granite (Del Moro & Visonà, 1982), minor gabbros (Inset 4) and some roofing quartz-phyllites, the latter showing Variscan greenschist facies metamorphism (Baggio et al, 1969). To the north the pluton is bounded by the North-Giudicarie and Pusteria lines of the Periadriatic System, whereas to the south the basement is overlain by Permo-Mesozoic cover units of the Dolomites (not included in our map).…”