Extension in the Tyrrhenian Sea and shortening in the Apennines as result of arc migration driven by sinking of the lithosphere

Abstract

Previously proposed models for the evolution of the Tyrrhenian basin‐Apenninic arc system do not seem to satisfactorily explain the dynamic relationship between extension in the Tyrrhenian and compression in the Apennines. The most important regional plate kinematic constraints that any model has to satisfy in this case are: (1) the timing of extension in the Tyrrhenian and compression in the Apennines, (2) the amount of shortening in the Apennines, (3) the amount of extension in the Tyrrhenian, and (4) Africa‐Europe relative motion. The estimated contemporaneous (post‐middle Miocene) amounts of extension in the Tyrrhenian and of shortening in the Apennines appear to be very similar. The extension in the Tyrrhenian Sea is mostly accomplished in an E‐W direction, and cannot be straightforwardly related to the calculated N‐S Africa‐Europe convergence. A model of outward arc migration fits all these constraints. In a subducting system, the subduction zone is expected to migrate outward due to the sinking of the underthrusting plate into the mantle. The formation of a back‐arc or internal basin, i.e. of a basin internal to the surrounding belt of compression, (in this case the Tyrrhenian Sea) is then expected to take place if the motion of the overriding plate does not compensate for the retreat of the subduction zone. The sediment cover will be stripped from the underthrusting plate by the outward migrating arc of the overriding plate, and will accumulate to form an accretionary wedge. This accretionary body will grow outward in time, and will eventually become an orogenic belt, (in this case the present Apennines) when the migrating arc collides with the stable continental foreland on the subducting plate. An arc migration model satisfactorily accounts for the basic features of the Tyrrhenian‐Apennine system and for its evolution from 17 Ma to the present, and appears to be analogous to the tectonic evolution of other back‐arc settings both inside and outside the Mediterranean region. An interesting implication of the proposed accretionary origin of the Apennines is that the problematic “Argille Scagliose” (scaly clays) melange units might have been emplaced as overpressured mud diapirs, as observed in other accretionary prisms, and not by gravity slides from the internal zones.

Stratigraphic units of the Apulian Tavoliere plain (Southern Italy): Chronology, correlation with marine isotope stages and implications regarding vertical movements

“…The Apulian Tavoliere belongs to the Bradanic Trough domain (Migliorini, 1937;Malinverno and Ryan, 1986;Royden et al, 1987;Scandone, 1989, 2001;Doglioni, 1991). From a structural point of view, the Tavoliere is a part of the "Fossa Bradanica" basin (Bradanic Trough) which formed, beginning in the Lower Pliocene, between the Southern Apenninic chain and the Apulian-Dinaric foreland (Fig.…”

New insights on morpho-structures and seismic stratigraphy along the Campania continental margin (Southern Italy) based on deep multichannel seismic profiles

“…2; D 'Argenio et al 1973), located between the eastern side of the Tyrrhenian sea and the Southern Apenninic chain and produced from the back-arc extension that accompanied the NE-verging accretion of the Apenninic thrust belt during the rollback of the subducting foreland plate (Malinverno and Ryan 1986;Faccenna et al 1996). The western sector of the Naples Bay is surrounded by the Phlegrean Fields volcanic district, where volcanism has been active for at least 50 ky (Rosi and Sbrana 1987).…”

“…The late onset of the arc volcanism with respect to the duration of the extension in the Tyrrhenian-Ionian system has been explained as a consequence of the initial stages of thinned continental lithosphere (Ritsema 1979;Malinverno and Ryan 1986;Sartori 2003). Age and trends of rifting in the Tyrrhenian sea have been already summarized (Sartori and Capozzi 1998); a Tortonian to Pliocene episode of back-arc extension, when the Sardinia margin and the Vavilov Plain were formed indicating arc migration from W to E; a Pleistocene episode, when the Marsili basin was generated, indicating migration from NW to SE.…”

Morphostructure of the Lucania Apennines front between the Basento and Salandrella rivers (Southern Italy)

“…Doglioni, Moretti, & Roure, 1991;Malinverno & Ryan, 1986;). The architecture of the southern Apennines is broadly characterized by two distinct orogenic wedges (e.g.…”