Recently, new data have been presented which imply that major block rotations took place in the Central Mediterranean during the Pleistocene, between 1.0 and 0.7 Ma. Kinematic solutions for the spatial and temporal distribution of rotational data in the Central Mediterranean such as oroclinal bending of the Calabrian Arc and rotation of the Adria Plate are being discussed. Phases of neotectonic rotations appear to be confined to distinct phases of contractions and compressive interplate stress. We present a model in which the middle Pleistocene rotations are caused by a distribution of deformation in the Central Mediterranean through strike-slip motions along a number of major shear zones which define a free boundary between the African and the Adria Plates. One of the main features is the Trans-Mediterranean Mobile Zone, which separates areas with opposite rotations. The timing of the rotations is compared to the evolution of volcanism, basin development, subsidence and uplift patterns, contractional tectonics and seismicity patterns. From this comparison we hypothesize that the Late Pliocene-Recent geodynamic evolution of the Central Mediterranean comprises the following three episodes: (1) A Late Pliocene arc migration episode shows drifting of the Calabrian block and spreading of the back-arc basin without the associated oroclinal rotations that were previously assumed in literature. (2) An Early Pleistocene contraction episode shows a gradual increase of compressive interplate stress, and culminates in a middle Pleistocene "stress release phase" which is associated with block rotations, transpressional tectonics and a rupturing of the subducted slab. (3) A Late Pleistocene-Recent restabilisation episode is characterized by rapid isostatic adjustments, with extensional collapse of the Apennine thrust-wedge and the Tyrrhenian back-arc area related to rebound of non-detached lithosphere remnants and sinking into the mantle of the detached slab.
The kinematics of intra‐arc shear zones play a key role in the secondary shaping of orogenic arcs such as the Calabrian Arc (central Mediterranean). Comparison of the Neogene structural development of the Petilia‐Rizzuto Fault Zone and the basement structure of the bordering Sila massif reveals that the fault zone is the surface expression of a deep NW–SE trending sinistral crustal oblique shear zone. This shear zone continues over a length of more than 130 km across the northern segment of the Calabrian Arc and shows a post‐Eocene sinistral displacement of about 50 km. The late Neogene forearc basin development and syndepositional tectonics along the fault zone are reconstructed in great detail by analyzing the middle Miocene‐Recent tectonic sequence stratigraphy. A strike‐slip cycle can be recognized whereby the subsequent activity of Riedel shears, tensional faults, and P shears, positive flower structures and principle displacement wrench faults, can accurately be traced in time. Observed phenomena are discussed in terms of the activity of a conjugate system of oblique thrust zones within the growing accretionary complex. The evolution of special types of thrust belt basins is illustrated. These include oblique thin‐skinned pull‐apart basins, oblique rhomboidal “harmonica” basins, and “detached slab” basins (new terms introduced here), evolving one into the other. A new feature illustrated is the recurrent basin inversion which generated passive roof duplexes through back‐shear motion and out‐of‐sequence thrusting along the wedge. The fault patterns and the style of inversion tectonics imply an E–W directed axis of effective compressive stress in this part of the arc. This resulted from an interaction of (1) local E–W directed compression related to a differential displacement of two parallel segments of the arc (generated by the migration to the southeast of the Calabrian Arc and opening of the Tyrrhenian backarc basin); (2) alternating NW–SE directed compression and extension (related to pulsating thrust wedge dynamics with phases of accretion and underthrusting respectively) and (3) regional, compressive interplate stress (middle Messinian‐middle Pliocene). All structures are overprinted by post middle Pleistocene extensional faulting (related to rapid uplift of intra‐arc massifs) and reversal along thrust planes and transcurrent faults. This extensional collapse reflects isostatic adjustments in response to plate rupture which was provoked by regional compressive stress.
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