Evolution of a poly-deformed relay zone between fault segments in the eastern Southern Alps, Italy
Published:January 01, 2007
D. Zampieri, M. Massironi, 2007. "Evolution of a poly-deformed relay zone between fault segments in the eastern Southern Alps, Italy", Tectonics of Strike-Slip Restraining and Releasing Bends, W. D. Cunningham, P. Mann
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In the eastern Southern Alps (NE Italy), Liassic north–south extensional structures are prominent. The southern Trento Platform also experienced extension during the Palaeogene, when reactivation of some pre-existing faults occurred, coupled with nucleation of new faults. During Neogene shortening, these structures were reactivated once again, but with strike-slip kinematics. In this framework, the Gamonda–Tormeno restraining stepover represents the final result of an overlap zone which evolved through time. In the first stage (Lias to Early Cretaceous) a prominent splay developed at the tip of the Gamonda Fault by lateral propagation and breaching of independent segments. At the same time, there was kinematic interaction between the antithetic Gamonda and Tormeno faults, followed by diachronous motion on crossing faults and the development of a narrow graben. During the second stage of extensional tectonics (Palaeocene to Early Oligocene), the reactivation and propagation of the overlapping faults along with the generation of new faults led to deepening of the graben. In the third stage (Miocene to present), the final structure of a strike-slip restraining stepover was accomplished. Due to the mechanical stratigraphy and complex inherited architecture of the relay zone where stratigraphic sequences with different rheological properties are juxtaposed, the style of shortening is different in the western and eastern sides of the stepover. The Gamonda–Tormeno structure represents a unique example of how a relay zone may change through time.
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Tectonics of Strike-Slip Restraining and Releasing Bends
Restraining and releasing bends are common, but enigmatic features of strike-slip fault systems occurring in all crustal environments and at regional to microscopic scales of observation. Regional-scale restraining bends are sites of mountain building, transpressional deformation and basement exhumation, whereas releasing bends are sites of topographic subsidence, transtensional deformation, basin sedimentation and possible volcanism and economic mineralization. Because restraining and releasing bends often occur as singular self-contained domains of complex deformation, they are appealing natural laboratories for Earth scientists to study fault processes, earthquake seismology, active faulting and sedimentation, fault and fluid-flow relationships, links between tectonics and topography, tectonic and erosional controls on exhumation, and tectonic geomorphology.
This volume addresses the tectonic complexity and diversity of strike-slip restraining and releasing bends with 18 contributions divided into four thematic sections: (1) a topical review of fault bends and their global distribution; (2) bends, sedimentary basins and earthquake hazards; (3) restraining bends, transpressional deformation and basement controls on development; (4) releasing bends, transtensional deformation and fluid flow.