Core complex exhumation in peri-Adriatic extension, and kinematics of Neogene slip along the Saddle Mountains thrust
Casale, Gabriele Medcalf
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Abstract The geometry and kinematics of map scale faults are the record of tectonic mountain building processes. This study focuses upon three distinct faults in three distinct orogens, the Alpi Apuane detachment in the Northern Apennines, the Mid-Bosnian Schist detachment in the internal Dinarides, and Saddle Mountains fault in eastern Washington. Mountain building in the Central Mediterranean is controlled by convergence between the African and Eurasian continental plates, yet local kinematics and structural trends owe their genesis to a complicated interplay between discrete and often poorly defined continental and Oceanic fragments. The Peri-Adriatic sub-region of the Central Mediterranean is dominated by the Adria continental micro-plate; interaction between Adria and neighboring plates has given rise to the Eastern Alps, Apennines, Dinarides and Albanides. Of particular interest is a contrast in the role of extension along the convergent margins of the Adria plate. Along the western margin of Adria, subduction of Adria lithosphere beneath the Apennines has maintained syn-convergence extension from at least middle Miocene to the present; this process is manifested as a sustained cycle of burial, metamorphism, and subsequent exhumation along normal faults of Adria crust, and overlying fore-deep sediments. In the Dinarides, along the eastern margin of Adria, Jurassic-Eocene subduction of the distal oceanic portion of the Adria plate beneath Eurasia was concluded by collision and a change in subduction dynamics as the thick continental Adria lithosphere entered the subduction zone. In the first two chapters of this study I use field, microstructural, and thermochronometric techniques to determine the nature of shear zone tectonites and the thermal conditions during normal faulting in the Apennines, and the polarity and timing of slip along a detachment that cut to at least the middle crust in the internal Dinarides. The third chapter of this study focuses upon elucidating the kinematics of fault slip using sub-surface seismic data within the Yakima fold-and-thrust belt in eastern Washington. In areas of active shortening, assessment of seismic hazards is difficult without a-priori knowledge of fault geometry. I determined geometric aspects of the Saddle Mountains anticline from a seismic reflection profile, and using kinematic forward modeling techniques, inverted for kinematically viable end member fault geometries representative of extant geometric models currently in use for seismic hazard assessment.