Kinematic analysis and mechanical modeling of roof sequence response to blind thrustin

An unresolved problem with blind duplex development is the mechanisms by which the roof sequence accommodates duplex emplacement without being part of the fault system. This problem stems from a lack of detailed kinematic data from rocks adjacent to blind duplexes and limited mechanical models for evaluating possible kinematic responses. This dissertation addresses this problem by focusing on the deformed roof sequence in the Appalachian Plateau adjacent to the blind Wills Mountain duplex. Geologic analyses and finite element models describe kinematically the roof sequence behavior and the mechanical controls on deformation processes.;The Wills Mountain duplex accommodated 17.5 km of blind thrusting by flat-on-flat duplication of thick Cambro-Ordovician carbonates. Kinematic analysis of the Paleozoic stratigraphy beyond Wills Mountain into the foreland reveals that the roof sequence records about two-thirds of this shortening. Mesoscale and smaller processes account for over 75% of the two-thirds with the remainder accommodated by macroscale folding and faulting. Thus, forethrusting dominated kinematically as roof deformation is concentrated in the foreland of the duplex. The shortening imbalance between the duplex and the younger roof sequence was probably accommodated by forethrusting further into the foreland.;Finite element modeling reveals that roof sequence deformation during blind duplex emplacement is controlled by sliding interface friction and thrust displacement magnitude. Roof sequence deformation is accomplished by rigid-body translation and internal distortion where the proportions are controlled by the frictional resistance of the sliding interfaces. Forethrusting and backthrusting of the roof sequence occurs to accommodate imposed displacement.;Together, geologic analyses and finite element models suggest that the forethrusting observed in the study area reflects the availability of weak decollements in the foreland of the Wills Mountain duplex. The finite element models suggest that a zone of ductile deformation proceeds a propagating fault tip for thrust surfaces with high frictional resistance but not for very weak surfaces. The development of a detachment fold in the two sliding interface model is in agreement with previous geometric models for detachment fold formation.