Thesis (Ph. D.)--University of Hawaii at Manoa, 1991. / Includes bibliographical references (leaves 161-173) / Microfiche. / xvi, 173 leaves, bound ill., maps 29 cm

The Atnarko complex located in west-central British Columbia comprises pre-Early Jurassic metavolcanic and metasedimentary rocks, termed the Atnarko assemblage, which is structurally interleaved with Late Triassic to Early Cretaceous orthogneiss. The Atnarko assemblage correlates with continental margin assemblages found within the Coast plutonic complex. Tectonic interaction between the Insular and Intermontane superterranes resulted in several phases of deformation including; 1) poorly preserved Jurassic deformation, 2) Early to mid-Cretaceous, southwest to west directed, compression, 3) mid-Cretaceous, north to northeast directed, compression, 4) mid- to Late Cretaceous dextral and sinistral ductile/brittle shearing, and 5) post latest Cretaceous brittle faulting. Peak metamorphism coincides with generation of migmatite in the Early Cretaceous (~117-115 Ma) and is contemporaneous with penetrative ductile fabrics. The Atnarko complex had cooled below 350°C by the Late. Comparison of the Atnarko complex to equivalent portions of the orogen along strike, indicates a post mid-Cretaceous change in structural style. To the northwest the orogen records continued southwest-directed compression which dominates the deformation style; while to the southeast large dextral strike-slip faults dominate. Relative plate motions between ca. 70-60 Ma indicate that dextral transpression occurred between the Kula and North American plates. Strain during this transpressive deformation was partitioned into compressive and translational regions. The Atnarko complex area is situated at the transition between translation and compression. The conditions of the lower and middle crust within the orogen were established by how strain was partitioned across the orogen. The distributed strain also shaped how the orogen responded to Tertiary extension. Continued compression to the northwest of the Atnarko complex led to increased crustal thickness and partial melting of lower and middle crust in the Tertiary. Conversely, the cessation of compression in the southeast lead to a more stable (i.e. cooler) crustal lithosphere. A change in relative plate motions in the early Tertiary triggered full-scale, orogen-perpendicular, collapse in the northwest facilitated by decoupling between the middle and lower crusts along thermally weakened layers. Localized orogen-parallel extension occurred in the southeast which was kinematically linked to large dextral strike-slip faults where the upper crust remained coupled to the middle and lower crust.

The Alpine Fault is the major structure of the Pacific-Australian plate boundary through New Zealand�s South Island. During dextral reverse fault slip, a <5 million year old, ~1 km thick mylonite zone has been exhumed in the hanging-wall, providing unique exposure of material deformed to very high strains at deep crustal levels under boundary conditions constrained by present-day plate motions. The purpose of this study was to investigate the fault zone rheology and mechanisms of strain localisation, to obtain further information about how the structural development of this shear zone relates to the kinematic and thermal boundary constraints, and to investigate the mechanisms by which the viscously deforming mylonite zone is linked to the brittle structure, that fails episodically causing large earthquakes. This study has focussed on the central section of the fault from Harihari to Fox Glacier. In this area, mylonites derived from a quartzofeldspathic Alpine Schist protolith are most common, but slivers of Western Province-derived footwall material, which can be differentiated using mineralogy and bulk rock geochemistry, were also incorporated into the fault zone. These footwall-derived mylonites are increasingly common towards the north. At amphibolite-facies conditions mylonitic deformation was localised to the mylonite and ultramylonite subzones of the schist-derived mylonites. Most deformation was accommodated by dislocation creep of quartz, which developed strong Y-maximum crystallographic preferred orientation (CPO) patterns by prism (a) dominant slip. Formation of this highly-oriented fabric would have led to significant geometric softening and enhanced strain localisation. During this high strain deformation, pre-existing Alpine Schist fabrics in polyphase rocks were reconstituted to relatively well-mixed, finer-grained aggregates. As a result of this fabric homogenisation, strong syn-mylonitic object lineations were not formed. Strain models show that weak lineations trending towards ~090� and kinematic directions indicated by asymmetric fabrics and CPO pattern symmetry could have formed during pure shear stretches up-dip of the fault of ~3.5, coupled with simple shear strains [greater than or equal to]30. The preferred estimate of simple:pure shear strain gives a kinematc vorticity number, W[k] [greater than or equal to]̲ 0.9997. Rapid exhumation due to fault slip resulted in advection of crustal isotherms. New thermobarometric and fluid inclusion analyses from fault zone materials allow the thermal gradient along an uplift path in the fault rocks to be more precisely defined than previously. Fluid inclusion data indicate temperatures of 325+̲15�C were experienced at depths of ~45 km, so that a high thermal gradient of ~75�C km⁻� is indicated in the near-surface. This gradient must fall off to [ less than approximately]l0�C km⁻� below the brittle-viscous transition since feldspar thermobarometry, Ti-inbiotite thermometry and the absence of prism(c)-slip quartz CPO fabrics indicate deformation temperatures did not exceed ~ 650�C at [greater than or equal to] 7.0-8.5�1.5 kbar, ie. 26-33 km depth. During exhumation, the strongly oriented quartzite fabrics were not favourably oriented for activation of the lower temperature basal(a) slip system, which should have dominated at depths [less than approximately]20 km. Quartz continued to deform by crystal-plastic mechanisms to shallow levels. However, pure dislocation creep of quartz was replaced by a frictional-viscous deformation mechanism of sliding on weak mica basal planes coupled with dislocation creep of quartz. Such frictional-viscous flow is particularly favoured during high-strain rate events as might be expected during rupture of the overlying brittle fault zone. Maximum flow stresses supported by this mechanism are ~65 Mpa, similar to those indicated by recrystallised grain size paleopiezometry of quartz (D>25[mu]m, indicating [Delta][sigma][max] ~55 MPa for most mylonites). It is likely that the preferentially oriented prism (a) slip system was activated during these events, so the Y-maximum CPO fabrics were preserved. Simple numerical models show that activation of this slip system is favoured over the basal (a) system, which has a lower critical resolved shear stress (CRSS) at low temperatures, for aggregates with strong Y-maximum orientations. Absence of pervasive crystal-plastic deformation of micas and feldspars during activation of this mechanism also resulted in preservation of mineral chemistries from the highest grades of mylonitic deformation (ie. amphibolite-facies). Retrograde, epidote-amphibolite to greenschist-facies mineral assemblages were pervasively developed in ultramylonites and cataclasites immediately adjacent to the fault core and in footwall-derived mylonites, perhaps during episodic transfer of this material into and subsequently out of the cooler footwall block. In the more distal protomylonites, retrograde assemblages were locally developed along shear bands that also accommodated most of the mylonitic deformation in these rocks. Ti-in-biotite thermometry suggests biotite in these shear bands equilibrated down to ~500+̲50�C, suggesting crystal-plastic deformation of this mineral continued to these temperatures. Crossed-girdle quartz CPO fabrics were formed in these protomylonites by basal (a) dominant slip, indicating a strongly oriented fabric had not previously formed at depth due to the relatively small strains, and that dislocation creep of quartz continued at depths [less than or equal to]20 km. Lineation orientations, CPO fabric symmetry and shear-band fabrics in these protomylonites are consistent with a smaller simple:pure shear strain ratio than that observed closer to the fault core (W[k] [greater than approximately] 0.98), but require a similar total pure shear component. Furthermore, they indicate an increase in the simple shear component with time, consistent with incorporation of new hanging-wall material into the fault zone. Pre-existing lineations were only slowly rotated into coincidence with the mylonitic simple shear direction in the shear bands since they lay close to the simple shear plane, and inherited orientations were not destroyed until large finite strains (<100) were achieved. As the fault rocks were exhumed through the brittle-viscous transition, they experienced localised brittle shear failures. These small-scale seismic events formed friction melts (ie. pseudotachylytes). The volume of pseudotachylyte produced is related to host rock mineralogy (more melt in host rocks containing hydrated minerals), and fabric (more melt in isotropic host rocks). Frictional melting also occurred within cataclastic hosts, indicating the cataclasites around the principal slip surface of the Alpine Fault were produced by multiple episodes of discrete shear rather than distributed cataclastic flow. Pseudotachylytes were also formed in the presence of fluids, suggesting relatively high fault gouge permeabilities were transiently attained, probably during large earthquakes. Frictional melting contributed to formation of phyllosilicate-rich fault gouges, weakening the brittle structure and promoting slip localisation. The location of faulting and pseudotachylyte formation, and the strength of the fault in the brittle regime were strongly influenced by cyclic hydrothermal cementation processes. A thermomechanical model of the central Alpine Fault zone has been defined using the results of this study. The mylonites represent a localised zone of high simple shear strain, embedded in a crustal block that underwent bulk pure shear. The boundaries of the simple shear zone moved into the surrounding material with time. This means that the exhumed sequence does not represent a simple 'time slice' illustrating progressive fault rock development during increasing simple shear strains. The deformation history of the mylonites at deep crustal P-T conditions had a profound influence on subsequent deformation mechanisms and fabric development during exhumation.

The Indo-Australian Plate is actively deforming at its margins and within its interior. In south-central Australia, more than 3000 km from the closest active plate boundary, a geomorphically rugged and apparently youthful mountain range has developed, rising up to 1.1km above the adjacent flat-lying outback plains. These ‘Flinders’ and ‘Barrier’ Ranges are seismically active and bound by major reverse fault scarps with clear evidence for Plio-Quaternary displacements, implying that young and active intraplate tectonism has played a fundamental role in their development. Palaeoseismic investigations and optically stimulated luminescence (OSL) chronology indicate faulting occurred in response to a series of large magnitude (~M6.6 to M7.3) palaeo-earthquakes with recurrence intervals of ~1:20,000 to~1:80,000 yrs and long-term fault slip rates of ~50 m Myr-1. Geomorphic observations and 10Becosmogenic nuclide dating indicate surprisingly high and spatially variable rates of bedrock erosion from fault-affected catchments in the Flinders Ranges. Slowly eroding bedrock summit surfaces have been uplifted up to 12 m in the last 60,000-100,000 years relative to more rapidly eroding valley floors and bounding piedmonts, indicating Late Quaternary increases in elevation and relief in response to intraplate tectonism and erosion. However, both facies changes and sediment aggradation-dissection cycles in alluvial fan sequences are out-of-synch within dividual tectonic events, indicating that an aspect of climate (aridification, changing flood frequency-magnitude distributions) has governed the spatial-temporal distribution of range front sedimentation.

The Gulf of California in western Mexico is a prime example of a young passive margin that is currently undergoing the transition from continental rifting to seafloor spreading. With less than ~25 km of the width of the original continental surface area submerged, the northern Gulf Extensional Province represents a key area to assess the history of strain localisation during the early stages of continental extension. Geological mapping revealed that the basins and ranges of the Sierra San Felipe, located in the hanging wall of the Main Gulf Escarpment, are bounded to the east by an en-echelon array of left-stepping moderate- to low-angle normal faults that represent the next dominant set of normal faults from the break-away fault in direction of transport. Structural displacement estimates suggest up to ~4.5–9 km of broadly east-directed extension on the Las Cuevitas, Santa Rosa and Huatamote detachments. Fault kinematics suggest a transtensional stress regime with NE- to SE-directed extension and permutating vertical and N–S subhorizontal shortening. Clockwise vertical-axis block rotations and constrictional folding of the detachments were an integral part of the late Miocene to Pleistocene deformation history of the San Felipe fault array. This overall constrictional strain regime is indistinguishable from the present-day deformation in the Gulf Extensional Province and indicates that the fault array formed during a single phase of integrated transtensional shearing since rifting began in the late Miocene. / Apatite fission track (AFT) and (U-Th)/He results of Cretaceous crystalline basement samples from the Sierra San Felipe record a three-stage Cenozoic cooling history. Moderate cooling (~4–7ºC/m.y.) during late Paleocene to Eocene times is attributed to progressive down-wearing and bevelling of the ancestral Peninsular Ranges. Beginning at ~45–35 Ma, a period of tectonic quiescence with cooling rates of ≤1ºC/m.y. marks final unroofing of the basement and the development of a regional Oligocene to Miocene peneplain. Thermal modelling of samples from the footwall of the Las Cuevitas and Santa Rosa fault systems indicates that accelerated cooling began at ~9–8 Ma. This cooling pulse is attributed to tectonic denudation of the footwall and implies that faulting initiated synchronously on both detachments at ~9–8 Ma. Late Miocene deformation occurred distributed throughout the Sierra San Felipe, but started waning after the Pacific-North America plate boundary had localised into the Gulf of California by ~4.7 Ma / During a late Pliocene structural reorganisation in the northern Gulf, the locus of extension shifted from the Tiburón to the Delfín basins, thereby initiating strike-slip faulting on the Ballenas fracture zone, a transform fault located approximately 1.5–4.5 km offshore in central Baja California. This is consistent with low-temperature thermochronometric data from two horizontal transects perpendicular to the strike of the transform, which document a pronounced late Pliocene to Pleistocene heating event that is related to the structural and/or magmatic evolution of the transform fault. During reheating, maximum paleotemperatures reached >100–120ºC near the coast, but did not exceed ~60ºC some 5–8 km further inland. Highly non-systematic overprinting patterns are best explained by circulating hydrothermal fluids, which are most likely associated with magmatic leaking along the transform fault. / AFT and (U-Th)/He ages from a vertical profile collected on the Libertad escarpment, which forms part of the Main Gulf Escarpment in central Baja, pre-date Neogene extension and indicate that rift-related denudation was insufficient to expose samples from temperatures higher than the sensitivity zones of the two systems. One sample from the base of the escarpment however, records a middle to late Miocene hydrothermal overprint and suggests that extension in central Baja California likely initiated before ~10–8 Ma.

Thesis (M.S.)--University of Nevada, Reno, 2007. / "May, 2007." Includes bibliographical references (leaves 155-165). Online version available on the World Wide Web.

Thesis (Ph.D.)--University of Melbourne, School of Earth Sciences, 2007. / Typescript. Includes bibliographical references (leaves 197-215).

Thesis (Ph.D.) - University of Glasgow, 2007. / Ph.D. thesis submitted to the Department of Geographical and Earth Sciences, Physical Sciences Faculty, University of Glasgow, 2007. Includes bibliographical references. Print version also available.

Thesis (MS)--Montana State University--Bozeman, 2008. / Typescript. Chairperson, Graduate Committee: David R. Lageson. Includes bibliographical references (leaves 85-93).

Thesis (Ph. D.)--University of Washington, 1999. / Vita. Includes bibliographical references (leaves 114-131).