Thesis. 1978. Ph.D.--Massachusetts Institute of Technology. Dept. of Earth and Planetary Science. / Microfiche copy available in Archives and Science. / Vita. / Bibliography: leaves 257-274. / Ph.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Sciences, 1981. / Microfiche copy available in Archives and Science. / Bibliography: leaves 102-106. / by Joann Miriam Stock. / M.S.

The timing, duration, and pressure-temperature (P-T) conditions of metamorphism provide a direct record of the physical and chemical evolution of the crust and inform our knowledge and understanding of plate tectonics. The characteristic timescales and length-scales of metamorphism vary by orders of magnitude, depending on the driving tectonic process. Two fundamental problems with the retrieval of this information from the metamorphic rock record are insufficient temporal resolution and processes that overprint or obscure the full record of metamorphism. Understanding what processes are recorded, and why they are recorded, is critical for accurate models of tectonics. This dissertation examines these processes in the metamorphic rock record in two settings: the central Appalachian orogen and the Western Alps fossil subduction zone. Chapters 2 and 3 focus on poly-metamorphic migmatites from the Smith River Allochthon (SRA) in the central Appalachians. A combination of petrography, thermodynamic modeling, and geochemistry is used to document and quantify the metamorphic evolution of the SRA and determine the petrologic processes that control metamorphic re-equilibration in high-temperature metamorphic systems. Chapter 2 presents new constraints for Silurian high-temperature (~750℃, 0.5 GPa) contact metamorphism in response to mafic magmatism and a cryptic Alleghanian metamorphism (~600℃, 0.8 GPa). A combination of extensive and highly variable melt loss followed by H2O-flux melting during contact metamorphism is shown to produce a range of modified bulk rock compositions and domains with variable fertilities for metamorphic re-equilibration during the Alleghanian. In chapter 3, monazite, allanite, and zircon laser ablation split-stream petrochronology are used to constrain the timing of poly-metamorphism and develop a tectonic model for the SRA. The SRA preserves evidence for at least three orogenic events, each with a relatively short duration (< 10 Myr.), likely due to repeated magmatic heating. The full record of this punctuated heating is obscured by dissolution-reprecipitation reactions that variably recrystallize monazite and decouple trace element chemistry from isotopic age and significantly restrict equilibrium length-scales. Chapters 4 and 5 examine the dynamic interplay between transient fluid flow, episodic metamorphism, and deformation in subduction zones. In chapter 4, diffusional speedometry is applied to eclogite breccias from the Monviso ophiolite to quantify the periodicity of transient deformation and metamorphism at eclogite facies P-T conditions. The maximum timescale for repeated fracturing is constrained to ~1 Myr., likely caused by cyclic variations in fluid pressure and strain rate (not necessarily seismicity). While difficult to preserve and detect in the rock record, this periodic metamorphism may play an important role in detachment and exhumation processes in subduction zones worldwide. Finally, in chapter 4 a combination of thermodynamic modeling and Sm-Nd garnet geochronology are used to construct a model for subduction and exhumation of the Voltri ophiolite. Garnet growth occurs rapidly and close to peak P-T conditions (~520℃, 2.4 GPa) across the ophiolite, with large (>10 km2) areas preserving near-identical ages, suggesting that the Voltri ophiolite was exhumed as several large coherent units, aided by the presence of buoyant serpentinites. / Doctor of Philosophy / Metamorphism provides a direct record of the physical and chemical evolution of Earth's crust and informs our knowledge and understanding of how plate tectonics works on Earth. Differences in the physical conditions (e.g. pressure, temperature) and timescales of metamorphism can provide clues for the operation of unique tectonic processes, such as the intrusion and cooling of magma deep underground or the collision of two tectonic plates and formation of a mountain range. The key is to correctly "read" the metamorphic rock record. One inherent difficulty in reading and interpreting metamorphic rocks is that few current methods are able to resolve very short timescale events (much less that 1 million years (Myr.) in duration), such as earthquakes, in the rock record. Moreover, metamorphic rocks experience numerous distinct 'events', which partly overprint one another and produce a complicated and near impossible puzzle for geologists to unravel. Solving this puzzle is critical to fully understand how plate tectonics works on Earth. This dissertation addresses these problems and examines metamorphism in two locations: the core of the ancient supercontinent Pangea (central Appalachians) and a fossil subduction zone (the Western Alps). Chapters 2 and 3 focus on the central Appalachians. Chemical and textural analysis of metamorphic rocks are used to understand the major heat sources that operated in the crust during the formation of the Appalachians and determine the processes that control metamorphic re-crystallization at extremely high temperatures. Chapter 2 presents new constraints for high-temperature (~750℃) metamorphism in response to magmatic heating and provides evidence for a younger metamorphic event that is cryptically recorded. A combination of compositional changes caused by earlier high-temperature metamorphism and the later addition of water along reactive grain boundaries are shown to be important factors in the cryptic record of the younger metamorphic event. In chapter 3, U-Pb geochronology is used to the determine the timing of metamorphism and construct a tectonic model for the central Appalachians, which preserves evidence for at least three tectonic events over ~200 Myr, but with each occurring over a relatively short duration (< 10 Myr.). These events are interpreted to represent repeated magmatic heating 'pulses' during the formation of Pangea. However, the full record of this punctuated heating is partly obscured by subsequent fluid alteration. Chapters 4 and 5 examine the dynamic interplay between transient fluid flow, earthquakes, and metamorphism deep in subduction zones. In chapter 4, fracture sets within metamorphic garnet crystals from the French Alps (Monviso) are used to determine the timescale of repeated fracturing and recrystallization during subduction. The fracture timescales are estimated to be much less than 1 Myr. and are interpreted to record repeated fluid "pulses" and possibly deep earthquakes. While difficult to preserve and detect in the rock record, this process may play an important role in bringing metamorphic rocks back from deep in subduction zones to Earth's surface. In chapter 4, a combination of mineral chemistry and geochronology are used to construct a tectonic model for the subduction and exhumation of a portion of the Italian Alps (Voltri). Metamorphic reactions occur synchronously and immediately before exhumation across a wide area (> 10 km2). This suggest that large (> 10 km2) pieces of oceanic crust can metamorphose, detach, and exhume deep in subduction zones.

The Pacific-North America plate boundary in central and southern California has a complex tectonic history, and constraints are poor for inception of an extensional fault system linked to the southern San Andreas fault, a major tectonic element of this plate boundary. Furthermore, decades of research has shown relationships between climate, tectonics, and surface processes in most orogens across the globe (e.g. Alps, Himalaya, Andes, Alaska Ranges), however the role climate plays in modulating erosion and mass fluxes from extensional mountains blocks to sedimentary basins over 104-5 yr timescales is debated. In the eastern California-Walker Lane shear zone, exposures of sedimentary basin fill allow inversion of erosion- and sediment-flux rates from a linked catchment-fan system within an extensional block. In this dissertation, I present two field and geo-thermochronology based studies that explore research topics related by common tectonic setting and geography within the Pacific-North America plate boundary. First I present new low-temperature thermochronology (apatite U-Th-Sm/He) and thermal history modeling to document the kinematic evolution of the Santa Rosa mountains, where the cooling history constrains initiation timing of the west Salton Detachment fault, and the southern San Andreas fault system. I document an age of ca. 8 Ma for exhumation initiation of the Santa Rosa block, from paleodepths of ~4.5–3 km, at vertical rates of ~0.15–0.36 mm/yr, accelerating to ~1.3 km/Ma since ca. 1.2 Ma during initiation of the San Jacinto fault zone. Second, I present a new data set of cosmogenic radionuclide-derived burial ages and paleodenudation rates (26Al/10Be) from the Pleasant Canyon complex in the Panamint Range, and show that denudation rate and sediment flux have varied by a factor of ~2x since the middle Pleistocene. I conclude high frequency variability is driven by climate change, and not tectonic perturbations, as supported by published constraints for exhumation timing. The middle Pleistocene transition from 40–100 ka periodicity may drive the observed changes, a tentative conclusion that makes testable predictions for stratigraphic records of past climate in other locations. Empirical evidence for climate-modulated erosion and sediment flux provides valuable constraints for numerical models of landscape evolution and sedimentary basin architecture. / Ph. D.

I've titled my thesis, "Intrinsics" because my architectural design is an attempt to respond to what is inherent in the materials, in the way materials are joined, in the flow of forces through the structure, in the site and surroundings, and in the human nature of a person using the building type I'm designing. This is a tectonic approach, so my thesis is also "An Exploration of Tectonic Expression" with a Montessori school as a project vehicle. The site is next to the Roanoke Public Library in Elmwood Park in Roanoke, Virginia. The primary materials are glue-laminated wood beams and arches, metal connectors, and reinforced concrete walls. I explored what can happen if each layer of a glue-laminated member is allowed to act independently, separating from the girder in appropriate places to recombine into a new whole. The monolith transforms into a pattern of parts. / Master of Architecture

Between the intangible and tangible is the realm in which this thesis investigation takes place. The material presented here in a roughly chronological progression represents an exploration over the course of a year. This organization of thoughts and images will illustrate the processes and discoveries which occurred during this exploration. In architecture, the realm of the intangible represents ideas. Ideas are catalysts for further study and ultimate action. It was the aim of this thesis to not simply let an idea exist without further action, but to explore the evolution of an idea to the point where it may ultimately manifest in built form. The realm of the tangible, in this case the physical object, is also not the emphasis of this thesis. It is simply part of the whole, not to be confused with some sort of final end result. The built object, when studied, helps inform the original idea. The emphasis of this thesis is on the area between the intangible and the tangible. This is where explorations take place, discoveries are made, and where transformations occur. In essence, this is where the multitude acts of design transform ideas into the realm of architecture. / Master of Architecture

Graduation date: 1996

Thesis (Ph. D.)--University of Oregon, 2005. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 173-185). Also available for download via the World Wide Web; free to University of Oregon users.

Θεματικός πυρήνας της συγκεκριμένης εργασίας είναι η αναγνώριση και ερμηνεία των τασικών πεδίων που έδρασαν στην ευρύτερη περιοχή της νήσου Λήμνου-η οποία δεν εντάσσεται σε κάποια από τις γνωστές τεκτονοστρωματογραφικές ενότητες διότι δεν έχουμε εμφανίσεις των πετρωμάτων υποβάθρου- ,τα οποία οδήγησαν στην ενεργοποίηση ορισμένων ομάδων ρηγμάτων . Η αναγνώριση των τάσεων στηρίχθηκε τόσο σε παλαιότερες προσπάθειες συσχέτισης της γεωμετρίας των ρηγμάτων και της κινηματικής τους , με τις τάσεις που τα προκαλούν, όσο και σε συλλογή και επεξεργασία δεδομένων που συλλέχθηκαν στην ύπαιθρο μέσω του λογισμικού TECTONICSFP. / The core subject of this particular study is the recognition and structural interpretation of the stress regime of Lemnos island- which cannot be categorized in any of the tectonostratigraphic units, due to the fact that there are no rocks exposed on the island to help us determine a single unit that may fit-which led to fault activation. The recognition of the stress tensors was based not only in older tries of correlation between the geometry of the faults and their kinematics, but also in collecting geological data and processing them with the use of the software TECTONICSFP.

<div>Paleozoic-Mesozoic stratigraphy exposed in the central Alaska Range includes a diverse assemblage of tectonostratigraphic basement terranes overprinted by late Mesozoic basin</div><div>formation and Cenozoic strike-slip displacement. In this thesis, I present a stratigraphic and structural framework for upper Paleozoic-Cretaceous strata exposed in Denali National Park and Preserve. The stratigraphic architecture of the study area is characterized by two distinct Upper Paleozoic-Mesozoic stratigraphic packages that are unconformably overlain by the Upper Cretaceous Cantwell Formation. Sedimentological, provenance, and geologic mapping data suggest that one basement assemblage, the Northern package, consists of Upper Triassic-Lower Cretaceous submarine strata deposited along the northwestern Laurentian margin. The other assemblage, termed the Southern package, is exotic to the ancestral continental margin and is associated with Permian-Upper Triassic submarine strata of the Farewell terrane. Provenance data from this package place new constraints on the Late Paleozoic paleogeographic position of the Farewell terrane prior to its accretion to the continental margin, likely by the Late Jurassic. The results of geologic mapping along the Toklat River corridor show that the Northern and Southern packages are deformed and structurally juxtaposed within a triangle zone bounded by the Hines Creek and Denali fault systems. This is the best exposure of stratigraphy associated with the Farewell terrane juxtaposed with strata representative of the ancestral continental margin known to date. New 1:24,000-scale geologic mapping coupled with a stratigraphic and provenance analysis of the Cantwell Formation provides new insights into sedimentation and deformation during the post-collisional phase of development of the Alaska Range suture zone (ARSZ). Results of this study define three stages of basin development. These stages are represented by alluvialfluvial, tidally influenced fluvial, and marginal marine deposits, respectively. Results of geologic mapping record progressive Late Cretaceous-Eocene deformation of the Cantwell Formation in a triangle zone and the transition from compressional to strike-slip tectonics in the Eocene. This deformation coincides with regional exhumation of the ARSZ and reconfiguration of the paleosouthern Alaskan margin with the establishment of the modern convergent margin configuration.</div>