This investigation focuses on the Jurassic-Eocene sedimentary record of northwestern Montana and the geometry and kinematics of the thrust belt, in order to develop a unifying geodynamic-stratigraphic model to explain the evolution of the Cordilleran retroarc of this region. Provenance and subsidence analyses suggest the onset of a foreland basin system by Middle Jurassic time. U-Pb ages of detrital zircons and detrital modes of sandstones indicate provenance from accreted terranes and deformed miogeoclinal rocks. Subsidence commenced at ∼170 Ma and followed a sigmoidal pattern characteristic of foreland basin systems. Jurassic deposits of the Ellis Group and Morrison Formation accumulated in a back-bulge depozone. A regional unconformity/paleosol zone separates the Morrison from Cretaceous deposits. This unconformity was possible result of forebulge migration, decreased dynamic subsidence, and eustatic sea level fall. The late Barremian(?)-early Albian Kootenai Formation is the first unit in the foreland that consistently thickens westward. The subsidence curve at this time begins to show a convex-upward pattern characteristic of foredeeps. The location of thrust belt structures during the Late Jurassic and Early Cretaceous is uncertain, but provenance information indicates exhumation of the Intermontane and Omineca belts, and deformation of miogeocline strata, possibly on the western part of the Purcell anticlinorium. By Albian time, the thrust belt had propagated to the east and incorporated Proterozoic rocks of the Belt Supergroup as indicated by provenance data in the Blackleaf Formation, and by cross-cutting relationships in thrust sheets involving Belt rocks. From Late Cretaceous to early Eocene time the retroarc developed a series of thrust systems including the Moyie, Snowshoe, Libby, Pinkham, Lewis-Eldorado-Steinbach-Hoadley, the Sawtooth Range and the foothills structures. The final stage in the evolution of the compressive retroarc system is recorded by the Paleocene-early Eocene Fort Union and Wasatch Formations, which are preserved in the distal foreland. A new ∼145 Km balanced cross-section indicates ∼130 km of shortening. Cross-cutting relationships, thermochronology and geochronology suggest that most shortening along the frontal part of the thrust belt occurred between the mid-Campanian to Ypresian (∼75-52 Ma), indicating a shortening rate of ∼5.6 mm/y. Extensional orogenic collapse began during the middle Eocene.

The Kuiper belt is a population of planetesimals outside the orbit of Neptune. The high inclinations and eccentricities exhibited by many belt members, and its very low mass (M 0.1M) present an enigma to planetesimal accretion scenarios: the high relative encounter velocities (vrei 1 km s-1), and infrequent collisions of the largest members make the growth of Pluto-sized bodies impossible over the age of the Solar system. Accretion in the early stages of planet-building must have been in a more dense environment allowing large objects to grow before growth was halted. The current Kuiper belt population is the left-over relic of accretion, which has undergone collisional re-shaping since the epoch of accretion. The shape of the size distribution can provide constraint on the accretion timescale, the primordial Kuiper belt mass, and the collisional processing the belt has undergone. Thus, a measure of the size distribution provides one of the primary constraint on models which attempt to explain the formation of the Kuiper belt. We have performed a large-scale ecliptic Kuiper belt survey, with an aerial cov¬erage of 3.3 square degrees to a limiting magnitude m(R) 27. From these ob¬servations, we have discovered more than 100 new Kuiper belt objects. Using this survey we have provided the best measurement of the Kuiper belt luminosity function to-date, from which we have inferred the size distribution. We have found that the size distribution is well described by a power-law for large objects with a steep slope q1 = 4.8, that breaks, or rolls over to a shallower power-law with slope q2 = 2 at ob¬ject diameter ~ 60 km. The steep large object slope is indicative of a short accretion phase, lasting no more than a few 100 Myr. The large break diameter demonstrates that the Kuiper belt has undergone substantial collisional processing. We have developed a collisional evolution model which we have used to study the effects of planetesimal bombardment and disruption on the size distribution. We have found that, in the current Kuiper belt, little to no evolution is occurring, or has occurred for the observable Kuiper belt. We conclude that the large break diameter cannot be produced in the current environment over the age of the Solar system. A period of intense collisional evolution in a much more dense, and hence, more massive belt is required. These findings are consistent with accretion models; the typical finding is that growth of the largest Kuiper belt objects over the age of the Solar system requires a much more massive belt than currently observed. These results point to a history in which an initially much more massive Kuiper belt underwent a short period of quiescent accretion producing Pluto size bodies. Some event then occurred, which dynamically excited the planetesimals, producing an erosive environment which effectively halted planet growth and rapidly depleted the majority of the primordial mass. The remnant of this depletion is the Kuiper belt we observe today.

Ultra-wide Trans-Neptunian Binaries (TNBs) are extremely sensitive to perturbation, and therefore make excellent probes of the past and present dynamical environment of the outer Solar System. Using data gathered from a host of facilities we have determined the mutual orbits for a sample of seven wide TNBs whose periods exceed one year. This characterized sample provides us with new information about the probable formation scenarios of TNBs, and has significant implications for the early dynamical and collisional history of the Kuiper Belt. We show that these wide binaries have short collisional lifetimes, and use them to produce a new estimate of the number of small (~1 km) objects in the Kuiper Belt. Additionally, these systems are susceptible to tidal disruption, and we show that it is unlikely that they were ever subjected to a period of close encounters with the giant planets. We find that the current properties of these ultra-wide Trans-Neptunian Binaries suggest that planetesimal growth in the Cold Classical Kuiper Belt did not occur through slow hierarchical accretion, but rather through rapid gravitational collapse. / Graduate

What tectonic processes were operating in the Archean, and whether they were similar to the “modern-style” plate tectonics seen operating today, is a fundamental question about Archean geology. The Superior Province is the largest piece of preserved Archean crust on Earth. As such it provides an excellent opportunity to study Archean tectonic processes. Much work has been completed in the southern part of the Superior Province. A well-documented series of discrete, southward younging orogenies related to a series of northward dipping subduction zones, has been proposed for amalgamating this part of the Superior Province. The tectonic evolution in the northwestern Superior Province is much less constrained, and it is unclear if it is related to the series of subduction zones in the southern part of the Superior Province, or if it is related to an entirely different process. Such ideas need to be tested in order to develop a concise model for the Meso – and Neoarchean tectonic evolution of the northwestern Superior Province. To this end, a field mapping, U-Pb geochronology, Nd isotope, and lithogeochemistry study was undertaken in the Island Lake greenstone belt. This granite-greenstone belt is part of the northern margin of the North Caribou terrane, a larger reworked Mesoarchean crustal block located in the northwestern Superior Province. U-Pb TIMS zircon geochronology data shows that the Island Lake greenstone belt experienced a long and complex geological history that included the deposition of three distinct volcanic assemblages at ca. 2897 Ma, 2852 Ma, and 2744 Ma, as well as a younger clastic sedimentary group, the Island Lake group. All of these volcanic assemblages include felsic and mafic volcanic rocks, as well as a suite of contemporaneous plutonic rocks. The U-Pb data set shows that the Savage Island shear zone, a regional fault structure that transects the Island Lake greenstone belt, is not a terrane-bounding feature as correlative supracrustal assemblages are observed on both sides of it. The Nd isotope data shows that the volcanic assemblages and contemporaneous plutons have been variably contaminated by an older ca. 3.0 Ga crustal source. The mafic volcanic rocks in the assemblages have two distinct geochemical signatures, and show a pattern of decreasing crustal contamination with decreasing age. Together these data suggests that the Meso – and Neoarchean volcanic assemblages are part of an intact primary volcanic stratigraphy that were built on the same ca. 3.0 Ga basement and have autochthonous relationships with each other. This basement is the North Caribou terrane. The youngest sedimentary group in the belt, the Island Lake group, was deposited between 2712 Ma and 2699 Ma. It consists of “Timiskaming-type” sedimentary rocks, and is the youngest clastic sedimentary package in the belt. A detailed study of detrital zircons in units from the stratigraphic bottom to the top of the sedimentary group indicates an age pattern of detrital zircons that is most consistent with a scenario in which sediments were deposited in inter-diapiric basins created by diapirism and sagduction (i.e., vertical tectonic) processes. During the diapiric ascent of the felsic material, inter-diapiric basins were formed in the synclines between adjacent domes, into which sediments were deposited. U-Pb zircon TIMS geochronology identified two ages of deformation in the Island Lake greenstone belt. Two dykes that crosscut an older, D1 foliation place a minimum age of ca. 2723 Ma on the D1 deformation, and two syn-kinematic dykes date movement along two transpressional shear zones to 2700 Ma. Together all these data indicate that the tectonic evolution in the Island Lake greenstone belt and in the northwestern Superior Province took place in three main stages. The first two stages involved the generation of Meso – and Neoarchean volcanic assemblages and contemporaneous plutonic rocks due to southward dipping subduction under the North Caribou micro-continent. The third stage involved the deposition of late “Timiskaming-type” sediments during vertical tectonic processes in conjunction with horizontal tectonic movement along late transpressional shear zones at ca. 2.70 Ga. At the end of this process the North Superior superterrane was terminally docked to the North Caribou terrane along the North Kenyon fault. This study shows that while a version of horizontal or “modern” style plate tectonics were operating in the Archean, vertical tectonic processes were also occurring and that these processes operated synchronously in the Neoarchean.

There are forty four known small planetary bodies with orbits that are contained within the heliocentric distances of Jupiter and Neptune. It is thought that the origin of these bodies is the Kuiper Belt, the predicted reservoir of the current short period comet population. Yet, only two bodies, Chiron and C/NEAT (2001 T4), have been shown to possess a visible coma. We've undertaken an observational survey of these bodies to obtain detailed characterization of the physical properties of the Centaurs to search for evidence of activity, and to use the physical characteristics to make inferences about primordial conditions in the outer solar nebula and evolutionary processes among different dynamical regimes in the outer nebula. We present the results of optical observations of 24 Centaurs, which yield a 3-σ correlation of color with semimajor axis, with redder Centaurs being farther from the Sun. The survey also revealed the rotation light curve period for 2 Centaurs, and the phase-darkening slope parameters, G, for 5 Centaurs which range from -0.18 to 0.13, agreeing with the steepest of main belt asteroid phase curve responses. We show spectral evidence of a variegated surface for 1999 UG5 and find the second reddest Centaur object is the active Centaur C/NEAT (2001 T4). We also present spectral evidence of crystalline water ice and ammonia species on our comparison object, the Uranian satellite Miranda.

Part of the Slave Structural Province, the Hope Bay Greenstone Belt is a 82 km long north-striking sequence of supracrustal rocks dominated by mafic volcanic rocks with lesser felsic volcanic and sedimentary rocks. Mapping of two transects in the southern section and two transects in the northern section have contributed to a robust stratigraphic framework the belt. Three recently discovered Archean lode gold deposits in the Hope Bay Greenstone belt have associations with major structures and specific lithologies (Fe-Ti enriched basalts). The Flake Lake and the Clover Transects are in the southern part of the belt and the Wolverine and Doris-Discovery Transects are in the northern part of the belt. This work subdivides the volcanic rocks into distinct suites based upon field, petrologic, geochemical, and geochronologic criteria. Some of the suites are stratigraphically continuous and can be correlated tens of kilometres along strike thereby linking the two parts of the Hope Bay Greenstone Belt. U-Pb geochronology supports work by Hebel (1999) concluded that virtually all the supracrustal rocks in the Hope Bay Greenstone Belt were deposited over at least 53 m.y. (2716-2663 Ma), with the majority of the volcanism occurring after 2700 Ma. A number of basalt groups are identified and include the normal basalt, the LREE-enriched basalt, the Ti-enriched basalt and the Ti-enriched Al-depleted basalt groups. They have chemical signatures that vary in trace elements particularly HFSE and REE’s, and can be easily be distinguished by geochemical screening. The felsic volcanic suites are also divided into three main groups, tholeiitic rhyolite, calc-alkaline dacite and calc-alkaline rhyolite groups. Nd and Hf isotope signatures are consistent with trace element signatures in identifying mafic and felsic volcanic groups, with the tholeiitic rhyolite showing highly variable signature. The Hope Bay Greenstone Belt has been show to have a number of felsic and volcanic cycles. An early construction phase of the belt is made up of primarily mafic volcanics which is followed by felsic volcanism equalled mafic volcanism which lacks basalts enriched in Ti. The geodynamic environment that created the Hope Bay Greenstone Belt can be explained by plume influenced subduction zone.

The deformed Permian Dun Mountain Ophiolite Belt (DMOB) forms the basement of the Dun Mountain-Maitai terrane and is traceable through the entire length of New Zealand. The DMOB contains a variably serpentinised mantle portion and a crustal portion containing gabbros, dolerites, cross cutting dikes and extrusives, together they are similar to oceanic crust. The initial crustal portion, however, is atypical when compared to other ophiolites, being thin and lacking a sheeted dike complex, but has well spaced inclined intrusive sheets and sills. At least four post-Permian deformation periods affect the DMOB; collision and rotation during emplacement of the DMOB on the Gondwana margin, compression during Mesozoic orogenies, extensional deformation during the Gondwana break-up and transpressive deformation related to the modern plate boundary through New Zealand. Structural work in the Northern Bryneira Range focused on well preserved outcrops to investigate crustal growth and contemporaneous deformation during the Permian. Structural evidence of Permian deformation was determined by examination of pseudostratigraphy, structures constrainable to the Permian, and the geometric relationships with the overlying Maitai sedimentary sequence. Crosscutting by intrusive phases was used to determine a chronological order of crustal growth and deformation episodes. It was concluded that all deformation was extensional and that two major phases of magmatism were separated by a period of deformation and were followed by ongoing syn-sedimentary deformation during the deposition of the Maitai Group. After removal of Mesozoic rotation, the resulting orientations of paleo-horizontal markers and diverse orientations of intrusive sheets were analysed. Two hypothesises were tested to assess the origin of inclined intrusive sheets: a) that the diverse orientations were the result of tectonic rotation coeval with the intrusion of dikes. b) that primary orientations of the sheets had been diverse. Results show that the sheets were intruded with diverse orientations, probably related to variation in the principle horizontal stress over time. Further rotation of the assemblage of sheets occurred during the last stages of magmatism and during the subsequent period of sedimentation. The last stage probably relates to large scale normal faulting during the development of the sedimentary basin. iii

Thesis(M.S.)--Auburn University, 2005. / Abstract. Vita. Includes bibliographic references.

Submitted by Everaldo Pereira (pereira.evera@gmail.com) on 2017-02-19T21:13:10Z No. of bitstreams: 1 Dissertacao_Andre_Luis_Santos.pdf: 10542532 bytes, checksum: 392e6cfaed5318d19eb1f54fa34fc56c (MD5) / Made available in DSpace on 2017-02-19T21:13:10Z (GMT). No. of bitstreams: 1 Dissertacao_Andre_Luis_Santos.pdf: 10542532 bytes, checksum: 392e6cfaed5318d19eb1f54fa34fc56c (MD5) / O Greenstone Belt de Umburanas (GBU), de idade arqueana, está localizado na porção centro-oeste do Estado da Bahia. Encontra-se inserido no segmento crustal do Bloco Gavião (BG), no Cráton do São Francisco. O GBU é formado por três unidades litoestratigráficas principais que encerram três ciclos vulcânicos: (i) Unidade Inferior, contendo, na base, rochas vulcânicas metaultramáficas komatiíticas, acompanhadas de meta-basaltos toleiíticos e metadacitos compondo o primeiro ciclo vulcânico, seguidas por quartzitos com leitos meta-conglomeráticos, meta-sedimentos químico-pelíticos (BIF’s, cherts, metacarbonatos e rochas calcissilicáticas) e pulsos discretos de meta-vulcânicas félsicas, atribuídas ao segundo ciclo vulcânico; (ii) Unidade Média, dominada por rochas meta-vulcânicas félsicas do terceiro ciclo vulcânico, com intercalações subordinadas de seus equivalentes piroclásticos, epiclásticos e de derrames máficos e; (iii) Unidade Superior, constituída essencialmente de meta-carbonatos. As rochas meta-komatííticas da Unidade Inferior do GBU, objeto deste estudo, apresentam-se como faixas tectonicamente interrompidas, seguindo os contatos com o embasamento e com os maciços graníticos de Umburanas e Serra do Eixo. Apresentam coloração variando de cinza a cinza esverdeado, granulação fina e uma foliação incipiente. As principais ocorrências dessas rochas estão situadas na Folha cartográfica de Brumado, próximo a estrada de ferro, nas imediações da Serra do Sucuiu e na Folha cartográfica de Tanhaçu, na Serra do Eixo, mais precisamente nas imediações da Fazenda Eixo da Serra. Estudos petrográficos realizados nas rochas meta-komatiíticas revelaram a presença de texturas do tipo cumulática, maciça e spinifex. As rochas foram submetidas a variados graus de serpentinização apresentando uma mineralogia primária constituída por olivina e piroxênio e a secundária composta por serpentina, talco, tremolita e antofilita, e proporções menores de clorita. Apesar dos variados graus de serpentinização, diagramas de mobilidade mostraram pouca mobilização dos elementos químicos. As rochas meta-komatiíticas foram classificadas como peridotitos komatiíticos. Possuem, em média, altos teores de MgO (~33%), Cr (4067 ppm) e Ni (1488 ppm) e baixos conteúdos de álcalis (~0,05%). As razões CaO/Al2O3 e Al2O3/TiO2 caracterizaram as rochas meta-komatiíticas em komatiítos não depletados em Al. Em geral, todos os grupos de meta-komatiítos (cumulato, spinifex e maciço) mostram em maior ou menor proporção enriquecimento em elementos traço altamente incompatíveis (Th, LREE) em relação a uma abundância moderada de elementos incompatíveis litófilos e possuem anomalias negativas de Nb e Sr. Utilizando a temperatura do líquido calculada através da relação T (oC) = 20xMgO+1000 a temperatura dos meta-komatiítos do GBU varia entre 1572° a 1711°C. Os meta-komatiítos da Unidade Inferior do GBU foram derivados provavelmente de plumas rasas dentro de um manto empobrecido, gerando fusão em profundidades menores do que 200 km, pois estas rochas mostram padrões de elementos terras raras pesados plano a quase plano, juntamente com enriquecimento em elementos terras raras leves e elementos incompatíveis, e fracionamento de Nb e Sr. Adicionalmente, anomalias negativas de Nb e Sr e positivas de Th observadas nos pontos apresentados para rochas do Bloco Gavião (BG), provável embasamento do GBU, indica que as rochas gnáissicas-migmatíticas do BG poderiam ser o provável contaminante das rochas meta-komatiíticas do GBU. Recomenda-se a realização de dados isotópicos Sr-Nd para confirmação ou não desta hipótese. / ABSTRACT - Umburanas Greenstone Belt (GBU) of Archean age, is located in the central-western portion of Bahia state. It is inserted into Gavião Block the crustal segment, in the São Francisco Craton. The GBU consists of three main lithostratigraphic units that contain three volcanic cycles: (i) Lower Unit, in the base, containing meta-komatiites rocks, accompanied by tholeitic meta-basalt rocks and meta-dacitic rocks composing the first volcanic cycle, followed by quartzites with meta-conglomerates, chemical-pelitic meta-sediments (BIF's, cherts, meta-carbonates and calcissilicatic rocks) and discrete pulses of felsic meta-volcanic, assigned to the second cycle volcanic, (ii) Unit Average, dominated by felsic meta-volcanic rocks of the third cycle, with subordinate intercalations of pyroclastic equivalents, epiclastics and mafic flows and (iii) Higher Unit, consisting essentially of meta-carbonates. The meta-komatiites rocks of the Lower Unit of GBU, object of this study, are presented as ranges disrupted tectonically, following contacts with the gnaissic-migmatitic basement and Umburanas and Serra do Eixo granite massifs. These meta-komatiite rocks show gray to greenish gray color, fine grained and incipient foliation. The main occurrences of these rocks are located in Brumado cartographic Sheet, near the railroad, near the Serra do Sucuiu and Tanhaçu cartographic Sheet, in the Serra do Eixo, more precisely near of the Eixo da Serra Ranch. Petrographic studies carried out in meta-komatiite rocks revealed the presence of three types of textures: cumulate, massive and spinifex. These rocks show variable degrees of serpentinization process with a primary mineralogical association consisting of olivine and pyroxene and a secondary mineralogy of talc, anthophyllite, tremolite and chlorite in smaller proportions. Although of variable degrees of serpentinization, the diagrams show little mobility dispersion of chemical elements. viii The meta-komatiite rocks were classified as komatiitic peridotites. They have, on average, high amounts of MgO (~ 33%), Cr (4067 ppm) and Ni (1488 ppm) and low content in alkalis (~ 0.05%). The CaO/Al2O3 and Al2O3/TiO2 ratios characterized the meta-komatiite rocks in aluminium undepleted komatiites. In general, all groups of meta-komatiites (cumulato, spinifex and massive) show a greater or lesser extent enrichment in highly incompatible trace elements (Th, LREE) for a moderate abundance in litophile incompatible elements and they have negative anomalies of Nb and Sr. Using the liquid temperature calculated by the relationship T (°C) = 20x1000+MgO the temperature of the metakomatiite rocks of GBU varies between 1572 ° to 1711 °C. The meta-komatiites of Lower Unit of GBU were derivated probably doof the shallow depleted mantle, causing melting at depths less than 200 km, because these rocks show patterns of heavy rare earth elements plan to almost flat, with LREE and incompatible elements enrichment, and fractionation of Nb and Sr. In addition, negative anomalies of Nb and positive Th observed in the gneissic-migmatitic rocks of Gavião Block, probable basement of the GBU, indicates that the gneissic-migmatitic rocks could be the likely contaminant of the rocks of the meta-komatiites. It is recommended that to be made Sr-Nd isotopic analyzes to confirm this hypothesis or not.

Asymmetric gait, or a difference in functioning between legs during human locomotion, is a health concern that can lead to secondary complications such as chronic musculoskeletal injury or a more sedentary lifestyle. Restoration of gait symmetry requires a gait adaptation, or a change in the way that an individual walks. Further knowledge of how to best promote a gait adaptation could lead to the creation of future rehabilitative protocols geared towards restoration of symmetric gait. To address this, a variable practice paradigm was implemented in able-bodied individuals walking asymmetrically on a split-belt treadmill. Individuals were assigned into one of three practice groups (from least variable to most: serial, random blocked, random) and walked on the treadmill for 720 strides of motor skill acquisition according to their given paradigm. They were asked to return 24 hours later and were given one of two tests for motor learning: retention or transfer. Three-dimensional kinematic and kinetic data were collected throughout the experimental protocol and used to analyze walking performance between the three practice groups. Results indicated that random blocked practice resulted in the best retention and transfer of mediolateral balance control variability, while serial practice had the highest variability on the transfer test. It was further demonstrated that this paradigm resulted in a unique mechanical strategy implemented by each practice group that further describes the role of variable practice in gait adaptation: random practice during acquisition, random blocked during retention, and serial during transfer. A principal component analysis showed that variable practice also results in the adoption of specific coordinative structuring of joint and segmental kinematics. These structures were mostly different across practice groups during the acquisition and retention phases. While it was generally hypothesized that random practice, which induces the highest amount of stepping errors during acquisition, would result in the best retention and transfer of the adapted gait pattern, this practice group did not perform as well as expected on the measured outcomes. Random blocked practice, on the other hand, may provide the optimal level of challenge and variability to best facilitate a gait adaptation. This dissertation includes previously published and unpublished co-authored material.