Reprocessing of Appalachian Ultradeep Core Hole (ADCOH) southern Appalachian seismic reflection data was focused on improving the reflection imaging and hence interpretability of seismic signatures previously interpreted as duplexes created by thrust stacking of thin beds of Paleozoic shelf strata. The reprocessed data are used to determine a more unique depth domain geometry for one of the proposed duplexes. Reprocessed data are partially improved through an increase in both stacking velocity coverage and datum statics velocity coverage as well as an appropriate use of residual statics. Interpretability increases from the improvement in resolution and the consideration of geologic strike direction relative to profile direction. Initial shotpoint ray trace modeling shows the chaotic nature of raypaths and some of the problems associated with the imaging of reflections when complex geology is involved. Data reprocessing and two-dimensional ray trace modeling yield results which suggest that the studied seismic signature is part of a broad hinterland-dipping duplex. At the trailing edge of the duplex itself beds appear to be successively fault truncated, perhaps explaining the increased amplitude and reflectivity in this zone. The truncations result in a wedge-shaped geometry that resembles the trailing edge of an antiformal stack duplex. The improved data also show 1) a shallow band of reflections that correlate with the Shope Fork and Chunky Gal Mountain faults within the Blue Ridge allochthon, 2) thrust ramping initiated by basement faulting that extends only a short distance into the overlying sedimentary strata, 3) a more highly faulted Grenville basement surface and, 4) almost intact Paleozoic shelf strata (?) being carried along the thrust surface serving and bounding the hinterland-dipping duplex. / M.S.

M.S.

Broken-formations (Hsu, 1974; Harris and Milici, 1977) occur in the lower part of the Pulaski thrust sheet and contain some of the most strongly deformed sedimentary rocks in the Valley and Ridge province of the southern Appalachians. Deformation in this zone ranges from grain-scale cataclasis to regional-scale faulting. The broken-formations are distinguished from rocks structurally higher on the sheet and from rocks of the underlying Saltville sheet by (1) a sharp increase in the variability of fold and fault styles, (2) greater ranges in fold plunges and dips of axial surfaces, (3) a low degree of preferred orientation of folds and faults, (4) an increase in the frequency of mesoscopic structures, and (5) the presence of Max Meadows tectonic breccia. Structural analyses indicate that deformation in the broken-formations is Alleghanian in age and that the deformed zone formed under elastico-frictional conditions, possibly under elevated fluid pressures with temporally variant stresses and that lithology may have played an important role in localizing the broken-formations along the base of the Pulaski sheet. / Ph. D.

Tian Shan is one of the most important orogenic belts in central Asia. It has been reactivated as a result of the Cenozoic India-Eurasia collision. Dating of the late Cenozoic tectonic deformation of Tian Shan and its piedmonts is important for understanding the mountain building as well as evaluating seismic hazards in the region. This study is focused on the applications of optical dating to the late Quaternary uplift and thrust activity along Manas River, in the northern piedmont of the Tian Shan, China. The sediments on river terraces were dated with optical dating. The elevations were measured with the kinematic global position system (GPS). The results suggest that two phases can be identified according to the significantly different river incision rates. One phase was from ~20 ka to ~4.8 ka, with a much slower incision rate of ~ 2.2 ± 0.6 mm/yr. The other phase was from ~4.8 ka to present, with a faster incision rate of ~ 13.5 ± 0.6 mm/yr. The accelerated incision rate of Manas River was mainly attributed to the tectonic forces, suggesting that the tectonic uplift was significantly intensified since ~4.8 ka in the northern piedmont of Tian Shan. The study region has suffered from multiple thrust activities during the late Quaternary, which led to the intensive deformations of the river terraces. By studying the deformed terraces, I evaluated the timing of the past thrust activities as well as the vertical slip rate of the thrust faults. The results demonstrated that the thrust activity intensified during the late Holocene, as manifested by the more frequent thrust activities and higher vertical slip rates. Both quartz and potassium feldspar can be as dosimeters for optical dating of sediments. However, quartz OSL is sometimes seriously impeded with problems such as very dim signals and insufficient bleaching problems. K-feldspar has attractive advantages over quartz, despite of problem of anomalous fading. K-feldspar was explored in this study, by investigating the relationship between the infrared stimulated luminescence (IRSL) and blue light stimulated luminescence (BLSL) signals. For IRSL and BLSL at 60 °C, it was suggested that most of the IRSL could be bleached by blue light (BL), while the BLSL could only be partially bleached by infrared (IR) stimulation. Besides, the fast and medium components of BLSL were mainly associated with the IRSL. If IR stimulation temperature was raised from 60 to 200 °C, at least two portions of the IRSL signals at 200 °C were observed. One portion could be bleached by BL at 60 °C and the other portion was hardly bleached by BL at 60 °C. Dating of K-feldspar from the various signals provided cross-checking for the reliability of quartz OSL for dating sedimentary samples. / published_or_final_version / Earth Sciences / Doctoral / Doctor of Philosophy

Thesis (M.S.)--University of Texas at El Paso, 2008. / Title from title screen. Vita. CD-ROM. Includes bibliographical references. Also available online.

Thesis (M.S.)--Brigham Young University. Dept. of Geology, 2007. / Includes bibliographical references (p. 86-88).

Thesis (Ph. D.)--University of Montana, 2007. / Title from title screen. Description based on contents viewed Oct. 10, 2007. Includes bibliographical references.

No description available.

This study focuses on a series of thrust sheets exposed in the Appalachian Valley and Ridge Province Blacksburg-Pembroke area in southwest Virginia. Structures in the hanging wall of the Saltville thrust (Saltville thrust sheet) and the footwall of the Saltville thrust (Narrows thrust sheet) are examined. The first part of this study involves the construction of a series of thrust transport-parallel 1:24,000 scale geologic cross sections to constrain the subsurface geometry of fault and fold structures within the Saltville and Narrows thrust sheets. The second part of the study involves an outcrop-scale study of geologic structures exposed along a series road cuts in the footwall of the Saltville thrust and the geometric and relative timing relationships between folding, cleavage formation and thrust faulting. The cross sections show a series of interconnected splay faults branching off of the Saltville thrust and cutting both its hanging wall and footwall. Angle of dip and magnitude of dip-slip displacement on thrust and splay faults progressively decrease from hinterland to foreland within this fault system that is referred to as the Spruce Run Mountain-Newport (SRMN) fault system. Bedding within this fault system essentially forms a structural transition zone between the Saltville and Narrows thrust sheets, defining a km-scale fractured synform-antiform fold structure that has many structural attributes usually associated with fault propagation folding. In the road cut outcrops, early meter-scale faults are folded by later foreland-(NW) vergent folds. Although cleavage defines convergent cleavage fans about these folds, subtle obliquities between folds and cleavage indicate that folding post-dates early layer-parallel shortening and associated foreland-vergent thrusting. / Master of Science

La chaîne pyrénéenne présente des structures de déformation bien exposées et des roches sédimentaires syntectoniquesbien conservées qui en font un objet idéal pour étudier les failles. En effet, les textures, structures, compositions chimiques etisotopiques enregistrées par le coeur de la faille chevauchante peuvent renseigner sur les conditions et mécanismes de ladéformation et aussi contraindre dans le temps l’activité de la faille étudiée. Dans la présente thèse, trois chevauchements duversant sud Pyrénéen ont été étudiés pour mieux appréhender le comportement mécanique, chimique et isotopique desphyllosilicates dans des roches sédimentaires déformées. Ces roches sont d'âge éocène à triasique et sont impliquées dans degrand chevauchements (zone cisaillantes) à vergence sud. Ce travail combine observation pétrographique, analyse chimique,modélisation thermodynamique et technique de datation radiométrique 40Ar/39Ar sur des minéraux de moscovite/illite et dechlorite. La première faille étudiée est le chevauchement du Pic de Port Vieux (PPV), chevauchement de second ordre lié auchevauchement majeur de Gavarnie dans le sud-ouest de la Zone Axiale Pyrénéenne. Des mécanismes de pression-dissolutionet recristallisation, accompagnés d’interactions avec un fluide très réducteur sont les principaux paramètres responsables deschangements minéralogiques/chimiques observés dans la zone centrale de la faille. L'indice Kübler de la moscovite et lesdonnées thermométrique sur chlorite suggèrent des températures de 285°C ± 28°C pour l'activité de PPV. De plus, la datation40Ar/39Ar de la moscovite syn-cinématique indique que la faille a fonctionné il y a 36.9 ± 0.2 Ma, ce qui coïncide avec l’âge del'activité du chevauchement de Gavarnie. Les deux autres failles étudiées sont le chevauchement de Lakora qui est situé sur lebord sud de la zone Nord Pyrénéenne et celui de Monte Perdido (au niveau de Torla) situé dans la partie ouest de la zone Sud-Pyrénéenne. Ces deux chevauchements ont été affectés (déformés) par la mise en place de chevauchement de Gavarnie. Lesobservations pétrographiques et les analyses microstructurales ont démontré que la déformation est marquée par du plissement,du boudinage, par le développement d'une schistosité intense, de surfaces de cisaillement, de veines et par un enrichissement enphyllosilicates au coeur de la zone de faille des deux chevauchements. De manière similaire au chevauchement du Pic de PPV,les mécanismes de pression-dissolution et recristallisation sont les principaux mécanismes qui contrôlent la déformation et ilssont à l’origine de l'enrichissement en phyllosilicates néoformés dans les zones de failles des deux chevauchements. En se basantsur les mesures de l'indice de Kübler, il apparait que la déformation de Lakora et Torla s'est produite dans des conditions detempérature plus basse que celles enregistrées pour le chevauchement du PPV. Par ailleurs, es âges les plus jeunes obtenus parla technique 40Ar/39Ar ne peuvent être rattachés à l'âge de la déformation car ils sont plus vieux que les âges des sédimentsimpliqués dans les zones de faille. D'autres hypothèses sont proposées à la fin de cette thèse afin de comprendre les raisons decette incohérence dans les âges et afin de dater la déformation de Lakora et Torla. Ainsi l'ensemble des résultats de cette thèsemontrent que les minéraux phyllosilicatés peuvent être des outils thermochronologiques fiables permettant de dater avecprécision l'activité des failles lorsqu'ils ont été combinés avec des préparations d'échantillons précises et caractérisation détailléedes échantillons. / The Pyrenees belt features well-exposed deformation structures and well preserved syntectonic sedimentary rocksthat make it ideally suited to study thrust faults. The texture, structure and chemical-isotopic compositions of synkinematicphyllosilicates are widely used to estimate the deformation conditions-mechanisms and timing of fault activities. Therefore, inthe present thesis, three thrusts from the Pyrenean orogen have been studied to better understand the mechanical, chemical andisotopic behavior of phyllosilicates from deformed sediments of Eocene-Triassic age that have been involved in large southvergingshear zones. This work combined petrographic observation, chemical analyses, and thermodynamic modeling with40Ar/39Ar geochronology on muscovite/illite and chlorite. The first studied fault is the Pic de Port Vieux thrust (PPVT), a secondorderthrust related to the major Gavarnie thrust (GT) in the south-western part of the Pyrenees Axial Zone. The dissolutionrecrystallization,pressure solution mechanisms, and interaction with highly reductive fluids are the main parameters responsiblefor the mineralogical and chemical changes in the fault core zone. The Kübler index and chlorite thermometry suggest upperanchizoneto epizone conditions with a temperature of 285°C ± 28°C for the PPVT activity. Moreover, the 40Ar/39Ar step-heatingdating of synkinematic muscovite indicates that the fault activity occurred at 36.9 ± 0.2 Ma which coincides with the activity ofthe GT. The two other faults are: Lakora thrust that is located on the southern edge of the North Pyrenean Zone, and the MontePerdido thrust (Torla location) situated on the western part of the South Pyrenean Zone. The two thrust are affected (deformed)by the emplacement of the Gavarnie thrust. The petrographic-microstructural analyses on these faults demonstrated thatdeformation is marked by folding, boudinage, intense cleavage, shear surfaces/veins and enrichment of phyllosilicates in thefault zone of both thrusts. Similar to the PPVT, pressure-solution and dissolution-recrystallization mechanisms are the mainmechanisms that control deformation and enhanced the enrichment of the newly-formed phyllosilicates in the fault zones ofboth thrusts. Based on the Kübler index measurements, the deformation in the Lakora and Torla faults occurred at relativelylower temperature compared to the PPVT. The youngest total gas ages obtained by the 40Ar/39Ar technique are very old for theactivity time of both thrusts as they are older than the depositional ages of the sediments in the fault zones. Further investigationsare proposed at the end of this dissertation in order to better understand this anomaly in age and to successfully obtain the rightage of the two thrusts activity.Based on the results of this thesis, phyllosilicate minerals proved to be reliable thermochronological tools for fault activity atlow-grade metamorphism, when such tools are combined with careful sample preparations and detailed sample characterization.