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.

Globally, deformation along obliquely converging plate margins produce a wide variety of complex fault patterns, including crustal pop-ups, fault duplex structures, restraining bends, and flower structures. Depending on the plate velocity, plate obliquity, crustal rheology, length-scale, and climate, the evolution of faulting into translational and vertical strain can range in complexity and fault slip partitioning (i.e. vertical vs. horizontal strain). In this dissertation I studied two restraining bends to understand how these factors influence patterns of deformation along two major plate boundaries: The North American-Caribbean and the North AmericanPacific plate boundaries. First, I estimate the exhumation and cooling history along the Blue Mountains restraining bend in Jamaica using multiple thermochronometers. Three phases of cooling have occurred within Jamaica: 1) initial rock crystallization and rapid emplacement of plutons from 75-68 Ma, 2) slow cooling from 68-20 Ma, and 3) two-stage exhumation from 20 Ma – Present. During the most recent phase of Jamaica’s cooling history, two stages of exhumation have been identified at 0.2 mm/yr (20 – 5 Ma) and ~1 mm/yr (5 Ma – Present). Given the plate velocity to exhumation rate ratio during the most recent phase, we suggest that the climate of Jamaica increases the erosivity of the Blue Mountain suite, whereby the Blue Mountains may be in an erosional stead-state. Second, I studied the long-term evolution of a restraining bend at San Gorgonio Pass in southern California by relating fault kinematics within the uplifted San Bernardino Mountains to the nearby Eastern California shear zone. Using highresolution topography (i.e. UAV and lidar surveys), I studied the plausibility of faulting along two potentially nascent faults within the San Bernardino Mountains, namely the Lone Valley and Lake Peak faults. We found that while both faults display evidence for Quaternary faulting, deciphering true fault slip rates was challenging due to the erosive nature of the mountainous landscape. Coupled with evidence of Quaternary faulting along other faults within the San Bernardino Mountains, we suggest a western migration of the Eastern California shear zone. / PHD

Le Tibet est le plateau le plus élevé et le plus étendu au monde. La formation de ce plateau, en arrière de l’Himalaya, résulte d’interactions complexes entre facteurs tectoniques et climatiques, ainsi que de la morphologie antérieure au soulèvement. Afin d’évaluer l’influence relative de ces différents facteurs, cette thèse s’appuie sur l’étude de l’évolution du relief des bordures du plateau en couplant analyse géomorphologique, étude de la sédimentation syn-formation du plateau et reconstitution de l’exhumation à partir de la thermochronologie de basse température.Cette approche a permis de mettre en évidence que le plateau du Tibet était déjà haut, aussi bien sur ses bordures est que ouest dès 35 Ma, soit seulement 20 Ma après la collision Inde-Asie. Il apparait donc que le plateau se serait soulevé soit en un bloc, soit de façon précoce par ses marges Ouest et Est, plutôt qu’en se propageant du sud vers le nord et vers l’est comme proposé par de nombreux modèles.Dans l’Ouest Tibet, l’existence d’un réseau de drainage anciennement connecté avec celui de l’Indus, a permis le développement précoce d’un relief significatif (supérieur à 1000 m) avant 35 Ma lors de la surrection du plateau. Ce relief est ensuite préservé dans un contexte d’érosion très faible (quelques dizaine de mètres par million d’années) associé à une évacuation des produits d’érosion vers le bassin de l’Indus. Cette connexion avec l’Indus est ensuite coupée probablement suite aux mouvements de la faille du Karakorum.A l’Est, la formation du relief est probablement plus ancienne que dans l’Ouest Tibet, car vers 35 Ma cette région, bien que déjà surélevée, est caractérisée par l’existence d’un vaste réseau fluviatile en tresse, impliquant une faible pente, ainsi qu’un relief local soumis à des précipitations plus au nord. La création du relief actuel, marqué par des rivières fortement encaissées, est probablement liée à l’évolution de la mousson sud-est asiatique ainsi qu’au fonctionnement de la faille du Fleuve rouge. / Tibet is the widest and highest plateau on Earth. Tectonics, climate evolution and ante-surrection geomorphology are the main factors controlling the plateau formation. In order to assess the relative influence of these factors, we study the relief evolution on the plateau edges using geomorphic analysis, sedimentology and exhumation rates based on low-temperature thermochronometry.The results show that the western and eastern plateau edges were already at high elevation at ca 35 Ma, only 20 Ma after the India-Asia collision. This favors an “en bloc” uplift model for the plateau.In western Tibet, the hydrographic network was connected to the Indus river, allowing the early development of a >1000 m amplitude relief, probably before 35 Ma. The relief was preserved due to low erosion conditions. Western Tibet was then isolated from the Indus drainage network due to the Karakorum fault slip.The relief formation in Eastern Tibet is older than in western Tibet: at ca 35 Ma, in the Jianchuan area (northern Yunnan), which was already at high elevation, was a large braided river system. This implies a moderate regional slope. It also implies a local relief further north and significant precipitations.