Understanding how mountain landscapes respond to variations in tectonic forcing over a range of temporal scales in active mountain belts remains as a prominent challenge in tectonic and geomorphological studies. Although a number of empirical and numerical studies have examined this problem, many of them were complicated by issues of scale and climatic variability. More specifically, the relative efficiencies of fluvial and glacial erosion, which are presumably controlled by climate, are difficult to unravel. The Teton Range in Wyoming, which results from motion on the crustal-scale Teton fault, is an ideal natural laboratory for addressing this challenge as the tectonic uplift boundary condition and the variation of uplift along strike is well-documented by previous studies and due to its relatively small size, climate can be reasonably expected to vary consistently along strike. Here, we present the results from a study that examines how the Teton landscape responds across the longest (106-7 yrs) and shortest (102-4 yrs) temporal scales. Long-term canyon incision rates determined from apatite (U-Th)/He (AHe) analysis of major drainages are highest (0.24 mm yr-1) where measured uplift rates and duration are highest (near Mount Moran), leading us to propose that tectonic forcing operates as the first order control on long-term Teton erosion. Short-term denudation rates, which are derived by determining sediment volumes in Moran Bay that are deposited in catchments generated during the most recent glacial interval (Pinedale, ~15.5 ka), are 0.00303 – 0.4672 mm yr-1. We compare these rates to previous work, which found that high rock fall rates (1.13-1.14 mm yr-1) deposit large talus volumes in Avalanche and Moran Canyons. Despite their magnitude, such high rates of mass wasting are not sustained over long periods of time, as measured lake sediment volumes (0.007 km3) are. We conclude that the Tetons are transport limited during the interglacial and large volumes of canyon sediment generated during this time cannot be moved absent the advance of valley glaciers. That is, fluvial systems in small mountain systems are substantially less effective than glaciers in denuding mountain topography.

The magnitude of global sediment flux from streams to the oceans over the last 5 Ma is poorly quantified, yet important for predicting future fluxes and deciphering the relative control of tectonic uplift, climate change, vegetation, and related feedback mechanisms on landscape evolution. Despite numerous proxy studies on global sediment delivery to the oceans, it remains uncertain whether bulk sedimentation increased, decreased, or remained approximately constant across one of the most significant global climate changes: the Plio-Pleistocene transition. New developments and strategies in the application of cosmic-ray-produced isotopes, in part developed by this thesis, provide records of pre-historic denudation of confined fluvial catchments in Texas and Yukon. Non-glaciated, tectonically passive regions were targeted in contrast to other studies on modern sedimentation rates in order to isolate the climate influence from glacial and tectonic controls. The results suggest that average catchment temperature, and surficial processes and other factors such as vegetation cover associated with temperature, are the primary controls on the variation in landscape denudation in regions lacking tectonics and direct glacial cover. Specifically, warmer temperatures yield higher denudation rates, both at the scale of glacial-interglacial climate change and over the Plio-Pleistocene transition. The implication is that stream sediment flux to the ocean from tropical and temperate regions was higher during the Pliocene than in the Quaternary. However, this may have been balanced by an increase in sediment flux from regions covered by warm-based glaciers during glacial periods, or by increased temporary continental storage during interglacial periods.

Ce manuscrit concerne l'analyse tectonique et géomorphologique du système de failles de Longriba (LFS), localisé à l'Est du plateau tibétain à environ 200 km au Nord-ouest de la chaîne des Longmen Shan. Le LFS est constitué de deux zones de failles décrochantes dextres, parallèles et d'orientation N55°E : la faille de Longriqu, au Nord, et la faille de Maoergai, au Sud. Le rôle géodynamique de ce système est primordial puisqu'il accommode 5 ± 1 mm/an de la composante décrochante induite par la convergence oblique du bloc Aba, elle-même liée à la collision Inde-Asie. De plus, le LFS partitionne la déformation de la marge Est tibétaine; les structures des Longmen Shan étant essentiellement chevauchantes. Cependant l'histoire long-terme du LFS est mal contrainte. L'objectif de cette thèse est donc d'apporter des informations spatio-temporelles sur l'activité du système à l'échelle du Cénozoïque. Pour cela trois études ont été réalisées. La première a permis de mieux contraindre le comportement sismogénique des deux zones de failles à l'aide d'images satellites de basse (90m) et très haute résolution (50cm). L'analyse des déplacements cumulés le long de la faille de Maoergai a permis de proposer que celle-ci était active vers ~15Ma. La seconde étude a mis en évidence un contrôle du système sur la répartition des taux de dénudation au travers de la marge Est tibétaine à l'échelle de l'Holocène. Enfin, les données de thermochronologie basse température suggèrent que la faille de Maoergai a accommodé un mouvement vertical vers ~10Ma. Ce mouvement est probablement lié au rebond isostatique de la marge, découplé du mouvement décrochant qu'elle accommode à la même période. / This manuscript concerns the tectonic and geomorphic analysis of the Longriba fault system (LFS), located in the eastern Tibetan plateau at about 200 km north-west of the Longmen Shan. The LFS consists of two dextral strike-slip fault zones, parallel and N55 °-trending: the Longriqu fault to the north and the Maoergai fault the south. The geodynamic role of the system is essential as accommodates 5 ± 1 mm / year of the slip component induced by the oblique convergence of the Aba block, itself linked to the India-Asia collision. In addition, the LFS partitions the deformation of the east Tibetan margin; the structures of the Longmen Shan are mainly thrust faults. However the long-term history of LFS is poorly constrained. The objective of this thesis is to bring spatial and temporal information on system activity throughout the Cenozoic. To do so, three studies were performed. The first led to better constrain the seismogenic behavior of the two fault zones with low resolution (90m) and very high resolution satellite images (50cm). The analysis of cumulative displacements along the Maoergai fault allowed to propose that it was active at ~ 15 Ma. The second study showed that the system controls the distribution of the denudation rates over the EastTibetan margin throughout the Holocene. Finally, the low-temperature thermochronology data suggest that, in particular, the Maoergai fault has accommodated a vertical movement at ~ 10 Ma. This movement is probably related to the isostatic rebound of the margin, decoupled from the strike-slip movement it accommodates at the same period.