| Despite profound interactions of climate, tectonics and topography, tracing landscape evolution during orogeny remains difficult and controversial. This work uses the isotopic and elemental composition of authigenic minerals preserved in intermontane basins to reconstruct regional and basin-scale changes in hydrology and topography of the developing central North American Cordillera during Late Cretaceous and Paleogene (Laramide) time. In particular, the work focuses on the sedimentary records of large (>5,000 km2) lakes present at that time in sequential intraforeland basins of Utah, Wyoming and Colorado.;First, isotopic profiles of Paleogene Lakes Uinta, Flagstaff, and Claron in Utah reveal relatively large (>5‰) shifts to lower delta 18Ocalcite values that are diachronous among the basins. The results also indicate intense evaporation of lake water during intervals of hydrologic closure. The large shifts are interpreted as a combination of increased mean elevation of basin catchments and related freshening associated with basin infilling. Increasing catchment hypsometry is thought to result from the expansion of distal catchments into areas of active magmatism in the hinterland, thus adding to growing evidence that topographic development and dissection of the Cordilleran landscape occurred at large spatial scales and proceeded from north to south during the Early Cenozoic.;Second, to test the hypothesis of evolving drainage patterns, Sr isotope data was collected in order to identify sudden changes in the provenance of catchments feeding the largest lake, Uinta. The expanded isotopic record from the Uinta Basin demonstrated significant variations in 87Sr/ 86Sr ratios that record inflows from the Greater Green River Basin in Wyoming via the Piceance Creek Basin in northwest Colorado. The results thereby document integration of axial drainage over >1000 km, and serve as a warning to paleoaltimetry studies premised on too few isotopic systems, samples or localities.;Lastly, in order to further illuminate the hydrological linkages among the sequential Green River Lake basins, isotopic and elemental profiles of the Piceance Creek Basin were assembled. Interpreting the cumulative results of this dissertation in the context of an extensive dataset of O, C and Sr isotope stratigraphies from sedimentary basins throughout the Paleogene North American Cordillera, I argue that the hydrological linkages of the Green River lakes are emblematic of evolving drainage patterns throughout the Cordillera. Specifically, the data reflect (1) a period of throughgoing foreland rivers heading in the Sevier fold-and-thrust belt and flowing east, (2) ponding of freshwater lakes in the foredeep as Laramide uplifts blocked drainage, (3) hydrologic closure that led to both intensive evaporation in the terminal sink of the Piceance Creek Basin and integration of catchments over length-scales >1000 km, and (4) infilling of basin accommodation by southward migrating magmatism in distal catchments, leading to the freshening and demise of intraforeland lakes that also stepped south over time.;Samples from the Piceance Creek, Uinta, Flagstaff and Claron Basins were analyzed for their oxygen, carbon, hydrogen and strontium isotope composition, and concentrations of calcium, magnesium and strontium were also measured. Research was conducted and is presented in three stages, each building upon the previous:... |
