Fluvial response to Late Pleistocene−Holocene climate change in the Colorado River drainage, central Texas, USA

We documented the impact of Late Pleistocene−Holocene climate change on terrace deposits and preserved channels in the unglaciated drainage of the Colorado River in central Texas (south-central United States) using integrated channel morphology and provenance analysis. Detrital zircon (DZ) U-Pb ages (n = 1850) from fluvial terrace deposits and new quantitative analysis of fluvial channel morphology based on LiDAR data were used to reconstruct sediment provenance and shifts in paleohydraulic conditions during Late Pleistocene to Holocene aridification. These data reveal a reduction in fluvial channel size and discharge temporally coupled with a rapid shift in erosion locus and dominant sediment sourcing, from the Southern Rocky Mountains to the Llano area, during the glacial-interglacial transition. Geomorphic mapping and morphometric analysis show narrowing of river channels linked to diminishing Colorado River discharge. DZ data show an abrupt shift to erosion in the lower drainage basin and the remobilization of older terraces due to river incision and lateral channel migration. We attribute these systematic changes to upper-basin contraction caused by drainage reorganization and aridification during the Late Pleistocene, as well as the onset of enhanced convective precipitation sourced from the Gulf of Mexico, driving focused erosion along the topographic edge of the Llano uplift in central Texas since the early to mid-Holocene.