The Interplay Between Basin and Channel Response Timescales Controls Alluvial Architecture: A Comparison of Global River Response to the Paleocene–Eocene Thermal Maximum

Reconstructing river response to the Paleocene–Eocene Thermal Maximum (PETM) may provide useful insights into modern river response to global warming. While extensive work has documented river response to the PETM for individual basins, seldom work has compared basin response. Here we investigate the factors that determined how PETM response varied in space. To do this, we explore PETM response in three basins: the Bighorn Basin (Wyoming, USA), the Piceance Basin (Colorado, USA), and the Tremp–Graus Basin (Pyrenees, Spain). We find the apparent PETM response varies between basins, and we investigate the origin of this variability. For each basin, we use catchment boundary conditions and the BQART sediment flux model to predict the response magnitude. Then, we use catchment boundary conditions, predicted sediment fluxes, and observed channel geometries to reconstruct the basin and channel response timescales associated with the response. For each basin, we contextualize our predictions with observations of pre-PETM, syn-PETM, and post-PETM strata. Using the geological outcrop labeling tool, Outcrop Sketch, we compile stratigraphic observations at each stratigraphic hierarchical level/scale, which include channel-belt, intra-channel belt, barform, bedform, and grain scales. We find that each basin records PETM response at different hierarchical levels, and that the hierarchical level at which PETM response is observed reflects the ratio between the basin response timescale and channel response timescale. These results emphasize the importance contextualizing stratigraphic observations with the hierarchical level at which they were observed, and with catchment boundary conditions.