INTERPLAY OF FLEXURE AND FAULTING IN THE RIO GRANDE RIFT, NEW MEXICO

Deformation during continental rifting is controlled by localized faulting in the upper crust and more distributed flexural isostatic responses to extension. The combination of these multi-scale responses within the crust is responsible for the morphology of narrow rift basins surrounded by high, linear mountain belts within uplifted rift flanks. This study presents geodynamic models that combine flexure and faulting to investigate deformation within and surrounding continental rift basins. The Rio Grande rift lies along the eastern margin of the Colorado Plateau and formed in response to Neogene extension along a zone of crustal thickening and high topography during the Laramide orogeny. The idealized models presented here explore the role of Neogene extensional deformation and its interactions with brittle faulting in generating deformation and topography surrounding the Rio Grande rift. Particular attention is devoted to understanding how flexural bending might be modified by or interact with faults in both the hanging wall and footwall blocks, and whether these interactions might explain elevated rift-flanks on both sides of asymmetric half-grabens such as the Española Basin in the northern Rio Grande rift. The results of this study have important implications for understanding the relative contributions of Neogene rifting vs. earlier tectonic events in shaping present-day deformation and subsequent topography along the eastern margin of the Colorado Plateau.