2024 CSDMS meeting-009


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Climate modulation of spatial and temporal fault slip in the Sangre de Cristo Mountains, Colorado

Sean Gallen, (he/him),Colorado State University Fort Collins Colorado, United States. sean.gallen@colostate.edu
Cece Hurtado, Colorado State University Fort Collins Colorado, United States. Cecilia.Hurtado@colostate.edu

The impact of climate on tectonics has been the muse of tectonic geomorphologists for more than 30 years. However, few natural examples exist where connections between climate and tectonics are clear. Here, we present a study of the Sangre de Cristo Mountains (SCM), CO, a normal fault system at the northern tip of the Rio Grande Rift. The SCM represents an ideal natural setting to explore the impact of climate on spatial and temporal slip patterns along the range-bounding fault. Preserved glacial moraines and trimlines are used with the Glacier Reconstruction (GlaRe) toolbox to model glacial extents during the last glacial maximum (LGM). A simple line load model is used to explore the impact of glacial melting on clamping stress along the range front fault, and a flexural isostatic model is applied to estimate the footwall response to deglaciation. Results show that glacial melting reduces fault clamping stress, perhaps enabling accelerated fault slip in the post-glacial period. Flexural isostatic results suggest modest footwall uplift of ~4 m due to ice removal. We compare our results to fault displacement, measured from scarps preserved in Pleistocene and Holocene alluvial fans. The spatial pattern and magnitude of Holocene fault displacement are consistent with our flexural isostatic results. Furthermore, Holocene slip rates are at least a factor of three higher than Pleistocene slip rates. We infer that the flexural isostatic response to footwall deglaciation primarily controls the spatial and temporal fault slip patterns during the Holocene. Our results show that climate-modulated glacial ice loading and unloading can pace the spatial and temporal slip on a range-bounding normal fault system.