OUT-OF-SEQUENCE THRUSTING AND DENDRITIC CHANNEL NETWORKS DEVELOPMENT ON CHARON: IMPLICATIONS FOR TIDAL EVOLUTION AND THERMAL STATE

Though Charon has been interpreted as geologically inactive, the presence of a global dichotomy, along with troughs and scarps, suggests a geologically active past. Previous studies interpreted the troughs and scarps in the rugged northern highlands (Oz Terra) as grabens and normal fault scarps, indicating global extension. This global extension model gained support from the rift shoulder uplift observed along Charon's largest graben, Serenity Chasma. However, a recent study with systematic geomorphological mapping and landform analysis have revealed a potential influence from thrusting and glaciation on north-trending, eastward-convex, arcuate ranges and dendritic trough systems in Oz Terra. In this study, we conduct a quantitative analysis of topography and structure of these landforms to determine their origins and to explore their implications. We conducted a landform spectral analysis to understand the origin and evolution of topography in different wavelengths. After filtering out longer-wavelength topography that is likely related to tectonics, flow patterns consistent with the observed west-converging dendritic pattern emerge. This correspondence indicates that landscapes co-evolve due to out-of-sequence thrusting and surface erosion. This interpretation is further supported by the observation of the diverted troughs along the arcuate ranges, resembling the drainage rearrangement due to the anticline growth caused by tectonic activity on Earth. We applied an elastic dislocation model to quantitatively and systematically study the thrust geometry. The best fits suggest the fault dips to be 25~30 degrees, consistent with the prediction of the Mohr-Coulomb Failure Criteria. The best-fit elastic thickness of the ice shell is estimated to be 30~40 km during thrust development. The lower-latitude distribution and the roughly north-south trends of the thrusts is consistent with the predicted tectonic pattern of a despun planet, indicating a tidal dissipation origin. Orbital dynamic studies suggest Charon’s tidal evolution to have ceased 1~10 Myr after accretion, and the tidally driven thrusts potentially recorded the spinning rate and thermal state of Charon in its early stage.