Reconstructing the Early Flow and Deposition Geometry Through the Accretion Surfaces on the Jezero Western Delta Fan, Mars

Abstract The western delta fan in Jezero crater hosts one of Mars's best‐preserved examples of fluvial accretion surfaces, recently investigated by NASA's Perseverance Rover. Erosional windows reveal this geologic unit, which records evidence of fluvial point bar deposition. On Earth, accretion surfaces are used to reconstruct meander‐belt evolution and paleoenvironments, but their use in Martian fluvial deposits is less explored. Here, we use orbital HiRISE and CTX data sets for a detailed, geometric planform characterization of fluvial accretion surfaces on a western fan. Our analysis expands on Perseverance's investigation as our study region extends significantly beyond where the rover visited. We identified significant exposures of accretion surfaces and analyzed the various bedding geometries and their relationships, resulting from meander‐bend migration patterns and their combinations in an ancient meandering fluvial system. We also show that these deposits are thicker than previously reported, occupying ∼65 m of stratigraphy, suggesting a regionally extensive meandering fluvial system that existed on the delta plain. The close relationship of these deposits with inverted channels possibly suggests that the top of the fan represents a continuum of fluvial processes as opposed to end‐members in delta stratigraphy. Finally, we investigate the consistent accretion direction of the deposits toward the east and propose a model to explain this with stronger paleoflow influence from the northern inlet during the early stages of the development of the Jezero Western Fan. Overall, this study provides a detailed orbitally derived characterization of a key sampling unit for Mars Sample Return.