Evidence for Multiple Superposed Fluvial Deposits Within Reuyl Crater, Mars

Reuyl is an 85-km-diameter crater located east of the Aeolis Dorsa region. We present results from geomorphic mapping and high-resolution image analyses of Reuyl to understand the provenance of alluvial fans, superposed deposits, channels, and sinuous ridges. We distinguish 29 fans or other deposits associated with channels based on their characteristics. Two sinuous ridges are associated with the alluvial fans formed between the wall and peak region. On the southern floor, a sinuous ridge associated with an alluvial fan with channel inversion is orthogonally superposed by another wall-originated fan deposit. On the western floor, a sinuous ridge associated with an alluvial fan is superposed by wall-originated deposits. We also observe bajadas, stacked deposits, deposits with incised channels, and overlapping fan ridges, which suggest diverse and long-lived depositional activity related to a fluvial environment. The central peak is surrounded by a mound deposit with several discontinuous channels. One large fan from the western wall appears more intact than the others, being less eroded and lacking ridges. Reuyl aged as similar to 3.63 Ga, whereas the first-order analysis of the fan deposits implies similar to 3.5 Ga and the large intact deposit is estimated to belong to the Amazonian epoch. We suggest that Reuyl crater likely witnessed and recorded the transition from alluvial fan to large younger intact deposits, which possibly suggests a decrease in water/volatile-related activity and/or change in sediment supply. Overall, the diverse superposed fan deposits within Reuyl reveal noncoeval activity and provide comprehensive evidence for long-lived fluvial activity during the post-Noachian epoch.