41-4 Fluvial and Catastrophic Flood Activity Late in Mars Geologic History: Implications for Late Paleoclimate Changes?

Session: Philosophy of Extreme Events and Landscape Evolution on Earth and Other Planets: Thinking Geologically in the Spirit of Victor Baker

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Our analyses of various erosional valley, channel, and gully landforms using CTX and HiRISE images reveal that Mars’ surface experienced both fluvial and catastrophic flood activity much more recently than previously thought. We find that in the Navua Vallis region along the N/NE rim region of Hellas Basin, fluvial, catastrophic, and paleolake formation continued periodically from the Late Noachian into the Late Amazonian (Hargitai et al. 2017, 2018, 2019). Catastrophic floods and fluvial activity emanated along the southern flanks of Hadriaca and Tyrrhena volcanos. In the Chryse region, we find that the Osuga Valles outflow channel was also periodically active from the Hesperian through the late Amazonian (Spurling et al. 2024). We find that Osuga experienced multiple episodes of catastrophic flooding with estimated maximum discharges close to 10⁸m³/s, declining to ~10⁶ m³/s in later episodes (Portillo et al. 2023; Portillo, 2025, M.S. Thesis). Osuga Vallis exhibits several paleoflood indicators (PFI; e.g., streamlined islands, bars, and grooves), which are also seen in the Channeled Scablands. Osuga is intriguing because like most Martian outflow channels, groundwater erupted catastrophically in source regions, but unlike other outflow channels, Osuga flows appear to have re-entered the groundwater system in terminal collapse depressions. There is no evidence that floods continued to flow on the surface towards the Northern Lowlands like many other outflow channels (Naor et al. 2019; 2023; submitted). Finally, our studies of gully formation on Mars indicate that fluvial activity was active recently both in the Northern Lowlands (Gulick et al. 2019, Huang and Gulick, 2025) and in the Southern Highlands (e.g., Gulick and Glines, 2019, 2021). Gullies formed integrated tributary systems, eroded several 10s of meters into underlying resistant rock and sediment layers, exhibit concave longitudinal profiles and V-shaped cross profiles, similar to their terrestrial counterparts (Gulick et al. 2019; Huang and Gulick, 2025). Finally, we find that the crater gully systems we have studied formed adjacent to periglacial and glacial features, in craters with lobate ejecta. The crater’s lobate ejecta margins imply that groundwater was incorporated into the ejecta blanket, suggesting the presence of a near-surface groundwater table. Such impacts would form an impact-induced hydrothermal system, which may have resulted in local hydrologic cycling of groundwater, releasing both liquid water and steam into the crater’s local environment.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-10834

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