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Fluvial and Eolian Bedforms as a Record of Paleoenvironment

Bedforms are wave-like patterns that develop when a fluid flows over a granular bed. They exist in both fluvial and eolian environments, under the form of, e.g., ripples and dunes. Because their formation results from the interaction of sediment and fluid flow, bedform deposits record information about the environment in which they formed, and thus are potentially useful proxies to reconstruct past hydrological and atmospheric conditions. However, using bedforms as a paleoenvironmental proxy, especially under different planetary conditions, requires that we understand the mechanics of their formation. Our contributions on the subject include (1) the development of a scaling relation to predict the equilibrium size of current ripples and that can be applied to Earth, Mars, and Titan; (2) the identification of a new type of eolian bedforms on Mars and their likely formation mechanism; and (3) the identification of large-wind-ripple cross-stratification in sandstones of the Burns formation at Victoria crater, Mars, and interpretation in terms of atmospheric density at the time of deposition (~ 3.8 Gyr).