Sediment‐Rich Flow Morphology and Stratigraphy as Records of Emplacement Pressures on Mars

Abstract Abundant geologic evidence suggests that sediment transport by liquid water on Mars took place across a wide range of atmospheric pressures, from at least ∼100 mbar in the Noachian-Hesperian to ∼7 mbar average of today. Because these low pressures do not occur naturally on Earth, experimental studies in Mars pressure chambers are required to understand and interpret sediment flows and their deposits. Previous experimental studies show that low surface pressures (∼5–13 mbar) affect the transport and deposition of sediments by liquid water. Building on these studies, we conducted experiments to explore how pressure affects the morphology and stratigraphy of warm-temperature (>293 K) basaltic sediment-rich flows under varying Mars-like pressures (7–1,013 mbar), representative of warmer conditions in the Noachian, Hesperian, and Amazonian epochs. At low pressures, over a warm surface, vaporization-related processes dominate, resulting in deposits with numerous lobes and surface features like vugs, levees, and high surface roughness and slope. Their stratigraphy is characterized by wavy to convoluted bedding that is laterally discontinuous, consistent with burial and entrainment. In contrast, at higher pressures, deposits have sub-planar bedding, fewer lobes, and surfaces lacking vugs and levees.