Reconstructing Martian environmental change across a major unconformity at Gale crater: sedimentology of the Stimson formation at the Greenheugh pediment

摘要: The basal Siccar Point group unconformity observed at the Greenheugh pediment is a major regional break in sedimentation within Gale crater. Below unconformity, mudstones and sandstones of Murray formation records predominantly lacustrine palaeoenvironment that was likely habitable. Overlying distinctive fan-shaped, erosion-resistant, tabular stratal unit (~2-6 m thick) informally called capping unit. This has been identified as part Stimson formation, which encodes signature surfaces processes climate crater postdating unconformity. Between Sols 2633 2781, Curiosity rover used to investigate unit, where detailed observations sedimentary architecture, facies sediment texture were obtained. Textural grain-size analyses sandstone show it comprises well-sorted, medium-grained, well-rounded with an average grainsize ~425 μm, suggests aeolian transport dominant structure are cross-bedded composed 2-4 mm thick, uniform-thickness cross-laminations, typical wind ripple stratification. Architectural reveal compound cross-sets, sets 0.2-0.7 form cosets up 2.5 thick. These lead us conclude accumulated result processes, wind-blown dunes migrated across leaving preserved cross strata. Further this, our texture, architecture consistent Emerson plateau, Naukluft plateau buttes areas. We pediment-capping up-slope equivalent drapes over ~500 elevation range. expression dry dune field, extreme aridity, when would have devoid surface water. juxtaposition desert deposits overlying lake indicates change palaeoclimate