New evidence for climate and erosion history in Gale crater, Mars, from Curiosity’s ascent onto the Greenheugh pediment - CNRS - Centre national de la recherche scientifique Accéder directement au contenu
Communication Dans Un Congrès Année : 2020

New evidence for climate and erosion history in Gale crater, Mars, from Curiosity’s ascent onto the Greenheugh pediment

Valerie Fox
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Résumé

Curiosity’s southward traverse up the lower north slope of Mt. Sharp (in Gale crater, Mars) and across Glen Torridon has brought it in contact with the organics-bearing sediments of the Knockfarril Hill member, the light-toned, nodule-rich strata found at Western, Central, and Tower buttes, and to the abrupt truncation of these altered Murray sediments at the Greenheugh pediment. Curiosity ascended the steep northern edge of the Greenheugh pediment near Tower butte, thus accessing strata identified ~20 years ago as recording a major environmental transition in the history of Gale. The basal truncation surface of the pediment is the Siccar Point group (SPg) basal unconformity, which extends past Vera Rubin ridge (VRR) to the north. Above the unconformity lies a <~5m thick cross-bedded sandstone capping unit interpreted to be an outcrop of the aeolian Stimson formation. Locally, these rocks exhibit extensive nodule formation. The pediment capping unit is lithified and is itself erosionally truncated, exposing a washboard pattern of low amplitude (~1m) ridges with ~6-12m wavelength. Eventual pediment scarp retreat may have been episodic as evidenced by sloping mantles of regolith flanking parts of the pediment escarpment. These new rover observations suggest that the Gediz Vallis (GV) ridge likely overlies the Stimson sandstone, and consists of layered boulder-bearing sediments, likely of fluvial and/or debris flow origin, interstratified with finer-grained sediments. The bedding within the GV ridge dips much less than the planation surface, supporting an interpretation that the sediments may have entered a succession of lakes. At the most distal end of the Gediz Vallis ridge, boulder deposits may be traceable across Glen Torridon and onto VRR suggesting the GV ridge sediments post-date the Stimson, as well as at least the initial development of the Glen Torridon trough. One possible sequence of climate-driven events that could explain these observations is: termination of Murray lake deposition; erosional planation; sand erg formation; sand lithification and nodule formation; a second erosional truncation event above the Stimson, pediment scarp retreat forming the initial Glen Torridon trough; successive sedimentation events from Gediz Vallis, desiccation and erosion to form the modern landscape.
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Dates et versions

hal-03082702 , version 1 (18-12-2020)

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Citer

Alexander B Bryk, William E Dietrich, Michael P. Lamb, John P. Grotzinger, Ashwin Vasavada, et al.. New evidence for climate and erosion history in Gale crater, Mars, from Curiosity’s ascent onto the Greenheugh pediment. AGU Fall Meeting, American Geophysical Union, Dec 2020, Online, United States. ⟨hal-03082702⟩
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