Conference proceeding
Chemistry of the materials above and below an unconformity between the Murray and Stimson Formations in Gale Crater, Mars
American Geophysical Union Fall Meeting, Vol.2015
American Geophysical Union 2015 fall meeting
12/2015
Abstract
MSL began investigating a contact between Murray formation, (fine grained lake deposits) and the younger Stimson formation at Marias Pass in May 2015, on the lower slopes of Mt. Sharp. Images show that the Murray formation, with numerous calcium sulfate veins compared to the Stimson, is truncated at an erosional contact. MAHLI images show a white layer a few mm thick at the contact that might be calcium sulfate. The lowermost beds of the Stimson unit in the Missoula area comprise horizontally laminated or cross-laminated sandstones. The sandstones are poorly sorted with floating granules and very coarse sand grains set in a fine- medium-grained sand 'matrix'. This material directly above the contact is a resistant, basal ledge-forming layer that also forms numerous blocks of float on top of the eroded Murray. This basal layer contains light toned fragments, possibly calcium sulfate, eroded from the Murray. The poor sorting and presence of sub-angular grains, together with the absence of preferential sorting into size sorted layers would seem to rule out eolian processes for the lowermost beds of the Stimson and suggest fluvial processes were responsible for deposition of these beds. For chemostratigraphy, the distance of each ChemCam or APXS observation above or below the contact was determined from images and the NavCam stereo mesh. The top of the Murray near the Missoula area is variable in composition, and additional analyses are planned to determine if weathering occurred at the eroded surface. Above the contact, the lowest 2 cm of the resistant slab is higher in SiO (sub 2) , and lower in Al (sub 2) O (sub 3) , K (sub 2) O and Na (sub 2) O, relative to other Stimson analyses. In a few points with low totals, there is a correlation between Ca and missing components (presumed to be mostly S). These points could be connected to calcium sulfate in the form of cements and/or incorporation of eroded clasts of Murray vein materials.
Details
- Title: Subtitle
- Chemistry of the materials above and below an unconformity between the Murray and Stimson Formations in Gale Crater, Mars
- Creators
- Horton E. Newsom - University of New MexicoInes BelgacemRoger C. WiensJens FrydenvangOlivier GasnaultSylvestre MauricePatrick James GasdaSamuel M. CleggAgnes CousinWilliam RapinRyan JacksonZoltan VaciBeth HaDiana L. BlaneyNathan BridgesRaymond FrancisValerie PayreSanjeev GuptaSteven BanhamJeff SchroederFred J. CalefKenneth S. EdgettDeirdra M. FeyMartin R. FiskRalf GellertLucy M. ThompsonGlynis M. PerrettJohn P. GrotzingerDavid M. RubinAmy WilliamsLinda C. KahRachel Emily Kronyak
- Resource Type
- Conference proceeding
- Publication Details
- American Geophysical Union Fall Meeting, Vol.2015
- Conference
- American Geophysical Union 2015 fall meeting
- Publisher
- American Geophysical Union
- Alternative title
- AGU 2015 fall meeting
- Language
- English
- Date published
- 12/2015
- Academic Unit
- Earth and Environmental Sciences
- Record Identifier
- 9984318343102771
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