[X] My Assistant

[aldo12xu]

With the Spirit rover sitting in one spot, it's given me a chance to come up with an updated summary of the various Gusev and Columbia Hills rock types, geochemistry and latest geological interpretations. There have been several good papers but there hasn't been one comprehensive paper to put everything together (that I know of). And the one key component to interpreting the data that is still missing is a detailed structural model of the Columbia Hills. Nevertheless, I've tried my best to make sense of all the various information out there.

There are still a number of uncertainties and inconsistencies -- which are open to discussion here -- but in general terms I think this is the stratigraphic sequence we're looking at, with various alteration processes overprinting this stratigraphy:

ADIRONDACK basaltic flows related to the volcano Appollinaris Patera, 300 km to the north
BACKSTAY & IRVINE late stage mafic intrusive dikes cut through all Columbia Hills units
HOME PLATE maar type volcanism emplaced through Columbia Hills, interacting with groundwater
DESCARTES, CLOVIS & WATCHTOWER meteorite impact ejecta deposits mixing different rock types
INDEPENDENCE & WOOLY PATCH phyllosilicates derived from chemical weathering of volcaniclastics
WISHSTONE tuff or pyroclastic deposit (impact origin not fully discounted*)
PEACE sandstone produced by wind erosion of older ultramafic units
SEMINOLE mafic to ultramafic intrusive or extrusive rocks

The link to the summary is on my homepage.

[aldo12xu]

Thanks for the link. tglotch. It's a very comprehensive resource and I've added it to my links page, which I've recently expanded. I assume you were referring to the Powder X-Ray Diffraction page that has "mineral compositions in terms of major oxide phases, e.g. what APXS gives us on Mars"