Physics
Scientific paper
Dec 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009agufm.p12a..06a&link_type=abstract
American Geophysical Union, Fall Meeting 2009, abstract #P12A-06
Physics
[0486] Biogeosciences / Soils/Pedology, [1023] Geochemistry / Composition Of The Biosphere, [1824] Hydrology / Geomorphology: General, [5415] Planetary Sciences: Solid Surface Planets / Erosion And Weathering
Scientific paper
The “etched terrain” on Mars is reported to consist of mesas, pits, ridges, etc. formed by differential erosion of layered sedimentary deposits (Griffes et al. 2007). Here we present our work on a unique landscape in northern Chile that possesses many of the features of etched terrain on Mars, offering an Earth-based perspective on the eolian and aqueous processes involved in the formation of these landscapes. The Quillagua-Llamar Basin is largely infilled by Miocene to Pliocene aged lacustrine and salt deposits, and likely represented the terminal, and highly saline, facies of an internally drained river system that originated in the Andes (Sáez et al., 1999). This deposition continues more slowly today, with water, sediment and salts delivered to portions of the basin by streams originating to the east. The surficial deposits in the present Salar Llamara consist of a complex of Tertiary to Holocene alluvial fans and nearly pure Tertiary Ca-sulfate and halite outcrops. Ancient sulfate deposits exhibit complex topography with large (eolian?) depressions and modest soil weathering in the largely hyperarid climate. Fluvial deposits have experienced apparent deflation (relative to the coeval sulfate deposits) of several m, have a pronounced stepped topography caused by differential deflation of soil horizons of sulfate, and exhibit an accumulation of dark fluvial gravels and sand in the deflation zones. Most halite outcrops, in contrast, are highly impacted by frequent fog and quickly develop (~ 103 y) a cobbly or “nut like” surface of halite fragments that undergo repeated hydration and dehydration. The halite cobbles are habitats for abundant photosynthesizing organisms. Isolated saline lakes contain unusual stromatolitic structures. Additionally, halite deposits contain occasional sink holes and caves caused by long term aqueous dissolution of the soluble matrix. Satellite imagery, field observations, and geochemical analyses of the surficial deposits will be presented to provide insights into the origin of this unique landscape and its relationship to Mars. Griffes, J.L. et al. 2007. J.G.R. 112 doi:10.1029/2006JE002811 Sáez, A. et al. 1999. Palaeo., Palaeo., Palaeo. 151:5-37.
Amundson Ron
Chong Guishu
Demergasso Cecilia
Heimsath Arjun M.
Jungers M.
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