307 Planetary Geology (Posters)

Wednesday, 4 November 2015
9:00 AM - 6:30 PM
Exhibit Hall

ASSESSING THE REACTIVE SURFACE AREA OF SEDIMENTS FROM END-MEMBER CLIMATES: IMPLICATIONS FOR EARTH & MARS

Paper number: 307-23
Program: Technical Sessions
Time: 9:00 AM – 6:30 PM

Authors

Abstract

It has long been assumed that higher rates of chemical weathering are associated with higher temperatures and greater precipitation. However, climate conditions may also affect the reactive surface area of sediments, providing a third control on weathering rates and fluxes. This study investigates the reactivity of terrestrial sediment samples collected from end-member climate regions with similar bedrock lithology (Denton Glacier and Onyx River in the McMurdo Dry Valleys, Antarctica -cold & dry; Anza Borrego, CA, USA - hot & dry; and Puerto Rico -hot & wet) to further understand how climate conditions affect the reactive surface area of fluvial sediments. These results can be applied to sedimentary records on both Earth and Mars to interpret their climate histories.

Sediments were wet sieved and treated to remove organics & carbonates prior to BET analyses of specific surface area. Surface area normalized, single-point batch reactor experiments were used to compare the reactive surface area of sand (125 µm-2000µm) and mud (<62.5 µm) fractions collected in each field area. Sediments from Denton Glacier were an order of magnitude more reactive than sediments from Anza Borrego and Puerto Rico. Puerto Rico sediments were the least reactive, likely due abundant non-reactive clay minerals. Denton Glacier sediments were significantly more reactive than Onyx River sediments collected <20 km downstream, which suggests that the sediments lost reactivity rapidly during transport, likely due to weathering. Denton Glacier sediment produces high solute concentrations due to primary mineral phase weathering, as indicated by high Al & Si solute concentrations. Higher rates of primary mineral weathering than expected within these polar sediments suggest that Mars glacial sediments may also have high reactive surface area, priming them for chemical weathering when liquid water is available, despite low water:rock ratios.