HR: 14:00h
AN: B23C-02    [Abstracts]
TI: Microbialite Formation across Chemical and Photosynthetic Gradients in Pavilion Lake, BC
AU: * Slater, G F
EM: gslater@mcmaster.ca
AF: McMaster University, 1280 Main St. West, Hamilton, ON L8S 4K1 Canada
AU: Lim, D S
EM: dlim@arc.nasa.gov
AF: NASA Ames Research Center, Building 245, MS 245-3, Moffet Field, CA 94035 United States
AU: Laval, B
EM: blaval@civil.ubc.ca
AF: University of British Columbia, 2324 Main Mall, Vancouver, BC V6T1Z4 Canada
AU: Schulze-Makuch, D
EM: dirksm@mail.wsu.edu
AF: Washington State University, Webster Physical Sciences #1148, Pullman, WA 99164 United States
AU: Airo, A
EM: aairo@stanford.edu
AF: Standford University, Building 320, Stanford, CA 94305 United States
AB: Large, varied microbialite carbonate structures occur in Pavilion Lake, BC, Canada. Variations in the occurrence and form of these carbonate structures occur concurrently with the gradient in photosynthetically active radiation (PAR) that occurs in the lake which has led to the suggestion that these microbialite carbonate structures are the result of photosynthetic activity. However, the primary water source for the lake is the local groundwater that recharges through the limestone of the local limestone bedrock. Steep gradients in geochemical conditions at the sediment-water interface (SWI) where this water discharges into the lake may also be capable of precipitating carbonates. The goal of current research is to use isotopic and geochemical tracers to determine the mechanism of formation of the carbonate structures in the lake and the interplay between the microbial communities and the carbonate structures which occurs across the gradients of PAR and geochemistry at the SWI of the lake. Samples of surface and groundwater chemistry and isotopic composition show distinct differences between regional groundwater and surface lake water indicating a steep gradient at the SWI. Isotopic analyses of carbonates from the structures show permil variations in ¹³C for different zones of the carbonate structures that are associated with different levels of microbial activity. Phospholipid fatty acid (PLFA) analysis of the structures show a mixed microbial community comprised of both phototrophic and heterotrophic components. Ongoing ¹³C and ¹⁴C analysis of dissolve inorganic carbon, carbonates and PLFA will further constrain the relative roles of biotic and abiotic processes in the formation of these unique carbonate structures and the residual biomarkers associated with them that may play a role in interpreting geologic carbonates and their formation on earth and potentially on Mars.
DE: 0406 Astrobiology and extraterrestrial materials
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0419 Biomineralization
DE: 0424 Biosignatures and proxies
DE: 0454 Isotopic composition and chemistry (1041, 4870)
SC: Biogeosciences [B]
MN: Fall Meeting 2005