See more from this Division: Topical Sessions
See more from this Session: Microbialites: A 3.5-Billion-Year Record of Microbe-Sediment Interactions
Abstract:
Isotopic analysis of 13C and 14C of surface water Dissolved Inorganic Carbon (DIC), porewater DIC, groundwater DIC and associated carbonate minerals indicates that the primary source of carbon is from the atmosphere with a 12-26% input from groundwater/subsurface sources. 14C analysis further demonstrates that these microbialites are actively growing at a rate of 6 cm/thousand years over the last thousand years.
Stable isotopic fractionation between surface water DIC and microbialite surface carbonate showed 13C-enrichments of up to 2 above predicted equilibrium carbonate values. These observations are indicative of biologically induced 13C-enrichment of the residual DIC pool due to photosynthetic activities. Such enrichment has the potential to be preserved in ancient carbonate structures. However, up to now δ13C values of interior carbonates from the microbialites have shown no evidence of similar isotopic enrichment suggesting that this signal may not be preserved. Microscopy to determine the physical relationship between microbes and precipitated carbonate and the crystal form of the carbonate minerals may elucidate this potential for remineralization and loss of isotopic biosignatures.
See more from this Division: Topical Sessions
See more from this Session: Microbialites: A 3.5-Billion-Year Record of Microbe-Sediment Interactions