Stromatolites in High-Altitude Andean Lakes of Catamarca Province (Argentina): An Astrobiological Analogue to Life in Extreme Environments?

High-altitude lakes in the Puna region, Catamarca province, Argentina, are an excellent target for astrobiological research. These lakes occur within dominantly basaltic bedrock and, in this highly arid region, receive fluid input primarily from spring snow melt. High rates of evaporation through the rest of the year result in concentration of lake waters mineral precipitation within an extensive microbial mat system. Mineralization within these lakes results in the preservation of a wide variety of stromatolitic morphologies, including laminar mats, interconnected low-relief mounds, and isolated mounds with generally high relief. In cross section, mineralized mounds revel distinct banding in both color and texture, implying differential influences from biology and ambient fluid chemistry during growth. At present, however, there exists no baseline information about either the lake chemistry, biotic assemblages, or mineralized precipitates.

The superb organic and mineral preservation of these microbial carbonates greatly increases the potential for microscopic textural, biological, and geochemical attributes to be preserved. Initial mapping of the Puna lake region was undertaken in May 2008 (Argentian winter) and was accompanied by detailed sampling of water chemistry (temperature, pH, total alkalinity, dissolved oxygen), bedrock samples, lake soils, and mineralized microbial mats. Here we present initial results of our study, including geochemical and isotopic analysis of lake waters; high-resolution petrographic, geochemical, and isotopic analysis of mineralized precipitates; and initial morphological identification of microbial elements. Ultimately, we expect more detailed analysis of organic material and a multi-seasonal sampling of the Puna lakes to help us understand the environmental conditions in which these microbial deposits developed and the relative roles of lake chemistry and microbial communities on precipitation of mineral components. Such integrated study of these recent microbial carbonates will improve our understanding about similar deposits developed during early Earth history and could help to develop strategies and tools for astrobiological purposes.