Microbialites in a high-altitude andean lake: multiple controls in carbonate precipitation and lamina accretion

Abstract

Microbialites comprise the mineralized record of early life on Earth and preserve a spectrum of fabrics that reflect complex physical, chemical, and biological interactions. The relatively rarity of microbialites in modern environments, however, challenges our interpretation of ancient structures. Here we report the occurrence of microbial mats, mineral precipitates, and stromatolitic oncolites in the Laguna Negra, a high-altitude Andean lake in Catamarca Province,Argentina. Extreme environmental conditions, including high UV-radiation, salinity, and temperature extremes, restrict multicellular life so that mineralization reflects a combination of local hydrologic conditions, lake geochemistry, and microbial activity. The resulting carbonate microtextures are strikingly similar to those observed in Proterozoic stromatolites, providing insight into potential mechanisms of mineralization. Here, increased saturation in carbonate minerals due to mixing of spring-fed inlets and lake waters favors microbialite formation and preservation. This highlights the importance of hydrological mixing zones in microbialites formation and as taphonomic windows to record microbial activity. Recent discoveries of minerals related to evaporating playa-lake systems on Mars further highlights the potential of Laguna Negra to provide critical insight into biosignature preservation in both terrestrial and extraterrestrial settings.