BIOSEDIMENTOLOGY OF THERMAL FEATURES OF THE UZON CALDERA, KAMCHATKA, RUSSIA

Modern hot springs provide a habitat for microorganisms that are similar in metabolism, morphology, and cellular structure to the organisms that existed relatively early in Earth’s history. These organisms provide architectural framework for the deposition of silica, and thus leave their trace in the form of microfossils and sinter fabrics. These traces of the original microbial community are known as biosignatures and an understanding of the formation of these modern biosignatures increases our ability to interpret the microbial interactions that contributed to the characteristics of the ancient analogs. Analysis of the role of microorganisms in the formation of sinter fabric is essential to our understanding of the evidence for early life provided by stromatolites. While stromatolites have long been considered important biosignatures, recent research indicates that many features of stromatolites may form in the absence of biology. Further elucidation of the role that microorganisms play in the development of modern sinter fabric is essential for us to distinguish biotic and abiotic stromatolites in the rock record.

The Uzon Caldera, on the Kamchatka peninsula of far eastern Russia, is home to a wide variety of hot springs of disparate temperature, pH, geochemistry, and microbiology. Analysis of the biosedimentology of hot springs with distinct geochemistries in the Uzon Caldera allows for an examination of the role played by microbiology, detrital sedimentation, and authigenic mineral precipitation in the formation and preservation of biofabrics. The potential for the preservation of biofabrics is compared in four of these thermal features, which differ in their level of detrital sedimentation, mineral precipitation, and biofilm development. Examination of biosedimentation in these thermal features involved SEM analysis of the relationship between microorganisms and minerals, thin section analysis of sinter fabric, XRD determination of mineralogy, and optical microscopy of the living mat and biofilm-forming microbial communities.