PRESERVATION OF MICROBES IN HALITE: A COMPARISON OF PERMIAN AND MODERN EPHEMERAL ACID SALINE LAKE DEPOSITS

Identifying microbes in ancient deposits presents a number of challenges, including ruling out sample contamination and alteration. However, primary, unaltered fluid inclusions in halite crystals provide an ideal microenvironment for rapid entrapment and preservation. We present preliminary results of our analysis of suspect microbes within fluid inclusions in halite from ephemeral acid saline lake deposits from the Permian Nippewalla Group (likely Leonardian/Kungarian, ~275 million years ago) from a core drilled in western Kansas. We also compare our observations to microbes preserved within fluid inclusions in modern halite from environmentally-analogous acid saline lakes in Western Australia. Plane transmitted light microscopy was used to determine the size, shape, and color of suspected microbes, and cross-polarized light was used to further differentiate putative microbes from minerals. Additionally, UV-vis light microscopy was used to observe autofluorescent response of suspected microbes. Laser Raman microscopy was used to confirm compositions of both suspected microbes and organic compounds. Prokaryotes and eukaryotes are well-preserved in fluid inclusions in modern halite. Prokaryotes range in size from 1 to 2 microns in diameter and exhibit both rod and cocci shapes. Larger, 4 to 6 microns in diameter, yellow, sub-spherical eukaryotes surrounded by thin gel-like films are suggestive of Dunaliella algae. Microbes in modern halite exhibit blue-green fluorescence. Organic compounds, identified by laser Raman analysis as carotenoids, fluoresce orange in UV-vis light. In comparison, suspect microbes in Permian halite range in size from 1 to ~10 microns, are typically sub-spherical, and vary from colorless to dark red. Autofluorescence is common, and includes yellow, orange, and green. Yellowish-orange crystals, possibly carotenoids, are commonly associated with suspect microbes. Laser Raman analysis of Permian suspect microbes is hindered by the bright fluorescence of suspect objects. Similar to modern acid-precipitated halite, Permian halite from the Nippewalla Group also preserves 'hairy blobs', organic features interpreted as clumps of sulfate crystals and acidophilic and halophilic bacteria, archaea, and fungi.