Petrography Reveals That Acid-Precipitated Halite and Gypsum Preserve Small Fossils Well

Evaporite minerals can grow rapidly at and near the Earth's surface, effectively trapping and preserving bits of hydrosphere, atmosphere, and biosphere. Halite and gypsum that form in modern and ancient acid saline lakes seem to be particularly good fossilizers. Field observations show that halite and gypsum can grow around small organisms while they are still alive. Bacteria/Archea, fungi, algae, diatoms, and insects living in and at these acid saline lakes all become trapped as fossils by the halite and gypsum. In addition, biological material that is physically transported into the environment by winds and floods, such as pollen, spores, leaf fragments, wood, and animal hair, are represented as fossils. Optical petrography serves as the basic identification tool of these fossils. Further simple lab procedures, such as dissolution of halite and gypsum followed by filtering, can extract microfossils for further petrographic examination. Petrography should serve as an initial investigatory method for any study of evaporites for biological remains. Evaporites on Mars should be targeted for microfossil evaluation in the search for possible past life on Mars.