Hot springs microbes hold key to dating sedimentary rocks
From Physorg.com, an example of biogeochemistry where microorganisms contribute to the deposition of sediments. Looking at Angel Terrace in Yellowstone National Park, the rate of precipitation of calcium carbonate (CaCO3) was reduced when there was not microbes. So depending on the layers of limestone, the age of the rock can be determined. Also, the microbes seem to create a pattern in the calcium carbonate crystals.
