The occurrence of calcified planktonic green algae in freshwater carbonates

Phacotus and Coccomonas, two carbonate-secreting, non-marine, planktonic chlorophyte genera, are important sediment contributors mainly in hard water lakes. The calcite loricae of these flagellate algae exhibit characteristic features easily recognizable under the microscope, making Phacotus and Coccomonas important facies fossils for the recognition of ancient non-marine environments. The fossil record of Phacotus can be traced back to the Miocene and it is probable that further research could extend this record into pre-Tertiary periods.