Biostratigraphic analysis using diatoms applies to both freshwater and marine systems and can offer age-dating information back into the Cretaceous, in the right sediments. Other algae groups with mineralized parts can also be used for biostratigraphic analysis, such as the figure illustrating the ranges of some calcareous nannofossils show below. Chrysophyte algae have siliceous scales on the vegetative cells and form siliceous cysts at times which can also offer biostratigraphic and environmental information.
Calcareous Nannofossil Biostratigraphy, ODP Leg 178, Hole 1196