Fossil group

Calcareous nannofossils

Microflora & algae · Triassic – Recent

Microscopic calcite plates (coccoliths) shed by single-celled marine algae. They settle in vast numbers to build chalk and deep-sea ooze, and their rapid turnover makes them key index fossils for marine strata since the Triassic.

A broad fossil group rather than a single taxon — the units below record it among their fauna or flora.