Where in NZ Well preserved in fine-grained marine sediments
When Triassic (200 million years ago) to present
Scale 20 – 200 µm

What are they?

  • Marine or fresh-water unicellular algae that possess two flagella which move them through the water, and have a variety of lifestyles.
  • Most are planktonic, living in the surface waters of seas and, less commonly, lakes where they are an important part of the food chain.
  • The majority are plant-like, containing chloroplasts and feeding by photosynthesis. The remainder are heterotrophic and feed on other organisms.
  • The motile dinoflagellate wall (or theca) is quickly destroyed by bacterial action after death, but the resting cyst is composed of highly resistant organic material and is often fossilized.

Used for?

  • In biostratigraphy for dating marine and terrestrial sediments
  • Correlating strata both within and beyond New Zealand (Australia and Antarctica) by looking at evolutionary changes such as speciation and extinction events.
  • Understanding changes in the ocean environment and climate.

See some examples in our image gallery.