Micropalaeontology is a discipline of palaeontology mainly concerned with fossils (generally >63 microns) that require microscopes for study including foraminifera, ostracoda, radiolaria and diatoms.
Associated identification of key minerals, fragments of small invertebrates, evidence for bioturbation and drilling artefacts (i.e. mud additive) are also important during analysis. Microfossils have great utility in accurately interpreting the stratigraphic age and environment of deposition.
Foraminifera inhabit most marine-marginal marine environments and are often very abundant, accounting for over 90% of deep sea biomass. They are single-celled protists with an external shell/test composed of calcium carbonate, aragonite or cemented agglutinated grains. They are a principal microfossil group used to age-date and correlate marine sedimentary rocks of Late Palaeozoic, Mesozoic and Cenozoic age. Moreover, planktonic foraminifera which are geographically widespread and have rapidly evolving lineages and some smaller benthonic foraminifera are widely used for regional stratigraphy.
Radiolaria single celled microplankton that produce intricate mineral skeletons usually composed of silica. They are found throughout the ocean systems of the world, and their skeletal remains rain down onto the ocean bed as a siliceous ooze. This group has been present since the Cambrian, and their rapid evolution throughout geological time makes them an excellent biostratigraphic tool.
Ostracods are a class of Crustacea, sometimes informally known as “seed shrimp”. These tiny crustaceans have bivalve-like shells protecting their inner bodies; these shells are chitinous or calcareous, and their preserved remains date back to the early Ordovician. In marine environments, they inhabit the upper layers of the ocean floor sediments. They can also be found in freshwater environments, as well as in humid forest soils in the terrestrial realm. They can be used for biostratigraphic delineation and are also very useful for palaeoenvironmental intepretation, especially when integrated with other groups.
Are a major group of unicellular algae, producing silica skeletons, and living as solitary organisms or as part of colonies. They are photosynthetic, generating around 20% of the oxygen produced on our plant annually. They take a variety of shapes, including; zig-zags, ribbons, fans or stars. Fossil evidence indicates this group originated in the Early Jurassic, and inhabit both marine and non-marine environments. They have undergone rapid evolution making them useful biostratigraphically.
Micropalaeontology has proven to be a reliable biostratigraphic tool for rocks dating ranging from Cambrian to Holocene (modern day).
Microfossils are highly sensitive to environmental changes and can be present from the terrestrial (ostracods and diatoms) to the deep marine (foraminifera, radiolaria, ostracods, diatoms). Therefore, relative changes in a microfossil assemblage composition throughout a section can be a versatile tool to interpret the environment of deposition and distance from palaeo-shoreline.
Principally this is achieved by investigating: