- Radiolarians spend their lives suspended in the sunlit layers of the ocean, forming part of the zooplankton population. They exist to one degree or another from the equator to the Arctic and Antarctic. They subsist on other zooplankton and algae, forming rigid silica shells. When they die, their shells sink to the ocean floor, forming wide bands of sedimentary deposits rich in silica. As they are buried by succeeding layers of sediment, they become embedded in layers of sedimentary rock.
- Layers of fossilized radiolarians are present in most layers of marine sediment, which includes strata present in many modern landmasses that were formerly submerged. Various species of radiolarians regularly arise and go extinct throughout the fossil record. Since they are so widely preserved and well-documented, radiolarians are used as a marker to help pinpoint the age of specific strata. This can provide valuable context for more isolated fossil forms.
- Some periods of geological time were more likely to produce rich oil deposits than others, depending on climate, the configuration of the continents and common forms of life. By examining layers of radiolarians, geologists working in the field of oil exploration are able to link areas of explorations to specific epochs and oceanic conditions. Just as paleontologists use radiolarian deposits to date fossils, petroleum geologists use them to orient themselves in geological time when drilling exploratory bores.
- The concentrations of radiolarians, as with most forms of zooplankton, are markedly higher at the equator than in the colder oceans of the Arctic and Antarctic. By studying the concentration of radiolarian populations at various oceanic temperatures, climatologists are able to extrapolate the state of the Earth's climate at the time various radiolarian deposits were formed. Higher temperatures would result in wider bands of radiolarian ooze, while ice ages would restrict rich radiolarian deposits to more equatorial areas.
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