Siliceous oozes are sediments dominantly composed dominantly of SiO2 (silica).
Two dominant groups of organisms that contribute siliceous remains: diatoms and radiolarians.
Diatoms are the most common plankton. Diatoms are phytoplankton (single-celled microscopic marine plants).
• Diatoms are most common in polar regions, but are also know from tropical and subtropical regions as well.
• Very important for upwelling nutrients (where deep water rich in .
• Diatoms have many economic uses including in beer filters, pool filters, and optical glass.
A radiolarian is a single-celled aquatic animal (zooplankton) that has a spherical, amoeba-like body with a rigid spiny skeleton of silica. There are hundreds of known species of radiolarians (See a list on radiolaria.org website).
Figure 6.85 is a photomicrograph depicting the siliceous tests of ten species of marine radiolarians.
Upon death, their tests can accumulate on the seafloor and form siliceous marine sediments known as radiolarian ooze (a form of siliceous ooze). Radiolarians first appear in the geologic record in early Cambrian time and have experienced several periods of proliferation and extinctions as recorded in the geologic record.
Today, radiolarians are more common in equatorial regions.