Why are Forams Important?

Cluster of planktonic forams (Credit: NOAA Paleoclimatology Program, US Department of Commerce)

Foram tests have six key characteristics that make them useful to scientists.

1. Small

Foram tests are typically about the size of a grain of sand or smaller. Scientists who study marine geology often only have small samples of material to work with, such as from a piston core. Consequently, in these small samples a small fossil is much more likely to be present and undamaged than a big fossil would be.

2. Abundant and geographically distributed

Foram tests are common constituents of marine sediments, and they have been common for a long time. In some instances, tests can accumulate in such great numbers (sometimes in thicknesses of up to 1km!) that the marine rock is named after them. These rocks are called foraminiferal oozes. Even if they are not found in this abundance, a few tests in a single sample can help guide scientists in their work.

3. Test shape and size differs through time

Foram tests have differed through the ages. Scientists built on this fact, and learned to tie specific test shapes to specific time periods. This knowledge permits them to estimate a sample's geologic age without having to perform expensive and time-consuming absolute age-dating analyses. In addition, scientists have also tied specific test shapes to water depth. Some tests are found only in shallow water environments; others in moderate depths, and still others are found only in deep water environments.

4. Existed for more than 500 million years

Forams first appeared in the rock record during the Cambrian geologic time period and they are thriving today. Because their record is so long in duration, it is easier to recognize changes in test shape, species abundance and species distribution.

5. Short reproductive cycles

The reproductive cycle for modern forams is relatively short (6 months to 1 year), making them particularly useful to scientists looking for pollution-related growth deformities.

6. Trace element chemistry preserved in test

As forams construct their test, trace elements may be scavenged from the water column and incorporated into the test wall. These elements tell scientists about ocean water chemistry and temperature at the time the test was formed.


Yanko, V., Arnold, A.J., Parker, W.C. (1999). Effects of marine pollution on benthic Foraminifera. In Sen Gupta, B.K. (ed.) Modern Foraminifera, Kluwer Academic Publishers, Great Britain, p. 217-235.