Why are Forams Important?
tests have six key characteristics that make them useful to scientists.
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.
Abundant and geographically distributed
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.
See how piston cores are collected
Cluster of planktonic forams
(Credit: NOAA Paleoclimatology Program, US Department of Commerce)
Test shape and size differs through time
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.
Existed for more than 500 million years
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
cycle for modern forams is relatively short (6 months to 1 year), making
them particularly useful to scientists looking for pollution-related
Trace element chemistry preserved in test
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
How do marine geologists use forams to determine geologic age?
Go to Forams for Correlation to find out!
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.
January 2, 2005