Forams in the Ocean Drilling Program
JOIDES Resolution, one of the IODP research vessels.
The IODP is an international research program dedicated to studying the history of the Earth by drill sampling beneath the sea floor. IODP drillers collect long tubes of rock called cores that researchers analyze in depth.
The fastest and most cost efficient way to determine the age of a sample is by biostratigraphic correlation - using tiny fossils, such as forams, to identify the age. Researchers are able to determine the age by looking at the set of foram species that are found together. Scientists can say with confidence that particular sets of foram species are evidence of particular geologic time periods, because of all the painstaking work done previously on individual species (see Foram Evolution).
How does the researcher determine the age of a sample onboard the IODP ship? First, a small sample is taken from the core and placed in a mesh sieve. Running water washes away the mud and sediment leaving behind only the tiny foram tests. Next, the tests are examined under a microscope and the foram species are identified based on their characteristic test shape. The age or "biozone" of the sample is assigned by looking at the set of species present in that sample.
Paleontologists Mark Leckie (foreground) & Jason Eleson (background) work on assigning ages to a core. (Credit: Integrated Ocean Drilling Program, http://www-odp.tamu.edu/public/life/index.html)
Biostratigraphic correlation is useful not only to date samples within a single drill hole, but its real power comes from dating samples between drill holes. Let's say we have the same biozone in hole #1 and hole #2. This means that sediments deposited at the same geologic time period are present in both drill holes. If you find the same biozone in many different wells, the geologist can construct maps to picture how the earth looked during that geologic time period.
Would you like to see how maps like this are made?
Go to Forams in the Petroleum Industry to find out more!
Revised on: January 3, 2005