Initial Publication Date: August 18, 2014

Analyzing Sediment Cores

Part D: Observations from the Core Lab: Working in the Paleontology Lab

Collaboration and teamwork are essential for a successful expedition and critically important for determining the ages of sediments while on board the JOIDES Resolution. Determining sediment ages requires constant communication between the paleomagnetists and micro paleontologists onboard the ship.

Microscopic organisms, such as diatoms, radiolarians, and foraminifera, living in the ocean can reveal a great deal of information about past conditions on earth. Since some of these organisms live during relatively short periods of time they can be used to determine the approximate ages of sediments. The types and abundance of microscopic organisms living in the ocean changes when the climate changes. Therefore, the presence or absence of certain types of microfossils in sediments can also reveal information about past climate.

Analyzing microfossils: refining your age estimate

Your case is coming together nicely, but you need more evidence and data to accurately define the ages of sediments at site U1417. You will return to "The Core Lab" visualization, and this time you will take on the role of a paleontologist. As a paleontologist you will examine and note the presence and/or absence of microfossils, and the types of microfossils that you see. The types of microfossils preserved at site U1417 are diatoms (phytoplankton microscopic floating plants, mainly algae, that live suspended in bodies of water and that drift about because they cannot move by themselves or because they are too small or too weak to swim effectively against a current. ) and radiolarians protozoa with amoeba-like bodies and radiating filamentous pseudopods (latin for false feet). and may be helpful for in determining sediment ages or other environmental conditions at the time of deposition.

Lab Procedure

  1. Click on the "Show" button under "Core Feature Rollovers" in order to see the microfossils.
  2. Scroll through the core and examine the microfossils present throughout the core in the round rollover hotspots.
  3. Use the table provided by your teacher (Table 3: Microfossil Data Sheet (Acrobat (PDF) 53kB Nov4 21), a sample is pictured below), to keep track of the types and abundance of microfossils present. Record your data in order from youngest (top of core) to oldest (bottom of core).
  4. Be sure to note interesting information that could provide evidence for the age of the sediments or past climatic conditions.

The Core Lab from TERC & informmotion

*This video replaces a Flash interactive.

Stop and Think

12. How do the types and abundance (total number) of microfossils change throughout the length of the composite core?

13. What do the types and abundance of microfossils reveal about the climate when these sediments were being deposited?

14. Based on microfossil and paleomagnetic data, what is your best estimate for the relative ages of the sediments from site U1417B? Support your answer with evidence from the core.


As you observed in Part B of this activity, there is a distinct change in the types of sedimentary features present throughout the core. Find the point in the core that you started to observe a change in the sedimentary features, and determine the age of the sediments where this change started to occur. Compare your age of the sediments to the Neogene-Quaternary timeline.

  • What events were occurring at this time in the Earth's history?
  • What inferences can you make about the Earth's past climate in the Gulf of Alaska from the microfossils and sedimentary features you have observed?

Explain how your evidence compares to global climatic events.