Initial Publication Date: August 18, 2014

Analyzing Sediment Cores

Part B: Observations from the Core Lab: Gathering Evidence to Solve a Climate Mystery

It's time to put your observational skills to work and collect some data! You will be examining a section of core that was retrieved from ~260 meters below the seafloor to ~360 meters below the seafloor from site U1417B.

As a sedimentologist in the ship's Core Lab, it is your responsibility to make detailed observations on different features that you see throughout the section of core. Keep track of your observations in your notebook or on the table provided by your instructor. Pay close attention! The observations you make here will provide you with evidence about the Earth's changing past!

As you examine the core, try to answer the following questions:

1. How have environmental conditions in in the Gulf of Alaska changed during the time when the sediments in this core were deposited?

Remember, indicators of environmental change include differences in the type of sediment being deposited, changes in the flora and fauna as documented by microfossils, and evidence of bioturbation.

2. What does the occurrence of different types of diatoms microscopic unicellular marine or freshwater colonial alga having cell walls impregnated with silica. (plants) and their abundance in the core reveal about the timing of the cycles of the advance and retreat the glaciation?

Lab Procedure

The Core Lab from TERC & informmotion

*This video replaces a Flash interactive.

1. Obtain the Sedimentology Data Sheet from your instructor or download it here. (Acrobat (PDF) 42kB Nov3 21)

2. You will use The Core Lab visualization to examine a section of core from site U1417B.

3. Make sure the "Hide" button is clicked under "Core Feature Rollovers".

4. Begin at the top of the core (in younger sediments), and scroll down through the core. Be sure to note any interesting sedimentary features you encounter (including grain size variations, evidence for life, etc.) on the Sedimentology Data Sheet, below. You may refer back to the "Core Description Glossary" to help identify different features, if needed.

5. After you have made some initial observations, click the "Show" button under "Core Feature Rollovers." Use your mouse to scroll over the square magnifying glasses (ignore the round magnifying glasses for now). These rollover boxes contain valuable information about sedimentary features in the core. Be sure to note any additional observations on your data sheet. (Refer to The Core Lab video below for this step.)

The Core Lab from TERC & informmotion

*This video replaces a Flash interactive.

Stop and Think

5. Based on your observations of the sedimentary features in core U1417B, what can you infer about the environmental conditions in S. Alaska during the period when these sediments were deposited?

6. Using your initial observations from the core, test the hypothesis that Earth's climate has changed in the Gulf of Alaska during the time the sediments were deposited.

7. Were all the sediments in this section of the core deposited under the same climatic conditions? Explain your reasoning, citing evidence from the core.