Exploring Marine Sediments at the OSU Marine and Geology Repository:
A Core Lab Activity
Become aware of the many types of marine sediments found on the seafloor, how we sample them, where we find them, why we find them there and what they can tell us about Earth’s system and its history.
Some geoscientists study how earth has changed over very long periods, on the order of tens of thousands to millions of years. In order to do this, they need to cut a slice through the earth to see how layers of rock and sediment have built up over time. By studying the physical and chemical properties of the layers revealed in these slices, they can get a sense of how geologic conditions have changed at that particular place on Earth.
One way to get access to geologic records is to find an outcrop. This is a location where a hillside has been cut away or fallen away, revealing earth’s interior. For example, when you drive on mountain roads you can often see outcrops at places where the mountain was cut away to make way for the road. Rock quarries and river banks are other places where we can find good outcrops. However, sediments on land are eroded and modified by vegetation; a better record can be found at the ocean floor.
To collect sediment from the ocean, we need to take cores of rock and sediment in order that will give us a cross-section through Earth’s history. Two common ways in which we collect ocean cores is by coring and by scientific ocean drilling.
Coring: Box cores, multi cores, piston cores, vibracores, kasten cores, and push cores are different methods scientists use to collect samples of the seafloor. These techniques collect cores to a maximum of 30-60 m when piston coring is used. To learn more about these methods you can visit the virtual repository at http://osu-mgr.org/virtual-repository-tour/
Scientific ocean drilling: Ocean drilling using a rotary drill bit can penetrate more than 2000 m below the seafloor and can collect both sediment and hard rock cores. To view how this is done, you can visit the information provided by the International Ocean Discovery Program (IODP) at https://www.youtube.com/watch?v=wC9lDPvvze0
Types of Marine Sediment:
As you will see in this lab activity, there is a wide range of sediment types found in the world’s oceans. A summary of the marine sediments found in the cores of this lab activity is provided here. You may want to refer to these core descriptions as you work through this activity.
There are three components to this lab:
Part 1: You will learn how science advances using an example from an IODP (International Ocean Discovery Program) expedition with geoscientists studying marine sediments to reconstruct climate changes in the past.
Part 2: You will learn how to describe and interpret sediment cores using local Oregon samples from OSU’s Marine and Geology Repository.
Part 3: You will interpret cores on your own and place them into context of the global distribution of marine sediments, in order to understand the processes that led to their deposition.
As you work through this 3-part lab, answer the questions provided on the lab write-up. Your instructor may have you complete this by hand or to submit online. View lab write-up here.
PART 1: How Science Works
Watch the following youtube video “How Science Works” highlighting the process of science during an IODP expedition: https://youtu.be/JH0_xC7q9tU
After watching the video, answer questions 1-2 on your lab write-up.
PART 2: Tour of Four Oregon Cores
The OSU Marine and Geology Repository houses over 12,000 cores from around the world’s oceans. Researchers use these cores to explore all kinds of questions about Earth’s history. Part 2 of the lab focuses on just four of these cores- four cores that were collected in Oregon by OSU researchers and students. Follow the link below to learn about these cores, then answer questions 3-7 on your lab write-up.
PART 3: Explore a Core
Now that you have learned about how scientists study cores, it’s time for you to explore some cores on your own. The links below highlight 3 additional cores at OSU-MGR. Click on each link to see data about each core. As you do so, complete the table in question 8 of your lab write-up. If you need help, refer back to the background information of this lab activity
Below is a map showing a generalized distribution of sediment types around the world’s oceans (figure from Brown et al. 1989). The map also gives the locations of 5 cores at the OSU-MGR. Considering the information you filled out in the table, which location best fits each of the cores? Explain your answer in Question 9 on the lab write-up.