Reconstructing Earth's Climate History. Kristen St. John
left to right. Section 1 of Core 2 is at the top of the drilled interval, and the core catcher (CC) is at the bottom of the cored interval. The shipboard paleontologists took a sample (PAL) from the base of the core catcher to provide a preliminary age determination for Core 2. Site 1215 was cored during Ocean Drilling Program Leg (i.e. Expedition) 199. Note that an interstitial water sample (IW) was taken from the bottom of Section 3. Photo from: http://iodp.tamu.edu/database/coreimages.html
5 Site 1215 was planned for 57.5 hours of drilling during Expedition 199. During this time, they were able to drill 75.4 m into the seafloor at a single location (Hole 1215A). What was the average drilling rate (m/hr) for Hole 1215A? Show your work.
6 While they drilled 75.4 m into the seafloor at Hole 1215A, they only recovered 68.27 m of core. What was the percent core recovery for Hole 1215A? Propose a hypothesis to explain why core recovery would be less than the maximum drill depth.
7 A typical ocean drilling expedition lasts ~60 days and costs ~$6 million. At Hole 1215A on ODP Leg 199, 68.74 m of core were obtained during the 57.5 hours of drilling. What is the cost of 1 m of core from Hole 1215A? Show your work.
8 Sometimes scientific ocean drilling and NASA space exploration are compared because these are both large‐scale, technologically dependent programs that are designed to help teams of scientists unravel the history of Earth and our solar system by exploring in remote and challenging settings. Compare the cost of obtaining a core from the seafloor to the cost of obtaining rocks from the moon:The Apollo 11 mission cost $355 million in 1969. Approximately 21.8 kg of moon rock were obtained on this successful and historic mission to the moon. What was the cost of 1 kg of moon rock in 1969? Show your work.When you calculated the cost of a seafloor core in #26 it was the cost per meter of core. To make a comparison to the cost of the moon rock, we need to determine the cost per kg of core (so we will need to convert units). Use your skills in geometry to figure this out: The average density of cores from Hole 1215A is ~1.3 g/cm3. The core is a cylinder with a radius of 3.5 cm and a length (or height) of 1 m (100 cm). The volume of a cylinder is equal to πr2h. Recall from #26 that a scientific ocean drilling expedition is typically 60 days and costs ~$6 million. What is the cost of 1 kg of core? Show your work.How does this compare to the cost of 1 kg of moon rock?
Part 1.3. Owens Lake – An Introductory Case Study of Paleoclimate Reconstruction
Earlier in this chapter, you were introduced to a range of terrestrial and marine archives of past climate change. Here, the Owens Lake sediment core record will serve as an introductory paleoclimate case study; you will describe and interpret the clues that this archive and its proxies can offer us about climate in western North America over the past 800 000 yr.
1 Use your library resources and/or the online supplement to read A Record of Climate Change from Owens Lake Sediment by Kirsten Menking. This is a chapter from the 2000 book The Earth Around Us: Maintaining a Livable Planet, edited by Jill Schneiderman.Then use the space on the next page to:Make a visual representation (i.e. a sketch) of the Owens Lake sediment core. Use different patterns or colors to represent the different layers described in the article, with the oldest at the bottom and the youngest at the top.Adjacent to your sketch, list the types of proxy data (e.g. salt layer, pebbles, ash, microfossils,…) obtained from the different intervals of the core.Next to the list of proxies, give an interpretation of the data with respect to past climatic and/or environmental conditions (e.g. dry, cold, volcanic eruption,…).
2 What are three methods used to determine age within the lake core?
3 What evidence is there that part of the Owens Lake record is missing (i.e. that a hiatus exists)?Workspace for Question 1:Sketch of coreType of data analyzedPaleoclimatic/environmenta interpretation of that data
4 What could cause layers of lake sediment to be missing from the record?
5 What evidence would support the hypothesis that humans impacted the environment in and/or around Owens Lake?
6 Use Owens Lake to explain why a multiproxy approach is valuable in reconstructing past climatic and/or environmental change:
References
1 Bender, M., Sowers, T., and Brooke, E. (1997). Gases in ice cores. Proceedings of the National Academy of Sciences of the United States of America 94: 8343–8349.
2 Cronin, T. (1999). Principles of Paleoclimatology, vol. 592. Columbia University Press.
3 Menking, K.M. (2000). A record of climate change from Owens Lake sediment. In: The Earth Around US: Maintaining a Livable Planet (ed. J.S. Schneiderman), 322–335. New York: W.H. Freeman and Company.
4 Ruddiman, W.F. (2008). Earth's Climate Past and Future, 2e, vol. 388. Freeman.
Chapter 2 Seafloor Sediments
FIGURE 2.1. Kelsie Dadd (Sedimentologist, Macquarie University, Australia) and Mea Cook (Sedimentologist, Williams College, USA) describe the sediment color of a core section from Site U1340 in the Bering Sea.
Photo credit: Carlos Alvarez Zarikian, IODP/TAMU; Photo ID: exp333_083; http://iodp.tamu.edu/scienceops/gallery.html.
SUMMARY
This chapter explores marine sediments using core photos and authentic datasets in an inquiry‐based approach. Your prior knowledge on seafloor sediments is explored in Part 2.1. In Part 2.2, you will observe and describe the physical characteristics of sediment cores. In Part 2.3, you will use composition and texture data from smear slide samples taken from the cores to determine the lithologic names of the marine sediments. In Part 2.4, you will make a map showing the distribution of the primary sediment lithologies of the Pacific and North Atlantic Oceans and develop hypotheses to explain the distribution of the lithologies shown on your map.
Learning Objectives
After completing this chapter, you should be able to:
1 Describe the physical characteristics of sediment cores (Figure 2.1).
2 Identify major sediment components and their origin.
3 Use composition and texture data from smear slide samples to determine the lithologic names of the marine sediments.
4 Make a map showing the distribution of the primary modern sediment lithologies of the Pacific and North Atlantic Oceans.
5 Explain the distribution of modern marine sediments on your map.
6 Accurately predict what the modern sediment lithologies are at other locations on the seafloor (e.g. in the Indian Ocean).
Part 2.1. Sediment Predictions
1 What kinds of materials do you expect to find on the seafloor?
2 Do you expect any geographic pattern of these materials in the global ocean? Explain