Kristen St. John - Reconstructing Earth's Climate History

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:

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.

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.

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 characteristicsof sediment cores. In Part 2.3, you will use composition and texture datafrom smear slide samples taken from the cores to determine the lithologic namesof the marine sediments. In Part 2.4,you will make a mapshowing the distribution of the primary sediment lithologies of the Pacific and North Atlantic Oceans and develop hypothesesto 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).

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 your reasoning.

In this exercise, your instructor will assign you one or more cores from Table 2.1 . A corresponding photo of each core can be accessed in the supplemental resources.Note that all of the cores in Table 2.1are either core numbers 1, 2, or 3. This means that these cores are at or close to the top of the sediment sequence on the seafloor. Therefore, the sediment in these cores represents modernor very recent environmental conditions at that location in the ocean. For a review of the nomenclature for core identification, see Chapter 1, Part 2( Figures 1.10and 1.11).

TABLE 2.1. Seafloor cores.

1The letter indicating the type of drilling (e.g. A for advanced piston coring) is not always included in the core identification (Column 1 of Table 2.1). This is because early on in the drilling program, there was only one type of coring (rotary), and thus no special notation was needed. Core identification in Table 2.1will match the core identification on the related core photos, which are accessible in the online supplemental materials.