Passage VII

Glaciers deposit till (a poorly sorted sediment). If glaciers repeatedly advance over an area and then melt back, thick till deposits may form. Figure 1 shows a vertical core taken through layers of till, non-glacial sediments, and bedrock at a site in Canada. The resistivity (an electrical property of a material) and CO2 measurements taken along the core are also shown. Resistivity is related to a sediment's particle sizes, compaction, and mineral composition. Table 1 shows the average percent sand, silt, and clay contents and descriptions of the various till layers.

Figure 1 and Table 1 adapted from E. A. Christiansen, "Pleistocene Stratigraphy of the Saskatoon Area, Saskatchewan, Canada: An Update." ©1992 by the Geological Association of Canada.

40. The sediments being deposited at the present time at the site where the core was taken have a much higher CO2 content than any of the tills. Given this information and the information in Figure 1, the CO2 content of sediments recently deposited at the site would most likely be in which of the following ranges?

Answer and Explanation

Your Answer is

Correct Answer is J

Explanation

The content of CO2 is larger than that of other sedimentary layers in the middle of the title. According to figure 1, the largest CO2 content in the figure is about 35 mL/g , so it should be greater than 35 mL/g