Reconstructing Earth's Climate History. Kristen St. John
Note, while the above five marine sediment lithologies are the most distinctive sediment types, mixed lithologies are common (Mazzullo and Graham, 1988). In addition, the lithologies can also change within a core. For example, the sediment could alternate between red clay and siliceous ooze, or gradually change from one to another. In any marine sediment lithology, but especially in biogenic oozes and deep‐sea red clays, layers of volcanic ash may be distinguishable, as a minor lithology.
TABLE 2.2. Smear slide composition and textural data, plus presence/absence of pebbles on core surface. A copy of this table in Excel format can be found in the online Supplemental Resources.
Part 2.4. Seafloor Sediment Synthesis
1 Use the following color scheme to plot the dominant lithologies of the sediment in your core (from Part 2.3) on your base map (Figure 2.2) and on the class base map. For example, sediment that is 100% calcareous ooze would be plotted as a blue circle on the class map. A good way to plot mixed or alternating sediment types is with a simple pie diagram (e.g. a sediment type that is an equal mix of calcareous and siliceous ooze would be a circle that is ½ blue and ½ yellow). Through group effort, the class map should ultimately contain all of the exercise core locations in the Pacific and North Atlantic Oceans and their sediment types.
● Blue = Calcareous Ooze ● Brown = Terrigenous Sediment
● Yellow = Siliceous Ooze ● Green = Glaciomarine Sediment
● Red = Red Clays
1 Make a list of your observations about the distribution of these marine sediment lithologies on the map your class constructed. Consider factors such as distance from the continents, water depth, and latitude/longitude, among others.
| Sediment lithologies | Observations about distribution |
| Calcareous ooze | |
| Siliceous ooze | |
| Red clay | |
| Terrigenous sediment | |
| Glaciomarine sediment |
1 Based on your observations (#2 above), develop hypotheses to explain the distribution of each of these lithologies. Since sediment lithologies (e.g. calcareous ooze) are named for their dominant grain types (e.g. calcareous microfossils), a good explanation will address what controls the relative abundances of different grain types that accumulate on the seafloor.
| Sediment lithologies | Hypotheses to explain lithologic distributions |
| Calcareous ooze | |
| Siliceous ooze | |
| Red clay | |
| Terrigenous sediment | |
| Glaciomarine sediment |
1 Compare your class map of seafloor sediment lithologies to a published map of seafloor sediment lithologies (e.g. see the map from Rothwell, 1989 distributed by your instructor). Are they generally similar? If not, where are the discrepancies? What might cause these discrepancies?
2 Compare the North Pacific and North Atlantic sediment distributions:In what basin are glaciomarine sediments more abundant? Propose a hypothesis to explain your observations.Is calcareous ooze in the North Atlantic found at the same depth, shallower depths, or deeper depths than in the North Pacific (see Table 2.1 or Figure 2.2 for water depths)? Propose a hypothesis to explain your observations.
3 The map you constructed represents the modern distribution of sediment lithologies in the Pacific Ocean. Do you think this map would also represent the distribution of marine sediment lithologies in the geologic past or in the geologic future? Why or why not?
References
1 Aumento, F., Melson, W.G. et al. (1977). Initial Reports of the Deep Sea Drilling Project, vol. 7. Washington, DC: U.S. Government Printing Office.
2 Austin, J.A. Jr., Christie‐Blick, N., Malone, M.J. et al. (1998). Proceedings of the Ocean Drilling Program, Initial Reports, vol. 174A. College Station, TX: Ocean Drilling Program https://doi.org/10.2973/odp.proc.ir.174a.1998.
3 Barker, P.F., Camerlenghi, A., Acton, G.D. et al. (1999). Proceedings of the Ocean Drilling Program, Initial Reports, vol. 178. College Station, TX: Ocean Drilling Program https://doi.org/10.2973/odp.proc.ir.178.1999.
4 Bougault, H., Cande, S.C., Brannon, J.C. et al. (1985). Initial Reports of the Deep Sea Drilling Project, vol. 82. Washington, DC: U.S. Government Printing Office.
5 Bralower, T.J., Premoli Silva, I., Malone, M.J. et al. (2002). Proceeding of the Ocean Drilling Program, Initial Reports, vol. 198. College Station, TX: Ocean Drilling Program https://doi.org/10.2973/odp.proc.ir.198.2002.
6 Carter, R.M., McCave, I.N., Richter, C. et al. (1999). Proceedings of the Ocean Drilling Program, Initial Reports, vol. 181. https://doi.org/10.2973/odp.proc.ir.181.2000.
7 Creager,