Distribution of Lithologies at the Surface

Although soil maps are available for each of the continents and seafloor maps are available for each of the ocean basins, there are no continental-scale maps that show the distribution of lithologies at the Earth's surface. Surficial lithologic maps are needed to serve as a base for determining areas of different kinds of rocks exposed to weathering and erosion.

Distribution of Sources and Sinks

Prerequisites for studies of biogeochemical cycling are maps of sources and sinks of detrital and dissolved materials. These are essential to quantify global fluxes and to identify sensitive areas that are prone to rapid change. Just as topographic maps are needed for land-use planning and geologic maps are needed for resource exploration, sources and sinks maps are needed for studies of global cycles and global change.

In terms of sources, there is a need for accurate mapping to estimate the areas of different types of environment on a global scale. Accurate surficial lithological maps on a global scale will be required, with emphasis on both soluble rocks and rocks and sediments that are readily eroded physically. Special attention should be given to determining the location of rock types that are sensitive to erosion.

Global sinks maps would show the accumulation rates of different types of sediments or the rates of consumption of cycling components (e.g., CO2).

Rates

The response times for environmental changes need to be determined. Rates of environmental change from Pleistocene to Holocene conditions are probably among the most rapid in the geologic evolution of the planet. However, it is questionable whether we know enough about more ancient geologic times to be sure that spatial and temporal climatic variability then was less than it is now.

Expanded Time Scales for Processes/Fluxes

To determine response times there is a need for additional well-dated high-resolution geologic records, especially those of short-term events. Some lakes, for example, are likely to have a sedimentary record of atmospheric fluxes as detailed as that obtained from ice cores.

To determine past flux rates we need high-resolution dating of small (1 to 5 mg) samples with a resolution of ± 30 years. The use of accelerator mass spectroscopy (AMS) determined 14C is one of the most promising techniques for high-resolution dating. However, there are a variety of other dating techniques, such as tree rings, coral growth bands, varves, and layering in ice cores that can be used to achieve annual resolution.

Anthropogenic Influence

Finally, we must answer the question: When will (or when did) anthropogenic activities so perturb global fluxes that they exceed (or exceeded) the range of variability inherent in natural processes?

REFERENCES

Cita, M.B., C. Vergnaud-Grazzini, C. Robert, H. Chamley, N. Ciaranfi, and S. D'Onofrio (1977). Paleoclimatic record of a long deep sea core from the eastern Mediterranean, Quaternary Research 8, 205-235.


Degens, E.T., and D.A. Ross (1974). The Black Sea: Geology, Chemistry, and Biology, American Association of Petroleum Geologists Memoir 20, Tulsa, Oklahoma, 633 pp.



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