ABSTRACT
The relations of calcium, magnesium, and strontium in the sand-size carbonate fraction of South African coastal and offshore sediments have been determined. Ca/Mg ratios are lowest on the inner and middle continental shelf, and either increase landward and seaward, or alternate in low-high-low belts. This distribution reflects the distribution of organisms containing varying amounts of magnesium. Sr/Ca ratios also are generally higher inshore, rather than offshore where low-strontium organisms are more abundant.
The South African beach-dune environment has a higher mean Ca/Mg ratio (59.4) than the marine (44.4), reflecting the greater numbers of high-magnesium calcite organisms in the latter environment. The beach-dune environment also has a higher mean Sr/Ca ratio than the marine (7.5 versus 5.4), because of the abundance of strontium-bearing organisms in the former environment.
