The responses to attrition and redistribution of the skeletal elements of the major sediment-contributing taxa govern interpretation of the depositional environments of skeletal carbonate sediments. The sediments, biotas, and physical conditions of the Bermuda platform provide data for such an integrated interpretation.
Inward from the margin of the Bermuda carbonate platform there is a succession of environments: (1) a reef-front terrace; (2) a reef tract; and (3) a shallow central lagoon. The southwestern half of the lagoon is characterized by reef flats and clusters of patch reefs; these subdivide the lagoon into small basins. The northeastern half occupies a single large basin. The beaches of the Bermuda Islands, a series of Pleistocene dune ridges on the southern edge of the platform, constitute a fourth environment. Carbonate muds are found on deeper bottoms in the more protected basins, molluscan-algal sands in the less protected basins and at the shallower depths, and coralline-foraminiferal-algal sands in the reef tract and reef-front terrace.
Trend-surface analysis of sedimentary and biotic data (based on approximately 300 grab samples and supported by direct observations made by snorkeling and SCUBA diving), stratified according to depth, indicates a clear correlation with factors in the physical environment. The sediment textural parameters are related to those organisms contributing to the sediment and are related to the depositional environment by discriminant function and factor analysis. Artificial “sediment” obtained from the breakdown of hard parts of assemblages of Bermuda organisms in laboratory tumbling-barrel experiments compare closely with sediments on the platform.
The sedimentary record is a product of (1) the ecologically controlled distribution of organisms, (2) the size distributions resulting from the breakdown of the hard parts of the major sediment contributors, (3) the sorting and transport of the skeletal detritus, and (4) the degree of mixing of sediments derived from different environments.