PROCESS DYNAMICS OF HOLOCENE OOID TIDAL SAND SHOALS: EMERGENT PROPERTIES AND PREDICTION ACROSS SCALES

Stratigraphy records the history of Earth surface systems through time. At one scale, stratigraphy reflects the influence of external forcing mechanisms such as eustatic change, sediment supply, and subsidence. At the scale of individual facies or geomorphic bodies, however, these signals can be masked by shorter-term influences of feedback and autogenic sedimentary processes. The purpose of this talk is to explore the roles of feedback processes in the development of facies bodies in Holocene tidal oolitic sand shoals, as archetypal emergent geomorphic systems.

Systematic characterization of the sedimentology, geomorphology, and hydrodynamics of Bahamian oolitic sand shoals reveals that although these systems are complex, feedbacks lead to systematic and quantitative links and trends among sedimentological attributes, sizes, and shapes of oolitic geobodies. The formation of ooids is aided by elevated aragonite supersaturation of Bahamian marine waters and repeated transport provided by tides. These flows, which create the sediment, also transport and deposit it. These oolitic accumulations in turn modify the flow patterns, creating a feedback loop within individual bar forms and shoals, and trends in sedimentology related to geomorphic setting. Comparison among shoals suggests that granulometrical attributes are closely related to the maximum size of individual bar forms and the width of oolitic shoals as a whole, which are influenced by the hydrodynamic setting.

The results of this study illustrate how oolitic sand shoals concomitantly are shaped by, and control the patterns of, the same tidal flows that create the sediment which make up the shoal. These linked autogenic processes form systematic patterns that can provide the basis for enhanced prediction in the stratigraphic record.