LINKS AMONG SEDIMENTOLOGY, GEOMORPHOLOGY, AND HYDRODYNAMICS IN A MIXED CARBONATE-CLASTIC TIDAL DELTA

Comparison studies of the modern link physical parameters such as winds, tides, and currents with spatial changes in sedimentology and geomorphology. This quantitative information provides a process-based approach for understanding heterogeneity in similar ancient systems. Bear Cut, located near Miami, Florida, is a mixed carbonate-clastic tidal inlet and delta system. The influence of tidal hydrodynamics on granulometrics is investigated by integrating flow observations with lateral changes in grain size, sorting and type in the inlet and deltas. A high-resolution (ca. 100 m), three-dimensional coastal ocean model and sediment transport model provide additional insight about flow patterns, tidal asymmetries, and residual currents, as well as grain size distribution in Bear Cut.

Substantial variability in grain size and sorting occurs within the tidal delta system, yet, within a geomorphic framework spatial patterns are predictable and are closely related to hydrodynamic processes. The magnitude and direction of the tidal currents play an important role in distributing sediments; regions of high velocities (ca. 110 cm/s), such as the inlet throat, have the largest and least well-sorted grains (very coarse sand to pebble-sized grains), whereas regions of lower velocities (ca. 20 to 40 cm/s) outward within the ebb and flood deltas are coincident with lateral transitions to finer-grained sediments (coarse to fine sand sizes).

The 3-D hydrodynamical model is an effective tool to study the horizontal and vertical structure of the tidal currents, and reveals significant spatial asymmetries and preferential flow pathways in the inlet and delta system. A particle tracking model for suspended and bed-load sediment transport is used to investigate deposition patterns due to tidal currents as a function of grain sizes. The results from the flow and sediment transport models are in agreement with the hydrodynamical processes and sediment characteristics observed in the tidal inlet system. Therefore, the models provide a sound basis to further investigate the complex interactions between flow and sedimentology in Bear Cut and similar systems. Overall, the integrated study of sedimentology and hydrodynamics offers a unique approach to investigate a modern analog for ancient systems.