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Florida Scientist


This study examined the coastal response of central Brevard County to rising Holocene sea level as it has been recorded in sediments of Indian River lagoon. The typical Holocene sediment sequence, in ascending order, consists of: (1) depauperate marsh muds, (2) sandy muds and muddy sands that contain a restricted marine fauna, and (3) sands and muddy sands that contain an abundant, more normal marine fauna. This transgressive sequence developed as rising Holocene sea level flooded a Pleistocene topographic depression (paleolagoon). It is often capped by (4) a coarser sand that exhibits a decrease in faunal abundance and diversity. The origin of this sediment type remains problematic. "Muck", a fine-grained, organic-rich sediment, occurs in bathymetric depressions of the lagoon and was not identified at any other stratigraphic position. This observation supports the hypothesis that "muck" is an anthropogenic sediment type. Stratigraphic cross-sections along the axis of the lagoon reveal a concomitant increase in mud and decrease in sand from south to north. This sediment gradient is logically related to the morphology of the present barrier island system. In the northern area, the relatively broad width of the barrier island and its well-developed ridge-and-swale topography may have limited the flux of quartz sand into the lagoon during major storms and hurricanes.

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