SEA LEVEL AND STRATIGRAPHY: IMPLICATIONS FOR FLORIDA'S PLIO-PLEISTOCENE RECORD

Despite its spectacular fossil record, one of the fundamental shortcomings of peninsular Florida's Plio-Pleistocene record is the difficulty associated with constraining the chronostratigraphy of the shell beds that dominate the region's sedimentary record. Given the paleontologic importance of this sequence, it is critical to understand the temporal completeness of individual stratigraphic units and the duration of bounding unconformities. Although a wide range of approaches have been used to place these units into a temporal framework, due to the various limitations inherent in each of the techniques employed, there still is considerable uncertainty and debate concerning the chronostratigraphic position of these biostratigraphically constrained units.

Because Florida is situated on a passive margin characterized by limited tectonic activity and is beyond the region impacted by post-glacial isostatic rebound, its stratigraphic record should readily record eustatic sea-level history. Furthermore, given the broad, gentle slope of the underlying platform, its limited depth even during maximum highstand, and relative sediment starvation, the record should dominantly reflect eustatic highstand events. Here, we use Miller et al.'s (2005) detailed sea-level curve in an attempt to elucidate when sea level was sufficiently high to submerge the Florida platform. During the past 3 Ma, there are relatively few intervals when sea level was sufficiently high to broadly inundate the platform. At approximately 0.8 Ma, there was an important transition from largely obliquity- to eccentricity-dominated climate. Prior to this, sea-level fluctuations were less pronounced and consisted of longer intervals when numerous highstands were sufficiently high to flood the platform. This resulted in the deposition of the Pinecrest Beds, Caloosahatchee, and at least a portion of Bermont sediments. This was followed by an interval characterized by much less frequent highstands, although potentially of longer duration. We suggest that although there are likely to be hiatuses within all of the defined units, those that divide the Pleistocene sequence are likely to represent much longer intervals.