Evidence for High-Frequency Sea-Level Oscillations During the Late Holocene: Implications for Modeling Sediment Body Initiation and Evolution

Sarah Gelsanliter, Harold R. Wanless

The fine-scale definition of south Florida stratigraphic sequences, coupled with the reevaluation of previous radiometric data sets, provides evidence that high-frequency sea-level oscillations are imbedded within the overall late Holocene sea-level rise. A high-frequency sea-level oscillation is a sea-level drop and re-rise occurring over a several hundred year period. Holocene sea-level data along the Gulf and South Atlantic coasts suggest at least two high-frequency oscillations during the overall sea-level transgression of the past 4,000 years. Especially convincing is lithologic and radiometric evidence for a high-frequency sea-level oscillation in the interval 2,900 to 2,500 years before present.

In south Florida this late Holocene sea-level oscillation is visible in sediment sequences as fluctuations in peat types, the deposition of strandplains in response to sediment disequilibrium, timing and level of the initiation of coastal deposits, timing of rapid sediment recycling, and presence of non-marine wetland and upland horizons within wetland and marine sequences. In addition, as individual radiometric dates related to sea level are evaluated, most correlate best with an oscillating sea level curve rather than the traditional smoothed curve of decelerating sea level rise.

Recognition of high-frequency sea-level oscillations in the late Holocene sea-level history provides an opportunity for a complete reevaluation of the sediment body initiation and evolution models that have been derived based on smooth or hinged sea-level curves.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995