Paper No. 30
Presentation Time: 8:00 AM-12:00 PM
CREATING A MODERN FORAMINIFERAL DATASET FROM SOUTH AFRICA FOR RECONSTRUCTING HIGH-RESOLUTION LATE HOLOCENE SEA LEVEL
Holocene sea level records are absent, incomplete or low-resolution in much of coastal South Africa. In order to produce high-resolution sea level records in this region, new chronological control (AMS 14C, 137Cs, and 210Pb dating) on valid sea level index points (known relationship between index and sea level) are required. Foraminiferal environmental distribution displays narrow vertical zonation associated with tidal inundation period and frequency. Benthic agglutinated salt marsh foraminifera will be used to develop a regional modern foraminiferal dataset that establishes the relationship between salt marsh foraminifera and tidal inundation. Currently, Holocene sea level records extend to 8500 years BP, but the resolution of these records are often inadequate (meters of uncertainty) with poorly constrained chronology (~100 yrs). To develop a regional dataset, four modern transects of foraminiferal assemblages, vegetation, elevation, and salinity from Langebann Lagoon and Knysna Estuary in southern South Africa will be analyzed. Preliminary studies from Kariega Estuary (central coastal South Africa) and Langebann Lagoon (western South Africa) show that this method may provide the much needed high-resolution RSL records (geologic sea level context) necessary to help evaluate the future of South African sea level. Presently, tide-gauge records (1956-2006) show that the southern region of South Africa is experiencing sea-level rise at a rate of up to 1.48 mm/yr (0.42 mm/yr eustatic). A dataset of statistically-derived zonations of foraminiferal-elevation assemblages will be evaluated for utility and precision. Using this dataset to predict downcore elevations of fossil foraminiferal assemblages in basal peats will provide high-resolution reconstructions of late Holocene South African sea level.