RECONCILIATION OF GEOLOGICAL AND INSTRUMENTAL RECORDS OF RAPID SEA LEVEL CHANGE USING MICROFOSSIL BASED TRANSFER FUNCTIONS, OUTER BANKS, NORTH CAROLINA

Concerns surrounding accelerations in the rate of sea level rise have focused attention on linking short term instrumental observations with longer term geological signals of relative sea level (RSL). Reconciliation of these two records provides improved confidence in the elucidation of sea level signals from geological archives. An ultimate goal of this research is the development of new records with sufficient resolution and duration to reliably establish sea level trends and estimates of the rate of glacial isostatic adjustment. The microfossil transfer function approach is one technique which may be effective in establishing these kinds of records.

Transfer functions using foraminifera and diatoms were developed to reconstruct RSL based upon the contemporary relationship between microfossils and elevation. The modern data set was composed of three sites on the Outer Banks, North Carolina with different salinity regimes due to their varying distance from a major barrier inlet. Results imply a potential precision of ~0.06m; the degree of precision does not vary significantly with the microfossil employed.

The transfer function was used to produce a high resolution RSL curve from a fossil assemblage on the Outer Banks for the period since ~1940AD. These results were consistent with instrumental tide gauge records and therefore illustrate the utility of microfossil based transfer functions in accurately and precisely reconstructing RSL. Use of this technique to temporally extend the RSL record can therefore be justified with confidence. Preliminary application of the transfer function showed that between 1300AD and 1800AD RSL rose at a mean rate of ~0.8mm/yr. The rate of sea level rise accelerated circa 1800AD to ~4mm/yr. This sharp rise may be associated with anthropogenic global warming.