HEALY-WILLIAMS, N., and C. E. CLINE, University of South Carolina, Columbia, SC
The morphological characteristics of fossil foraminiferal tests are the basis for making phylogenetic and taxonomic, as well as paleoecological inferences about fossil species. A complete understanding of the taxonomic and paleoenvironmental information contained in the morphology of foraminifera depends heavily on quantitative methods to describe phenotypic and ecophenotypic variation. Automated image analysis is used to quantify the shape characteristics of planktonic and benthic foraminifera. There are three main components to our quantitative image analysis system: (1) computer based image digitizer, (2) Fourier series analysis in closed form, and (3) multivariate statistical analysis. The advantages of such a system are that shape characteristics can be objectively determined and that large numbers of specimens can be analyzed. The focus of our research has been to improve the utility of foraminifera in paleoenvironmental and biostratigraphic application. The Globorotalia menardii/Globorotalia tumida group and the Globigerinoides obliquus/Globigerinoides extremus complex from Neogene sediments from DSDP Site 502 in the Caribbean have been examined via image analysis. In both groups we are able to determine distinct morphotypes that change relative proportion with time. We are able to utilize this information to define morphotypes within each group that are independent of taxonomically defined zones. Changes in the proportions of each end member are also correlated with paleoceanographic events of the Neogene such as the initiation of Northern Hemisphere glaciatio and the Messinian event. Signal processing techniques, such as cross correlation, spectral analysis, and cross spectral analysis are also used in our investigations. Applying these techniques to the data in conjunction with stable isotope record for Site 502 allows us to determine correlations with the isotopic record and the similarities in the frequencies in the morphological records.
AAPG Search and Discovery Article #91004 © 1991 AAPG Annual Convention Dallas, Texas, April 7-10, 1991 (2009)