Date of Award

Fall 1988

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Ocean & Earth Sciences

Program/Concentration

Geology

Committee Director

Stephen J. Culver

Committee Member

Randall S. Spencer

Committee Member

David B. Scott

Call Number for Print

Special Collections LD4331.G4 C65

Abstract

Fifty-three species of recent benthic foraminifera and thecamoebians have been documented and described from the Breton and Stake Island area, northern Gulf of Mexico, and from a core from Barataria Basin, Mississippi delta.

Cluster analysis of benthic assemblages using presence/absence and transformed abundance data reveals the presence of a marsh and shallow water marine biofacies. Based on the results of a presence/absence cluster analysis, the shallow water marine biofacies can be subdivided into a miliolid biofacies am an Ammonia beccarii/Elphidium species biofacies. Cluster analysis of transformed abundance data, however, shows that the shallow marine biofacies can be subdivided into four biofacies: a miliolid biofacies, an Ammonia beccarii/Elphidiurm species biofacies, an Elphidiurn species/ Ammonia beccarii/ biofacies am an Elphidiurm gunteri biofacies. The marsh biofacies is restricted to Breton Island, the Ammonia beccarii/ Elphidiurm species biofacies is restricted to the forebar locality of Breton Island, the Elphidiurn qunteri biofacies is restricted to Stake Island, the Elphidiurm species/ Ammonia beccarii biofacies occurs mainly in the back island lagoon locality of Breton Island, am the miliolid biofacies is located on Breton and Stake Islands.

Canonical, discriminant function analysis of physical and chemical variables at (a) the surface sediment-water interface am (b) the water mass approximately an above the seabed shows that the four localities (Breton Islam barrier island (1), forebar (2), back island lagoon (3) am Stake Island barrier island (4)) are significantly different from each other. Grain size variations are the primary discriminators at the surface sediment-water interface. An interaction of variables discriminates the water masses, although turbidity, Eh and concentration of dissolved oxygen appear to be the primary discriminators. Variations in the percentages Ammonia beccarii and Elphidiurm species within the forebar am back island lagoon localities of Breton Islam may be due to variations in concentration of dissolved oxygen in the water mass.

Assemblages within the Barataria Basin core indicates a decrease in salinity up the core. No simple correlation of core assemblages with the surface biofacies of Breton am stake Islands was observed.

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DOI

10.25777/fct9-0h61

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