SGER: Degradation of the Organic Matrix as a Measure of Alteration of Fossil Mollusk Shells

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The organic matrix permeates the structure of calcareous shells, enveloping the individual crystals and binding them together. It is essentially invisible in the scanning electron microscopy (SEM) of cut of fractured shell sections, and has received little attention as a structural component. It is important in the taphonomy of fossil shells, for as long as it remains intact the original crystallography is preserved. One technique does exist for the SEM investigation of the organic matrix in its normal relationship to shell microstructure. This involves cutting, polishing, and etching a section through the shell, and preserving the exposed organic matrix in place by critical point drying. This project will examine the utility of this technique in determining the degree of degradation of organic matrix in fossil mollusks. Four collections of fossils will be examined, representing both calcite and aragonite in a variety of microstructures and over a range of preservational quality. If measures of matrix degradation can provide a consistent means of determining early stages of alteration in fossil shells, it will open up new avenues of study in the field of taphonomy, and provide a source of supporting data for studies on fossil geochemistry.