FURTHER EVIDENCE FOR APPARENT PARABOLIC RACEMIZATION KINETICS IN QUATERNARY MOLLUSKS

The extent of racemization of the amino acids leucine and valine, and degree of isoleucine epimerization, in molluscan fossils of Late Quate rnary age from southern Australia may be described using an apparent p arabolic kinetic model. Linear regression of the extent of racemizatio n (epimerization) against the square root of fossil age indicates a hi gh level of correlation for each amino acid (i.e. r greater-than-or-eq ual-to 0.98) for samples up to about 225 ka old. Results from this stu dy indicate that the apparent parabolic kinetics previously reported f or planktonic foraminifera also apply to marine molluscs. The kinetic model evaluated, avoids some of the uncertainties inherent in previous ly developed racemization kinetic models, offers the opportunity for n umeric dating and improved age resolution, and represents a useful app roach for describing a complex and difficult to define kinetic pathway .