BIOGEOCHEMICAL CRITERIA FOR ESTIMATING THE DEGREE OF DIAGENESIS OF FOSSIL MOLLUSK SHELLS

Abstract

In the past few years much attention has been given to studying the degree of preservation of the initial composition of the fossil skeletons of invertebrates. This is due to the fact that without corrective allowance for the degree of diagenetic transformation of fossil skeletons, one cannot make sufficiently sound paleogeographic and paleoecological reconstructions based on paleobiogeochemical information. Reliable biogeochemical criteria for estimating diagenesis are fully applicable to age dating. The degree of diagenetic variability in the fossil skeletons of invertebrates can be used to ascertain the very earliest stages of diagenesis of the host deposits, which cannot be detected by the usual lithologic methods. The magnesium ratios of the oyster shells in deposits of the same age are subject to very small variations. It is established that the MgW/Mgc ratio reliably reflects the degree of diagenetic change in calcite shells.