Geochemistry: a matter of preservation

Abstract

The fossil record is well known to be biased by the unevenness of the geographical and stratigraphical sampling effort and inequality in the rock record available for sampling (1). There is increasing evidence that a similar unevenness biases the geological record of the generation and evolution of the continental crust. In a recent study, Campbell and Allen (2) reemphasized the link between peaks in the distribution of the uranium- lead (U-Pb) crystallization ages of the mineral zircon (which reflect the ages of the parent igneous rocks) and the development of supercontinents. It is not clear, however, why the development of supercontinents should be associated with the generation of unusual volumes of igneous rocks. Instead, peaks of crystallization ages in the continental record are likely to reflect biases in preservation.