Do sedimentary records that record rapid fluctuations in seawater chemistry reflect major perturbations, diagenetic overprinting or analytical artifacts?

Abstract:

Marine sediments have always been a rich archive for the reconstruction of changes in seawater chemical composition over earth history and shed light on how these fluctuations relate to changes in Earth’s climate and tectonics. Secular variations in oxygen, carbon, sulfur and strontium isotopes are well known and have been recorded in carbonates, evaporates and fossils. Superimposed on these records are relatively sharp excursions, suggestive of rapid changes and major perturbations. Several studies report relatively rapid fluctuation for elements that at present are conservative in the ocean and have residence times in the order of several million years (e.g. S, Sr, Li, Ca, Mg). What are the implications of such data? Are such rapid changes possible and under what conditions? A few examples for such “events”, approaches for identifying diagenetic impacts on the record and discussion of the implication of such records to our understanding of Earth’s processes will be presented.