Application of Amino Acid Racemization to the Dating of Foraminifers and the Identification of Remanié Fossils and Reworked Sediments

Abstract

The reworking of sediments and fossils is a pervasive element of the stratigraphical record and is frustrated by the fact that the taphonomic nature of fossils may not always reliably indicate the presence of remanié fossils. In this work, the extent of racemization of amino acids, a measure of fossil age based on an increasing ratio of D- to L-amino acids, is used to evaluate the integrity of the sedimentary record in selected case studies, based on the analysis of single foraminifers or samples containing fewer than 10 individuals. The short lifespan of foraminifers (c. 2–24 months), enhances their application for defining the age of sedimentary events, as they more closely relate to the age of the depositional event. The selected case studies range in spatial scale from defining the taphonomically active zone in geologically recent shallow marine sediments, to the application of foraminifers in reef island sediment budgets in Tarawa, to the reworking of foraminifers from Late Pleistocene calcarenites into modern beach sediments. The species Elphidium macelliforme, Amphistegina sp., and Lamellodiscorbis dimidiatus are shown to be particularly suited for amino acid racemization investigations of sediment reworking.