Radiocarbon-calibrated amino acid racemization ages from Holocene sand dollars (Peronella peronii)

Abstract

Amino acid racemization (AAR) is widely used as a cost-effective method to date molluscs in time-averaging and taphonomic studies, but it has not been attempted for echinoderms despite their paleobiological importance and distinct biomineralization. Here we demonstrate the applicability of AAR geochronology for dating Holocene Peronella peronii (Echinodermata: Echinoidea) collected from Sydney Harbour (Australia). Using standard HPLC methods we determined the extent of AAR in 74 Peronella tests and performed replicate analyses on 23 tests.

Aminochronology and time averaging of Quaternary land snail assemblages from colluvial deposits in the Madeira Archipelago, Portugal

“…To fully quantify time averaging, the degree of age mixing of individual shells needs to be evaluated relative to the expected age variation brought about by uncertainties related to the dating methods. Evaluation of the quality of radiocarbon/AAR calibration can determine the extent and significance of artificial time averaging in tested samples (e.g., Kowalewski et al, 1998; Yanes et al, 2007; Dominguez et al, 2016; Kosnik et al, 2017). Multiple sources of uncertainty contribute to error in age estimates, including: regression uncertainties, analytical error, conversion of 14 C ages to calendar ages, reservoir age estimate, and effects of different postdepositional temperature history on the rate of AAR.…”

“…The standard method to evaluate the scale and structure of time averaging is by directly dating individual fossils within a geologic stratum and then using the ages of fossils to infer the extent and shape of age mixing (e.g., Flessa et al, 1993; Kowalewski and Bambach, 2008). Much of our knowledge of scale and structure of time averaging of fossils is based on Holocene (last 11.7 ka) remains of marine bivalves (e.g., Kidwell, 1998; Kidwell et al, 2005; Dominguez et al, 2016; Vidović et al, 2016; Schnedl et al, 2018), brachiopods (Carroll et al, 2003; Krause et al, 2010), and more recently echinoderms (Kosnik et al, 2017; Kowalewski et al, 2018). Estimates of time averaging in continental fossil assemblages have received less focus.…”

“…Because the rate of racemization/epimerization is dependent on both taxon and temperature, it is necessary to calibrate the method for the locality and taxon to be investigated by using an independent dating method, such as radiocarbon dating, which uses radiocarbon present in samples to determine a numerical age that can be then calibrated to calendar years. The relatively new carbonate-target accelerator mass spectrometry (AMS) radiocarbon dating method described by Bush et al (2013) is rapid and cost-effective and has been increasingly used for dating Holocene marine carbonate-bearing fossils and calibration of AAR ages (e.g., Dominguez et al, 2016; Kosnik et al, 2017; Kowalewski et al, 2018).…”

Direct AMS 14C Analysis of Carbonate

“…To quantify time over which an assemblage formed, time-averaging, a dozen or more ages are typically required, making graphite target AMS 14 C ages cost prohibitive for most researchers. Many studies have used 14 C-calibrated AAR to determine the age of shell as the cost per date is favourable despite lower precision (e.g., Kosnik et al 2017). Even with relatively imprecise age estimates the age variability in a fossil assemblage is much larger than the uncertainty of the ages (e.g., Dominguez et al 2016).…”

“…The methods applied in these papers require only minimal effort in sample preparation and less time of AMS measurement, allowing quick and inexpensive analysis of many more samples within a given project budget for a number of different purposes. They include survey of deep-sea coral ages for their population dynamics and past bio-geography (Longworth et al 2013), age distribution of fossil corals collected at a study site (McGregor et al 2011;Bush et al 2013;Grothe et al 2016), high-resolution and continuous records of young-speleothem 14 C (Welte et al 2016) and 14 C-based calibration of amino acid racemization (AAR) ages (Domignuez et al 2016;Kosnik et al 2017).…”