Amino acid racemization dating : method development using African ostrich (Struthio camelus) eggshell
Ostrich eggshell (OES) is ubiquitous in archaeological sites in Africa and is a favoured substrate for amino acid racemisation (AAR) geochronology, yielding consistent results and thought to approximate a closed system with respect to protein diagenesis. It was found that the intra-crystalline fraction in OES can be isolated by oxidative pre-treatment and that these amino acids are resistant to leaching and unaffected by changes in the environmental pH (between pH 5 and 9). The intra-crystalline fraction in OES therefore effectively operates as a closed system with respect to protein diagenesis. This intra-crystalline fraction is likely to be a superior sample compared to whole-shell samples, removing uncertainty introduced through variable leaching rates, different ground water conditions and potentially exogenous contamination. Kinetic studies on modern OES indicate that high temperature data should be treated with caution when used to extrapolate kinetic parameters at low temperatures. This reinforces previous work that indicates the underlying mechanisms driving protein diagenesis need to be better understood in order to estimate accurate kinetic parameters, as the pathways of diagenesis are different
Crisp, Molly Katherine
Amino acid racemization dating : method development using African ostrich (Struthio camelus) eggshell. Ostrich eggshell (OES) is ubiquitous in archaeological sites in Africa and is a favoured substrate for amino acid racemisation (AAR) geochronology, yielding consistent results and thought to approximate a closed system with respect to protein diagenesis. It was found that the intra-crystalline fraction in OES can be isolated by oxidative pre-treatment and that these amino acids are resistant to leaching and unaffected by changes in the environmental pH (between pH 5 and 9). The intra-crystalline fraction in OES therefore effectively operates as a closed system with respect to protein diagenesis. This intra-crystalline fraction is likely to be a superior sample compared to whole-shell samples, removing uncertainty introduced through variable leaching rates, different ground water conditions and potentially exogenous contamination. Kinetic studies on modern OES indicate that high temperature data should be treated with caution when used to extrapolate kinetic parameters at low temperatures. This reinforces previous work that indicates the underlying mechanisms driving protein diagenesis need to be better understood in order to estimate accurate kinetic parameters, as the pathways of diagenesis are different
amino_acid dating method development use african eggshell eggshell ubiquitous archaeological_site africa favour substrate amino_acid yield consistent thought approximate close system respect protein diagenesis find intra fraction isolate pre treatment amino_acid resistant unaffected change environmental intra fraction therefore effectively operate closed system respect protein diagenesis intra fraction likely superior sample compare whole shell sample remove uncertainty introduce variable rate different ground water condition potentially contamination study modern indicate_high temperature data treat caution use extrapolate parameter low temperature reinforces previous_work indicate underlie mechanism drive protein diagenesis need well_understood order estimate accurate parameter pathway diagenesis different