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Amino acid racemization dating of marine shells: A mound of possibilities.

Demarchi B, Williams MG, Milner N, Russell N, Bailey G, Penkman K - Quat Int (2011)

Bottom Line: Only species which pass both tests can be considered suitable for further studies to obtain reliable age information.This amino acid geochronological technique is also applied to midden deposits at two latitudinal extremes: Northern Scotland and the Southern Red Sea.Results obtained in this study indicate that the application of this new method of AAR dating of shells has the potential to aid the geochronological investigation of shell mounds in different areas of the world.

View Article: PubMed Central - PubMed

Affiliation: BioArCh, Department of Chemistry, University of York, Heslington, York YO10 5DD, UK.

ABSTRACT
Shell middens are one of the most important and widespread indicators for human exploitation of marine resources and occupation of coastal environments. Establishing an accurate and reliable chronology for these deposits has fundamental implications for understanding the patterns of human evolution and dispersal. This paper explores the potential application of a new methodology of amino acid racemization (AAR) dating of shell middens and describes a simple protocol to test the suitability of different molluscan species. This protocol provides a preliminary test for the presence of an intracrystalline fraction of proteins (by bleaching experiments and subsequent heating at high temperature), checking the closed system behaviour of this fraction during diagenesis. Only species which pass both tests can be considered suitable for further studies to obtain reliable age information. This amino acid geochronological technique is also applied to midden deposits at two latitudinal extremes: Northern Scotland and the Southern Red Sea. Results obtained in this study indicate that the application of this new method of AAR dating of shells has the potential to aid the geochronological investigation of shell mounds in different areas of the world.

No MeSH data available.


(a) Asx THAA vs FAA dl ratio for Strombus and Chicoreus. Note the increase in d/l values for Strombus with increasing heating time, while Chicoreus Asx d/ls cluster at higher values. Error bars represent one standard deviation around the mean. (b) “Spider diagram” illustrating the increase of THAA d/l values for Asx, Glx, Ala and Val with increasing heating time, for Strombus (square symbols) and Chicoreus (diamond symbols). Error bars represent one standard deviation around the mean.
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fig3: (a) Asx THAA vs FAA dl ratio for Strombus and Chicoreus. Note the increase in d/l values for Strombus with increasing heating time, while Chicoreus Asx d/ls cluster at higher values. Error bars represent one standard deviation around the mean. (b) “Spider diagram” illustrating the increase of THAA d/l values for Asx, Glx, Ala and Val with increasing heating time, for Strombus (square symbols) and Chicoreus (diamond symbols). Error bars represent one standard deviation around the mean.

Mentions: Further confirmation of the closed system behaviour of the intracrystalline proteins was sought by examining the diagenesis patterns by means of THAA vs FAA d/l plots (Fig. 3a) and “spider diagrams” (Fig. 3b) (e.g. O’Neal et al., 2000; Wehmiller et al., 2009). In a closed system, the extent of racemization measured in the FAA and the THAA fractions should be highly correlated. When the THAA d/l values are plotted against the FAA d/l values (Fig. 3a):•


Amino acid racemization dating of marine shells: A mound of possibilities.

Demarchi B, Williams MG, Milner N, Russell N, Bailey G, Penkman K - Quat Int (2011)

(a) Asx THAA vs FAA dl ratio for Strombus and Chicoreus. Note the increase in d/l values for Strombus with increasing heating time, while Chicoreus Asx d/ls cluster at higher values. Error bars represent one standard deviation around the mean. (b) “Spider diagram” illustrating the increase of THAA d/l values for Asx, Glx, Ala and Val with increasing heating time, for Strombus (square symbols) and Chicoreus (diamond symbols). Error bars represent one standard deviation around the mean.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3117143&req=5

fig3: (a) Asx THAA vs FAA dl ratio for Strombus and Chicoreus. Note the increase in d/l values for Strombus with increasing heating time, while Chicoreus Asx d/ls cluster at higher values. Error bars represent one standard deviation around the mean. (b) “Spider diagram” illustrating the increase of THAA d/l values for Asx, Glx, Ala and Val with increasing heating time, for Strombus (square symbols) and Chicoreus (diamond symbols). Error bars represent one standard deviation around the mean.
Mentions: Further confirmation of the closed system behaviour of the intracrystalline proteins was sought by examining the diagenesis patterns by means of THAA vs FAA d/l plots (Fig. 3a) and “spider diagrams” (Fig. 3b) (e.g. O’Neal et al., 2000; Wehmiller et al., 2009). In a closed system, the extent of racemization measured in the FAA and the THAA fractions should be highly correlated. When the THAA d/l values are plotted against the FAA d/l values (Fig. 3a):•

Bottom Line: Only species which pass both tests can be considered suitable for further studies to obtain reliable age information.This amino acid geochronological technique is also applied to midden deposits at two latitudinal extremes: Northern Scotland and the Southern Red Sea.Results obtained in this study indicate that the application of this new method of AAR dating of shells has the potential to aid the geochronological investigation of shell mounds in different areas of the world.

View Article: PubMed Central - PubMed

Affiliation: BioArCh, Department of Chemistry, University of York, Heslington, York YO10 5DD, UK.

ABSTRACT
Shell middens are one of the most important and widespread indicators for human exploitation of marine resources and occupation of coastal environments. Establishing an accurate and reliable chronology for these deposits has fundamental implications for understanding the patterns of human evolution and dispersal. This paper explores the potential application of a new methodology of amino acid racemization (AAR) dating of shell middens and describes a simple protocol to test the suitability of different molluscan species. This protocol provides a preliminary test for the presence of an intracrystalline fraction of proteins (by bleaching experiments and subsequent heating at high temperature), checking the closed system behaviour of this fraction during diagenesis. Only species which pass both tests can be considered suitable for further studies to obtain reliable age information. This amino acid geochronological technique is also applied to midden deposits at two latitudinal extremes: Northern Scotland and the Southern Red Sea. Results obtained in this study indicate that the application of this new method of AAR dating of shells has the potential to aid the geochronological investigation of shell mounds in different areas of the world.

No MeSH data available.