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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) Glx vs Asx THAA d/l plot for Strombus samples investigated for the closed system test (white symbols) and for the archaeological applications on the Farasan island shell middens. Note that all samples fall on a coherent trajectory of protein degradation. Error bars represent one standard deviation around the mean. (b) “Spider diagram” for archaeological and “test” unheated Strombus shells from the Farasan Islands comparing the THAA d/l values for Asx, Glx, Ala and Val with the calibrated 14C ages of the archaeological layers.
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fig7: (a) Glx vs Asx THAA d/l plot for Strombus samples investigated for the closed system test (white symbols) and for the archaeological applications on the Farasan island shell middens. Note that all samples fall on a coherent trajectory of protein degradation. Error bars represent one standard deviation around the mean. (b) “Spider diagram” for archaeological and “test” unheated Strombus shells from the Farasan Islands comparing the THAA d/l values for Asx, Glx, Ala and Val with the calibrated 14C ages of the archaeological layers.

Mentions: A plot of THAA Glx d/l vs THAA Asx d/l showed that all the samples fall on a coherent trajectory of increase in the extent of degradation, thus confirming the good closed system behaviour of the intracrystalline fraction. Samples from JE0004, KM1057 and KM1367 displayed a higher extent of protein degradation than the unheated “test” Strombus samples (Fig. 7a). This was also confirmed when Asx, Glx, Ala and Val THAA d/l values were considered (Fig. 7b). This provides a maximum age for these specimens, indicating that the test samples are younger than 1520–1270 cal BC.


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) Glx vs Asx THAA d/l plot for Strombus samples investigated for the closed system test (white symbols) and for the archaeological applications on the Farasan island shell middens. Note that all samples fall on a coherent trajectory of protein degradation. Error bars represent one standard deviation around the mean. (b) “Spider diagram” for archaeological and “test” unheated Strombus shells from the Farasan Islands comparing the THAA d/l values for Asx, Glx, Ala and Val with the calibrated 14C ages of the archaeological layers.
© Copyright Policy
Related In: Results  -  Collection

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

fig7: (a) Glx vs Asx THAA d/l plot for Strombus samples investigated for the closed system test (white symbols) and for the archaeological applications on the Farasan island shell middens. Note that all samples fall on a coherent trajectory of protein degradation. Error bars represent one standard deviation around the mean. (b) “Spider diagram” for archaeological and “test” unheated Strombus shells from the Farasan Islands comparing the THAA d/l values for Asx, Glx, Ala and Val with the calibrated 14C ages of the archaeological layers.
Mentions: A plot of THAA Glx d/l vs THAA Asx d/l showed that all the samples fall on a coherent trajectory of increase in the extent of degradation, thus confirming the good closed system behaviour of the intracrystalline fraction. Samples from JE0004, KM1057 and KM1367 displayed a higher extent of protein degradation than the unheated “test” Strombus samples (Fig. 7a). This was also confirmed when Asx, Glx, Ala and Val THAA d/l values were considered (Fig. 7b). This provides a maximum age for these specimens, indicating that the test samples are younger than 1520–1270 cal BC.

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.