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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) THAA concentration (powder) for unheated intracrystalline Strombus, Chicoreus, Anadara, Tibia and Trochus samples. Note that only Strombus and Chicoreus intracrystalline values can be considered significantly higher than the limit of detection. The Limit Of Detection (LOD) was calculated on the basis of the amino acid concentration detected in procedural blanks used in this study: LOD = Xblank + k∗σblank; where Xblank is the mean of the blank measures, σblank is the standard deviation of the blank measures, and k = 3. (b) Loss of amino acids in water for Strombus and Chicoreus after 48 h of isothermal heating at 140 °C, compared to the LOD.
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fig2: (a) THAA concentration (powder) for unheated intracrystalline Strombus, Chicoreus, Anadara, Tibia and Trochus samples. Note that only Strombus and Chicoreus intracrystalline values can be considered significantly higher than the limit of detection. The Limit Of Detection (LOD) was calculated on the basis of the amino acid concentration detected in procedural blanks used in this study: LOD = Xblank + k∗σblank; where Xblank is the mean of the blank measures, σblank is the standard deviation of the blank measures, and k = 3. (b) Loss of amino acids in water for Strombus and Chicoreus after 48 h of isothermal heating at 140 °C, compared to the LOD.

Mentions: T. insulaechorab curta, T. dentatus and A. erythraeonensis showed very low concentrations of intracrystalline amino acids in the bleached powders, in both the FAA and the THAA fractions. The concentrations were comparable with background levels and, in most cases, fell below the limit of detection (Fig. 2a).


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) THAA concentration (powder) for unheated intracrystalline Strombus, Chicoreus, Anadara, Tibia and Trochus samples. Note that only Strombus and Chicoreus intracrystalline values can be considered significantly higher than the limit of detection. The Limit Of Detection (LOD) was calculated on the basis of the amino acid concentration detected in procedural blanks used in this study: LOD = Xblank + k∗σblank; where Xblank is the mean of the blank measures, σblank is the standard deviation of the blank measures, and k = 3. (b) Loss of amino acids in water for Strombus and Chicoreus after 48 h of isothermal heating at 140 °C, compared to the LOD.
© Copyright Policy
Related In: Results  -  Collection

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

fig2: (a) THAA concentration (powder) for unheated intracrystalline Strombus, Chicoreus, Anadara, Tibia and Trochus samples. Note that only Strombus and Chicoreus intracrystalline values can be considered significantly higher than the limit of detection. The Limit Of Detection (LOD) was calculated on the basis of the amino acid concentration detected in procedural blanks used in this study: LOD = Xblank + k∗σblank; where Xblank is the mean of the blank measures, σblank is the standard deviation of the blank measures, and k = 3. (b) Loss of amino acids in water for Strombus and Chicoreus after 48 h of isothermal heating at 140 °C, compared to the LOD.
Mentions: T. insulaechorab curta, T. dentatus and A. erythraeonensis showed very low concentrations of intracrystalline amino acids in the bleached powders, in both the FAA and the THAA fractions. The concentrations were comparable with background levels and, in most cases, fell below the limit of detection (Fig. 2a).

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.