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Amino acid geochronology of the type Cromerian of West Runton, Norfolk, UK.

Penkman KE, Preece RC, Keen DH, Collins MJ - Quat Int (2010)

Bottom Line: Two genera of freshwater gastropods (Valvata and Bithynia) are used to explore the value of using multiple amino acids from the intra-crystalline fraction, which should be more protected from the effects of diagenesis than the inter-crystalline component.In order to put the amino acid data from the West Runton Freshwater Bed into perspective, statistical analyses are used to compare them with results from the Hoxnian (MIS 11) site at Clacton-on-Sea, Essex.The data are also compared with results from Waverley Wood, an important archaeological site in the English Midlands falling within the 'Cromerian Complex'.

View Article: PubMed Central - PubMed

Affiliation: BioArCh, Dept of Chemistry, University of York, York YO10 5DD, United Kingdom.

ABSTRACT
Aminostratigraphic studies of continental deposits in the UK have hitherto relied almost exclusively on data from the aragonitic shells of non-marine molluscs for dating Pleistocene sequences. This is usually based on the d/l value of a single amino acid, d-alloisoleucine/l-isoleucine (A/I), in the total shell proteins. Two genera of freshwater gastropods (Valvata and Bithynia) are used to explore the value of using multiple amino acids from the intra-crystalline fraction, which should be more protected from the effects of diagenesis than the inter-crystalline component. Results are compared from both the aragonitic shells and opercula composed of calcite, a more stable form of calcium carbonate. In order to put the amino acid data from the West Runton Freshwater Bed into perspective, statistical analyses are used to compare them with results from the Hoxnian (MIS 11) site at Clacton-on-Sea, Essex. Twelve protein decomposition indicators revealed that the results from the shells were not as clear-cut as those from the opercula. Five indicators from the Valvata shell suggest that West Runton is older than Clacton (at a 95% significance level), but two actually suggested a younger age. Seven indicators show that the Bithynia shells from West Runton are older than congeneric shells from Clacton. In marked contrast, all 12 indicators isolated from the opercula demonstrate that West Runton is significantly older than Clacton. The data are also compared with results from Waverley Wood, an important archaeological site in the English Midlands falling within the 'Cromerian Complex'. Contrary to earlier interpretations, the new amino acid data from Bithynia opercula indicate that West Runton is older than Waverley Wood, a relationship now consistent with the available biostratigraphy.

No MeSH data available.


Related in: MedlinePlus

Difference in the means and 95% confidence intervals between Clacton and West Runton for racemization and decomposition in the FAA (A) and THAA (B) fractions of Valvata piscinalis (Vp) and Bithynia (B) shell and opercula. The y-axes for the [Ser]/[Ala] data are plotted in reverse, so that the direction of increased protein degradation for each of the indicators remains the same. The dashed line (0.00) indicates that there is no difference between the mean of the two sites. If the 95% confidence intervals fall below this zero line, then it is not possible to discriminate between Clacton and West Runton. The opercula are clearly better at discriminating between the sites than the shells, because they show a greater difference in means and have much smaller error bars. The use of opercula therefore increases the statistical confidence and temporal resolution.
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fig2: Difference in the means and 95% confidence intervals between Clacton and West Runton for racemization and decomposition in the FAA (A) and THAA (B) fractions of Valvata piscinalis (Vp) and Bithynia (B) shell and opercula. The y-axes for the [Ser]/[Ala] data are plotted in reverse, so that the direction of increased protein degradation for each of the indicators remains the same. The dashed line (0.00) indicates that there is no difference between the mean of the two sites. If the 95% confidence intervals fall below this zero line, then it is not possible to discriminate between Clacton and West Runton. The opercula are clearly better at discriminating between the sites than the shells, because they show a greater difference in means and have much smaller error bars. The use of opercula therefore increases the statistical confidence and temporal resolution.

Mentions: The results of the 2-tailed t-tests allow the direct comparison of the degrees of difference between the two biominerals. The difference in the means between the two sites for each biomineral, along with the 95% confidence limits, can be compared. If the difference between the means is greater for one biomineral than the other, then the level of resolution using that biomineral is also greater. It is also important, however, to attempt to quantify the range of the data for each biomineral, which is represented by the 95% confidence limits calculated for the differences in the means. If the 95% confidence limits encompass the zero value, then no discrimination is possible at that level of confidence using that protein decomposition indicator. These results are presented graphically in Fig. 2.


Amino acid geochronology of the type Cromerian of West Runton, Norfolk, UK.

Penkman KE, Preece RC, Keen DH, Collins MJ - Quat Int (2010)

Difference in the means and 95% confidence intervals between Clacton and West Runton for racemization and decomposition in the FAA (A) and THAA (B) fractions of Valvata piscinalis (Vp) and Bithynia (B) shell and opercula. The y-axes for the [Ser]/[Ala] data are plotted in reverse, so that the direction of increased protein degradation for each of the indicators remains the same. The dashed line (0.00) indicates that there is no difference between the mean of the two sites. If the 95% confidence intervals fall below this zero line, then it is not possible to discriminate between Clacton and West Runton. The opercula are clearly better at discriminating between the sites than the shells, because they show a greater difference in means and have much smaller error bars. The use of opercula therefore increases the statistical confidence and temporal resolution.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2991590&req=5

fig2: Difference in the means and 95% confidence intervals between Clacton and West Runton for racemization and decomposition in the FAA (A) and THAA (B) fractions of Valvata piscinalis (Vp) and Bithynia (B) shell and opercula. The y-axes for the [Ser]/[Ala] data are plotted in reverse, so that the direction of increased protein degradation for each of the indicators remains the same. The dashed line (0.00) indicates that there is no difference between the mean of the two sites. If the 95% confidence intervals fall below this zero line, then it is not possible to discriminate between Clacton and West Runton. The opercula are clearly better at discriminating between the sites than the shells, because they show a greater difference in means and have much smaller error bars. The use of opercula therefore increases the statistical confidence and temporal resolution.
Mentions: The results of the 2-tailed t-tests allow the direct comparison of the degrees of difference between the two biominerals. The difference in the means between the two sites for each biomineral, along with the 95% confidence limits, can be compared. If the difference between the means is greater for one biomineral than the other, then the level of resolution using that biomineral is also greater. It is also important, however, to attempt to quantify the range of the data for each biomineral, which is represented by the 95% confidence limits calculated for the differences in the means. If the 95% confidence limits encompass the zero value, then no discrimination is possible at that level of confidence using that protein decomposition indicator. These results are presented graphically in Fig. 2.

Bottom Line: Two genera of freshwater gastropods (Valvata and Bithynia) are used to explore the value of using multiple amino acids from the intra-crystalline fraction, which should be more protected from the effects of diagenesis than the inter-crystalline component.In order to put the amino acid data from the West Runton Freshwater Bed into perspective, statistical analyses are used to compare them with results from the Hoxnian (MIS 11) site at Clacton-on-Sea, Essex.The data are also compared with results from Waverley Wood, an important archaeological site in the English Midlands falling within the 'Cromerian Complex'.

View Article: PubMed Central - PubMed

Affiliation: BioArCh, Dept of Chemistry, University of York, York YO10 5DD, United Kingdom.

ABSTRACT
Aminostratigraphic studies of continental deposits in the UK have hitherto relied almost exclusively on data from the aragonitic shells of non-marine molluscs for dating Pleistocene sequences. This is usually based on the d/l value of a single amino acid, d-alloisoleucine/l-isoleucine (A/I), in the total shell proteins. Two genera of freshwater gastropods (Valvata and Bithynia) are used to explore the value of using multiple amino acids from the intra-crystalline fraction, which should be more protected from the effects of diagenesis than the inter-crystalline component. Results are compared from both the aragonitic shells and opercula composed of calcite, a more stable form of calcium carbonate. In order to put the amino acid data from the West Runton Freshwater Bed into perspective, statistical analyses are used to compare them with results from the Hoxnian (MIS 11) site at Clacton-on-Sea, Essex. Twelve protein decomposition indicators revealed that the results from the shells were not as clear-cut as those from the opercula. Five indicators from the Valvata shell suggest that West Runton is older than Clacton (at a 95% significance level), but two actually suggested a younger age. Seven indicators show that the Bithynia shells from West Runton are older than congeneric shells from Clacton. In marked contrast, all 12 indicators isolated from the opercula demonstrate that West Runton is significantly older than Clacton. The data are also compared with results from Waverley Wood, an important archaeological site in the English Midlands falling within the 'Cromerian Complex'. Contrary to earlier interpretations, the new amino acid data from Bithynia opercula indicate that West Runton is older than Waverley Wood, a relationship now consistent with the available biostratigraphy.

No MeSH data available.


Related in: MedlinePlus