Aminochronology and time averaging of Quaternary land snail assemblages from colluvial deposits in the Madeira Archipelago, Portugal

2019 ◽  
Vol 92 (2) ◽  
pp. 483-496 ◽  
Author(s):  
Evan New ◽  
Yurena Yanes ◽  
Robert A.D. Cameron ◽  
Joshua H. Miller ◽  
Dinarte Teixeira ◽  
...  
Keyword(s):  
Land Snail ◽  
Time Averaging ◽  
Radiocarbon Age ◽  
Amino Acid Racemization ◽  
Madeira Archipelago ◽  
Dating Methods ◽  
Dating Method ◽  
Volcanic Islands ◽  
Geologic Record ◽  
Age Estimates

AbstractUnderstanding the properties of time averaging (age mixing) in a stratigraphic layer is essential for properly interpreting the paleofauna preserved in the geologic record. This work assesses the age and quantifies the scale and structure of time averaging of land snail-rich colluvial sediments from the Madeira Archipelago (Portugal) by dating individual shells using amino acid racemization calibrated with graphite-target and carbonate-target accelerator mass spectrometry radiocarbon methods. Gastropod shells of Actinella nitidiuscula were collected from seven sites on the volcanic islands of Bugio and Deserta Grande (Desertas Islands), where snail shells are abundant and well preserved in Quaternary colluvial deposits. Results show that the shells ranged in age from modern to ~48 cal ka BP (calibrated radiocarbon age), covering the last glacial and present interglacial periods. Snail shells retrieved from two of the colluvial sites exhibit multimillennial age mixing (>6 ka), which significantly exceeds the analytical error from dating methods and calibration. The observed multimillennial mixing of these assemblages should be taking into consideration in upcoming paleoenvironmental and paleoecological studies in the region. The extent of age mixing may also inform about the time span of colluvial deposition, which can be useful in future geomorphological studies. In addition, this study presents the first carbonate-target radiocarbon results for land snail shells and suggests that this novel, rapid, and more affordable dating method offers reliable age estimates for small land snail shells younger than ~20 cal ka BP.

scholarly journals Dating Recent Peat Accumulation in European Ombrotrophic Bogs

Radiocarbon ◽  
2013 ◽  
Vol 55 (3) ◽  
pp. 1763-1778 ◽  
Author(s):  
Johannes van der Plicht ◽  
Dan Yeloff ◽  
Marjolein van der Linden ◽  
Bas van Geel ◽  
Sally Brain ◽  
...  
Keyword(s):  
Binding Sites ◽  
Drainage Network ◽  
Surface Layers ◽  
Spheroidal Carbonaceous Particles ◽  
Carbonaceous Particles ◽  
Peat Deposits ◽  
Dating Methods ◽  
Dating Method ◽  
The Difference ◽  
Age Estimates

This study compares age estimates of recent peat deposits in 10 European ombrotrophic (precipitation-fed) bogs produced using the 14C bomb peak, 210Pb, 137Cs, spheroidal carbonaceous particles (SCPs), and pollen. At 3 sites, the results of the different dating methods agree well. In 5 cores, there is a clear discrepancy between the 14C bomb peak and 210Pb age estimates. In the upper layers of the profiles, the age estimates of 14C and 210Pb are in agreement. However, with increasing depth, the difference between the age estimates appears to become progressively greater. The evidence from the sites featured in the study suggests that, provided aboveground plant material (seeds, leaves) is selected for dating, the 14C bomb peak is a reliable dating method, and is not significantly affected by the incorporation of old carbon with low 14C content originating from sources including air pollution deposition or methane produced by peat decomposition. 210Pb age estimates that are too old may be explained by the enrichment of 210Pb activity in the surface layers of peat resulting from a hypothesized mechanism where rapidly infilling hollows, rich in binding sites, may scavenge 210Pb associated with dissolved organic matter passing through the hollow, as part of the surface drainage network. Until further research identifies and resolves the cause of the inaccuracy in 210Pb dating, age estimates of peat samples based only on 210Pb should be used with caution.

AMINOCHRONOLOGY AND TIME-AVERAGING IN QUATERNARY LAND SNAIL ASSEMBLAGES FROM THE MADEIRA ARCHIPELAGO

2017 ◽  
Author(s):  
Evan New ◽  
◽  
Yurena Yanes ◽  
Robert A.D. Cameron ◽  
Dinarte Teixeira ◽  
...  
Keyword(s):  
Land Snail ◽  
Time Averaging ◽  
Madeira Archipelago

Taphonomic bias and time-averaging in tropical molluscan death assemblages: differential shell half-lives in Great Barrier Reef sediment

Paleobiology ◽  
2009 ◽  
Vol 35 (4) ◽  
pp. 565-586 ◽  
Author(s):  
Matthew A. Kosnik ◽  
Quan Hua ◽  
Darrell S. Kaufman ◽  
Raphael A. Wüst
Keyword(s):  
Great Barrier Reef ◽  
Time Averaging ◽  
Burial Depth ◽  
Barrier Reef ◽  
Amino Acid Racemization ◽  
Sedimentary Environments ◽  
Depositional Setting ◽  
Lagoonal Sediment ◽  
Water Carbonate ◽  
Age Estimates

Radiocarbon-calibrated amino acid racemization ages of 428 individually dated shells representing four molluscan taxa are used to quantify time-averaging and shell half-lives with increasing burial depth in the shallow-water carbonate lagoon of Rib Reef, central Great Barrier Reef, Australia. The top 20 cm of sediment contains a distinct, essentially modern assemblage. Shells recovered at depths from 25 to 125 cm are age-homogeneous and significantly older than the surface layer. Taxon age distributions within sedimentary layers indicate that the top 125 cm of lagoonal sediment is thoroughly mixed on a sub-century scale. The age distributions and shell half-lives of four taxa (Ethalia, Natica, Tellina, and Turbo) are found to be largely distinct. Shell half-lives do not coincide with any single morphological characteristic thought to infer greater durability, but they are strongly related to a combined durability score based on shell density, thickness, and shape. These results illustrate the importance of bioturbation in tropical sedimentary environments, indicate that age estimates in this depositional setting are sensitive to taxon choice, and quantify a taxon-dependent bias in shell longevity and death assemblage formation.

Geochronological Potential of Isoleucine Epimerization in Calcite Speleothems

1994 ◽  
Vol 41 (1) ◽  
pp. 52-58 ◽  
Author(s):  
Stein-Erik Lauritzen ◽  
John Erik Haugen ◽  
Reidar Løvlie ◽  
Helge Gilje-Nielsen
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Acid Concentration ◽  
Northern Norway ◽  
Amino Acid Racemization ◽  
Dating Methods ◽  
Absolute Age ◽  
Amino Acid Concentrations ◽  
Age Independent ◽  
Age Estimates

AbstractThe extent of isoleucine epimerization in a calcite speleothem was determined to evaluate the amino acid racemization method in abiotic calcite. A 5.5-cm-thick flowstone slab from Hamarnesgrotta, northern Norway, was analyzed for amino acid concentration, composition, and isoleucine epimerization at 26 levels through the sequence. U-series dates provide an independent chronologic control. Epimerization increases monotonically with stratigraphic depth and linearily with U-series age, independent of amino acid concentrations. The rate of epimerization is calibrated against the U-series dates, and extrapolation into lower strata beyond the U-series limit yields absolute age estimates that are consistent with paleomagnetic data from the same speleothem. The results suggest that, if adequately calibrated, amino acid dating is applicable to speleothem material reaching time spans beyond the range of conventional dating methods. Amino acids in the speleothem were probably derived from surface soils and are associated with brown humic stains in the calcite.

scholarly journals Non-Concordance of Radiocarbon and Amino Acid Racemization Deduced Age Estimates on Human Bone

Radiocarbon ◽  
1983 ◽  
Vol 25 (2) ◽  
pp. 647-654 ◽  
Author(s):  
R E Taylor
Keyword(s):  
Amino Acid ◽  
Aspartic Acid ◽  
Human Bone ◽  
Amino Acid Racemization ◽  
Aspartic Acid Racemization ◽  
Order Of Magnitude ◽  
Direct Counting ◽  
Organic Fractions ◽  
Skeletal Samples ◽  
Age Estimates

Radiocarbon determinations, employing both decay and direct counting, were obtained on various organic fractions of four human skeletal samples previously assigned ages ranging from 28,000 to 70,000 years on the basis of their D/L aspartic acid racemization values. In all four cases, the 14C values require an order of magnitude reduction in age.

scholarly journals CALCINED BONE AS A RELIABLE MEDIUM FOR RADIOCARBON DATING: A TEST USING PAIRED NORTH AMERICAN SAMPLES

2017 ◽  
Vol 82 (3) ◽  
pp. 593-608 ◽  
Author(s):  
James C. Chatters ◽  
James W. Brown ◽  
Steven Hackenberger ◽  
Patrick McCutcheon ◽  
Jonathan Adler
Keyword(s):  
British Columbia ◽  
Pacific Northwest ◽  
Radiocarbon Dating ◽  
Bone Collagen ◽  
Organic Media ◽  
Radiocarbon Age ◽  
Cross Dating ◽  
Chronometric Analysis ◽  
Calcined Bone ◽  
Age Estimates

Radiocarbon dating using charcoal and bone collagen, two standards of archaeological chronology, can be difficult to impossible in environments where natural burning is common and bone does not preserve well. In such settings, charcoal ages cannot always be trusted and collagen is unavailable. Calcined bone can be a viable alternative medium in these situations but it has rarely been exploited in the Americas. One area that could benefit from its use is the forested Pacific Northwest. We compare calcined bone ages with charcoal and/or collagen dates from individual features or discrete cultural strata in 10 Washington, Oregon, Idaho, and British Columbia sites dating between 9000 and 100 B.P. Resulting radiocarbon age estimates based on calcined bone closely match those based on charcoal and/or collagen in nearly all cases. We obtained calcined bone dates from three additional Holocene-aged sites that had not previously produced accurate results, obtaining findings consistent with estimates based on cross dating. Preserving well where all other organic media of cultural origin are lost or unreliable, calcined bone holds promise for dating sites in conifer forests and other acidic soil settings, and can allow researchers to refine archaeological sequences that have long defied accurate chronometric analysis.

Carbon Dating the Image of Apo Santo Cristo de Lubao: From Oral History to Scientific Inquiry

2014 ◽  
Vol 8 (1) ◽  
Author(s):  
RODRIGO M. SICAT ◽  
XYRIS GERARD A. FERNANDEZ
Keyword(s):  
Social Sciences ◽  
Oral History ◽  
Scientific Inquiry ◽  
Radiocarbon Dating ◽  
Scientific Information ◽  
Scientific Research ◽  
Radiocarbon Age ◽  
Carbon Dating ◽  
Highly Sensitive ◽  
Dating Method

Oral history is important in preserving significant milestones in humanexperience. This scientific research was conducted to identify the age of the holyCrucifix using radiocarbon dating method. Specifically, it aims to carry out thestudy by identifying the age of the sacred Cross of the Crucified Image of Christthrough radiocarbon dating procedures, and to provide scientific information tothe people vis-à-vis results of the carbon dating analysis. Based on the findings ofthe study, radiocarbon dating analyses showed that Beta-316804 (The WoodenCross) indicated a measured radiocarbon age Cal AD 1650 to 1690 (Cal BP 300to 260) compared to Beta-316805 (Image of Christ) Cal AD 1680 to 1730 (Cal BP 270 to 220) as identified by Beta Analytic Incorporated in 2012. Results showthat at 2-sigma statistics (95% probability), 2 dates yielded overlapping ranges,indicating that the results are statistically identical. Analyses of samples indicatedthat samples came from the same tree. Beta-316804 (The Wooden Cross) is slightly older than Beta-316805 (Christ’s Image). In conclusion, the study revealed the proximity of the radiocarbon dating analyses to the traditional accounts of thepeople of Lubao, Pampanga. Considering the highly sensitive nature of analyticalchemistry apparatuses, the time ranges (ages) drawn from the chemical analyseswere closely proximate to the dates asserted by oral accounts of the place. The results reveal the antiquity of the Crucifix (Cross and Image of Christ). The resultsvalidated the customary and traditional social and religious norms of the peopleas regards their reverence and devotion to the Crucifix even in this contemporarymilieu.Keywords: Social Sciences, oral history, religious artifact, image, Apo Sto Cristo, radiocarbondating, Philippines

Time averaging and stratigraphic unmixing: reconstructing ecological decline in molluscan production (Holocene, Brijuni, NE Adriatic)

2020 ◽  
Author(s):  
Adam Tomašových ◽  
Martin Zuschin ◽  
Ivo Gallmetzer ◽  
Alexandra Haselmair
Keyword(s):  
Accumulation Rate ◽  
Sediment Cores ◽  
Sediment Accumulation ◽  
Coralline Algae ◽  
Time Averaging ◽  
Sedimentation Rates ◽  
Amino Acid Racemization ◽  
Ecological History ◽  
Shell Bed ◽  
Warm Temperate

<p>The northeastern Adriatic seafloor is formed by warm-temperate bioclastic carbonates with coralline algae, bryozoans and mollusks. These sediments represent a mixture of past and present-day production owing to low sedimentation rates and bioturbation. Although low sedimentation rates do not allow resolution of ecological history at centennial or even millennial scales on the basis of raw stratigraphic data, age unmixing based on radiocarbon-calibrated amino acid racemization shows that one of the major molluscan sediment producers – the infaunal suspension-feeder Timoclea ovata  – markedly peaked in production ~5,000 years during the maximum flooding and earliest highstand phase and significantly diminished in abundance during the late highstand phase at Brijuni, with a large proportion of dead shells now present in surface sediments representing shells that are several centuries old. This species still occurs in living assemblages but our analyses indicate that its former production was by several orders of magnitude higher. In contrast, stratigraphic trends in absolute and proportional abundance of this species in ~1.5 m-thick sediment cores show a gradual or a very mild upcore decline, indicating that raw stratigraphic data do not efficiently detect millennial-scale ecological dynamic. The temporal decline in production of Timoclea ovata is associated with an increase in water depth and an increase in sediment-accumulation rate, and led to a transition from molluscan oyster-scallop shell bed to late highstand bryomol sediments.</p>

scholarly journals Formal Statistical Models for Estimating Radiocarbon Calibration Curves

Radiocarbon ◽  
2004 ◽  
Vol 46 (3) ◽  
pp. 1093-1102 ◽  
Author(s):  
C E Buck ◽  
P G Blackwell
Keyword(s):  
Calibration Curve ◽  
Statistical Models ◽  
Random Effect ◽  
Modeling Framework ◽  
Sources Of Uncertainty ◽  
Calibration Curves ◽  
Dating Methods ◽  
Diverse Data ◽  
Radiocarbon Calibration ◽  
Age Estimates

We report on the development and implementation of a model-based statistical method for the estimation of radiocarbon calibration curves using diverse data. The method takes account of uncertainty on both the 14C and calendar scales, coherently integrating data, the calendar age estimates of which arise from different dating methods. It also allows for correlation between observations, if they have particular sources of uncertainty in common. We adopt an approach based on a random walk model, tailoring it to take account of possible calendar age offsets between different data sources by adding a random effect component. The latter allows us to use the same modeling framework for constructing the new calibration curve IntCal04, the comparison curve NotCal04, the Southern Hemisphere curve SHCal04, and the marine calibration curve Marine04.

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