An Example of Hard-Water Error in Radiocarbon Dating of Vegetable Matter

Shotton, F. W.

doi:10.1038/240460a0

Cited by 78 publications

(37 citation statements)

References 1 publication

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“…However, in recent years, several studies, including this study, have demonstrated problems in radiocarbon dating the total organic carbon fraction in sediments, when compared to shell dates from the same time-stratigraphic unit (Filion et al, 1981;Andrews et al, 1985). The discrepancies in the dates have been attributed to the' type of laboratory pretreatment (Olsson, 1979), the availability of contemporaneous organic material in the catchment (Bjorck and Hakansson, 1982), or the "hard-water effect" (Shotton, 1972;Karrow and Anderson, 1975).…”

Section: Ice Extent During the Last Glacial Maximummentioning

confidence: 90%

Relative Sea Level Chronology Determined from Raised Marine Sediments and Coastal Isolation Basins, Northeastern Ellesmere Island, Arctic Canada

Retelle¹,

Bradley²,

Stuckenrath³

1989

Arctic and Alpine Research

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A new relative sea level curve for the Robeson Channel area contrasts with previously published curves for the area by inferring that rapid emergence may have commenced at ca. 7400 BP, as much as 1200 yr earlier than previously predicted. Subsequently, uplift may have occurred at much lower rates from ca. 6000 BP to present. A comparison of shell dates used for the relative sea level curve and dates on disseminated total organic carbon (TOC) fractiop from lacustrine and marine sediments from sediment cores from emerged coastal lakes shows wide discrepancies. Furthermore, several inifmite TOC dates (>27,7SO to >40,600 BP) from glaciomarine sediments may imply that the region was ice-free during the last glacial maximum, but the validity of the TOC dates from the sediment cores is questionable due to variable contamination with redeposited detrital organic matter.

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Section: Ice Extent During the Last Glacial Maximummentioning

confidence: 90%

Relative Sea Level Chronology Determined from Raised Marine Sediments and Coastal Isolation Basins, Northeastern Ellesmere Island, Arctic Canada

Retelle¹,

Bradley²,

Stuckenrath³

1989

Arctic and Alpine Research

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“…Bulk organic samples from the bottoms of lake cores avoid problems associated with marine samples such as marine reservoir variations (Mangerud, 1972;Hjort, 1973;Mangerud and Gullikson, 1975;Bard, 1988;Bard et al, 1994;Birks et al, 1996) and the influences of meltwater in the marine environment (Sutherland, 1986;Hillaire-Marcel, 1988;Rodrigues, 1992). However, lacustrine bulk sediment samples can also yield anomalous old ages for other reasons (Shotton, 1972;Oeschger et al, 1985;Andrée et al, 1986;Wohlfarth, 1996). Aquatic plants as well as other aquatic organisms, which are frequently a significant part of bulk organic samples from lake cores, acquire carbon from lake water in which the concentration of 14 C may be lower than the atmosphere.…”

Section: Discussion: An Accurate Terrestrial 14 C Chronologymentioning

confidence: 99%

Varve, paleomagnetic, and 14 C Chronologies for late Pleistocene events in New Hampshire and Vermont (U.S.A.)

Ridge¹,

Bensonen²,

Brochu³

et al. 2002

gpq

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A deglacial chronology for northern New England has been formulated using an atmospheric 14 C calibration of the New England Varve Chronology and paleomagnetic records. This 14 C chronology is based on 14 C ages from macrofossils of non-aquatic plants and is about 1 500 yr younger than existing chronologies that are based primarily on 14 C ages of bulk organic samples. The lower and upper Connecticut Valley varve sequences of Ernst Antevs (NE varves 2 701-6 352 and 6 601-8 500) overlap (lower 6 012 = upper 6 601) based on their crudely matching varve records and their similar paleomagnetic records. Three 14 C ages at Canoe Brook, Vermont (NE varve 6 150 = 12.3 14C ka) calibrate the lower Con necticut Valley sequence. New AMS and con ventional 14 C ages on woody twigs from Newbury, Vermont calibrate the upper se quence from 11.6-10.4 14 C ka (NE varves 7 440-8 660) and are consistent with the over lapping varve and paleomagnetic records, and the Canoe Brook 14 C ages. Deglaciation of the Connecticut Valley in southern Vermont began at 12.6 14 C ka (15.2 cal ka) and the Littleton-Bethlehem Readvance in northern New Hampshire and Vermont reached its maximum at11.9-11.8 14 C ka (14.0-13.9 cal ka) followed by recession of ice into Québec at about 11.5 14 C ka (13.4 cal ka). A lake persisted in the upper Connecticut Valley until at least 10.4 14 C ka (12.3 cal ka) and may have been seen by the first humans in the area.

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“…Attempts to quantify and correct for uncertainties must compare the age results of chemically and/or physically separable fractions (macrophytes, pollen, bulk organic matter, humate, and humin) from discrete intervals (Shore et al, 1995;Abbott and Stafford, 1996;Van Klinken and Hedges, 1998). Barring reservoir-water effects (those effects that occur when materials have incorporated carbon from aqueous bicarbonate derived from an old source; Shotton, 1972), age coherency between isolated fractions from a discrete interval can be taken as evidence for acceptance of an age of sedimentation. Age incoherency between fractions demands a plausible explanation for the discrepancy and elimination of the ''contaminating'' fraction(s).…”

Section: Introductionmentioning

confidence: 99%

Late Quaternary lake-level changes constrained by radiocarbon and stable isotope studies on sediment cores from Lake Titicaca, South America

Rowe

Guilderson

Dunbar

et al. 2003

Global and Planetary Change

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We present and compare AMS-14 C geochronologies for sediment cores recovered from Lake Titicaca, South America. Radiocarbon dates from three core sites constrain the timing of late Quaternary paleoenvironmental changes in the Central Andes and highlight the site-specific factors that limit the radiocarbon geochronometer. With the exception of mid-Holocene sediments, all cores are generally devoid of macrophyte fragments, thus bulk organic fractions are used to build core chronologies. Comparisons of radiocarbon results for chemically defined fractions (bulk decalcified, humate, humin) suggest that ages derived from all fractions are generally coherent in the post-13,500 yr BP time interval. In the pre-13,500 yr BP time interval, ages derived from humate extracts are significantly younger (300 -7000 years) than ages from paired humin residues. Gross age incoherencies between paired humate and humin sub-fractions in pre-13,500 yr BP sediments from all core sites probably reflect the net downward migration of humates. Ages derived from bulk decalcified fractions at our shallow water (90 m) and deep water (230 m) core sites consistently fall between ages derived from humate and humin subfractions in the pre-13,500 yr BP interval, reflecting that the bulk decalcified fraction is predominantly a mixture of humate and humin sub-fractions. Bulk decalcified ages from the pre-13,500 yr BP interval at our intermediate depth core site (150 m) are consistently older than humate (youngest) and humin sub-fractions. This uniform, reproducible pattern can be explained by the mobilization of a relatively older organic sub-fraction during and after the re-acidification step following the alkaline treatment of the bulk sediment. The inferred existence of this 'alkali-mobile, acid-soluble' subfraction implies a different depositional/post-depositional history that is potentially associated with a difference in source material. While internally consistent geochronologies can be developed for the Lake Titicaca sequence using different organic fractions, mobile organic sub-fractions and fractions containing mobile sub-fractions should generally be avoided in geochronology studies. Consequently, we believe humin and/or bulk decalcified ages provide the most consistent chronologies for the post-13,500 yr BP interval, and humin ages provide the most representative ages for sedimentation prior to 13,500 yr BP interval.Using the age model derived from the deep water core site and a previously published isotope-based lake-level reconstruction, we present a qualitative record of lake level in the context of several ice-core records from the western hemisphere. We find the latest Pleistocene lake-level response to changing insolation began during or just prior to the Bølling/Allerød period. Using the isotope-based lake-level reconstruction, we also find the 85-m drop in lake level that occurred during the mid-Holocene was synchronous with an increase in the variability of ice-core d 18O from a nearby icecap, but was not reflected in an...

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An Example of Hard-Water Error in Radiocarbon Dating of Vegetable Matter

Cited by 78 publications

References 1 publication

Relative Sea Level Chronology Determined from Raised Marine Sediments and Coastal Isolation Basins, Northeastern Ellesmere Island, Arctic Canada

Relative Sea Level Chronology Determined from Raised Marine Sediments and Coastal Isolation Basins, Northeastern Ellesmere Island, Arctic Canada

Varve, paleomagnetic, and 14 C Chronologies for late Pleistocene events in New Hampshire and Vermont (U.S.A.)

Late Quaternary lake-level changes constrained by radiocarbon and stable isotope studies on sediment cores from Lake Titicaca, South America

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