Application of the method to dating Pleistocene carbonates and comparison with other dating methods |
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Authors: | M. Gascoyne |
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Affiliation: | Atomic Energy of Canada Ltd., Nuclear Fuel Waste Management, Pinawa, Manitoba R0E 1L0, Canada |
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Abstract: | The dating method is described in detail and its usefulness investigated by comparing ages of sixteen Pleistocene carbonates (mainly cave deposits) with those determined by the and methods. The ages are found to be critically dependent on corrections for decay of 227Th prior to alpha counting and ingrowth of daughter isotopes of 232Th derived from clastic detritus. Of nineteen sets of ages determined for the sixteen samples, good agreement is found for only seven sets. Differences are attributed to low U content of some samples and the possibility of excess 227Th in the calcite of samples younger than ~50 ky, possibly due to the coprecipitation of 231Pa during formation. Calculated “negative” ages may be a direct result of this process and the fact that, unlike the other methods, the activity ratio is non-zero at zero age. Nevertheless, the is found to be a useful alternative dating technique for carbonates which are between ~50 and 300 ky, because no spiking is required. It also serves as a check for partial concordancy with ages dated by the other methods. |
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