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    Publication Date: 2018-05-21
    Description: Publication date: Available online 22 April 2018 Source: Quaternary Geochronology Author(s): Lauren J. Davies, Peter Appleby, Britta J.L. Jensen, Gabriel Magnan, Gillian Mullan-Boudreau, Tommy Noernberg, Bob Shannon, William Shotyk, Simon van Bellen, Claudio Zaccone, Duane G. Froese High-resolution studies of peat profiles are frequently undertaken to investigate natural and anthropogenic disturbances over time. However, overlapping profiles of the most commonly applied age-dating techniques, including 14 C and 210 Pb, often show significant offsets (>decadal) and biases that can be difficult to resolve. Here we investigate variations in the chronometers and individual site histories from six ombrotrophic peat bogs in central and northern Alberta. Dates produced using pre- and post-bomb 14 C, 210 Pb (corroborated with 137 Cs and 241 Am), and cryptotephra peaks, are compared and then integrated using OxCal's P_Sequence function to produce a single Bayesian age model. Environmental histories for each site obtained using physical and chemical characteristics of the peat cores, e.g. macrofossils, humification, ash content, and dry density, provide important constraints for the models by highlighting periods with significant changes in accumulation rate, e.g. fire events, permafrost development, and prolonged surficial drying. Despite variable environmental histories, it is possible to produce high-resolution age-depth models for each core sequence. Consistent offsets between 14 C and 210 Pb dates pre-1960s are seen at five of the six sites, but tephra-corrected 210 Pb data can be used to produce more coherent models at three of these sites. Processes such as permafrost development and thaw, surficial drying and local fires can disrupt the normal processes by which chronological markers and environmental records are incorporated in the peat record. In consequence, applying standard dating methodologies to these records will result in even greater uncertainties and discrepancies between the different dating tools. These results show that using any single method to accurately date peat profiles where accumulation has not been uniform over time may be unreliable, but a comprehensive multi-method investigation paired with the application of Bayesian statistics can produce more robust chronologies. New cryptotephra data for the Alberta region are also reported here, including the historical Novarupta-Katmai 1912 eruption, White River Ash (East), and glass from Mt. St. Helens, Mt. Churchill, and probable Aleutian sources.
    Print ISSN: 1871-1014
    Electronic ISSN: 1878-0350
    Topics: Geosciences
    Published by Elsevier
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