Dec 13, 2016 - 210. Authors. Lauren J Davies * · Duane G Froese · Peter Appleby · Simon van Bellen ... William Shotyk · Claudio Zaccone. University of Alberta.
B23C0598: Highresolution age modelling of peat bog profiles using pre and postbomb 14C, 210Pb and cryptotephra data from six Albertan peat bogs Tuesday, 13 December 2016 13:40 18:00 Moscone South Poster Hall
Age modelling of recent peat profiles is frequently undertaken for highresolution modern studies, but the most common techniques applied (e.g. 14 C, 210 Pb, cryptotephra) are rarely combined and used for testing and intercomparison. Here, we integrate three agedating approaches to produce a single age model to comprehensively investigate variations in the chronometers and individual site histories since 1900. OxCal’s P_Sequence function is used to model dates produced using 14 C (pre and postbomb), 210 Pb (corroborated with 137 Cs and 241 Am) from six peat bogs in central and northern Alberta. Physical and chemical characteristics of the cores (e.g. macrofossils, humification, ash content, dry density) provide important constraints for the model by highlighting periods with significant changes in accumulation rate (e.g. fire events, permafrost development, prolonged surficial drying). Subcm resolution output shows there are consistent differences in how the 14 C and 210 Pb signals are preserved in peat profiles, with 14 C commonly showing a slight bias toward older ages at the same depth relative to 210 Pb data. These methods can successfully be combined in a Bayesian model and used to produce a single age model that more accurately accounts for the uncertainties inherent in each method. Understanding these differences and combining the results of these methods results in a stronger chronology at each site investigated here despite observed differences in ecological setting, accumulation rates, fire events/frequency and permafrost development.
