Dating recent peat deposits
The bias in calculated ages increases with poorer limit of detection and the magnitude of the disparity increases with age.
The origin and magnitude of this effect are considered below, firstly for an idealised, theoretical Pb dating provides a valuable means of establishing peat and sediment chronologies.
Assumptions underlying the techniques available for dating peat deposits often are poorly understood and generally untested.
We outline the approaches used to establish depth-age relationships in peat chronologies, including brief descriptions of the theory, assumptions, methodology, and logistics of each technique.
Due to their ombrotrophic nature and the tendency for -derived peat to have high cation exchange capacity, peatlands are ideal archives of atmospheric pollution.
However, efforts to establish depth-age relationships in peats are complicated by the difficulty of dating deposits reliably.
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New approaches are needed to measure the impact of industrially derived carbon on recent sediment ages to provide more secure chronologies over the last few hundred years.
Based on counts of spheroidal carbonaceous particles (SCPs), the potential aging effect for SCP carbon was calculated and shown to be appreciable for samples from the early 20th century.
Ages corrected for this effect were still too old in some cases, which could be a result of fossil CO fixation, non-SCP particulate carbon, contamination due to imperfect cleaning of samples, or the “reservoir effect” from fixation of fossil carbon emanating from deeper peat layers.
We include both continuous dating methods (i.e., methods based on Pb, constant bulk density, acidinsoluble ash, moss increment, pollen density) and chrono-stratigraphic markers (i.e., fallout isotopes from the Chernobyl accident and nuclear weapons testing, pollen stratigraphies, isothermal remanence magnetism, charcoal particles, spherical carbonaceous particles, PAHs, PCBs, DDT, toxaphene) that can be measured in peat and correlated temporally with known historical events.
We also describe the relatively new radiocarbon application of wiggle matching and use hypothetical data to highlight the potential of this developing technique for dating recent peat.