C-14 AMS wiggle matching of raised bog deposits and models of peat accumulation

High-resolution Accelerator Mass Spectrometer (AMS) C-14 dates of selected plant macrofossils from the raised bog Engberts-dijksvenen (Eastern Netherl ands) show century-scale wiggles analogous to the radiocarbon calibration c urve. We used three relative time scales, viz., based on depth, mass, and p ollen concentration, respectively, to match the peat AMS dates to the calib ration curve. This procedure is repeated for one conventionally dated core. For each relative time scale, realistic confidence intervals are calculate d. Depth appears to be the best time scale for certain stratigraphical unit s of a core. This justifies using depth for wiggle matching conventionally dated mire cores published by others, even when C-14 errors are larger. Our evidence shows four major sources of C-14 variation for mire deposits comp ared to treerings: (1) dating error, due to sample composition. This includ es a reservoir effect demonstrated for many bulk peat samples; (2) hiatuses , causing a sudden 'leap' of peat C-14 age; (3) changing accumulation rates , apparent from a break in the slope of the peat C-14 ages; (4) sampling er ror. These results shed doubt on the assumed continuities in theoretical pe at accumulation models. Both mire stratigraphy and changing accumulation ra tes can be explained in qualitative hydrological terms. More evidence for a previously discovered reservoir effect in bog deposits is presented, thoug h the physical/biological mechanisms remain uncertain. (C) 2000 Elsevier Sc ience Ltd. All rights reserved.