Use of environmental magnetic measurements to validate the vertical extent of ice masses at the Last Glacial Maximum

Analysis of soil samples from above and below trimlines representing the upper limit of glacial erosion at the Last Glacial Maximum demonstrates that soils with prolonged weathering histories above such trimlines yield significantly different mineral magnetic signatures from soils below trimlines. The nature of the contrast is conditioned by lithology. Basalt soils above the trimline yield significantly higher values of concentration-dependent magnetic parameters (chi, chi(arm), IRM3T, soft IRM and hard IRM) than those below the trimline, due probably to transformation of non-magnetic iron-bearing minerals into magnetic forms. Conversely, for sandstone soils most magnetic parameters yield significantly lower values for above-trimline samples, probably reflecting loss of ferrimagnetic minerals by dissolution and oxidation to aniferrimagnetic forms. These significant contrasts represent a new approach to validating high-level weathering limits as periglacial trimlines cut at the Last Glacial Maximum. Copyright (C) 2002 John Wiley Sons, Ltd.