Evaluation of proposed early-Holocene advances of alpine glaciers in the North Cascade Range, Washington State, USA: constraints provided by palaeoenvironmental reconstructions

Many palaeoenvironmental reconstructions from across western North America indicate that the early to mid-Holocene was warmer and drier than present. The wide distribution of these records suggests that relatively mild and arid conditions were regionally ubiquitous during the early Holocene. In contrast, two recently proposed advances of alpine glaciers in the Cascade Range of Washington State, corresponding to equilibrium-line altitude depressions of 350 to 450 m, are placed in the early Holocene. The juxtaposition of the proposed major expansion of early-Holocene alpine glaciers with the constraint provided by a number of palaeoenvironmental reconstructions from directly adjacent areas results in palaeoclimatic gradients that are untenable. The apparent diachronous behaviour of adjacent palaeoenvironmental records may be an artifact of dating errors.