Mid-Holocene sub-blanket-peat alluvia and sediment sources in the upper Liffey valley, Co. Wicklow, Ireland

A recently exposed section across a first-order valley buried beneath the regional blanket peat on hillside slopes in the upper Liffey valley, Co. Wicklow, is described. The section shows two alluvia within a shallow valley form underlain by an extensive boulder and stone line over regional till and weathered granite. C-14 dates from wood in the alluvia indicate the older alluvium to have formed between 4324 +/- 53 BP and 4126 +/- 45 Bp and the younger between 3217 +/- 53 Bp and 2975 +/- 53 BP. The basal layer of the overlying peat yielded a date of 2208 +/- 61 Bp. The younger alluvium shows the effects of soil paludification prior to the peat expansion. Dated pollen analyses elsewhere in the upper catchment confirm the spread of blanket peat over most areas above 350 m after 4000-3600 Bp. The buried valley was contributing sediments to the mid-Holocene floodplains in the upper Liffey valley prior to the extension of blanket peat over the catchment after which sediment yields from it and the other catchment slopes declined. Copyright (C) 2003 John Wiley Sons, Ltd.