Palaeoenvironmental Interpretation of a Buried Soil at Achnacree, Argyll

Abstract

The relationships between a humus iron podsol buried beneath a field bank at Achnacree, Argyll, western Scotland, and a normal sub-peat profile on an adjacent site are considered. It is suggested that the coarse-textured parent material and Ericaceous vegetational characteristics of the site induced and promoted progressive degradation of the profiles, which was possibly aided and enhanced by primitive cultivation practices. Translocation of humus is much more marked under the normal profile which reflects the operation of a more intensive pedogenic process which may be related, in turn, to the temporal factor in soil formation. Parallels are drawn with a site at Loughaveema, Co. Antrim, and it is suggested that soil deterioration was partially responsible for bog growth during the Sub-Boreal and Sub-Atlantic. THE Moss of Achnacree lies some 8 km north-east of Oban and covers about 312 ha of the southern part of the Benderloch peninsula at the entry to Loch Etive. The Moss, lying at an altitude of 65 m covers an extensive fluvio-glacial deposit derived mainly from Ben Cruachan granites and Loch Lorn schists. The deposit is considered by McCann (1961) to mark a halt in the retreat of a valley glacier which occupied Loch Etive. Since the late eighteenth century the edge of the Moss has been cut back, partly for fuel and in part to increase the area of arable land available to crofts located on the perimeter of the Moss. In 1968, a bank or field wall was discovered at G.R. NM 921349 overlying an old land sur- face. Both the bank and the surface had subsequently been buried by the growth of the Moss. Thus the bank and the surface beneath the bank clearly antedate parts of the peat which has built up to a depth of about 1-5 m. The bank is visible for some 60 m behind Croft 3 at Black Crofts, North Connell, before it disappears under the present peat face; it is about I-8 m wide and 0-4 m high and consists of two parallel lines of rounded granite and flatter schist stones with a central infill of rounded and sub-angular stones up to 8 mm in diameter within a gravelly loam matrix. This infill was thrown in from shallow ditches cut just outside the bank walls. About 5 cm from the surface of the infill bleached sand grains occur, showing the weak development of an A2 (Eb) horizon.