Some stone-orientation results from the Forth Valley

Abstract

Synopsis This paper is based on 40 till fabric analyses undertaken in the Forth Valley, an ice-moulded lowland. Only 31 of the sites had significant (anisotropic) orientations as obtained by vector analysis. Of these, 17 were parallel to the presumed local direction of ice-movement—generally west to east, except for the Midlothian Basin, where it was south-west to north-east. Of the remainder, 1 was transverse to ice-movement; 8 were oriented in the direction of slope of the ground; and 5 appeared unrelated either to ice-movement or slope. The deflecting influence of numerous crags and hills may help to explain the absence of definite orientations at some sites. Orientation evidence, together with pH and particle-size analysis, has also revealed a clear distinction between ‘boulder clay’ and the superficial ‘sandy clay with stones’. The boulder clay was a compact, less-leached deposit, with a better organisation of stones, producing fabric diagrams that usually had a preferred orientation parallel to the local ice-movement. The results suggest that most of the sandy clay with stones was produced by washing of the upper parts of the boulder clay during immediate post-glacial times.