Welsh Journals

Periglacial Origin of Slope Deposits near Woolhope in the Welsh Borderland. R.A.SHAKESBY. Department of Geography, University College of Swansea (Received September 1980: in revised form December 1980) Abstract Analysis of sedimentary properties of slope deposits exposed about 7 km south east of Hereford is discussed. The following parameters have been examined: particle size composition, Atterberg limits, roundness and preferred orientation of stones, and heavy mineral assemblages. The results are generally typical of those obtained for head deposits investigated elsewhere in southern and western Brit- ain. The contribution of solifluction and slope wash processes in forming the deposits is discussed. It is suggested that the exposed sediments are no older than Late Devensian and probably formed mainly during the Loch Lomond Stadial. Introduction Since the mid 1960s it has become increasingly customary for British workers to employ quantitative techniques, such as shape and pre- ferred orientation of stones and sediment size properties, in disting- uishing and characterising solifluction (head) deposits. A number of examples of this approach can be found in the literature dealing with head deposits in west, central and south Wales (e.g. Watson and Watson, 1967; Potts, 1971; Harris and Wright, 1980). Thick accumulations of slope deposits are well exposed on the western fringe of the Woolhope upland area situated some 7 kms. south east of Hereford in the Welsh Borderland. Surprisingly, how- ever, no detailed analysis of these or any such deposits throughout the Hereford Basin has been published. Yet, verifying the presumed periglacial origin of the Woolhope deposits is important in terms of elucidating the regional glacial history since they lie in close juxta- position to (a) a weakly established limit of Late Devensian ice near Hereford and to (b) isolated hilltop gravel deposits dating from the earlier Older Drift glaciation (Luckman, 1970; Bowen, 1977) (Figure 1A). This paper presents the results of a detailed sedimentary analy- sis of the Woolhope deposits which provide the basis for discussion on their nature of formation and age. Determination of the following quantitative characteristics of these deposits has been carried out: particle size properties, Atterberg limits, orientation and shape of stones, and heavy mineral assemblages.