Origin and palaeoenvironmental interpretation of sarsens

Abstract

No detailed explanation has yet been provided for the origin of sarsens (silicified Cenozoic sediments) which are widely distributed across southern England (Fig. 1). The problem of sarsen formation is related to that of analogous terrestrial siliceous deposits recorded from every continent except Antarctica^1–7. In addition sarsens are of considerable archaeological interest as they were extensively used in the construction of megalithic monuments, notably those at Avebury and Stonehenge. It has been suggested that sarsens are glacially traitsported erratics^8,9, although this view has been challenged¹⁰. Their occurrence in areas in which other evidence of glacial activity is lacking, and the preservation on the surface of some sarsen stones of pockets of very weakly cemented sand, does not concur with the idea of long-distance transportation, but rather suggests local derivation from an original Cenozoic cover. Here the initial formation of sarsens is considered and recognition that they represent silcrete remnants enables broad conclusions to be drawn about their genesis and palaeoenvironmaental significance. From macromorphological, micromorphological and chemical comparisons with low latitude sileretes, primarily from southern Africa, it is concluded that sarsens represent remnants of surface and near-surface silicification developed on technically stable landsurf aces of minimal local reitet. Most sarsens seem to have formed under a semi-arid or arid climate, although there is evidence of development in a relatively humid environment for some occurrences.