Regional and Local Components in the Areal Distribution of Surface Sand Facies in the Breckland, Eastern England

Abstract

ABSTRACT The Breckland is a distinctive region of arenaceous deposits overlying the chalk escarpment of eastern England, covering an area of some 1000 sq km. The origin of these deposits is obscure, but it is commonly believed that they originated from the weathering of sandy till derived from the Neocomian Sandringham Sands to the north. This investigation, using both systematic- and nested-sample surveys, was designed to determine: (1) whether there are significant areal variations in the grain size of the surface sands; (2) if so, to what extent it is possible to disentangle regional and local components; and (3) which linear scale intervals are associated with the greatest grain size variance components. Trend-surface analysis pointed to significant regional variations in grain size, with a general coarsening towards the north-east. This was supported by a hierarchical variance analysis, which also indicated that: (1) variability in grain size increases successively with areal sub-division; (2) the total amount of variability is generally greater for coarse-grained facies; and (3) that the increments of variability differ at different areal levels. The greatest increments appeared at 17,000 m (contributing some 54 percent of the total variability), at about 8 m (22 percnt), and within the range of about 125 to 1000 m (18 percent). It is tentatively suggested that the regional variations (that is, at the scale of 17,000 m) might be explained by variations in the original till compositi n and/or by surface aeolian reworking. The variability at the most local level seems to accord with the dimensions of the periglacial polygon and stripe patterns which are characteristic of much of the Breckland, although the variability in the range [1]/[8] to 1 km is less obviously accounted for.