Geochemical provenancing of igneous glacial erratics from Southern Britain, and implications for prehistoric stone implement distributions

Abstract

Sixteen basic and intermediate composition igneous glacial erratics from Anglian (pre‐423,000 years) deposits in Hertfordshire and Buckinghamshire, southern Britain, were selected for chemical and petrographic analysis in order to determine their original source outcrops. Major and trace element compositions suggest that seven samples (plus two uncertain) originated in the Lower Carboniferous volcanics of the Scottish Midland Valley (SMV), four came from the Upper Carboniferous quartz dolerite association which crops out in Scotland, northern England (Whin Sill) and extends to Norway, and one came from the northern England Cleveland Dyke. One sample of altered dolerite is ambiguous but has some similarity to the Old Red Sandstone (Devonian) age lavas of the SMV, and one meta‐basalt sample may be from southwest Scotland or Scandinavia. These results identify specific outcrops which provided glacial erratics within currently accepted ice trails in the United Kingdom, and provide the first supporting evidence based on geochemistry, rather than petrography, for these ice movements. The distribution and provenance of glacial erratics are of importance in archaeological studies, because erratics provided a potential source of raw material for stone implement production. There is a marked geographical correlation between the distribution of prehistoric stone implements of quartz dolerite in the United Kingdom, and directions of ice movements from quartz dolerite outcrops within Britain. This correlation lends support to the hypothesis that prehistoric man made extensive use of glacial erratics for implement manufacture, as an alternative to quarrying at outcrops and subsequent long‐distance trade. © 1999 John Wiley & Sons, Inc.

Driving forces for the weathering and alteration of silica in the regolith: Implications for studies of prehistoric flint tools

“…Petro-archaeological studies of flints have difficulty in establishing a correlation between the artefact material and the potential sources of that material (Bressy, 2002;Briggs, 2001;Deflandre, 1935;Kars et al, 1990;Masson, 1981;Mauger, 1985;Sieveking et al, 1972;Valensi, 1957). Studies have been mostly on primary (in situ) and/or sub-primary sources, whereas gatherings of flints by prehistoric peoples were often probably made from secondary, redeposited materials such as glacial till and waterlaid gravels (Fernandes and Raynal, 2006;Hughes et al, 2010;Prothero, 1987, 1992;Stapert, 1976;Verri et al, 2004;Williams-Thorpe et al, 1999). Transformations of the flint cortex that can be identified from detailed petrographic studies are specific to some sedimentary environments (Fernandes, 2012;Fernandes et al, 2007).…”