A magnesian chamosite from the Wenlock Limestone of Wickwar, Gloucestershire

Abstract

The Little Avon river rises on the scarp slope of the Cotswolds near Hawkesbury, 14 miles north-east of Bristol, and flows in a westerly direction over Mesozoic strata, until half a mile south-east of Wickwar it cuts through the Triassic mantle and exposes to view three inliers of Wenlock Limestone (Whittard & Smith, 1944, p. 65 and map). The West Gloucestershire Water Company was interested in the valley as a possible site for an impounded reservoir, and as part of a preliminary survey a trial-shaft was sunk into the Wenlock Limestone of the southernmost inlier situated near Sturt Bridge. The shaft penetrated 28 feet of dolomitized siltstones and crinoidal limestones, and at a depth of 4 feet it entered a band of calcareous chamositic siltstone averaging 9 inches in thickness. The shaft had been completed and the sides boarded before we heard it had been sunk; the hand-specimens were therefore obtained from the tip-heaps, but there is no doubt that all the material originated from the same horizon.