The Petrography and Origin of Deposits filling Solution Pipes in the Chalk near South Mimms, Hertfordshire

Abstract
Summary: Pipes and other solution cavities in the Upper Chalk near South Mimms contain deposits unlike those found in similar situations elsewhere in Great Britain. The cavities were formed near the sub-Palaeogene surface, and most of the deposits in them were derived from the basal Palaeogene beds (Thanetian and Sparnacian). A dark brown and very porous clay, which lines many of the pipes, is composed partly of the insoluble residue from the Chalk and partly of clay eluviated from the Palaeogene deposits. The clay was deposited from percolating water in spaces formed by dissolution of chalk at the margins of the pipes.