A Romano-British puddingstone quarry in the Hertfordshire Chilterns

A 10.5 Ha site within three lobes of ancient woodland on the Gaddesden Estate, West Hertfordshire, was investigated using geological and archaeological techniques. 2-3 m of Paleogene silt-sand and gravel drapes the Chalk. Discontinuous lenses of pebbly conglomerate have been silicified to create concretions of Hertfordshire Puddingstone [HPS hereafter], one of which was in situ, a very rare find. The HPS is associated with a pure white sand and a previously un-reported lithology, a soft white pebbly Sarsen. During the Quaternary the feather edge of the Cenozoic cover was punctured following underlying dissolution features in the chalk to create 93 dolines, the largest concentration in the Chilterns AONB. As they grew the dolines were filled with Pleistocene loessic brickearth during the Wolstonian stage (MIS7) and captured blocks of HPS. These were exploited by the Romans as valuable raw material for quern-making. Shortly after the Roman Conquest in AD43 the site was cleared by felling and burning the tree cover. The cortex and poor-quality core stone were cut away from concretions with picks, manageable slices were detached using steel wedges and initial shaping was undertaken to produce blanks of querns to be finished elsewhere. Quarrying continued for, at most, fifty years. The excavated doline fills or upcast formed rims around the pits, which taken together protect the second largest remaining area of Roman ground surface in Hertfordshire. The site was abandoned and has been largely undisturbed apart from some quarrying of chalk and brickearth and offers further opportunities for research. (c) 2022 The Geologists' Association. Published by Elsevier Ltd. All rights reserved.

Automated summary

A 10.5 Ha site in West Hertfordshire was investigated using geological and archaeological techniques. It contains Paleogene sediments, Hertfordshire Puddingstone, and a previously unreported lithology. The site also features dolines created during the Quaternary, which were filled with Pleistocene brickearth containing blocks of Hertfordshire Puddingstone. The Romans quarried the site for raw materials and it later became the second largest remaining area of Roman ground surface in Hertfordshire.