Geology Site Account

Site name: St. Giles Church Puddingstone

Grid reference: TL 5113 1960

Description of site:

A large boulder of Hertfordshire puddingstone (140 centimetres long) is built into the base of the tower of St. Giles Church, Great Hallingbury. It is a typical 'Pagan Stone' upon which the church was built.

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Hertfordshire Puddingstone

Hertfordshire Puddingstone is an extremely hard rock with an interesting history.

About 60 million years ago, shortly after the extinction of the dinosaurs, this boulder was part of a beach of flint pebbles on the coast of a subtropical sea. About 55 million years ago the sea had retreated and the layer of pebbles was situated beneath the soil in a hot, dry climate similar to that of the Kalahari Desert today. During this time the pebbles were cemented together by quartz, forming an incredibly tough layer of rock.

During the Ice Age, about half a million years ago, rivers and glaciers broke up this layer and scattered the fragments over Hertfordshire and Essex. This boulder is one of these fragments and the original flint pebbles can be clearly seen. Puddingstone is so called because the pebbles give it the appearance of a plum pudding. It is usually called Hertfordshire Puddingstone because these boulders are most commonly found in East Hertfordshire. Some puddingstone is very colourful and in Georgian and Victorian times it was often cut and polished to make jewelry and decorative items such as snuff boxes.

The puddingstone at the base of St. Giles Church tower. (photo: G. Lucy)