Cleal, C.J. & Thomas, B.A. 1996 British Upper Carboniferous Stratigraphy. Geological Conservation Review Series No. 11, JNCC, Peterborough, ISBN 0 412 72780 3. The original source material for these web pages has been made available by the JNCC under the Open Government Licence 3.0. Full details in the JNCC Open Data Policy

Puddlebrook Quarry

Highlights

Puddlebrook Quarry is the only site showing the conglomeratic base of the Upper Carboniferous Trenchard Formation of the Forest of Dean (Figure 5.6).

Introduction

This disused quarry 1 km north of Drybrook, Forest of Dean, Gloucestershire [SO 646 183] is best known for the well preserved Lower Carboniferous plant fossils that it yields (see Palaeozoic Palaeobotany of Great Britain GCR volume 9, pp. 167–72 — Cleal and Thomas, 1995 for further description). However, overlying the Lower Carboniferous strata are Upper Carboniferous conglomerates belonging to the Trenchard Formation (Sibly and Reynolds, 1937; Trotter, 1942;_. Jones, 1972).

Interpretation

This is the only site to show the conglomeratic base of the Trenchard Formation. It contrasts markedly with the lowest preserved part of the Coal Measures in the southern part of the Forest of Dean, such as at Meezy Hurst, which is in typical Forest of Dean Pennant Formation facies. It tends to suggest that the more northerly areas represent more proximal parts of the fluvio-deltaic system, although this has to be seen in the context of the prevailing westerly palaeocurrents.

Conclusions

Puddlebrook Quarry is the only place where pebbly conglomerates can be seen at the base of the Coal Measures in the Forest of Dean. These rocks are about 306 million years old and are the remains of a river system that was flowing from an area that was being uplifted further north (known as the Usk Axis).

References