Portishead

PORTISHEAD

University of Bristol
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The best way to reach the site is from Portishead town centre, is to take the South Avenue then South Road, to the junction with Leigh View Road. There, turn right to park near the Royal Hotel. Steps nearby descend to the pebble beach to start of the section through the Pennant Sandstone near the Pier (map).

Ordnance Survey One-Inch Sheet 155 (Bristol & Newport)

1:40 000 Sheet 172 (Bristol & Bath)

Geological Survey One-Inch Bristol District

1:40 000 Sheet ST 47 (Clevendon & Portishead)

(Butler, Williams & Bradshaw (1972); Pick (1964 a & b); Stead and Williams (1973).

The area of interest goes from Portishead Pier near the Pennant Sandstone (see map above modified from Savage (1977)) in the East around Portishead or Battery point, to Kilkenny Bay to the south-west.

The rocks of Portishead date back to the Upper Palaeozoic (570-400 Mya). The rocks belong to the Old Red Sandstone facies of the Devonian (408-362 Mya) (picture below) and the Tournaisian and Westphalian stages of the Carboniferous are clearly exposed in these coastal sections. In addition, a discontinuous cover of Triassic Dolomitic Conglomerate is placed on the folded and faulted Upper Palaeozoic rocks.

The most common fossils found in this area are fish scales and plates (see pictures below for fossil and reconstructed Bothriolepis), burrows and crinoids, and if you are lucky complete fishes and maybe even eurypterids (giant-sea scorpions)!

These fossils are likely to be found within the Old Red Sandstone facies of the Devonian. The burrows can be seen (picture below) at Woodhill Bay (map) which is closer to Portishead Point.

After Woodhill bay, when the beach becomes rockier. Portishead Point has been reached. Here you can find lots of crinoid fragments. This indicates that the rocks were deposited in a high energy (near shore) environment and due to dolomitization in these rocks.

Bibliography

Butler, Williams, B. P. J. and Bradshaw R. (1972) A new exposure of the Old Sandstone-lower limestone Shale transition at Portishead, Somerset. Proceedings Bristol National Society, 32, 151-155, 2 figs.

Pick M. C. (1964 a). The Stratigraphy and sedimentary features of the Old Red Sandstone, Portishead coastal section, N. E. Somerset. Somerset. Proceedings Geological Association 75, 199-221, 7 figs.

Pick M. C. (1964 b). The Triassic Dolomitic Conglomerate and structure of the Old Red Sandstone Portishead coastal section, N. E. Somerset. Proceedings Bristol National Society, 30, 445-450, 1 figs., 1 pl.

Williams, B. P. J. and Hancock, P. L. (1977) in Geological Excursions in the Bristol District (ed. R. J. G. Savage), University of Bristol, pp. 29-46.

Savage, R. J. G. (1977) in Geological Excursions in the Bristol District. University of Bristol, pp. 29-46.

Stead, J. T. and Williams, B. P. (1973) The Pennant Sandstone of Portishead. Proceedings Bristol National Society, 32, 307-314, 2 figs., 2 pls.

Stensio, E. A. (1961)’Notes on the endocranium of a Devonian Cladodus’. Bulletin of geology of Institute of Upsala, 27, 128-144.