|WATCHET||University of Bristol
The area as a whole lies on the southern shore of the Bristol channel, and to the north of the Quantock Hills. The sections available for study and fossil collection are all coastal, expose rocks of both Jurassic and Triassic ages, and illustrate the transition from a continental to a marine environment. Many of the rocks show evidence of faulting, sedimentary structures (ripple marks), folding, and areas of intense veining, but especially contain many fossils.
The succession of rocks that
can be viewed include:
JURASSIC- Lower Lias, shales and limestones.
TRIASSIC- Rhaetic, shales,
limestones and marls.
Grey Marl, mudstones, siltstones and gypsum horizons.
Tea Green Marl, mudstones and siltstones.
Red Keuper marl, mudstones.
The map above shows the three localities that can be visited with accompanying photos below of the sections. The best approach to investigate this area is to start at Blue Anchor bay and move east to Watchet, and thn finally to St. Audries bay.
From Bridgwater take the A39 to Williton and turn right onto the B3191 towards Blue Anchor.
1. Blue Anchor Bay.
the road from Watchet first meets the coast again, vehicles can be parked
and access gained to the foreshore via the slipway at the east of the bay.
Continue eatwards along the foreshore and view the red Keuper marls that
are faulted further along the section, against green grey marls.
This northern down faulted block is composed of Tea green and Grey marls,
overlain by Sully beds, then Rhaetic strata, with Liassic sediments at
the top of the cliff.
Fossil specimens can be found within many different rocks here including:
-Westbury beds, gritty calcareous limestones with small black fish scales, fish teeth and dark shelly limestones with abundant bivalves.
-Cotham beds, Grey limestones, with abundant ripple marks.
-Lower Lias, Grey shelly limestones, with oysters and ammonites.
A unique feature in these rocks is the presence of abundant gypsum veining, with pink gypsum forming in intersecting sets, formed during the folding of the rocks.
Picture of veining.
2. Watchet. Return to the car park in the centre of Watchet and gain access to the foreshore via the steps at the side of the railway line at the rear of the harbour. Walk eastwards and view the Keuper marls depicting a uniform lithology and intense faulting. Further to the east near the steps to the chalets above, the mudstone rocks of the Blue Lias contain thick shelled and coarsely ribbed arietitid ammonites and many crinoid fragments (see pictures below).
3. St. Audries Bay. From Watchet proceed eastwards along the B3191 to Ryodon and take a left turn to Home farm holiday camp. Cars can be parked near the office for a modest fee, and access to the foreshore is via a zig-zag pathway. once on the beach proceed east to the waterfall, where both sides of the bay can be observed in some splendour. Looking east the headland named Blue Ben is visible with Lias rocks faulted against the red Keuper marl. To the west the rocks are predominantly those of the Blue Lias. Here ammonites are very common within the alternating layers of black shale, and splitting of large blocks will reveal specimens similar to those below.
D. Hamilton and A. Whittaker 1977, Coastal exposures near Blue Anchor, Watchet and St. Audrie's Bay, North Somerset, pg. 101-111, edt. R. Savage, University of Bristol.
Map of area modified from
original figures 1 and 3 in the above publication.