GNS Field Trip to Garden Cliff, Westbury-on-Severn (21 Feb 2009, contributed by Andrew Bluett)

The GNS field trip to Garden Cliff at Westbury-on-Severn took place on a gloriously warm and sunny day which had all the signs of a promising Spring about it. The meeting point at Westbury Village Hall proved to be a good location where cars could be left and the assembled company of 14 members led by Membership Secretary Andrew Bluett walked down Strand Lane to The Strand at the end of the public road on the river bank close to the western end of Garden Cliff.

After clambering down over the river wall onto the “beach” the members were led along the foreshore below the cliff to the eastern end, then up and over the river bank and back via the public footpath along the top of the cliff back to Strand Lane.

Garden Cliff is one manifestation of the mudstone beds that are evident throughout the Severn Valley and exposed at Wainlodes in the north, Garden Cliff, Newnham, Bullo and Box Wood (Awre) in the west, Hock Cliff in the east and Aust Cliffs (adjacent to the Severn Bridge) in the south. Sometimes referred to as Keuper Marls, the mudstone (which is so friable and soft as to barely warrant the title “rock”) was formed in the upper Triassic some 200+ million years ago and marks the boundary with the later Jurassic period. With its stripes of green-grey and red strata, Garden Cliff stands out as a visible landmark in the alluvial plain. Within the strata the stone is visibly globular and breaks down into characteristic near spherical and curved, sharp edged fragments and even in the light winds during the visit, was constantly being wind eroded with small falls of rock occurring most of the time. The beds were formed in arid, semi-desert conditions before being overlaid by brackish and marine water borne sediments of the early Jurassic.

At the eastern end of the cliff the strata dips down so that the overlying beds of shale, sandstone and limestone are visible and within reach. The foreshore at this point is littered with slabs of fossilised beach fragments, the ripples clearly visible and diagnostically marine formed as evidenced by their profile. (The varied strata in the cliff are clearly shown in this picture taken by Ingrid Twissel.)

Within these beds there are fossils of sea shells and marine creatures including fish whose teeth, scales and bones can be found along with Ichthyosaur and Pleisiosaur bones, coprolites (fossilized excrement), Shark’s teeth, and the remains of choristoderes, these being marine, lizard-like creatures which grew to 1m in length. It is also possible to find deposits of Pyrites (Fool’s Gold) with particles from dust size to crystals several millimetres across and in both gold and a copper-red colour, several members collected samples of both.

More detail on Garden Cliff and the other sites in this geological group is available here.

On arrival at the site it was immediately clear that the river level was at its lowest ebb, there were large expanses of sand exposed and covered with hundreds of Gulls of several species, mainly Lesser Black Backed interspersed with Greater Black Backed, Herring, Common and Black Headed Gulls and Crows. Within minutes of walking along the beach Colin Twissel had located the first of seven Smooth Newts (see Colin’s picture below) whilst turning over driftwood in search of insects. Much speculative discussion took place as to why these creatures were present in what appears to be an alien environment for them. One specimen could be seen to be accidental, but seven suggests something different. Is this in fact a habitat where they occur naturally? Or are the Newts casualties from washout of watercourses after the flooding and snow melt that have made landfall on the foreshore and taken temporary refuge? The question remains to be answered.

On the cliff face there was evidence of roosting Peregrine and Kestrel in the splashes of “whitewash” littered under several perching points, unfortunately neither bird was present, and 3 Mallards floated offshore.

At the eastern end of the cliff the party spent some time searching for fossils and for Pyrites with some success and with helpful comments on geological and paleontological matters from Dr Mike McEllin, before scaling the river bank and beginning the trek back along the cliff top footpath towards the start point.

In the fields stretching back from the cliff edge flowering Speedwell was located, two Rabbits and Two Hares were seen, there were Buzzards and a flock of up to 30 Reed Buntings frequenting the thorn thicket on the cliff edge and flying out from the bushes to alight and feed in the grass. Dead Elms were scattered along the cliff top, none more than 10 inches in diameter and all victims of Dutch Elm Disease. The first butterfly of the year, a small Tortoiseshell, flew by and a Raven called from somewhere across the river.

Other species noted during the walk were freshwater shrimps (Gammarus) under stones and driftwood, a singing Blackcap at The Strand, a Green Woodpecker and Little Owl calling near Moys Hill Farm and a Cormorant over the river. Footprints of a mammal were found on the foreshore, a round pad with five smaller round toe prints which were possibly Otter and there were a few Snowdrops in full flower on the walk back to the Village Hall.

Altogether a very enjoyable and successful walk with a few surprises and with both river and weather conditions being near perfect it was enjoyed by all present.

Field Trip Sound Files

Recordings made on the field trip to the Garden Cliffare available here:

20090221 GNS Garden Cliff 1 (1.7MB)

20090221 GNS Garden Cliff 2 (1.5MB)

The recordings are from Vernon Harwood’s radio show “The Spirit of Gloucestershire” made available by courtesy of Brian Bailey and BBC Radio Gloucestershire – copyright remains with BBC Radio Gloucestershire.

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