Tunstall and Sand-le-Mere are known for fossil-bearing glacial erratics, including material much older than the cliffs that contain it. The coast also records a complex Ice Age history, but erosion has seriously affected beach access; do not rely on the former route described in older guides.
FIND FREQUENCY: ♦♦♦ – Varied erratics are recorded, but beach cover and access determine whether collecting is possible.
CHILDREN: ♦ – Not recommended for a family collecting trip while erosion has removed the former safe access.
ACCESS: ♦ – Former access lost to erosion; obtain permission and current route advice from the holiday park.
TYPE: – Glacial cliffs and loose foreshore erratics; access-sensitive locality.
DIRECTIONS
♦ Approach Tunstall on the inland roads and follow the signs for Sand-le-Mere Holiday Park. Seaside Lane is closed near the eroding coast; do not follow an old map or satnav route towards the cliff edge.
♦ Ask at the holiday-park reception for permission and current advice before using any route through the site. Follow only an authorised, open route and the parking arrangements given by the park.
♦ Erosion warning: the former beach access was lost, and the beach was removed from the bathing-water list in 2023 because of access difficulties. Check the current position before travelling, obey closures and never improvise a descent down the clay cliff.
♦ Locality Ref: TA 31633 31510; this is not a confirmed beach descent.
FOSSIL HUNTING
When safe, lawful access is confirmed, concentrate on loose stones and naturally exposed fossils on the open beach. The till mixes rocks brought from different source areas, so a Jurassic ammonite found here was transported long after the animal died. Its discovery in a clay cliff does not make that cliff Jurassic.
Recorded Sand-le-Mere finds include the ammonites Dactylioceras and Arnioceras, the oyster Gryphaea and Carboniferous colonial corals identified as Lithostrotion. Coal, fossil wood, flint and chalk occur among the varied pebbles. Do not assume that every crystalline rock is a natural erratic: imported coastal armour can introduce similar material.
Examine weathered surfaces before considering preparation. A broken ammonite whorl, shell rib or coral section may be more recognisable than a complete outline. Keep the enclosing rock with the fossil and label it as a beach erratic unless its original geological source is securely identified.
Significant discoveries and geological milestones at Tunstall.
1900 – Erratic distribution compared
John Walker Stather included Tunstall in his comparison of coastal boulders, helping establish that the local deposits contained material transported from elsewhere.
1985 – Geological resurvey
N. G. Berridge resurveyed the Tunstall map area, contributing to the revised understanding of the superficial deposits of southern Holderness.
2020 – Complex glacial history reconstructed
Jenna Sutherland, Bethan Davies and Jonathan Lee analysed the coastal sediments and structures, challenging a simple interpretation based on two differently coloured tills.
2023 – Erosion changes the status of the beach
Tunstall lost its designated bathing-water status after cliff erosion made access and routine water sampling impracticable. The change underlines why historical collecting directions cannot be treated as a current safe route.
GEOLOGY
The cliffs are Quaternary superficial deposits rather than an exposed Jurassic succession. Ice moving through the North Sea region mixed older sedimentary rocks with clay, sand and gravel; modern waves now release and sort that mixture on the beach.
The local section has traditionally been described using the Skipsea and Withernsea tills within the Holderness Formation. Detailed work shows that the story is more complicated than two simple, uniform layers: deformation and local waterlaid deposits must also be considered. Younger freshwater sediments are distinct from the older marine fossils transported within the till.
Detailed geology and stratigraphy of Tunstall.
The framework below distinguishes the glacial deposits from younger surface material and older fossils carried within them. Exposure varies as beach sediment and landslips move.
CALEDONIA GLACIGENIC GROUP
NORTH SEA COAST GLACIGENIC SUBGROUP
Holderness Formation
These are the regional formal units for the Late Devensian glacial succession. Historical till names and local research subdivisions are explained below; a colour change alone does not prove a separate ice advance.
Skipsea Till Member and informal Withernsea Member: historical local correlation
Skipsea Till was formerly called Drab Till; Withernsea Till was called Purple Till. At Tunstall these names are useful historical labels, but the local lithofacies and structures provide a better guide to the observed section.
LFA 1 — dark diamicton
Dark, compact till, 0–6 m exposed in the northern study section; gravel lenses and stringers occur within it. Its base was concealed. A horizontal thrust surface separates repeated packages.
LFA 2 — reddish diamicton
Reddish sandy till overlies LFA 1 across a sharp contact. Grey interbeds, red/black streaks, sand–gravel laminations and a locally coarsening gravel pod record internal variation.
LFA 3 — waterlaid deposits
An uneven erosional base cuts into either till. Three local facies record waterlaid sedimentation; their distribution varies laterally, so they are not formal members or three continuous beds.
LF 3a — laminated fines
Dark clay and silt form horizontal laminations, locally coarsening upwards into the sandy facies.
LF 3b — fine sand
Fine sand is massive or bedded, locally cross-bedded, with thin seams of coal fragments. A thin sandy interval also overlies the local freshwater marl.
LF 3c — channel gravel
Rounded pebbles and cobbles form stratified, clast-supported gravel. Gravel fills channel-shaped hollows, with pebble concentrations along their erosional bases; some clasts show imbrication.
LFA 4 — freshwater marl
A discontinuous white calcareous silt, 0.20 m thick in the measured exposure, contains freshwater snails and small bivalves in life position. It lies within LFA 3, with sand above; it is not a coast-wide marker.
Surface and structural qualification
Thin soil caps the section. Fractures and thrust repetition complicate the apparent order. The four associations record glacial deposition and subsequent waterlaid sedimentation; older erratic fossils and indigenous freshwater shells must be distinguished.
Buried Chalk
Chalk is the regional bedrock but was not exposed in the published study section. No fixed depth beneath the beach is assigned here.
Sand-le-Mere submerged forest — historical foreshore exposure
The geological resurvey recorded tree stumps in peaty clay directly above till at TA 3204 3110. They were interpreted as remains of a former wetland exposed by coastal erosion, rather than trees felled and engulfed by advancing ice. This local post-glacial deposit is separate from the till succession; its present visibility is not assumed.
References
Berridge and Pattison (1994), Sand-le-Mere biogenic beds
Sutherland, Davies and Lee (2020), Tunstall litho-tectonic stratigraphy
BGS Lexicon: Holderness Formation
BGS Lexicon: Skipsea Till Member
BGS Lexicon: North Sea Coast Glacigenic Subgroup
SAFETY
Check the tide and sea conditions before setting out, and keep enough time and open beach for your return. Water can reach the cliff foot and cut off a route even when a distant tide prediction appears favourable. Never attempt to escape by climbing the clay cliffs.
Stay well clear of cliff faces, overhangs and the edge above. Rain-soaked till can slide without warning; fresh falls and soft mud are not safe collecting platforms. Wear grippy footwear, supervise children closely and turn back if the route is narrowing. For a coastal emergency call 999 and ask for the Coastguard.
EQUIPMENT
Take sturdy grippy footwear, tide information, a charged phone, a hand lens, a small soft brush, wrapping and rigid specimen boxes. Photograph each useful find and record the beach locality and date.
Loose surface finds are the priority. Do not dig into unstable till or disturb a standing section. If a permitted loose block genuinely needs splitting, use eye protection and keep other people clear; never strike sea defences, suspicious objects or a fossil-bearing surface blindly.
CLEANING AND TREATING
Begin with a soft brush and preserve the surrounding matrix. Robust limestone or flint specimens can be briefly rinsed in fresh water to remove salt and clay, but test a small area first and stop if the surface softens or flakes. Do not soak shale, pyrite, fragile shells or carbonised plant material.
Allow stable specimens to dry slowly at room temperature. Keep pyritic fossils dry and inspect them for cracking or powdery decay. Avoid acids, bleach and household varnish. If a fossil is crumbly, large or scientifically unusual, leave it unprepared and seek specialist conservation advice.
IDENTIFY YOUR FINDS
Need help identifying a fossil? Share clear photos, where you found it and its size with the community.
FURTHER READING
Deposits Magazine: a fossil hunter’s guide to the Yorkshire coast (regional background)
Tunstall glacial stratigraphy: Sutherland, Davies and Lee (2020)
BGS: Holderness Formation
East Riding Boulder Committee records
Defra: Tunstall bathing-water de-designation
ACCESS RIGHTS
Permission is required before using a route through the holiday park or other private land. Obey barriers and closure notices. The Sand-le-Mere coastal section is identified by Hull Geological Society as a local geological conservation site; avoid damage to standing exposures and take only modest loose finds where permitted.
It is important to follow our ‘Code of Conduct’ when collecting fossils or visiting any site. Please also read our ‘Terms and Conditions’.
LINKS
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