Weybourne Fossil Hunting

This is an idealised youngest-to-oldest account of Weybourne Hope and the cliffs eastwards. Glacial deformation, erosion and lateral changes prevent it from being treated as a single continuously exposed measured column.

Glacial and meltwater deposits

ALBION GLACIGENIC GROUP

Briton’s Lane Formation

Briton’s Lane Sand and Gravel Member

Later coarse-grained outwash survives as erosive remnants rather than as a continuous cap. Stratification and the mixed clast assemblage distinguish water-laid sediment from the underlying diamicton. Pawley and colleagues correlated outwash with the Briton’s Lane sand and gravel using sedimentary evidence and Scandinavian-derived clasts. Later work distinguished this outwash from channel bodies enclosed within the older deformed till. Basin geometry and deformation complicate the contact, so regional maximum thicknesses are not assigned to individual coastal exposures.

Sheringham Cliffs Formation

Sand-and-gravel bodies were historically described as outwash in large sag basins. The mapped 2013 study identifies a different origin for some bodies: subglacial drainage fills within the deformed till, distinct from later outwash. The till succession includes a chalk-rich Weybourne Town Till and sandy material incorporated into it during shearing. Published interpretations and terminology for the older sandy till have evolved; the important field observation is the mixing and repetition, rather than an apparently tidy succession of separate flat sheets.

The Weybourne Town Till is a member of the Sheringham Cliffs Formation. Its type section is the inland Weybourne Town Pit, a different site from this coastal guide. Neither the pit’s measurements nor the formation’s regional maximum thickness is used as the height of the coastal unit.

Weybourne Town Till Member: chalk-rich diamicton

The chalk-rich component is a highly calcareous, consolidated diamicton: clasts are dispersed in a finer matrix rather than sorted into ordinary gravel beds. It can be strongly banded, incorporating stretched and folded pieces of pre-existing sandy till. Its base can be a sharp shear or detachment surface against older sediment. The BGS definition permits contacts on Crag or older till, so a visible chalky band need not mark a new glacial advance each time it is repeated. “Marly Drift” is a historical term; it does not make this deposit a marine marl.

Sandy till components: Runton and Bacton Green correlations

Pawley and colleagues’ coastal study described a lower sandy Runton Till incorporated into the overlying chalk-rich till. The wider 2004 stratigraphy recognises sheared inclusions assigned to both Runton Till and Bacton Green Till in the Weybourne area. These sandy components and their attenuated folds must be described separately from the chalk-rich host, but they cannot be reconstructed as two intact, everywhere-present layers below it. The inland Town Pit has its own thrust-stacked geometry and is not used as a substitute for this cliff section.

Lowestoft Formation — alternative 2017 framework

West Runton Mélange Member — alternative framework

Weybourne Diamicton Member — alternative framework

The later tectonostratigraphical treatment by Lee and colleagues uses Weybourne Diamicton Member for the chalk-rich unit and West Runton Mélange Member for intensely deformed mixed sediment. West of Sheringham, that mélange incorporates interfolded chalk-rich diamicton as well as older material. These names reflect a revised structural interpretation and are not extra units to insert above the BGS till members. The section here retains BGS Lexicon names for the principal hierarchy while identifying the later usage, because bed order has been changed by ice-driven shearing and thrusting.

Return to the mapped coastal units and BGS lithostratigraphical framework. The following channel-fill descriptions are lithofacies within the deformed complex, not additional members assigned beneath the alternative Lowestoft heading.

Thicknesses in the mapped coastal study. Phillips and Lee’s 4.4 km Sheringham–Weybourne section records an upper Weybourne Town Till around 1–2 m thick, Bacton Green mélange locally up to 30 m, preserved Happisburgh Till up to 10 m, and Wroxham Crag about 1–5 m thick. These are observations across the mapped coastal section, not inland-pit measurements; they do not define one cumulative column or the thickness at Weybourne Hope. Erosion and structural repetition account for substantial local variation.

Subglacial sand-and-gravel channels: a revised interpretation

The detailed Sheringham–Weybourne mapping by Phillips and Lee separates sand-and-gravel bodies enclosed in the till mélange from later Briton’s Lane outwash. Concave erosional bases, locally preserved till caps and deformation shared with the enclosing diamicton indicate that the enclosed bodies formed during subglacial activity. The authors reject a purely gravitational “sag basin” origin for the bodies they studied. This revises the interpretation of particular exposures rather than demonstrating that all basins along the Norfolk coast formed in the same way.

Channel-fill facies and water-escape features

The mapped fills comprise coarse gravel packages, graded gravel-to-sand beds, cross-bedded or ripple-laminated sand, and local silt, clay and mass-flow layers. Cross-cutting packages record repeated shifts in meltwater flow rather than one continuous deposit. At TG 13458 43555 in the eastern Weybourne coastal section, folding and thrusting at a channel margin are cut by a 2–5 m wide steep water-escape conduit containing red-brown sand, interpreted as derived from underlying Crag. That width is a structural measurement of one feature, not the thickness of a named sedimentary bed.

Happisburgh Glacigenic Formation

Happisburgh Till Member: locally preserved below the mélange

The same western-coast study documents an older grey, relatively clay-rich till beneath the sandy mélange where preserved. It thins westwards and is ultimately cut out between the younger deformed sediment and the Chalk. Its discontinuous occurrence is important: it should neither be omitted from the documented coastal context nor drawn as a continuous basal member at Weybourne Hope. The full east-Norfolk succession, including Walcott Till and eastern lake beds, is not imported into this western section.

CRAG GROUP

Wroxham Crag Formation

Shelly sand, gravel and locally laminated finer sediment rest above the eroded Chalk. At Weybourne Hope the historical Weybourne Crag wedges out; farther east the succession becomes thicker and more varied. Marine shells occur with terrestrial material transported into the sea, so a land-mammal tooth does not make the enclosing bed a terrestrial soil or river deposit.

Modern fossil and amino-acid research places the named Weybourne Crag interval in the Early Pleistocene and supports correlation around 2.1–2.2 million years ago, with uncertainty in the exact equivalence of separate sites. This estimate should not be applied to every Wroxham Crag bed or to the overlying glacial deposits. Laminated and reworked silty material adds environmental complexity; the local succession is not labelled wholesale as the West Runton Freshwater Bed.

Upper laminated and reworked fine sediment towards Skelding Hill

Eastwards towards Skelding Hill, the pre-glacial succession includes laminated silty clay as well as sand and gravel. Published sections reach about 4 m in total, whereas the deposits thin sharply towards Weybourne Hope. Pollen from fine-grained material has been used to distinguish cold and cooler-temperate vegetation. At Skelding Hill the laminated clay above the historical Weybourne Crag was assigned to the Pastonian and has a reversed palaeomagnetic signal. These are lateral-section observations, not a claim that the entire 4 m sequence stands above every collecting point.

Shelly sands and gravels: the historical Weybourne Crag

The type-locality interval consists of shallow-marine shelly sand with laminated clay. Gravel includes rounded flint and far-travelled quartzose material, reflecting river supply to the coast. The marine fauna and the association of Macoma balthica with Mya arenaria have long been useful for correlation. Vole teeth, including Mimomys and Borsodia, supply additional age evidence. These land-derived remains occur in marine sediment and do not establish a separate freshwater bed wherever a tooth is found.

Clay-pebble and iron-cemented concentrations

Local erosion of fine-grained sediment produced clay clasts and conglomeratic concentrations within the cross-bedded sands. Grey silt clasts at Weybourne Hope contain pollen spectra and may have been reworked from laminated deposits like those farther east. Iron cement locally binds sand, gravel and fossil material, creating harder ledges. Such features should be recorded as local facies and reworking horizons; “iron pan” is a useful field description, not a separately established formation with a fixed coastwide age or thickness.

Mundesley Member: a mapping correlation, not a second shell bed

BGS mapping and the Weybourne slope study have included the coastal Crag in the marine Mundesley Member of the Wroxham Crag Formation. The historical name Weybourne Crag and this member assignment arise from different stratigraphical schemes and are not two successive deposits. Modern biostratigraphical work focuses on the older shell-bearing interval at the type locality; its approximate 2.1–2.2 Ma correlation must not be extended automatically to every sediment that older mapping grouped into the marine member. Nor is this marine Mundesley Member the glacial Mundesley Sand Member.

Basal erosion surface and soliflucted Chalk residue

The Crag rests unconformably on an uneven Chalk surface. Locally a thin chalk-rich residue, containing broken flint and chalk in a finer matrix, separates solid Chalk from shelly sand and gravel; it has been interpreted as pre-Crag solifluction material. Later dissolution, cryoturbation and glacial erosion also modified the junction. The order of processes matters: the brecciated chalky residue is not automatically a till laid down by the same ice that formed the higher glacial succession.

CHALK GROUP

WHITE CHALK SUBGROUP

Weybourne Chalk Member

The Campanian chalk is flinty, with softer lower beds and harder, nodular chalk above. The stratotype includes sections at Weybourne Hope and Weybourne Hope East. Published estimates of roughly 22–25 m describe the stratigraphical unit assembled across exposures, not a single cliff face of that height. Oysters are conspicuous in part of the succession, and upper omission surfaces lead towards the Catton Sponge Bed marker.

The eroded top separates the Chalk from the Crag across an enormous time gap. Modern sand and shingle may hide both units; loose fossils on the present beach can therefore be mixed even where their source strata are distinct.

Upper Weybourne Chalk and the Catton Sponge Bed boundary

At Weybourne Hope East the upper chalk alternates between harder and softer flinty intervals and contains two omission surfaces. The top of the Weybourne Chalk is defined in the regional scheme at the upper surface of Hardground II of the Catton Sponge Bed. The BGS Cromer account identifies the correlated Catton Sponge Bed as the lowest of three sponge-bearing horizons on the Sheringham foreshore, farther east. The paired marker is therefore essential to defining the unit, but the Catton Grove quarry log and its labelled flints are not imported as a measured Weybourne cliff section.

Weybourne 3, Weybourne 2 and Weybourne 1 faunal belts

Three informal, poorly delimited faunal belts have been recognised, numbered upwards from Weybourne 1 to Weybourne 3. In descending order, the upper belt approaches the hardground-bearing top; the middle belt is notably oyster-rich; and the lower belt occurs in the generally softer flinty chalk. These are palaeontological subdivisions, not sharply bounded formal members. The middle and upper chalk become harder and more nodular, with persistent flint bands. The available published summaries do not justify assigning a separate numerical thickness to each belt at the beach.

Oyster-rich middle chalk and hardground

In the stratotype succession, the middle chalk contains conspicuous oysters, including Pycnodonte and Hyotissa, together with a hardground. BGS regional synthesis gives a thickness of up to about 0.5 m for that hardground in the described succession; it is not a measurement of all oyster-bearing chalk or a guarantee of exposure at Weybourne Hope on a particular visit. A hardground records seabed cementation and interrupted sedimentation, rather than a volcanic or terrestrial rock layer.

Basal marker: Flint X and the underlying hardground

Published schemes have placed the base at Flint X or at an underlying hardground. Another BGS framework describes a sponge-bed hardground above Flint Z in the Weybourne Hope section. These definitions should remain tied to their original logs and not be collapsed into a newly invented composite “Flint X–Z Bed”. They show why a local flint band or a change in hardness alone may be insufficient to correlate an isolated exposure. The broad unit lies in the Late Campanian Belemnitella mucronata sensu lato succession; more finely divided belemnite schemes use additional names.

Pre-Weybourne Chalk beneath the named unit

The Cromer sheet explanation records about 5.4 m of older, Pre-Weybourne Chalk in the coastal succession eastwards from Weybourne Hope. This is additional to, not part of the quoted 22–25 m Weybourne Chalk estimate. The older chalk provides the lower side of the basal marker discussed above. Inland subdivisions such as Eaton Chalk and Basal Mucronata Chalk should not be assigned complete thicknesses here without the corresponding local log.

Glacial shearing of the chalk at Weybourne Hope

Close to the western end of the cliff section, low-angle shear planes displace flints and fossils within the Chalk. The nodular and broken appearance can therefore reflect deformation as well as original bedding and later dissolution. Sheared fossil fragments still belong to Cretaceous bedrock, but their displacement must be considered when following a horizon laterally. This structural modification is distinct from the younger till resting above the Crag.

References

BGS Lexicon: Wroxham Crag Formation

BGS Lexicon: Weybourne Town Till Member

BGS Lexicon: Sheringham Cliffs Formation

Weybourne Cliffs SSSI citation

Preece and colleagues (2020), The palaeontology and dating of the Weybourne Crag

Pawley and colleagues (2004), Middle Pleistocene sedimentology and lithostratigraphy of Weybourne

BGS Cromer district sheet explanation: Pre-Weybourne and Weybourne coastal Chalk

BGS synthesis: Weybourne Chalk and its marker definitions

Hopson (2005), Chalk framework: alternative basal-marker terminology

BGS East Anglia regional geology

Lee and colleagues (2004), revised glacial lithostratigraphy

Lee and colleagues (2017), tectonostratigraphical framework

BGS slope dynamics report: Weybourne case study

North Norfolk field guide: Weybourne chalk shear structures

Phillips and Lee (2013), Development of a subglacial drainage system: mapped Sheringham–Weybourne sections