Pegwell Bay Fossil Hunting

1852 – Thanet deposits described
Joseph Prestwich described the deposits that became known as the Thanet Sands. The Pegwell exposures subsequently became central to recognising the oldest Palaeogene succession exposed at the surface in south-eastern England.

1866–1872 – Thanet Beds terminology developed
William Whitaker preferred the name Thanet Beds because the Pegwell succession includes clays, silts and marls as well as sand. His divisions provided a basis for later subdivision of the formation.

1897 – Foraminifera and measured section published
Burrows and Holland published a study of the Thanet Beds foraminifera with a detailed measured section. The microscopic fauna subsequently became important for dating and comparing the otherwise sparsely fossiliferous lower beds.

1954 – Brickearth recognised as loess
Pitcher, Shearman and Pugh established the wind-blown character of the Pegwell brickearth, turning the low cliff-top deposits into an important record of cold-climate sedimentation as well as a former brickmaking resource.

1956–1958 – Microfossil succession refined
John Haynes studied the smaller foraminifera and refined the divisions of the Thanet Beds. His work helped establish the age and palaeoenvironmental significance of the Pegwell succession.

1965 – Five fish-otolith species described
Stinton described five new fish-otolith species from the Pegwell section. These small inner-ear stones added a vertebrate dimension to the site’s importance and were used to interpret the character of its Palaeocene marine environment.

1969 – Basal sediment mineralogy investigated
Mineralogical studies identified unusual zeolite-bearing material in the lowest Thanet deposits and examined the origin of the Bullhead Bed matrix. This work opened a route to recognising an altered volcanic component.

1977 – Post-hoverport exposures redescribed
David Ward documented the sections remaining after construction of the hoverport access cut the former continuous exposure. His account distinguished the Cliffs End and Car Park sections and provided the framework for subsequent palaeontological work.

1979 – Evidence for early Palaeogene ash falls
Robert Knox identified igneous grains associated with zeolites in the basal deposits, connecting material at Pegwell with early Palaeogene volcanic ash deposition.

1985 – Thanet magnetozone established
Townsend and Hailwood investigated the magnetic polarity of the Pegwell succession and established the normal-polarity Thanet magnetozone, adding an independent method of dating and correlation.

1987 – Nannofossils improved dating
Siesser, Ward and Lord found indigenous calcareous nannoplankton low in the sequence, improving age control below the better-known upper fossiliferous beds.

1994–1996 – Sequence relationships revised
New age and sequence studies refined correlations with boreholes and recognised a break between the Pegwell and Reculver intervals. The exposed succession is therefore more complex than one uninterrupted marine sand body.

2020 – Rapid dust-deposition phases dated
High-resolution luminescence dating identified two major phases of loess accumulation at Pegwell, centred on approximately 25–23.5 and 20–19 thousand years ago. The results connected the dust record with changing ice-sheet and atmospheric conditions.

2022 – Dust sources linked with meltwater pulses
Geochemical provenance research linked rapid loess accumulation at Pegwell with sediment supplied during changing Eurasian ice-sheet and meltwater conditions. The work strengthened the site’s value as a record of distant glacial processes.

2023 – Reserve access zoning mapped
Updated access mapping distinguished the vulnerable public-access chalk shore from protected saltmarsh and mudflat areas without coastal access. Geological visits must respect these wildlife zones.

2024 – Magnetic fabrics tested dust transport
Dominika Niezabitowska and colleagues examined the magnetic minerals and grain alignment of the Pegwell loess. The results supported dust-fall deposition and explored a possible southeasterly transport component, refining interpretations of the winds responsible for accumulation.

References
Shephard-Thorn (1988), Geology of the country around Ramsgate and Dover, sheets 274 and 290
Thanet Coast Project, Fossil Code
Hubbard (2021), Thanet anticline’s shifting shorelines: Two millennia of change
Thanet Coast Project, Nature designations
BGS OR/14/008, Lithostratigraphy of the London Basin and East Anglia
Daley & Balson (1999), Pegwell Bay, GCR 15
Mortimore, Wood & Gallois (2001), Thanet Coast, GCR 23
International Commission on Stratigraphy, ratified Global Stratotype Sections and Points
Kent Wildlife Trust, Sandwich and Pegwell Bay access and restrictions
Stevens and others (2020), Abrupt last glacial dust fall over southeast England associated with dynamics of the British-Irish ice sheet

CHALK GROUP

The white rock is a marine limestone accumulated from carbonate-rich sediment during the Late Cretaceous. Flint formed within the sediment after deposition rather than being a layer of lava.

WHITE CHALK SUBGROUP

The local succession belongs to the flinty and flint-poor white chalks traditionally included in the Upper Chalk. Formation boundaries are based on rock character, whereas the zones used in many older accounts are based on fossils.

Seaford Chalk Formation

Soft white chalk contains repeated nodular and tabular flint layers. In the Thanet sections the older name Broadstairs Chalk largely corresponds to this formation; it is not an additional overlying unit. The flints provide conspicuous markers, but faulting can repeat or remove portions of a cliff section.

Columnar Flint and lower Santonian beds
At the western end of Ramsgate’s Western Undercliff, the Columnar Flint and underlying flints record the lower part of the exposed Thanet Chalk succession. This eastern end of the wider Pegwell–Ramsgate coastal section includes ribbed inoceramid shells and other lower Santonian fossils. The named Pegwell Inoceramid Band is defined at West Cliff Promenade, Ramsgate, rather than at every exposure around the bay.

Whitaker’s Three-inch Flint beneath Pegwell Bay Hotel
The tabular marker can be followed at the short seawall beneath Pegwell Bay Hotel. Published records at this horizon include Platyceramus, Sphenoceramus, Cordiceramus cordiformis and abundant Conulus. Fault offsets and the changing height of this flint help reveal the structure of the bay’s Chalk cliffs.

Newhaven Chalk Formation

The local expression of this formation is the Margate Chalk Member. Its conspicuously flint-poor, marl-free appearance differs from the marl-rich succession at the formation’s Sussex type area.

Margate Chalk Member at the Palaeogene contact

Farther west, at Redcliff/Cliffs End, the younger chalk beneath the Thanet Formation belongs to the Marsupites testudinarius interval. This is younger than the lower Santonian Seaford Chalk farther east. The Palaeogene erosion surface cuts across the Chalk succession, so these are not interchangeable versions of one vertical log.

Chalk–Palaeogene unconformity
At Redcliff Point the contact dips south and places the basal Thanet deposits on an eroded Chalk surface. A thin secondary tabular flint, about 50 mm thick in the memoir section, locally occurs beneath and partly within the basal deposit. It is not Whitaker’s Three-inch Flint. The unconformity represents a substantial gap between Late Cretaceous marine chalk and late Palaeocene shelf deposits.

MONTROSE GROUP

The Thanet Formation belongs to the Montrose Group in current BGS nomenclature. It is not part of the overlying Lambeth Group.

Thanet Formation

The Cliffs End succession is a type/reference section for the formation, historically called the Thanet Sands or Thanet Beds. Its locally clayey and silty character explains why a simple description as sand is inadequate. Published estimates give about 24 m for the composite Pegwell succession, although no single clear face exposes that whole thickness and the formation’s top is not continuously visible.

Historical type area and modern stage boundary
Pegwell remains a key reference for the Thanet Formation and the historical Thanetian type area. The internationally ratified boundary point defining the base of the Thanetian Stage is at Zumaia in northern Spain, rather than Pegwell Bay. Formation type sections and a global time-boundary stratotype serve different purposes.

Base Bed Member

The basal division comprises the Bullhead Bed and the overlying Cliffs End Greensand Bed. Their contrasting textures record different parts of the early marine transgression.

Bullhead Bed
The memoir measured about 0.15 m of glauconitic sandy marl densely containing green-coated flints at Redcliff. The flints are largely residual material from dissolution of the underlying Chalk, modified and supplemented during marine transgression, rather than a typical beach of well-rounded transported pebbles. Reworked Chalk microfossils and the green glauconitic coating help distinguish it from the in-situ chalk.

Cliffs End Greensand Bed
Approximately 0.75 m of very fine glauconitic sandy marl overlies the Bullhead Bed in the memoir section. The lowest roughly 0.25 m is particularly rich in glauconite and includes occasional flint pebbles. Together with the basal bed, it records the initial establishment of the Palaeocene sea over the older Chalk landscape.

Stourmouth Silt Member

The historical Stourmouth Clays are now the Stourmouth Silt Member. At Pegwell they comprise around 4.4–4.5 m of greenish-grey silt and silty clay, finely alternating and often stained brown by weathered pyrite. Fossils are sparse, although iron-stained burrow fills occur. The change upwards to sandier sediment marks the passage into the Pegwell Silt Member.

Pegwell Silt Member

Formerly called the Pegwell Marls, this approximately 13 m interval contains grey-green, locally glauconitic and micaceous silts, silty clays and fine sands. The lower part is faintly banded and higher beds become sandier. Much of the interval has historically been poorly exposed. Foraminifera are more plentiful than conspicuous shells; recorded bivalves near its top include Arctica morrisi and Thracia oblata.

Black Band or crepidula Band
At the base of the historical Pegwell Marls, older measured accounts describe about 0.9 m of strongly burrowed glauconitic sandy marl with the foraminifer historically named Astacolus crepidula. Nannofossil work subsequently improved the dating of a thin interval near this level. The Black Band is a subordinate horizon, not another formation.

Reculver Sand Member

The former Reculver Silts are retained within the Thanet Formation as the Reculver Sand Member. At Pegwell the memoir records up to 5 m of yellow-grey fine silty sand, with glauconite, mica and redistributed bivalve shells. The basal shell-rich layer and cemented doggers are useful local markers. Later sequence work identified a depositional break between this division and the underlying Pegwell interval.

Basal Reculver shell bed and dogger horizons
A persistent shell concentration, about 0.15 m thick in the memoir, lies at the base of the Reculver division and is locally cemented. Further dogger bands were measured approximately 1.25 m and 2.5 m above it. Individual concretions were about 0.4 m thick and 1.5 m across. Arctica morrisi and Corbula regulbiensis occur in these deposits; the shell-rich top of the old maximum section was partly hidden by hoverport works.

Periglacial channel and Head
South of Little Cliffsend Tunnel a channel cut into the older rocks contains several phases of cold-climate slope deposits, frost disturbance and erosion. It is overlain by brickearth. This Quaternary feature cuts older bedrock and is separate from the Palaeogene member succession.

Channel phase a — frost-shattered Chalk
The lowest mapped part of the channel section is disrupted Chalk, broken by repeated freezing and thawing. It is the weathered bedrock substrate rather than a separate sedimentary formation.

Channel phase b — chalky-flinty solifluxion deposit
Chalk and flint debris above the shattered substrate records downslope movement of thawed material under cold-climate conditions. Its mixed composition reflects erosion of the nearby Chalk surface.

Channel phase c — flinty gravel
A distinct flint-rich gravel is separated from the earlier chalk-rich slope deposit in the mapped channel fill. It records another phase of sediment movement and reworking before the finer channel sediment accumulated.

Channel phase d — silty-loam fill
The channel contains a finer silty-loam fill, contrasting with the coarse flint gravels on either side of the local succession. The different sediment textures preserve separate episodes within the valley’s infilling.

Channel phase e — later solifluxion gravel
A later gravel deposited by cold-climate slope movement overlies the finer fill. Its position records renewed movement of coarse material before the final mantle of wind-blown silt.

Channel phases f–g — loess and fossil soil
Loess, traditionally called brickearth, mantles the older channel deposits. A fossil soil developed subsequently at its surface. These complete the seven-part succession shown in the mapped channel section and link it with the broader cliff-top loess record.

Loessic Head Brickearth and fossil soil
The cliff-top brickearth reaches about 4 m in the historical Pegwell section. Wind-blown silt is an important component; the upper part is darker and decalcified, while lower material remains calcareous. Frost disturbance affected flints at its base, and chalk locally preserves involutions formed above permafrost. A later soil and hillwash locally cap the loess. The loess, soil and later hillwash represent separate episodes of deposition and surface development.

Modern interpretation of the loess
Modern high-resolution luminescence work identifies two main episodes of rapid dust accumulation, around 25–23.5 and 20–19 thousand years ago. These dates replace a simple reliance on the older thermoluminescence estimates. Mineral-magnetic work in 2024 supports primary dust-fall deposition at Pegwell, while indicating that later alteration also affected the sediment. Its possible southeasterly wind signal shows that transport directions remain more complex than a single persistent northerly wind.

References

Shephard-Thorn (1988), Geology of the country around Ramsgate and Dover, sheets 274 and 290
BGS OR/14/008, Lithostratigraphy of the London Basin and East Anglia
Daley & Balson (1999), Pegwell Bay, GCR 15
Mortimore, Wood & Gallois (2001), Thanet Coast, GCR 23
International Commission on Stratigraphy, ratified Global Stratotype Sections and Points
Stevens and others (2020), Abrupt last glacial dust fall over southeast England associated with dynamics of the British-Irish ice sheet
Niezabitowska and others (2024), Mineral magnetism and palaeoenvironment recorded in loess in southern England
BGS Lexicon, Margate Chalk Member
BGS Lexicon, Newhaven Chalk Formation
BGS Lexicon, Pegwell Silt Member
BGS Lexicon, Reculver Sand Member
BGS Lexicon, Stourmouth Silt Member
BGS Lexicon, Thanet Formation