Compton Bay Fossil Hunting

2004 – Vectiraptor greeni material collected by Mick Green and Nick Chase
Material from a small predatory dinosaur was collected at Compton Bay in 2004 by Mick Green and Nick Chase. It later proved to belong to a new dromaeosaurid and became one of the most important theropod discoveries from the bay.

October 2012 – important Valdosaurus specimen found by Nick Chase
A significant specimen of Valdosaurus canaliculatus was discovered at Compton Bay in October 2012 by Nick Chase. This partially articulated skeleton is regarded as the most complete Valdosaurus specimen yet found, making it one of the key discoveries from the site.

2013 – Comptonatus chasei specimen found by Nick Chase
In 2013, Nick Chase discovered a remarkable iguanodontian skeleton in the cliffs at Compton Bay. The specimen later proved to represent a new dinosaur and is one of the most important modern finds from the Isle of Wight.

2021 – Vectiraptor greeni formally described
The Compton Bay predatory dinosaur material collected in 2004 was formally described in 2021 as Vectiraptor greeni. This confirmed that Compton Bay had produced a distinct small dromaeosaurid, adding to the scientific importance of the bay.

2024 – Comptonatus chasei formally described
The large iguanodontian discovered by Nick Chase in 2013 was formally named Comptonatus chasei in 2024. It has been described as the most complete dinosaur discovered in the UK in a century, and is one of the most significant fossils ever found at Compton Bay.

This account separates the Wealden exposures around Hanover Point and the Compton shore from the younger marine formations farther west, including the western foreshore and Compton Down road section. The CP labels are editorial divisions, not a measured numbered log, and fault-separated outcrops must not be added together as extra stratigraphic thickness.

WEALDEN GROUP

Wessex Formation (Lower Cretaceous — Barremian)

Lower And Middle Wessex Floodplain Beds

Bed CP1 — Lower Variegated Floodplain Mudstones

Purple, red and mottled mudstones with subordinate pale sandy interbeds and occasional greenish beds, representing overbank floodplain deposition on a low-relief alluvial plain. These are the classic Wessex “Wealden Marls” facies and make up much of the lower foreshore and cliff at Compton Bay where not hidden by beach deposits. Root traces, pedogenic mottling and local calcareous nodules indicate repeated emergence, soil formation and seasonal drying.

Bed CP2 — Early Crevasse-Splay And Channel Sandstones

Pale to yellowish or reddish sandstones, generally fining upward from basal grit or mudstone-clast conglomerate into sandy mudstone. These sandstones record crevasse-splay and small channel events across the Wessex floodplain and provide the first harder ledges within the otherwise mudstone-dominated section. Fossils are typically sparse outside the plant-debris beds, but isolated dinosaur bone fragments and wood may occur.

Hanover Point Brook Sandstone And Plant-Debris Bed Interval

Bed CP3 — Plant-Debris Bed CL1

A classic grey plant-debris bed at Hanover Point, representing one of Stewart’s Compton-level (CL) plant-debris horizons. Like the other Wessex plant-debris beds, it is a grey, basally conglomeratic, plant-rich mudstone or siltstone deposited in a floodplain depression or channel-related low. It may yield wood, comminuted plant debris and vertebrate material, though exposure is highly variable from year to year.

Bed CP4 — Pine Raft

A remarkable accumulation of stranded gymnosperm logs preserved on a point-bar surface near Hanover Point. The Hanover Point GCR describes logs up to about 40 cm across and several metres long. Larger wood reported from plant-debris beds elsewhere in the Wessex succession is not used as a measurement of the Pine Raft itself. The raft is not itself a plant-debris bed sensu strictu, but rather a log concentration stranded on a sandy bar. Nearby are co-occurring dinosaur footprints, including ornithischian and theropod tracks.

Bed CP5 — Brook Sandstone

A crevasse-splay sandstone forming one of the most important sandstone markers in the Compton–Brook sector. Sweetman notes that the Brook Sandstone is probably equivalent to the sandstone underlying plant-debris bed CL2 in Compton Bay. At Hanover Point and Brook Bay this sandstone was deposited onto a dinosaur-trampled mud surface, and casts of footprints are found on its underside and on the beach where erosion has exposed the base.

Bed CP6 — Plant-Debris Bed CL2

The best-described Compton Bay plant-debris bed. It rests sharply on the somewhat undulating top of the underlying crevasse-splay sandstone and begins with a basal conglomerate containing very poorly sorted plant material, allochthonous siderite clasts and autochthonous pyrite. Above this is a finely and irregularly laminated zone rich in comminuted plant matter, followed by very fine unlaminated siltstone and then an upward transition into massive colour-mottled overbank mudstone. This is one of the key vertebrate-bearing horizons in the Compton Bay Wessex succession.

CL2 basal conglomerate

A sharp, uneven sandstone contact is overlain by poorly sorted plant debris and reworked siderite clasts; pyrite formed within the deposit.

CL2 laminated plant-rich interval

Fine irregular lamination and abundant finely broken plant material distinguish the layer above the basal conglomerate.

CL2 fine unlaminated siltstone

Very fine siltstone overlies the laminated interval; it is a separate sedimentary component within the documented bed.

CL2 upward passage into floodplain mudstone

The upper bed grades into massive mottled mudstone, rather than ending at another sharply defined conglomeratic surface.

Bed CP7 — Plant-Debris Bed CL3

Formerly one of the thickest plant-debris beds in the Compton Bay section and very rich in macro- and microvertebrate remains. Sweetman’s 2007 study reported that much of CL3 had already been eroded from the then-exposed cliff. The documented material includes Lepidotes teeth; that historical observation is not a guarantee of its present visibility. Like most Wessex plant-debris beds, it illustrates the strongly lenticular geometry and limited lateral extent of these fossil traps.

Upper Wessex Beds

Bed CP8 — Upper Floodplain Mudstones And Upper Plant-Debris Horizon

Red and purple mudstones with thinner sandstones and plant-rich horizons forming the upper part of the Wessex Formation at Compton Bay. Toward the north-west part of the bay an unnumbered plant-debris bed near the top of the Wessex yielded the well-preserved partial skeleton of the large crocodilian Anteophthalmosuchus hooleyi. These upper beds show that the Wessex floodplain system remained highly fossiliferous right up to the transition into the lagoonal Vectis regime.

Bed CP9 — Topmost Wessex Beds And Regional Hypsilophodon-Bed Correlation

The uppermost red and mottled Wessex sediments pass into the pale basal Vectis sandstone and grey lagoonal beds. The name Hypsilophodon Bed is well established for the upper Wessex dinosaur-bearing horizon in the Barnes High–Cowleaze Chine succession. This regional correlation must not be treated as proof that the same fossil concentration or a continuously traceable island-wide bed is present at Compton. The local transition is retained here without importing the dinosaur abundance or measured detail of the Barnes High section.

Vectis Formation (Lower Cretaceous — Late Barremian To Earliest Aptian?)

Cowleaze Chine Member

Bed CP10 — White Rock Sandstone

A pale cemented sandstone, commonly about 1 m thick where well developed, at the base of the Vectis Formation. In middle Compton Bay the Wessex–Vectis boundary is marked by this sandstone, whose base preserves generally rather indistinct dinosaur foot-casts. It corresponds to the White Rock sandstone at the base of the Cowleaze Chine Member elsewhere on the south-west coast and marks the abrupt change from red floodplain deposits to dull grey lagoonal beds.

Bed CP11 — Lower Cowleaze Chine Mudstones And Siltstones

Finely interlaminated dark grey mudstone and pale grey siltstone to fine sandstone, locally arranged into thin fining-upward units. These beds represent shallow subaqueous to intermittently emergent lagoonal deposition, with fluctuating salinity. Ostracods and gastropods, including Viviparus, are characteristic, and the beds are much greyer and less oxidised than the Wessex floodplain mudstones below.

Bed CP12 — Upper Cowleaze Chine Lagoonal Beds

Continuation of the dark grey laminated mudstones and pale siltstones of the Cowleaze Chine Member, still arranged in thin fining-upward couplets in places. These beds record a quiet shallow lagoon with periodic influxes of slightly coarser sediment. Desiccation cracks and dinosaur footprints are known in the wider Vectis Formation and show that parts of the lagoon margin were periodically exposed.

Cowleaze Chine Member: Local Thickness Not Assigned Here

Barnes High Sandstone Member

Bed CP13 — Lower Barnes High Sandstone

The basal of the three coarsening-upward Barnes High sandstone bodies recognised in Compton Bay. It begins with finer, more laminated sand and silt and passes upward into more massive medium-grained sandstone. This sandstone represents a deltaic influx or sand-body incursion into the Vectis lagoon.

Bed CP14 — Middle Barnes High Sandstone

A second coarsening-upward yellow to grey sandstone separated from the lower unit by laminated mudstone. It is better developed and more clearly sandstone-dominated than the Cowleaze fines below and contributes to the stepped cliff profile where exposed. Deltaic or mouth-bar processes are likely to have supplied these sands into the lagoon.

Bed CP15 — Upper Barnes High Sandstone And Bivalve Conglomerate Cap

The uppermost of the three Barnes High sand bodies in Compton Bay, again coarsening upward and capped by a thin mudstone and bivalve conglomerate. This is the highest principal sandstone unit of the Vectis Formation and forms the middle sandy division of the formation between the more argillaceous Cowleaze and Shepherd’s Chine members.

Barnes High Sandstone Member: Three Local Sand Bodies; No Verified Local Total Assigned Here

Shepherd’s Chine Member

Bed CP16 — Lower Shepherd’s Chine Cyclic Mudstones And Fine Sands

Pale to dark grey fine-grained sandstones, siltstones and mudstones rhythmically bedded in numerous thin fining-upward units. These are low-energy lagoonal and mudflat deposits laid down after the major Barnes High sand influx had waned. The cyclicity reflects repeated minor flooding, infill and emergence on the margin of a shallow subtropical coastal lagoon.

Bed CP17 — Shelly Coquinas, Ironstones And Mud-Cracked Limestones

Thin, laterally persistent coquina limestones and other shelly beds within the Shepherd’s Chine Member, representing storm deposits within the lagoonal succession. In the wider Vectis outcrop these beds may be rich in brackish-water bivalves such as Filosina gregaria, and desiccation-cracked shelly limestones show periodic emergence of the lagoon floor.

Bed CP18 — Gutter Casts And Basal Fish Bone-Sands

At Compton Bay, especially in slumped upper exposures, cemented gutter casts from the Shepherd’s Chine Member can be found with a well-cemented basal bone-sand comprising mainly fish bones and teeth. These erosive gutter structures are among the most distinctive fossil-bearing facies of the upper Vectis and show that energetic scouring periodically affected the lagoonal muds and sands.

Bed CP19 — Upper Shepherd’s Chine Lagoonal Mudstones

Grey-green mudstones, fine sands, thin ironstones and shelly beds forming the uppermost part of the Vectis Formation at Compton Bay. These beds are commonly slumped and not always continuously visible, but they complete the island’s Wealden lagoonal succession below the marine Lower Greensand transgression. Fossils include fishes, plants, ostracods and brackish-water molluscs, with the upper part of the member particularly sensitive to salinity fluctuations.

Vectis Formation: About 34 Metres In The Published Western Compton Outcrop

Depositional Environment

The Compton Bay succession records a major environmental shift from the river-dominated alluvial plain of the Wessex Formation into the shallow subtropical coastal lagoon of the Vectis Formation. In the Wessex beds, dinosaur-trampled crevasse splays, stranded conifer logs and lenticular plant-debris beds capture floodplain “snapshots” rich in vertebrate and plant remains. The Vectis records the drowning of that landscape and replacement by lagoonal mudflats, shallow subaqueous muds, deltaic sand influxes and storm-reworked shell beds under fluctuating salinity.

Total Thickness: No New Combined Wessex–Vectis Estimate Is Assigned To This Faulted Composite

Western Compton: younger marine succession

The following units occupy the western Compton coastal tract and, for the higher Chalk, the Compton Down Military Road section. Landslips, steep dips and faults interrupt observation. Member definitions describe the published reference succession; they do not promise that every contact is visible today. Measurements from Chale, Red Cliff, Culver or the Needles are not substituted for Compton values.

LOWER GREENSAND GROUP

Atherfield Clay Formation

The BGS Lexicon names Compton reference sections for the members below, but BGS (2015) emphasises that vegetated mudslides conceal much of the formation and impede subdivision. The older local account estimated about 60 ft for the clay succession. That historical estimate is distinct from the much thicker Chale type section.

Perna Member

Basal bone-bearing grit and erosion surface

The marine transgression begins with gritty fossiliferous sediment above eroded Vectis strata. At Compton the 1889 account examined displaced masses showing brecciated underlying shale and rolled phosphate within the basal grit; these were not an upright in-situ log.

Lower sandy mudstone and upper calcareous sandstone

The member includes shell-bearing sandy mudstone beneath greenish coarse calcareous sandstone. Bivalves, fish debris and reworked phosphatic material distinguish the basal package; no Chale or Yaverland bed thickness is assigned to Compton.

Chale Clay Member

Basal brown mudstone and overlying pale clay

The reference member passes from chocolate-brown basal mudstone into pale blue-grey clay with ironstone nodules and shell remains. BGS records Compton as a reference section, while warning that modern slippage can obscure its limits.

Lower Lobster Member

Nodular and micaceous mudstone succession

Pale blue-grey mudstone with brown nodules passes into darker micaceous mudstone and sandy layers, ending in argillaceous sandstone. This identifies the member’s lithological range; the individually numbered Chale type beds and their thicknesses are not imposed on the obscured Compton face.

The Crackers Member

Hard sandstone and dogger-bearing interval

The member comprises relatively hard dark-blue to brown sandstone, with phosphatic seams and discontinuous fossiliferous doggers in its reference definition. Its resistant character contrasts with the surrounding muddy members; a separate measured Compton total is not asserted.

Upper Lobster Member

Alternating sandy mudstone and sandstone

Dark grey sandy mudstone alternates with firmer sandstone; flat nodules occur low in the reference member. The upper passage is into ferruginous sand, rather than a contact with the younger Sandrock.

Ferruginous Sands Formation

Compton ferruginous succession (76.7 m in BGS 2015)

The locally thinner formation includes bioturbated muddy sand and coarsening-upward glauconitic sand, with cemented fossiliferous concretions. Its iron-rich character and local total contrast with the thicker Chale section. Individual Chale member names cannot be confidently carried through the entire Compton outcrop.

Upper transition into Sandrock

Dark green-brown sand passes up to dark mud at the Sandrock base. Burrowing and local erosion or omission surfaces interrupt the apparently simple sand-dominated succession.

Sandrock Formation

Dark mud, laminated sand–clay and cross-bedded sand

The local succession contains clay-rich intervals and pale sands with wavy lamination, passing into stronger sand bodies. These reflect changing estuarine and subtidal-channel deposition. Individual cycles are not assumed complete everywhere.

Upper erosion surface

The Sandrock is truncated beneath the ferruginous, pebbly Monks Bay Sandstone. This contact represents a depositional break, not simply a colour change within one continuously accumulating sand bed.

Monks Bay Sandstone Formation (historical Carstone)

Basal pebble band and brown ferruginous sand (about 1.8 m locally)

The historical Compton log records a basal pebble band containing quartzite, phosphate and wood beneath brown sand. BGS gives 1.8 m for the formation here; this is not the much thicker Red Cliff section.

Upward passage into Gault

Ferruginous coarse sandstone grades into gritty green-grey and then dark grey mudstone. The lower contact is erosional, while the upper passage is gradational.

LOWER GREENSAND GROUP

Historical Compton lithological rows: 1889 reference comparison

These individually recorded intervals are presented in ascending order from the local nineteenth-century log. They preserve detail without forcing every old row into a modern member. Only clearly established thicknesses are used; the comparison is not an extra succession to add to the modern formation totals.

Pale-blue basal clay

Clay with the Perna interval at its base; the historical whole-clay estimate was about 60 ft.

Grey silty sand

Silty sediment with soft yellow sandstone bands low in the recorded package.

Yellow sand

Sand locally containing appreciable clay.

Pale-green sandy clay

Fossil-bearing pale-grey nodules occur within the sandy clay.

Weathered yellow sand

A separate yellow-sand interval was recorded below the red-brown grit.

Red-brown iron-rich grit

Iron-coated grains formed the cliff east of Compton Chine.

Overlying clay

A muddy interval succeeds the grit in the old ascending sequence.

Green silty sand

Silty green sediment separates clay below from harder sandy beds above.

Brown sandstone with lignite

Small pebbles and woody fragments occur throughout, with an impersistent silty band.

Lower green-grey silty interval

The old description records fucoid-like markings between sandstone beds.

Middle brown sandstone

A distinct resistant sandstone separates the silty intervals.

Upper green-grey silty interval

Another silty sand with similar markings occurs above the middle sandstone.

Upper brown sandstone

This precedes the green-grit and phosphate-bearing package.

Lower green grit

A gritty glauconitic interval begins the next local package.

Brown sandstone between green grits

A separate sandstone divides the lower and upper gritty beds.

Upper phosphate-bearing green grit

Pale-yellow phosphatic bodies include both rounded and cylindrical forms.

Laminated sand and clay

The old “foliated” sediment passes downward into paper-like shale.

Striped dark sand with phosphates

Small soft phosphate pebbles occur particularly near the base.

Rolled yellow-pebble band

A separate pebble seam contains soft yellow material and quartzite.

Lighter striped dark sand

Striped sediment lies beneath a particularly dark sandy or silty interval.

Very dark sand or silt

The original account regarded the dark colour as carbonaceous.

Lower hard white sand

A compact pale sand resembles the historically named ganister lithology.

Small-quartzite pebble seam

A discrete pebble concentration separates sandy intervals.

Plant-rich mixed sand and clay

Organic material concentrates upwards; the original authors compared its appearance with a root-bearing bed.

Upper hard white sand

Another compact white-sand interval is distinct from the organic-rich layer below.

Green-weathering clayey grit

The historical row includes a basal quartzite-pebble band.

Wavy-laminated white sand and blue clay

Alternating sand and clay produced iron-rich springs in the historical exposure.

Bright-yellow sand and basal iron seam

A separate yellow-sand body follows the laminated package.

Lower bounding pebble band

A thin pebble seam underlies the next greenish sand.

Grey-green sand with pyritised wood

Wood forms a layer within this sand and scattered fragments occur higher.

Upper bounding pebble band

A further pebble seam caps the greenish sand package.

Upper blue clay

Clay overlies the sand–pebble package below the Carstone.

Carstone basal pebbles and brown sand

The uppermost historical Lower Greensand interval corresponds to the modern Monks Bay Sandstone.

SELBORNE GROUP

Gault Formation

Lower blue clay

The historical Compton section distinguishes lower blue clay from a higher fish-scale-bearing blue-clay interval. The lower part has ammonite, gastropod and inoceramid records in the original account.

Fish-scale-bearing blue clay

Fish scales occur in several bands in the separately described higher blue clay; these are not treated as one universally persistent bone bed.

Greenish clay

A distinct greenish interval occurs above the blue-clay package in the historical log.

Higher deep-blue clay

Darker clay overlies the greenish interval and passes towards the sandy transition above. BGS 2015 reports about 29 m for the historical Compton Gault section; differences in where older workers placed Passage Beds must be retained.

Upper Greensand Formation

Passage Beds: pale silty sand and sandy clay

The lower transitional interval contains micaceous sandy clay and silty sand, with burrow-like markings. Although older classifications sometimes placed these beds in the Gault, BGS 2015 includes Passage Beds in basal Upper Greensand.

Alternating clayey and sandy bands

Hard blue clayey bands alternate with sandy sediment and contain pyrite in the older Compton account. These remain distinct from the underlying more uniformly muddy beds.

Higher fine sandstone and concretions

Glauconitic fine sandstone, sand and silt carry calcareous and siliceous concretions. The Compton equivalent of the regional Chert Beds contains little chert; a Gore Cliff chert-rich log is not imported here.

Heavily burrowed upper contact

GCR Figure 3.60 shows the topmost Upper Greensand strongly modified by burrowing beneath glauconitic chalk and coarse phosphatic material. This is a condensed, non-sequential transition into the Chalk.

CHALK GROUP

GREY CHALK SUBGROUP

West Melbury Marly Chalk Formation

Glauconitic Marl Member

Basal phosphatic and glauconitic beds

Coarse phosphate nodules occur above the burrowed Upper Greensand surface. Darker glauconitic marl passes upward into paler cyclically bedded marl in the actual Compton log.

West Melbury Marly Chalk Formation — Above The Basal Member

Cyclic marly chalk above the Glauconitic Marl

Alternating marly chalk and harder limestone define the overlying lower formation. Their cyclic bedding should not be read as equal-duration or equal-thickness chart rows.

Phosphatic pebble horizon at the dixonii-zone base

Figure 3.60 identifies a separate phosphate-bearing bed below a thicker limestone unit. The historical biostratigraphic marker is retained without deriving its thickness from the figure.

The Rib

A named hard limestone marker occurs above the thicker lower limestone package in the Compton graphical log.

The Bank of limestones

A conspicuous limestone group follows the Rib and is separated from the higher beds by further phosphate and marl markers.

Higher phosphate and dark-marl markers

A second phosphate-bearing horizon and a dark marker marl are distinguished above the Bank; dark Chondrites traces occur higher.

Tenuis Limestone and upper burrowed surface

The conspicuous burrowed limestone at the formation top corresponds to the Tenuis/B42–43 boundary marker. The Cast Bed above belongs to the Zig Zag Chalk, not to this formation.

Zig Zag Chalk Formation

Cast Bed

The basal fossiliferous silty chalk follows the upper burrowed limestone surface of the West Melbury succession.

Lower dark marly interval

The C2–C4 part of the plotted succession is markedly marly, with less clearly defined limestones.

C5 thin-limestone marker

A conspicuous thin-limestone level is distinguished within the lower rhythmic beds.

C10 paired limestones

Two particularly noticeable limestone beds occur at this named local correlation level.

C14 limestone group

A group of five conspicuous limestones precedes the upward change to more calcareous beds.

Thin-couplet and Zoophycos-bearing intervals

Higher thinly bedded couplets pass into limestone–marl alternations containing conspicuous Zoophycos traces. A thicker marl and a dark marl precede Jukes-Browne Bed 7.

Jukes-Browne Bed 7

More calcareous rhythmic chalk includes lenticular scratch-like traces in the local figure. Large Acanthoceras jukesbrownei are reported at its base.

White Bed

Paler massive chalk retains wispy or flaser-like marl streaks and some stronger marl seams at Compton. It differs from equivalent sections where these marly features are less evident.

Sub-Plenus erosion surface

The top of the White Bed is truncated beneath the Plenus Marls, marking the base of the White Chalk Subgroup.

WHITE CHALK SUBGROUP

Holywell Nodular Chalk Formation

Plenus Marls Member

Plenus marl–chalk beds

Jefferies recognised eight beds in the Compton Plenus interval. The alternating marl and chalk package rests above the sub-Plenus erosion surface; individual bed thicknesses are not invented here.

Gale’s Figure14 shows the Compton column independently: marl-rich lower intervals, intervening chalk-rich beds and a darker marly interval higher in the Plenus package. The plotted correlations can be compared with the classic numbered Plenus scheme, but the figure does not justify a confident individual lithological description of every local numbered bed. No thickness is taken from its drawing scale.

Melbourn Rock Member

Junction limestone and hard nodular chalk

The basal hard chalk succession above the Plenus Marls includes the Junction Limestone and strongly iron-stained nodular chalk. The modern formation boundary scheme is retained rather than treating the whole old “Middle Chalk” as one bed.

Holywell Nodular Chalk Formation — Above The Melbourn Rock

Meads Marl 1

The lowest named Meads marl is separately shown above the hard basal chalk.

Meads Marls 2–5

A closely spaced marl package follows; the inoceramid change across Meads Marl 4 helps characterise the Cenomanian–Turonian transition.

Meads Marl 6

A further separate marl caps this lower marker group.

Marl and intraclast level above Meads 6 (100 mm)

Figure 3.63 prints 100 mm for this separate marl seam with intraclasts above Meads 6. It is not merged with the Meads marl group.

Lower Holywell flaser-marl zone (200 mm)

The local graphic distinguishes a 200 mm griotte or flaser-marl zone within the higher shelly chalk.

Overlying Holywell marl/flaser interval (150 mm)

A separate 150 mm marl or flaser-marl zone succeeds the 200 mm horizon. These are printed individual-bed values, not measurements taken from the scale.

Shelly nodular chalk and flaser-marl intervals

Higher beds contain repeated concentrations of Mytiloides, locally large and flat shells, with distinct thin marls and flaser-marl zones. BGS 2015 gives about 25 m for the entire local Holywell formation.

Roveacrinus–Fagesia correlation level

Gale identifies a Roveacrinus Bed and Fagesia catinus level in the Holywell correlation framework and traces its position through the local column. This is the source’s correlated faunal marker; it is not a claim that every associated fossil has been collected from the present exposure.

Compton Pebble Marl

The higher Holywell marker named Compton Pebble Marl is separately traced in Figure14. It is retained as a distinct correlation level above the Roveacrinus–Fagesia interval, without assigning the thicker Eastbourne interval to this site.

Gun Gardens Main Marl

The named seam lies near the upper boundary in Figure 3.63; the transition into smoother New Pit chalk follows the highest strongly shell-rich nodular beds.

New Pit Chalk Formation

Lower marl group and late Mytiloides horizon

The local log distinguishes a triple marl group and a late Mytiloides-bearing band above the Holywell boundary.

Higher marl seams and pseudoflints

Conspicuous thin marl seams and pale siliceous nodules subdivide the massive chalk. BGS gives 14 m for Compton; GCR flags a possible fault-related error within the upper graphic, so no new precise total is calculated.

New Pit lower marl seam (100–150 mm)

The lower part of the local New Pit column shows this independently measured thin seam.

New Pit marl above pseudoflints (150 mm)

The 150 mm seam above the pseudoflint-bearing interval is separately shown before the part of the log flagged as possibly faulted.

Upper New Pit plastic marl (150 mm)

A further 150 mm plastic marl lies below the Spurious Chalk Rock. The source marks uncertainty in the intervening section, so these thicknesses do not establish a complete summed New Pit log.

Lewes Nodular Chalk Formation

Spurious Chalk Rock

The hard, glauconitic nodular bed marks the mapped base here. Its correlation with the Ogbourne Hardground and nearby Turonian marls has been debated; the GCR alternatives are not collapsed into one proven chronology.

Second glauconitic hardground

A thinner hardground is independently shown above the Spurious Chalk Rock.

Southerham Marl 1

The dark plastic marl above the hardgrounds is a separate marker in the Compton Down road section.

Vectensis Bed

A distinct faunal marker follows Southerham Marl 1 in the local graphic.

Caburn Marl

This grey marl is separately identified higher in the lower Lewes succession.

Bicavea rotaformis horizon

The original GCR graphic labels Bicavea rotaformis above the Caburn Marl. This historical faunal name is retained as the source’s marker, not silently revised or moved to the marl itself.

Bridgewick Flints and Bridgewick Marl 1

The flint group is followed by a dark grey marl; they provide separate lithological markers rather than one undifferentiated flinty chalk unit.

Bopeep Flints

A further flint marker occurs above Bridgewick and below the higher nodular-flint interval.

Lewes Tubular Flints

Conspicuous cylindrical burrow-form flints underlie the Lewes Marl.

Lewes Marl

The Compton marl contains abundant Micraster leskei and crinoid debris, including Isocrinus granulosus.

Upper sheet-flint and echinoid-bearing intervals

Sheet flints, nodular beds and echinoid-bearing chalk distinguish the upper part of the road-section succession.

Navigation Marls

The two named marls occur among strongly laminated and nodular upper Lewes beds.

Cliffe–Hope Gap interval

Micraster-bearing chalk, intraclast beds and the Hope Gap marl/associated hardground interval subdivide the upper formation. These are Compton reference correlations, not imported thicknesses from Culver.

Micraster normanniae interval

Figure 3.63 distinguishes a Micraster normanniae-bearing level below the higher nodular/intraclast package and Hope Gap marker.

Micraster decipiens interval

A separately labelled Micraster decipiens level occurs above the Hope Gap marker in the older Compton graphic.

Cremnoceramus crassus and Micraster horizon

Higher shell- and echinoid-bearing chalk contains the historically identified Cremnoceramus crassus association. Its separate position is retained below the highest Shoreham marl and sheet-flint markers.

Shoreham Marl 1

The highest named marl and an overlying sheet-flint occur near the transition to the softer Seaford succession in the local composite.

Seaford Chalk Formation

Basal Seaford beds in the higher road section

GCR records basal Seaford chalk in the highest Compton Down road exposures, with Platyceramus and Volviceramus. Only that local continuation is included; the full Scratchell’s/Needles or northern Whitecliff succession is outside this account.

Measurement provenance and exposure limits

The BGS formation estimates and older GCR graphical logs are separate published frameworks. No summed whole-bay thickness is calculated, and faults or displaced masses are not counted as additional stratigraphic beds. The local Vectis descriptions retain supported lithology and named units; no additional unverified bed numbers or thicknesses are assigned.

References

Sweetman, S.C. (2011). The Wealden of the Isle of Wight.
Stewart, D.J. (1978, 1981). South-west coast Wessex and Vectis sedimentology and logs.
Radley, J.D. & Barker, M.J. (1998). Stratigraphy, palaeontology and correlation of the Vectis Formation at Compton Bay.
British Geological Survey Memoir: Geology of the Isle of Wight.
British Geological Survey Lexicon: Cowleaze Chine Member, Barnes High Sandstone Member and Shepherd’s Chine Member.

BGS describes three coarsening-upward sandstone bodies separated by laminated mudstone in the Compton Barnes High interval. The lower, middle and upper sandstone descriptions above retain that local architecture. They do not import the single thick sand body or its 6–7 m measurement from the type section.

Checked source links: Hopson and Farrant (2015), Isle of Wight: Wealden to Chalk succession; Sweetman (2007), Microvertebrate fauna of the Wessex Formation, chapter1 pp.41–53; Benton and Spencer (1995), GCR10: Brook–Atherfield, Compton Bay localities1–4; Cleal and colleagues (2001), GCR22: Hanover Point; Barker (2023), thesis, chapter4 geological context of Compton Bay Vectis section.

Additional sources: GCR 23, Compton Bay, pp175–185 and Figures3.58–3.63; Bristow, Reid and Strahan (1889), Compton sections pp21–23 and63; BGS Lexicon member entries for Perna, Chale Clay, Lower Lobster, The Crackers and Upper Lobster.

Gale(1995), Cenomanian cyclostratigraphy, Figure14, printed p194: separate Compton and Culver correlation columns.