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.

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. Some logs are up to about 1 m in diameter and several metres long, though most are now broken into shorter sections. 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.

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. Much of it has now been eroded away, but remnants still crop out in the cliff and continue to yield vertebrate fossils, especially Lepidotes teeth. 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 — Hypsilophodon Bed

The topmost red sand and mudstone bed of the Wessex Formation, immediately beneath the White Rock sandstone of the Vectis Formation. This is the island-wide Hypsilophodon Bed, famous for abundant dinosaur debris and the occurrence of numerous Hypsilophodon remains in the western Isle of Wight succession. At Compton Bay it marks the very top of the fluvial floodplain facies before the abrupt environmental shift into the Vectis lagoon.

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.

Total Thickness Of Cowleaze Chine Member At Compton Bay: Approximately 7–8 Metres

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.

Total Thickness Of Barnes High Sandstone Member At Compton Bay: Approximately 6–7 Metres

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.

Total Thickness Of Vectis Formation At Compton Bay: Approximately 34 Metres

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 Covered Here: Approximately 80–120 Metres Of Wealden Group Stratigraphy, Though Exact In-Place Thickness Is Difficult To Fix Because The Wessex Section Is Fault-Repeated And Parts Of The North-Western Exposure Are Slumped

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.