The Bembridge Limestone Formation is a geological unit of Late

Eocene The Eocene ( ) is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (Ma). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene'' comes ...

age (Priabonian to early Oligocene), located in the northern Isle of Wight, southern England. It lies within the Solent Group, stratigraphically above the Headon Hill Formation and below the

Bouldnor Formation The Bouldnor Formation is a geological formation in the Hampshire Basin of southern England. It is the youngest formation of the Solent Group and was deposited during the uppermost Eocene and lower Oligocene. Stratotype and occurrence The Bo ...

Type locality and distribution

The formation's type section is found in the cliffs at the northern end of

Whitecliff Bay Whitecliff Bay is a sandy bay near Foreland which is the easternmost point of the Isle of Wight, England, about two miles south-west of Bembridge and just to the north of Culver Down. The bay has a shoreline of around and has a popular sand ...

, where about 9 meters of alternating

limestone Limestone is a type of carbonate rock, carbonate sedimentary rock which is the main source of the material Lime (material), lime. It is composed mostly of the minerals calcite and aragonite, which are different Polymorphism (materials science) ...

and marl beds are exposed. Additional coastal outcrops occur at Bembridge Ledges, Priory Bay, and

Seagrove Bay Seagrove Bay is a bay on the northeast coast of the Isle of Wight, England. It lies to the east of the village of Seaview facing towards Selsey Bill with a shoreline stretching from Nettlestone Point in the north to Horestone Point in the so ...

. Inland, the formation is visible at Tapnell Farm Quarry and Binstead Quarry.

Lithology and stratigraphy

The Bembridge Limestone Formation typically consists of three sedimentary cycles. Each begins with an erosional base, sometimes with intraformational conglomerates, followed by sequences of marl and marlstone, and capped by dense, micritic limestone. A notable middle unit contains “corbiculid beds” rich in bivalve fossils, representing a distinct clayey interval.

Depositional environment and facies

The formation was deposited in a freshwater to brackish, marginal lacustrine and palustrine environment, subject to periodic

subaerial In natural science, subaerial (literally "under the air") has been used since 1833,Subaerial
in the Merriam- ...

exposure. Sedimentary features such as micritic textures,

pedogenic Soil formation, also known as pedogenesis, is the process of soil genesis as regulated by the effects of place, environment, and history. Biogeochemical processes act to both create and destroy order (anisotropy) within soils. These alterations ...

overprinting, and laminated structures suggest frequent wetting and drying cycles in a nearshore continental setting.

Trace fossils A trace fossil, also called an ichnofossil (; ), is a fossil record of biological activity by lifeforms, but not the preserved remains of the organism itself. Trace fossils contrast with body fossils, which are the fossilized remains of part ...

, including ''Balanoglossites triadicus'', indicate occasional marine incursions into the predominantly nonmarine environment. These ichnofossils support brief phases of brackish or tidal influence.

Age and correlation

Magnetostratigraphic data from Whitecliff Bay show mostly reversed polarity (Chron C13r) with a short normal interval (Chron C13n) at the top. This dates the Bembridge Limestone Formation to approximately 34.0-33.9 million years ago, placing it near the

Oligocene The Oligocene ( ) is a geologic epoch (geology), epoch of the Paleogene Geologic time scale, Period that extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that defin ...

boundary.

Fossils and paleontology

The formation preserves freshwater and brackish

mollusks Mollusca is a phylum of protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant species of molluscs are recognized, making it the second-largest animal phylum after Arthropoda. The num ...

, especially

gastropods Gastropods (), commonly known as slugs and snails, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, freshwater, and from the land. Ther ...

such as ''

Galba Galba ( ; born Servius Sulpicius Galba; 24 December 3 BC – 15 January AD 69) was Roman emperor, ruling for 7 months from 8 June AD 68 to 15 January 69. He was the first emperor in the Year of the Four Emperors and assumed the throne follow ...

'' and '' Planorbina''. Shells are often replaced by calcite spar or preserved as molds. The

fauna Fauna (: faunae or faunas) is all of the animal life present in a particular region or time. The corresponding terms for plants and fungi are ''flora'' and '' funga'', respectively. Flora, fauna, funga and other forms of life are collectively ...

indicate low-diversity ecosystems typical of shallow, nonmarine conditions.

Economic and historical significance

Limestone quarried from the Bembridge Formation, particularly at Binstead, has historically been used as a local building stone, sometimes referred to as “Binstead Stone.” It was used in structures in

Southampton Southampton is a port City status in the United Kingdom, city and unitary authority in Hampshire, England. It is located approximately southwest of London, west of Portsmouth, and southeast of Salisbury. Southampton had a population of 253, ...

and

Winchester Winchester (, ) is a City status in the United Kingdom, cathedral city in Hampshire, England. The city lies at the heart of the wider City of Winchester, a local government Districts of England, district, at the western end of the South Downs N ...

. The porous, moldic texture left by dissolved gastropods gives the stone a distinctive appearance.

References

{{Reflist Geologic formations of England Geology of the Isle of Wight Eocene Series of Europe Paleogene England Limestone formations Lacustrine deposits Paleontology in England