Inferior Oolite

The Inferior Oolite is a sequence of Jurassic age sedimentary rocks in Europe. It was deposited during the Middle Jurassic.Weishampel, David B; et al. (2004). "Dinosaur distribution (Middle Jurassic, Europe)." In: Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press. Pp. 538–541. . The Inferior Oolite Group as more recently defined is a Jurassic lithostratigraphic group (a sequence of rock strata) in southern and eastern England . It has been variously known in the past as the Under Oolite (or Oolyte), the Inferior Oolite, the Inferior Oolite Series and the Redbourne Group.Waters, C.N. et al. 2007 Stratigraphical Chart of the United Kingdom: Southern Britain British Geological Survey (poster)

Outcrops The rocks are exposed from Dorset and Somerset eastwards and northwards through the English Midlands to Yorkshire.British Geological Survey 1:50,000 scale geological map (England & Wales) sheets It is present at depth in the Wessex-Weald Basin, where it reaches its greatest thickness of 120 m.

Lithology and stratigraphy

The group consists of up to 120 m thickness of oolitic limestones and subordinate sandstones and mudstones laid down during the Jurassic Period. In the East Midlands it consists of (in descending order i.e. oldest last) the Lincolnshire Limestone, Grantham and Northampton Sand formations whereas in the Cotswold Hills it consists of the Salperton Limestone, Aston Limestone and Birdlip Limestone formations.Waters, C.N. et al 2007 Stratigraphical Chart of the United Kingdom:Southern Britain British Geological Survey (poster) The Salperton Limestone contains the Clypeus Grit, a somewhat shelly grainstone that contains the large-diameter echinoid Clypeus ploti as well as Stiphothyris terebratulid brachiopods, and large mussel-like bivalves. The limestones are rich in organic material. The ammonite Parkinsonia parkinsoni, an index fossil for the Bathonian,Wynn Jones, R: Applied Paleontology. page 146, Cambridge University Press is native to the Inferior Oolite of Burton Bradstock.

Within Dorset, the Oolite is not subdivided into separately named formations, but is simply considered the Inferior Oolite Formation, sometimes subdivided into the Lower and Upper Inferior Oolite Formations. Within the vicinity of Yeovil it is divided into members which are in ascending order the Corton Denham Member, which predominantly consists of blue siltstone is about 2.5 m thick with the transitional top consisting of green Marl, the Oborne Ironshot Member, the term "ironshot" refers to ferruginised Oolite. The upper portion of which contains intensely bioturbated limestone. Moving Into the Upper Inferior Oolite the Sherborne Limestone Member, which consists of exposed yellow brown fresh grey bioclastic limestone, while the overlying Combe Limestone Member, consists of rubbly limestone and marl, a full stratigraphy of the locality is given below.

+Stratigraphy of the Inferior Oolite at Frogden Quarry, DorsetFormationMemberBedLithologyThicknessAmmonite ZoneUpper Inferior Oolite FormationCombe Limestone MemberBroken limestone and marlOver 5.6 metresGarantiana Zone-Parkinsoni ZoneSherborne Limestone MemberRedhole Lane BedsBlocky Limestone2 metresGarantiana Zone, Dichotoma SubzoneSherborne Building Stone BedsMottled, blocky limestone~1.5 metresAcanthothyris Beds"Brown sandy biomicrites interbedded with brown marls"Up to 1.5 metresLower Inferior Oolite FormationOborne Ironshot MemberOborne Road Stone BedBioturbated and intensely burrowed limestone~0.8 metresNiortense ZoneFrogden Ironshot BedFerruginous oolite~1.2 metresSauzei to Humphriesianum ZonesCorton Denham MemberGreen Grained White MarlMarl0.01-0.15 metresLaeviuscula ZoneBlue BedVery hard blue intensely burrowed siltstone0.85-1 metreLaeviuscula Zone, Trigonalis SubzoneCorton Denham BedsLenticular hard blue-grey siltstone, in channels. separated by nodular siltstoneSeen to 2 metresConcavum-Ovale Zones

Vertebrate fauna Ornithopod tracks geographically located in North Yorkshire, England. Ornithopod and theropod tracks present in North Yorkshire, England. A supposed dermal spine long thought to be from a stegosaur is actually a caudal vertebra referable to Archosauria indet.

Dinosaurs of the Inferior Oolite Genus Species Location Stratigraphic position Material Notes ImagesCetiosaurusC. epioolithicus North Yorkshire, England."Dinosaur distribution (Middle Jurassic; Europe; North Yorkshire, England)." Weishampel, et al. (2004). Page 539. Indeterminate Wiltshire, England."Dinosaur distribution (Middle Jurassic; Europe; Wiltshire, England)." Weishampel, et al. (2004). Page 540.DuriavenatorD. hesperis Dorset, England. "Skull elements.""Table 4.1," in Weishampel, et al. (2004). Page 73. MagnosaurusM. nethercombensis Dorset, England."Dinosaur distribution (Middle Jurassic; Europe; Dorset, England)." Weishampel, et al. (2004). Page 539. "Dentaries, vertebrae, pubis, femora, [and] tibiae."MegalosaurusM. hesperis Dorset, England."Skull elements."Moved to the new genus Duriavenator in 2008.Indeterminate Northamptonshire, England."Dinosaur distribution (Middle Jurassic; Europe; Northamptonshire, England)." Weishampel, et al. (2004). Pages 539-540. Somerset, England."Dinosaur distribution (Middle Jurassic; Europe; Somerset, England)." Weishampel, et al. (2004). Page 538.Indeterminate Megalosaurid material.ThyreophoraIndeterminatePeter M. Galton (2017). "Purported earliest bones of a plated dinosaur (Ornithischia: Stegosauria): a "dermal tail spine" and a centrum from the Aalenian-Bajocian (Middle Jurassic) of England, with comments on other early thyreophorans". Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen. 285 (1): 1–10. doi:10.1127/njgpa/2017/0667. Dorset, England.

Inferior Oolite

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