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The biostratigraphy of the upper Pliensbachian-Toarcian (Lower Jurassic) sequence at Ilminster, Somerset

The biostratigraphy of the upper Pliensbachian-Toarcian (Lower Jurassic) sequence at Ilminster, Somerset

Boomer, I., Lord, A.R., Page, K.N., Bown, P.R., Lowry, F.M.D. and Riding, J.B. (2009) The biostratigraphy of the upper Pliensbachian-Toarcian (Lower Jurassic) sequence at Ilminster, Somerset. Journal of Micropalaeontology, 28 (1). pp. 67-85. ISSN 0262-821X (Print), 2041-4978 (Online) (doi:10.1144/jm.28.1.67)

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Abstract

Temporary road sections for the A303 bypass at Ilminster, Somerset, revealed Upper Pliensbachian and Toarcian sediments from an alternating limestone–marl facies, in marked contrast to the limestone-dominated Dorset coast succession. The lithostratigraphy is described, with the standard ammonite zonation providing chronostratigraphical correlation. The uppermost Pliensbachian (Spinatum Chronozone) and much of the Toarcian (Serpentinum, Bifrons, Variabilis, Thouarsense and Pseudoradiosa chronozones) of the classic Dorset coast Lower Jurassic sequence are represented by the Beacon Limestone Formation, formerly the ‘Junction Bed’ (a highly condensed carbonate deposit). The Tenuicostatum Chronozone is largely missing from the sequence. Elsewhere in southern and eastern England this interval is poorly or rarely exposed. The argillaceous units have yielded rich microfaunas and -floras (foraminifera, ostracods, calcareous nannofossils and palynomorphs), the biostratigraphical distributions of which are analysed and discussed in relation to contemporary evolutionary patterns and other UK records. This study provides an insight into the micro-biostratigraphy of the Late Pliensbachian to Toarcian interval for onshore southern England.

Item Type: Article
Additional Information: [1] The Journal of Micropalaeontology (JM) is owned and published on behalf of The Micropalaeontological Society (TMS).
Uncontrolled Keywords: Pliensbachian–Toarcian, ostracoda, foraminifera, palynology, nannofossils
Subjects: C Auxiliary Sciences of History > CC Archaeology
Q Science > QE Geology
Faculty / Department / Research Group: Faculty of Engineering & Science
Related URLs:
Last Modified: 14 Oct 2016 09:22
Selected for GREAT 2016: None
Selected for GREAT 2017: None
Selected for GREAT 2018: None
URI: http://gala.gre.ac.uk/id/eprint/8994

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