The biostratigraphy of the Upper Pliensbachian-Toarcian (Lower Jurassic) sequence at Ilminster, Somerset
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Published:2009-05-01
Issue:1
Volume:28
Page:67-85
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ISSN:2041-4978
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Container-title:Journal of Micropalaeontology
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language:en
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Short-container-title:J. Micropalaeontol.
Author:
Boomer I.ORCID, Lord A. R., Page K. N., Bown P. R., Lowry F. M. D., Riding J. B.
Abstract
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.
Publisher
Copernicus GmbH
Reference79 articles.
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1. Global controls on phosphatization of fossils during the Toarcian Oceanic Anoxic Event;Scientific Reports;2021-12 2. The chemostratigraphy and environmental significance of the Marlstone and Junction Bed (Beacon Limestone, Toarcian, Lower Jurassic, Dorset, UK);Geological Magazine;2021-11-02 3. Biotic and stable-isotope characterization of the Toarcian Ocean Anoxic Event through a carbonate-clastic sequence from Somerset, UK;GEOL SOC SPEC PUBL;2021 4. The Toarcian Oceanic Anoxic Event: where do we stand?;Geological Society, London, Special Publications;2021 5. Biotic and stable-isotope characterization of the Toarcian Ocean Anoxic Event through a carbonate–clastic sequence from Somerset, UK;Geological Society, London, Special Publications;2021
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