Stratigraphy, palaeoenvironments and geochemistry across the Triassic–Jurassic boundary transition at Carnduff, County Antrim, Northern Ireland

Boomer, Ian; Copestake, Philip; Raine, Robert; Azmi, Azrin; Fenton, James P.G.; Page, Kevin N.; O’Callaghan, Matthew. 2021 Stratigraphy, palaeoenvironments and geochemistry across the Triassic–Jurassic boundary transition at Carnduff, County Antrim, Northern Ireland. Proceedings of the Geologists' Association, 132 (6). 667-687. https://doi.org/10.1016/j.pgeola.2020.05.004

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Official URL: http://dx.doi.org/10.1016/j.pgeola.2020.05.004

Abstract/Summary

The latest Triassic to earliest Jurassic transition has been widely studied due the occurrence of a major global extinction associated with a global hyperthermal event in this interval. Furthermore, a number of distinct geochemical events in the global carbon cycle can be recognised in the stable-isotope record across this boundary interval at many localities. Two fully-cored boreholes from East Antrim in Northern Ireland (Carnduff-1 and Carnduff-2) have penetrated sediments of latest Triassic to Early Jurassic age (Rhaetian to Early Sinemurian). Ammonites, foraminifera, ostracods and palynomorphs provide a robust chronology as well as insights to palaeoenvironmental conditions during this period. The sedimentary and palynological evidence support a largely marginal-marine setting for the sediments of the Triassic Penarth Group while a range of palaeontological evidence shows that the Early Jurassic Waterloo Mudstone Formation represents shallow-marine, shelf conditions that represent generally well-oxygenated bottom waters, with little evidence for dysoxia. Detailed ammonite biostratigraphy (ammonites first occur about 7.5 m up from the base of the Lias Group) indicates that the cores represent largely continuous sedimentation through the Hettangian and earliest Sinemurian (to Turneri Chronozone, Birchi Subchronozone). Stable-isotope analysis of both carbonate and organic carbon show a distinct carbon isotope excursion (CIE) in both fractions through the Cotham and Langport members (Lilstock Formation, Penarth Group, latest Triassic) which are considered to correlate with the distinctive ‘Initial’ CIE witnessed in SW England and probably the GSSP and other sites across the world.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	https://doi.org/10.1016/j.pgeola.2020.05.004
ISSN:	00167878
Date made live:	06 Oct 2020 11:32 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/528642

Item Type:

Publication - Article

Digital Object Identifier (DOI):

https://doi.org/10.1016/j.pgeola.2020.05.004

ISSN:

00167878

Date made live:

06 Oct 2020 11:32 +0 (UTC)

URI:

https://nora.nerc.ac.uk/id/eprint/528642