New age constraints for the Ordovician Tyrone Volcanic Group, Northern Ireland

Cooper, M.R.; Crowley, Q. G.; Rushton, A. W. A.. 2008 New age constraints for the Ordovician Tyrone Volcanic Group, Northern Ireland. Journal of the Geological Society, 165 (1). 333-339.

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New biostratigraphical evidence and a high precision ID-TIMS U-Pb zircon age provide refined age constraint for the Ordovician Tyrone Volcanic Group of the Tyrone Igneous Complex. In a graptolite fauna from Slieve Gallion, the presence of Isograptus victoriae lunatus, the index fossil of the victoriae lunatus graptolite zone, indicates a correlation with the Australasian Castlemainian (Ca1) Stage. The U-Pb zircon age of 473 ± 0.8 Ma dates a volcanic arc-related rhyolite body that sits stratigraphically below graptolitic mudstones of Slieve Gallion. The U-Pb isotopic and biostratigraphical age constraints match closely with an interpolated age for the base of the Middle Ordovician (Sadler & Cooper 2004), and indicate a Whitlandian age for the upper Tyrone Volcanic Group, which supports the regional correlation with the Ballantrae Complex, Midland Valley Terrane, Scotland.

Item Type: Publication - Article
Digital Object Identifier (DOI):
Programmes: BGS Programmes > Geological Survey of Northern Ireland
ISSN: 0016-7649
Additional Keywords: Age constraint Ordovician biostratigraphy U-Pb isotope dating Tyrone Volcanic Group Northern Ireland Ballantrae Midland Valley Terrane
NORA Subject Terms: Earth Sciences
Date made live: 31 Jan 2008 16:33 +0 (UTC)

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