%0 Generic %A Monaghan, A. A. %A Pringle, M. S. %D 2016 %T 40Ar/39Ar geochronology of Carboniferous-Permian volcanism in the Midland Valley, Scotland %U https://geolsoc.figshare.com/articles/dataset/_sup_40_sup_Ar_sup_39_sup_Ar_geochronology_of_Carboniferous-Permian_volcanism_in_the_Midland_Valley_Scotland/3454199 %R 10.6084/m9.figshare.3454199.v1 %2 https://ndownloader.figshare.com/files/5425253 %2 https://ndownloader.figshare.com/files/5425256 %2 https://ndownloader.figshare.com/files/5425259 %2 https://ndownloader.figshare.com/files/5425262 %2 https://ndownloader.figshare.com/files/5425265 %2 https://ndownloader.figshare.com/files/5425268 %2 https://ndownloader.figshare.com/files/5425271 %2 https://ndownloader.figshare.com/files/5425274 %2 https://ndownloader.figshare.com/files/5425277 %2 https://ndownloader.figshare.com/files/5425280 %2 https://ndownloader.figshare.com/files/5425283 %2 https://ndownloader.figshare.com/files/5425286 %2 https://ndownloader.figshare.com/files/5425289 %2 https://ndownloader.figshare.com/files/5425292 %2 https://ndownloader.figshare.com/files/5425295 %2 https://ndownloader.figshare.com/files/5425298 %2 https://ndownloader.figshare.com/files/5425301 %2 https://ndownloader.figshare.com/files/5425304 %2 https://ndownloader.figshare.com/files/5425307 %2 https://ndownloader.figshare.com/files/5425310 %2 https://ndownloader.figshare.com/files/5425313 %2 https://ndownloader.figshare.com/files/5425316 %K Dinantian magmatic pulses %K Garleton Hills Volcanic Formation %K Clyde Plateau Volcanic Formation %K Ma %K NW %K Carboniferous timescale tie points %K Midland Valley %K phase %K Ar %K Geology %X

Twenty-one new 40Ar/39Ar step-heating experiments on mineral separates from intrusive and extrusive Carboniferous and Permian igneous rocks in the Midland Valley of Scotland yielded 17 concordant experiments with a relative age precision better than 1% (2σ). These ages resolve inconsistencies between existing K-Ar dates on the same samples and their stratigraphical constraints correlated to recently published timescales. The precise 40Ar/39Ar dates are stratigraphically constrained to stage level and can contribute to Carboniferous timescale tie points at the Tournaisian-Visean boundary, within the Visean and at the Carboniferous-Permian boundary. Situated in the extending Variscan foreland, two distinct phases of extension-related transitional-alkaline volcanism have been resolved in the Dinantian: the Garleton Hills Volcanic Formation in the eastern Midland Valley near the Tournaisian-Visean boundary, 342.1 ± 1.3 and 342.4 ± 1.1 Ma; and the Clyde Plateau Volcanic Formation in the western Midland Valley during the mid-Visean, 335 ± 2–329.2 ± 1.4 Ma. Alkaline basic sills near Edinburgh, previously thought to be Namurian, appear to be coeval with the Clyde Plateau Volcanic Formation at 331.8 ± 1.3–329.3 ± 1.5 Ma. The new ages allow correlation between these short-lived Dinantian magmatic pulses and extensional and magmatic phases in the Northumberland-Solway and Tweed basins to the south. After late Westphalian, end-Variscan, compression and a regionally important tholeiitic intrusive phase at c. 301–295 Ma, alkaline magmatism related to post-Variscan extension occurred in the central and western Midland Valley during the latest Carboniferous or Permian from 298.3 ± 1.3 to 292.1 ± 1.1 Ma. This correlates well with post-Varsican extension and magmatism observed across the NW European foreland from 300 to 280 Ma.

%I Geological Society of London