Replication Data for "Dating the Ames Astrobleme, Oklahoma, USA: A possible new link to the Late Devonian"

The Ames impact structure (Oklahoma) is thought to have formed during the Ordovician Meteor Event, based on conodont biostratigraphy of its crater fill. Here, U–Pb zircon dates from its impact-melt portion, conducted using Secondary Ion Mass Spectrometry and Laser Ablation–Inductively Coupled Plasma–Mass Spectrometry (n = 37 spots), yield a Mesoproterozoic emplacement age for the impacted granodiorite (1401.2 ± 8.1 Ma, ±2σ, upper Concordia intercept). However, the youngest zircon dates define a weighted mean age of 369.7 ± 5.9 Ma (n = 10/11), with MSWD = 0.71 and p(χ²) = 0.7. Cathodoluminescence and electron backscattered diffraction images reveal that most zircons, including the youngest Devonian-age grains, show primary oscillatory zoning and lack deformation. However, two have impact-related textures, including regions of low-angle grain boundaries within microcracks and discrete arrays of granular zircon crosscutting oscillatory growth zoning. Plagioclase (n = 6 samples, 40Ar/39Ar) yields Late Carboniferous (~320.3 Ma) and Permian (267.3 ± 1.6 Ma) ages that overlap the timing of heating and hydrocarbon maturation in the crater, suggesting the argon system records post-impact thermal overprinting. Based on the youngest zircon dates, the Ames impact structure may record activity near the Frasnian–Famennian boundary, contemporaneous with other North American impacts.