From Newsgroup: sci.bio.paleontology
https://pubs.geoscienceworld.org/gsa/geology/article/doi/10.1130/G53121.1/653703/A-one-billion-year-old-Scottish-meteorite-impact
The Stoer Group in northwest Scotland is one of the oldest
well-preserved sedimentary successions in Europe and includes the Stac
Fada Member, an impact ejecta deposit. Here we report U-Pb analyses on
shocked zircon grains that yield an age of 990 -# 22 Ma, consistent with
an early Tonian Pb-loss event that affected the Stac Fada Member but not
its bounding strata. We interpret these data to record the timing of
impact, which occurred some 200 m.y. after the previously determined
1177 Ma alkali feldspar 40Ar/39Ar age. The alkali feldspar we find
within the Stac Fada Member yields Rb-Sr ages of ca. 1735 Ma and 1675
Ma, consistent with a detrital provenance from Paleoproterozoic
granites. Our new age constrains the Stoer Group to the early Tonian and suggests a new Neoproterozoic plate tectonic context for these rocks.
These data revise the age of some of the oldest known nonmarine
microfossils in the UK and their role for timing the eukaryotic
colonization of land.
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