A team of geologists has found 60 million-year-old ejecta from a previously unknown meteorite impact on the Isle of Skye, northwest Scotland. This is the first recorded mid-Paleocene impact event in the region and is coincident with the onset of magmatism in the British Paleogene Igneous Province.
The team, headed by Birkbeck University of London researcher Dr. Simon Drake, found a 3.6-foot (1.1 m) thick layer at the base of a 60 million-year-old lava flow on the Isle of Skye, Scotland.
“We thought it was an ignimbrite — a volcanic flow deposit,” Dr. Drake said.
“But when we analyzed the rock using an electron microprobe, they discovered that it contained rare minerals straight from outer space: vanadium-rich and niobium-rich osbornite.
“These mineral forms have never been reported on Earth. They have, however, been collected by NASA’s Stardust Comet Sample Return Mission as space dust in the wake of the Wild 2 comet.”
What’s more, the osbornite is unmelted, suggesting that it was an original piece of the meteorite.
Dr. Drake and co-authors also identified reidite, an extremely high pressure form of zircon which is only ever associated in nature with impacts, along with native iron and other exotic mineralogy linked to impacts such as barringerite.
A second site, 4.3 miles (7 km) away, proved to be a 6.5-foot (2 m) thick ejecta layer with the same strange mineralogy.
They pin the impact to sometime between 60 million and 61.4 million years ago.
“This discovery opens many questions,” the geologists said.
“Is the same ejecta layer found elsewhere in the British Paleogene Igneous Province? Where exactly did the meteorite hit? Could the impact have triggered the outpouring of lava that began at the same time, or be related to volcanism in the larger North Atlantic Igneous Province?”
So far, the researchers have collected samples from another site on Skye that also yield strange mineralogy, including another mineral strikingly similar to one found in comet dust.
“We were surprised that the ejecta layer had not been identified before. After all, the Isle of Skye is famously well-trampled by geologists,” Dr. Drake said.
“The second site had not been sampled in years. As for the first site, we suspect the steep, rough, and very boggy terrain probably discouraged previous workers from sampling the layer.”
A report on the discovery is published in the journal Geology.
Simon M. Drake et al. Discovery of a meteoritic ejecta layer containing unmelted impactor fragments at the base of Paleocene lavas, Isle of Skye, Scotland. Geology, published online December 12, 2017; doi: 10.1130/G39452.1
Source link: https://www.sci.news/geology/meteorite-impact-scotlands-isle-of-skye-05539.html