About 66 million years ago, a 10-km- (6.2-mile) wide asteroid crashed into Earth near the site of the small town of Chicxulub in what is now Mexico. While this impact is firmly linked to the end-Cretaceous extinction of non-avian dinosaurs and 75% of life on the planet, the temporal relationship of the lesser-known Boltysh impact structure in Ukraine to these events is uncertain, although it is thought to have occurred 2,000 to 5,000 years before the mass extinction. A new study, published in the journal Science Advances, shows that the Boltysh impact occurred 650,000 years after the end-Cretaceous mass extinction; at that time, the climate was recovering from the effects of the Chicxulub impact and Deccan Trap volcanism.
A part of the Boltysh impact structure near the village of Bovtyshka in Kivorohrads’ka oblast, Ukraine. Image credit: Wisetus / CC BY-SA 4.0.
The Boltysh impact structure is approximately 24 km (15 miles) in diameter with a 6-km- (3.7-mile) diameter central uplift.
Located in Kivorohrads’ka oblast, Ukraine, the structure is now buried beneath over 500 m (1,640 feet) of post-impact sediments.
Previous analysis of samples from Boltysh, undertaken decades ago, suggested that the meteorite may have struck the Earth between 2,000 and 5,000 years before the Chicxulub asteroid.
The Chicxulub impact is widely believed to have caused the mass extinction event which made non-avian dinosaurs extinct, and the climate event which created the geological signature known as the Cretaceous-Paleogene boundary.
However, questions still remained over whether the Boltysh impact might have occurred close enough in time to have had an effect on both.
The new analysis suggests that, in fact, the Boltysh impact happened around 650,000 years after the Chicxulub event.
“The results allow us to place the Boltysh impact more accurately in our timeline of what happened to the Earth in the period after the end-Cretaceous mass extinction event, and better understand our deep geological history,” said Dr. Annemarie Pickersgill, a researcher in the School of Geographical and Earth Sciences at the University of Glasgow.
To determine the date of the Boltysh impact more precisely than ever before, Dr. Pickersgill and colleagues selected four samples from two rock cores taken from the Boltysh crater, containing rocks generated during the impact event and lake sediments which accumulated over time after the crater was formed.
They determined the age of the samples using the argon-argon dating facility.
Argon-argon dating measures the radioactive decay of potassium to argon. The level of decay acts as a ‘rock clock’, which ticks down over geological time and allows researchers today to determine when the rocks were created during the Boltysh impact event.
“Our analysis suggests that the impact occurred very close to 65.39 million years ago,” Dr. Pickersgill said.
“That puts it firmly after the Chicxulub impact and the formation of the Cretaceous-Paleogene boundary, evidence for which is found in geological records around the world.”
The researchers draw links for the first time between the new dating of the Boltysh impact and evidence for a known ‘hyperthermal’ event found in the Earth’s sediment record, a period of extreme global heating called the lower C29N hyperthermal.
At that time in Earth’s history, volcanoes in India known as the Deccan Traps were releasing vast amounts of greenhouse gases into the atmosphere, accelerating a period of global climate change.
“Paleoclimatology aims to help us understand and adapt to today’s changing climate by studying how our atmosphere responded to environmental stresses in the past,” Dr. Pickersgill said.
“Being able to link the Boltysh lake sediments to the lower C29N hyperthermal is another piece of the jigsaw which will form a clearer picture of how our planet has responded to climate change in the past.”
Annemarie E. Pickersgill et al. 2021. The Boltysh impact structure: An early Danian impact event during recovery from the K-Pg mass extinction. Science Advances 7 (25): eabe6530; doi: 10.1126/sciadv.abe6530