Hiawatha impact crater in Greenland, formed ~58 million years ago

[Astronuc]

Huge asteroid slammed into Greenland just a few (~7-8) million years after the dinosaurs died out
https://www.space.com/greenland-impact-crater-hiawatha-age

after several years of additional research, two separate teams of scientists have determined its age to be far older: 58 million years. Researchers from the University of Copenhagen's GLOBE Institute discovered the structure, which they suspected to be a massive 20-mile-wide (31 kilometers) impact crater, in 2015 beneath Greenland's thick Hiawatha ice sheet.

. . . scientists at the Natural History Museum of Denmark and the GLOBE Institute at the University of Copenhagen in the same country sampled sand from the Hiawatha crater and heated it, using the argon gas released from the grains to date the impact event.

Scientists from Swedish Museum of Natural History independently sampled rocks from the crater and dated them using the uranium fingerprint of the mineral zircon.
https://www.eurekalert.org/news-releases/945636?

At the time the researchers have pinpointed, Greenland was not covered in an ice sheet, but rather was home to a temperate rainforest. When the asteroid that created the crater impacted Earth, it did so with a force estimated to be several million times stronger than that of an atomic bomb. While that impact certainly would have annihilated a large part of Greenland, scientists are not sure of the impact's effect on global climate.

That uncertainty is in contrast to the most famous asteroid impact, which formed the Chicxulub crater in Mexico and eradicated most of the dinosaurs 66 million years ago, just a few million years prior to the Greenland impact. The Chicxulub crater is nearly 6.5 times larger than Hiawatha.

A Late Paleocene age for Greenland’s Hiawatha impact structure​

https://www.science.org/doi/10.1126/sciadv.abm2434

 

[jim mcnamara]

We had some PF debate about this impact possibly being the cause of the Younger Dryas event - cooling event about 12000 ya. So a more definitive answer: "Hiawatha is not the cause". Rather warm water flow from North American glacier melt disrupting the AMOC -> seems to be the current understanding.
AMOC:
https://en.wikipedia.org/wiki/Atlantic_meridional_overturning_circulation
Event:
https://en.wikipedia.org/wiki/Younger_Dryas