Evidence found at the spectacular fossil bed at ‘Tanis’ has been trickling out for several years now. This site has remains that appear to be the result of a gigantic tsunami that was produce by the Chicxulub impact. The initial evidence was consistent with earlier findings that the impact was probably in the springtime.
This winter, two studies document the evidence of the springtime impact.
One study focusses on examination of the bones of the fish, which have seasonal growth rings not unlike tree rings [4]. The other study has a second indicator of growth, and also includes evidence that insects were spawning, which would presumably happen in spring [3]. Together, there is strong evidence that the animals were (a) alive at the time of the impact and (b) it was springtime.
Kewl!
One implication of this finding is that if it was springtime, then animals and plants might have been more vulnerable in the northern hemisphere than the south. South of the equator, animals would be entering fall dormancy. If the animals were in winter burrows, they might have been more protected from the immediate impact. Up north of the equator, animals and plants would have been in critical breeding periods, and possibly more vulnerable.
“It is therefore plausible that this phenomenon predisposed an asymmetric pattern of extinction between the northern and southern hemispheres.”
([4], p. 6)
“We postulate that the timing of the Chicxulub impact in boreal spring and austral autumn was a major influence on selective biotic survival across the Cretaceous–Palaeogene boundary.”
([3], p. 91)
Given earlier studies that indicated these same general conclusions, I was pleased but not surprised by these findings.
But I was surprised that the popular reports reported this seasonal dating as and “exciting new finding” [1, 2] (here, here). Sigh. Exciting? Yes. New? Not really.
Anyway, this site is giving us incredibly and detailed picture of that day.
One thing that has not been reported, as far as I know, is what they have found of dinosaurs. Early comments suggest that there may be direct evidence that dinosaurs were among the casualties. This would finally end any question of whether dinosaurs were extinct before the impact.
There may also be evidence for activity immediately after the disaster, such as scavenging, or the blooming of plants. This would tell us something about what might have survived the impact, and how the aftermath unfolded.
As Jonathan Amos puts it, “If you haven’t yet heard of Tanis, you’re going to – a lot – over the next few years.”
- Jonathan Amos, ‘Dinosaur asteroid’ wrought springtime devastation, in BBC News – Science & Environment, February 24, 2022. https://www.bbc.com/news/science-environment-60495951
- Kenneth Chang, The Dinosaur Age May Have Ended in Springtime, in New York Times. 2022. https://www.nytimes.com/2022/02/23/science/dinosaur-extinction-spring.html
- Robert A. DePalma, Anton A. Oleinik, Loren P. Gurche, David A. Burnham, Jeremy J. Klingler, Curtis J. McKinney, Frederick P. Cichocki, Peter L. Larson, Victoria M. Egerton, Roy A. Wogelius, Nicholas P. Edwards, Uwe Bergmann, and Phillip L. Manning, Seasonal calibration of the end-cretaceous Chicxulub impact event. Scientific Reports, 11 (1):23704, 2021/12/08 2021. https://doi.org/10.1038/s41598-021-03232-9
- Melanie A. D. During, Jan Smit, Dennis F. A. E. Voeten, Camille Berruyer, Paul Tafforeau, Sophie Sanchez, Koen H. W. Stein, Suzan J. A. Verdegaal-Warmerdam, and Jeroen H. J. L. van der Lubbe, The Mesozoic terminated in boreal spring. Nature, 2022/02/23 2022. https://doi.org/10.1038/s41586-022-04446-1