The Tanis death assemblage contains land and river life mixed together with large amounts of mud — mud which is made partly of molten rock granules.

The hypothesis is that it was formed from the rapid drainage of a flooded plain, and that the flood was probably caused by the Chicxulub event.

Thanks for posting this. I didn’t know about it and it’s lead me down quite the Wikipedia rabbit hole.

The 90 minute documentary mentioned in the article aired this week, has the real fossils mixed with animations of the creatures and coverage of the excavation you may enjoy (Dinosaurs: The Final Day).

It also has salt-water fish mixed up with fresh-water fish.

It's a very good point and got me wondering, how do we know the dinosaurs were killed by a single asteroid strike? What if there were many within a relatively short time scale?

If you're going to answer "parsimony", what if these events aren't independent?

(I'm not a paleontologist)

Apparently, when the impact hypothesis was first presented as more than just speculation (i.e. with the iridium layer as evidence), a majority of paleontologists rejected it, preferring one based on long-term high-intensity volcanism in Asia. I believe this hypothesis still has a few proponents.

The collision of comet Shoemaker-Levy with Jupiter occurred as several distinct impacts, due to gravitational disruption of the comet in a previous close encounter with the planet. Something similar is clearly possible on Earth (perhaps even gravitational dispersion of a comet passing close to the Moon just before impact?) but the Chicxulub crater is large enough to explain the extinction event by itself (unless you hew to the volcanic explanation, I suppose), so the question is whether there is any evidence for multiple impacts. As far as I know, the global distribution of the physical evidence is indicative of a single source, but not definitively so.

At that point, they didn't even believe the volcanism hypothesis, the bias toward gradualism was so profound.

It’s a good theory, and may have occurred by large objects breaking up during atmospheric entry or it was a cluster of objects in space.

The K/T impactor had linear dimensions comparable to the scale height of the atmosphere. Unless the impact was at an extremely shallow angle (unlikely) breaking up in the atmosphere would have no significant effect. The mass of atmosphere that could potentially transfer momentum with the impactor before impact would be much less than the mass of the impactor.

Wouldn't the break up be more influenced by the gravitational acceleration imparted by earth? Most asteroids are rather loosely bound.

That would be tidal forces. There wouldn't be enough time for that.

Shoemaker-Levy orbited Jupiter for quite a while before it broke up and went in.

I think if something lived for millions of years, and impacts on earth are not uncommon, it was bound to happen at some point.

On a long enough timeline, improbable events are expected.

I don't think gp was questioning that, so much as the likelihood of finding more than one fossil from the same event, given all the times we could have found fossils from.

Wouldn’t this single event have a super high chance of generating fossils though giving that a) it wiped out a ton of life in one go and b) it released a huge amount of debris ready to cover things up nicely and preserve them?

Yes. What was incredibly lucky was the fossil stratum being exposed again at a time when we could spot them. There must be megatons more of this stuff, wholly inaccessible.

Not even single day, single hour ! (Violent water sloshing mixing marine, freshwater and land life caused by seismic waves rather than the "direct" tsunami.)