Is the Chicxulub impact still the favored explaination for the extinction?

[aplomado]

I read "The Story of the Dinosaurs in 25 Discoveries" by Donald R. Prothero.  The author states that paleontologists now mostly do not think that the Chicxulub metor impact killed off the non-avian dinosaurs, and that other explainations are preferred.  He did not really explain this statement.

That certainly was news to me!  I am no professional though.

What's the truth?

[FranzBernhard]

13 minutes ago, aplomado said:

What's the truth?

There is no such thing like truth in science, there is only observation and theory. But have a look at this topic:

Franz Bernhard

[siteseer]

1 hour ago, aplomado said:

I read "The Story of the Dinosaurs in 25 Discoveries" by Donald R. Prothero.  The author states that paleontologists now mostly do not think that the Chicxulub metor impact killed off the non-avian dinosaurs, and that other explainations are preferred.  He did not really explain this statement.

That certainly was news to me!  I am no professional though.

What's the truth?

 

 

Part of it has to do with the time of the impact.   An interval of major volcanic eruptions in the area of India was happening across that time as well as a drop in sea level.  It's unclear how both of those affected the dinosaurs either by themselves or together simultaneously.  Certainly, the drop in seal level affected their environment.  The climate would have changed as the sea retreated.  It would have been cooler and drier.  It's unclear what the dinosaur populations worldwide were at the time because dinosaur-bearing rocks from the very end of the Cretaceous are known only from a rather small area of North America, but based on fossils they do have, it appears that dinosaurs were in decline before the impact. 

 

The thing that paleontologists find unsatisfying about the impact is that too many animals that should have been wiped out by  worldwide wildfires and freezing temperatures and acid rain aftereffects of the "nuclear winter" apparently lived on with little or no negative impact to their populations.  Look at frogs and salamanders.  They are very sensitive to changes in the environment.  Today, their numbers are declining worldwide due to loss of habitat and pollution in the air and soil.  It was a lot worse after a major asteroid impact but frogs and salamander fossils are found the the same areas in rocks deposited afterward.  Crocodiles and palm trees can't survive freezing temperatures either but we see both in Paleocene rocks in North America.  There is also evidence that while plant diversity changed across that time, there were extinctions before the impact as well, so the picture is more complicated than "everything was going great and then the impact nearly killed off everything."

 

I think a lot of paleontologists are left wondering if the impact and its aftereffects were so bad with the shock wave and worldwide fires followed by severe winter-like conditions for at least several months.  None of this is new.  There have been many publications questioning the "impact of the impact" including a well-known book, "Dinosaur Extinction and the End of an Era" (1996, Columbia University Press) by J. David Archibald.  In that book he talks about the impact and asks what the fossil evidence said at the time (and is still saying).  He'd been collecting evidence across the 80's and 90's up to that point. 

 

You'd really have to hear from a paleontologist who has been studying how life was affected and get an update.  You want to read about any criticism of Archibald's and other researcher's work too.  Of course, the public might prefer a hypothesis that has the last Tyrannosaurus running off a cliff with its skin on fire from an inescapable conflagration.  No one wants to hear that the greatest dinosaur of all time left this earth forever because of a boring, paragraph-long reason like habitat fragmentation.

 

Jess

 

P.S.  You might want to read another one of Prothero's books, "After the Dinosaurs" in which he did explain better with more detail and appropriate citations than I did.

[siteseer]

I should add that no one is saying, "There was no impact."  They're just questioning how severely it affected life worldwide.  Dinosaurs might have died out anyway.  Clearly, they are not known with certainty from any area of the world in the Paleocene.  Apparently, the asteroid happened to hit right at a low point in their diversity.

[Herb]

There were probably many reasons for the extinction, but the probable "nuclear winter" probably had a great effect. There have been many extinction events. The one during the Permian was probably climate related.

[Tidgy's Dad]

I would like to  point out that this wasn't just an extinction of the non-avian dinosaurs. 

Lots of mammals, birds, insects, plants, corals, ammonites and in total possibly as many as 75% of all species perished. 

Dinosaurs were only a tiny percentage of all those creatures effected so I honestly don't know why people keep going on about this and the whole 'oh, they were on the decline anyway' hypothesis or the 'No, they were doing fine' one either. 

Even though this also mainly mentions the bleeding dinosaurs, it's interesting and from this year. 

https://www.nytimes.com/2020/01/16/science/dinosaurs-extinction-meteorite-volcano.html