K/T Impact: support from an analysis of recovry and productivity!

[Winner]

What makes you say that? My understanding of the K/T extinction event (one of many throught the history of the Earth) was that it was bought about by changes in temprature in which certain species became progressively less adapted to the environment.

Also, the pattern of extinction is inconsistent with the effects of a meteroite impact at K/T.

Back me up boffins.

Well, I won't pretend I have some deep knowledge, but if I accept that there was a large impact event at that time, it must have had serious consequences.

Such large impacts cause years of "asteroid winter", global firestorms, destruction of ozone layer, global warming etc. It is enough to wipe out human civilization (although not the human species) and completely disrupt most of Earth's ecosystems. I think that it wouldn't be wise to underestimate it.

 

[The Last Conformist]

What makes you say that? My understanding of the K/T extinction event (one of many throught the history of the Earth) was that it was bought about by changes in temprature in which certain species became progressively less adapted to the environment.

Also, the pattern of extinction is inconsistent with the effects of a meteroite impact at K/T.

Back me up boffins.

Well, your understanding is heterodox.

First, it's beyond reasonable doubt there was a big impact at K/T - we've got the crater. Second, the exinction spike looks instantaneous compared to the resolution of the fossil record, which surely is exactly what we'd expect if the killer was an impact and its nuclear-winter-like aftermath.

It may help if you say what inconsistencies you see.

 

[happy_Alex]

Well, your understanding is heterodox.

???

There are plenty of paleontologists who attribute the extinctions to other causes, than the asteroid. Bob Bakkar for example.

First, it's beyond reasonable doubt there was a big impact at K/T - we've got the crater. Second, the exinction spike looks instantaneous compared to the resolution of the fossil record, which surely is exactly what we'd expect if the killer was an impact and its nuclear-winter-like aftermath.

It may help if you say what inconsistencies you see.

There was an impact, but thats a correlation, not necessarily causality. It might look like a spike on a graph, but as I said in my previous post, the KT extinction happened over 10,000 years. Is this time-scale inconsistent with the effects of an impact?

Also, when I talk about inconsistencies, I mean that some species went extinct while others remained. Selectivity is inconsistent with extinctions that would be caused by an asteroid impact, ie: why do some creatures survive, while others disappear, for example what's so different about ammonites that they get extinct while some other marine life survives?

 

[The Last Conformist]

???

There are plenty of paleontologists who attribute the extinctions to other causes, than the asteroid. Bob Bakkar for example.

Mr Bakker's most famous book is called The Dinosaur Heresies - he's heterodox and proud of it.

(I should perhaps say I don't know Bakker's present opinions of the KT. In Heresies he, IIRC, focuses solely on terrestrial animals, which of course is silly.)

There was an impact, but thats a correlation, not necessarily causality. It might look like a spike on a graph, but as I said in my previous post, the KT extinction happened over 10,000 years.

Where do you get that number from?

Is this time-scale inconsistent with the effects of an impact?

Not necessarily.

Also, when I talk about inconsistencies, I mean that some species went extinct while others remained. Selectivity is inconsistent with extinctions that would be caused by an asteroid impact, ie: why do some creatures survive, while others disappear, for example what's so different about ammonites that they get extinct while some other marine life survives?

Why do you think selectivity is inconsistent with asteroidal impact?

Within some radius of ground zero, everything will die no matter what. But on the larger part of the planet, the killer isn't the blast itself, but various indirect effects like storms, acid rain, temperature drop, and darkness. These are all selective agents.

 

[Eran of Arcadia]

Carboniferous. Cambrian is Є.

Right, forgot about Carboniferous.

The Triassic used to be a "Tr" ligature. With the demise of the Tertiary as a formally recognized unit, the simple T appears to've quietly reattached itselt to the Triassic.

Well, if the Tertiary no longer exists (side note: given that these divisions are all purely arbitrary, an attempt to create discrete categories where none exist, why do they need to keep changing them?) why still use it for the name of the K/T boundary?

 

[The Last Conformist]

Well, if the Tertiary no longer exists (side note: given that these divisions are all purely arbitrary, an attempt to create discrete categories where none exist, why do they need to keep changing them?) why still use it for the name of the K/T boundary?

Inertia. K/T rather flows of the tongue, everyone knows what it refers to, and it's unambiguous (it's not like there is a Cretaceous-Triassic boundary!), so people see little reason to stop using it. Still, K/Pg is making inroads, at least in the professional press.

I would dispute that the divisions of geological time are purely arbitrary. They were originally defined with respect to the appearance and disappearance of variou fossil groups, and thus their boundaries tend to fall at evolutionary turnpoints. The K/T is a case in point - the Cretaceous period gives way to the Palaeogene (and the Mesozoic era to the Cenozoic) at a mass extinction that changed the course of life forever.

As for the Tertiary, it was originally part of a very simple division of strata into Primary (roughly = Precambrian), Secondary (=Palaeozoic and Mesozoic), Tertiary, and Quartenary (=Pleistocene and Holocene, the last ~1.65Ma). Forever reason, the last two survived into more modern schemes as the grossly unequal periods of the Cenozoic era.

However, the basic reason for having a geological timescale at all is pragmatic, and it's not very practical to break down a larger unit so unequally - the Tertiary was close enough to synonymous with the Cenozoic, whereas the Quarternary had a length hugely smaller than any other period. It was found more useful to divide the Cenozoic into the Palaeogene (65-23 Mya) and Neogene (23-0 Mya) periods, but then the Tertiary and Quarternary had to go to make room in the hierarchy. Exit Tertiary.

 

[Eran of Arcadia]

So the Tertiary and Quaternary were basically renamed, and their dividing line moved a little. But they are both the two main divisions of the Cenezoic.

 

[The Last Conformist]

So the Tertiary and Quaternary were basically renamed, and their dividing line moved a little.

Moved by more than 10x the duration of the Quartenary.

Oh, and I wouldn't call it an instance of renaming - Palaeogene-Neogene and Tertiary-Quarternary were used in parallel for years, and even if the ICS doesn't recognize the later at all these days, I'm sure there's still people using them.

Some have used the Pg and Ng as subdivisions of the Tertiary ...

 

[Eran of Arcadia]

Well sure, it made the Quaternary 10 times as long, but it was only a difference of about 20 million years.

I mean, obviously there is a need for eras, but they will always be at least a little arbitrary - based off of extinctions, but with different criteria for which groups are more important, and how to group the subgroups.

 

[The Last Conformist]

I don't think you're entitled to say "only" 20 Ma when the entire Cenozoic era is 65 Ma.

 

[Eran of Arcadia]

Well, I am not 'entitled' to say much as I am not a professional. Still, like I said, we may be able to recognize discrete boundaries in the record, but the way we (ie actual professionals) name and group them is arbitrary.

Not that this really matters . . .

 

[happy_Alex]

Where do you get that number from?

Ummm... I read it somewhere. Okay guilty. But it is within the range, right?

 

[The Last Conformist]

Ummm... I read it somewhere. Okay guilty. But it is within the range, right?

The temporal resolution of the fossil record being what it is, you can't confine the extinctions to a temporal slice that thin. Unless somebody pulled it out of thin air, the number would thus have to derive from theoretical concerns.

 

[happy_Alex]

The temporal resolution of the fossil record being what it is, you can't confine the extinctions to a temporal slice that thin. Unless somebody pulled it out of thin air, the number would thus have to derive from theoretical concerns.

you mean as thin as 10,000 years?

 

[carlosMM]

Do "K" or "T" stand for something, though?

(sorry, I'm just curious)

K stand for German Kreide (chalk), the German name for the Cretaceous.

 

[carlosMM]

the K/T extinction occured over a period of 10,000 years. That it was caused by a meteorite is a sensationalist misconception.

Could you back this up with serious data, please?
Cause you directly contradict the article I poster, as well as many other articles......

 

[carlosMM]

???

There are plenty of paleontologists who attribute the extinctions to other causes, than the asteroid. Bob Bakkar for example.

Last I talked to Bob (Bakker, btw), he said he was running out of arguements......

There was an impact, but thats a correlation, not necessarily causality. It might look like a spike on a graph, but as I said in my previous post, the KT extinction happened over 10,000 years. Is this time-scale inconsistent with the effects of an impact?

Bring proof - neither the fossil record, nor isotopes, nor sedimentology backs you up.

Also, when I talk about inconsistencies, I mean that some species went extinct while others remained. Selectivity is inconsistent with extinctions that would be caused by an asteroid impact, ie: why do some creatures survive, while others disappear, for example what's so different about ammonites that they get extinct while some other marine life survives?

You seem to lack the necessary understanding of organisms (no offence intended); have you ever tried to answer your own question?
That fact that some certain groups die out and others survive should get you thinking about what the dead have in common, and what the living have in common, and if there is a pattern. And then you can ask, if this pattern fits an event or a process...... To me, it is pretty clear that the fossil record points to an event, as there are patterns that indicate a sudden huge catastrophe as is caused by a meteorite impact.

I can elaborate, but I'd prefer that you speak first, as you made the claim here.

 

[carlosMM]

you mean as thin as 10,000 years?

Well, the fossil record can be much much tighter, if you're lucky. but normally, you can use circumstancial evidence only.


With the K/T boundary, the evidence is this:
- there is NO trend for lower diversity before it, neither on land, nor in the seas
- there is clear evidence for catastrophic events (mega-tsunamis) in many places worldwide
- there are clear extinction patterns NOT consistent with a 'normal' climate change
- there are clear extinction patterns consistent with 'meteorite winters' and all the other follow-ups of a huge impact
- there is very close temporal correlation between the extinction and the impact

and so on.....


You interested in the die-out patterns?

 

[The Last Conformist]

you mean as thin as 10,000 years?

Exactly. You might be able to cut up things that fine, or finer, for a single locality, but no way for global extinctions. There's no way to tell, from the fossil record alone, if, say, Tethyan ammonoids went extinct the same time as Pacific ones, or tens of thousands of years later.

 

[Ansar]

K stand for German Kreide (chalk), the German name for the Cretaceous.

Cool, thanks!