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This struck me as precisely the type of thing that they were giving out about in the article. So I asked a geologist was there more to it. They said: The Creta

by ian0 8y ago

This struck me as precisely the type of thing that they were giving out about in the article. So I asked a geologist was there more to it. They said: The Cretaceous-Paleocene event is dated to 66m years ago [1]. The crater has been dated to 65m years ago [2]. The deccan traps was from 63-69m years ago with the bulk of activity 66m years ago [3]. Obviously both the volcano and the meteor were life-changing events. Of the three events the fossil record analysis is the hardest to analyse. But there are indications that the volcanos main activity may have preceded the meteor and that while the meteor did obviously contribute may not have been the main cause of the extinction. IE the dinosaurs may have been on their way out before it, or it may have been a "combination" of the two. [1] https://en.wikipedia.org/wiki/Cretaceous%E2%80%93Paleogene_extinction_event https://en.wikipedia.org/wiki/Cretaceous%E2%80%93Paleogene_e... [2] https://www.ncbi.nlm.nih.gov/pubmed/17789640 https://www.ncbi.nlm.nih.gov/pubmed/17789640 [3] https://link.springer.com/article/10.1007%2FBF02981139 https://link.springer.com/article/10.1007%2FBF02981139

pfdietz 8y ago
There is no evidence the dinosaurs were on their way out. The evidence is entirely consistent with abrupt extinction with no precursor decline. The global mass extinction killed things that can be much more precisely dated than dinosaurs. Forams, for example, go extinct right at the impact boundary, cut off like a knife.
- samth 8y ago
  The article is, roughly, about a geologist who studies exactly forams and disagrees.
  - pfdietz 8y ago
    Yes, and others who study forams have looked at the same evidence and come to different conclusions. Someone's inferences are not following the same logic as others, and the most parsimonious explanation is that it's this person -- who I understand has become somewhat notorious -- not the rest of the scientific community.
    - Drdrdrq 8y ago
      And you know better because...? The main point of the article is that the issue is far from settled, and that evidence for both sides is lacking. Until the consensus is reached through scientific means (instead of bullying) the matter is not closed.
    - stephengillie 8y ago
      Could you link to some of this purported notoriety?
- goatlover 8y ago
  The article states that some scientists disagree and have evidence to back their claim that life was on it's way out.
- furins 8y ago
  Geologist here: I've studied in 1997-2003, than I've had a PhD in stratigraphy in 2007. I researched on a similar subject trying to identify what caused "dinosaurs" appearence (spoiler: another extinction event). At that time the two hypotheses, at least in Europe, were still presented as equally valid. How these two phenomena can be equally the cause of the mass extinction at the end of Cretaceous? Two reasons, at least. The first is the uncertainty about how rapid was the decline of Life. Any geologic date has an error, so it is extremely hard to assess the velocity of geological events. Around the K/T boundary most rock samples cannot be dated with a precision greater than a million year, that means that 2 separate events have the same probability to be coeval or separated by hundreds of thousands years with 95% confidence. In these case the uncertainty cannot allow us to distinguish an abrupt event from a slow one. More precisely, some rocks can actually be dated with an error of ~10000 years, like the iridium anomaly, or like the Deccan's lava but forams does not live inside lava. So you have to correlate events, to find proxy signals like changes in water geochemistry and so on. This increases uncertainties when dealing with fossils, and may be an easy way to denigrate palaeontological studies, but there are still evidences of a progressive decline. The second reason is that the decline in marine ecosystems was sharp after the iridium anomaly, but we cannot explain why that precise impact killed big reptiles on sea and land whereas hundreds of other asteroids that hit the Earth during mesozoic had not. It was surely not the asteroid impact alone. There are evidences that all the mass extinction events are not instantaneous, but they are all related to a sequence of (misfortunated) events in rapid sequence. The emplacement of igneous provinces has proven to be a common menace for life on Earth. Asteroids too. What we actually "read" in the rocks is that Deccan's traps paved the way, the Yucatan impact provided a massive stroke, and the closeness of these two events finished the survivors. In my opinion the "war" between scientists was more an US phenomenon related to their need to get access to NSF funds. The cool one got all.
mirimir 8y ago
If that dating is at all accurate, it seems pretty obvious that both Deccan Traps and the Chicxulub impact contributed. I don't get why it's gotta be either-or.
- nimchimpsky 8y ago
  The impact caused the Deccan traps, like if you punch a jelly, stuff spurts out the opposite side.

by ian0 8y ago

pfdietz 8y ago

There is no evidence the dinosaurs were on their way out. The evidence is entirely consistent with abrupt extinction with no precursor decline. The global mass extinction killed things that can be much more precisely dated than dinosaurs. Forams, for example, go extinct right at the impact boundary, cut off like a knife.

samth 8y ago
The article is, roughly, about a geologist who studies exactly forams and disagrees.
- pfdietz 8y ago
  Yes, and others who study forams have looked at the same evidence and come to different conclusions. Someone's inferences are not following the same logic as others, and the most parsimonious explanation is that it's this person -- who I understand has become somewhat notorious -- not the rest of the scientific community.
  - Drdrdrq 8y ago
    And you know better because...? The main point of the article is that the issue is far from settled, and that evidence for both sides is lacking. Until the consensus is reached through scientific means (instead of bullying) the matter is not closed.
  - stephengillie 8y ago
    Could you link to some of this purported notoriety?
goatlover 8y ago
The article states that some scientists disagree and have evidence to back their claim that life was on it's way out.
furins 8y ago
Geologist here: I've studied in 1997-2003, than I've had a PhD in stratigraphy in 2007. I researched on a similar subject trying to identify what caused "dinosaurs" appearence (spoiler: another extinction event). At that time the two hypotheses, at least in Europe, were still presented as equally valid. How these two phenomena can be equally the cause of the mass extinction at the end of Cretaceous? Two reasons, at least. The first is the uncertainty about how rapid was the decline of Life. Any geologic date has an error, so it is extremely hard to assess the velocity of geological events. Around the K/T boundary most rock samples cannot be dated with a precision greater than a million year, that means that 2 separate events have the same probability to be coeval or separated by hundreds of thousands years with 95% confidence. In these case the uncertainty cannot allow us to distinguish an abrupt event from a slow one. More precisely, some rocks can actually be dated with an error of ~10000 years, like the iridium anomaly, or like the Deccan's lava but forams does not live inside lava. So you have to correlate events, to find proxy signals like changes in water geochemistry and so on. This increases uncertainties when dealing with fossils, and may be an easy way to denigrate palaeontological studies, but there are still evidences of a progressive decline. The second reason is that the decline in marine ecosystems was sharp after the iridium anomaly, but we cannot explain why that precise impact killed big reptiles on sea and land whereas hundreds of other asteroids that hit the Earth during mesozoic had not. It was surely not the asteroid impact alone. There are evidences that all the mass extinction events are not instantaneous, but they are all related to a sequence of (misfortunated) events in rapid sequence. The emplacement of igneous provinces has proven to be a common menace for life on Earth. Asteroids too. What we actually "read" in the rocks is that Deccan's traps paved the way, the Yucatan impact provided a massive stroke, and the closeness of these two events finished the survivors. In my opinion the "war" between scientists was more an US phenomenon related to their need to get access to NSF funds. The cool one got all.

mirimir 8y ago

If that dating is at all accurate, it seems pretty obvious that both Deccan Traps and the Chicxulub impact contributed. I don't get why it's gotta be either-or.

nimchimpsky 8y ago
The impact caused the Deccan traps, like if you punch a jelly, stuff spurts out the opposite side.