Talk:Permian–Triassic extinction event

From Wikipedia, the free encyclopedia

Portal This article is part of WikiProject Extinction, an attempt at creating a standardized, informative, comprehensive and easy-to-use resource on extinct animals, extinct plants and extinction in general. If you would like to participate, you can choose to edit this article, or visit the project page for more information.

	Earth sciences Portal Permian–Triassic extinction event is part of WikiProject Geology, an attempt at creating a standardized, informative, comprehensive and easy-to-use geology resource. If you would like to participate, you can choose to edit this article, or visit the project page for more information.
B	This article has been rated as B-class on the quality scale.
High	This article has been rated as high-importance on the importance scale.
	This page has been marked as needing immediate attention.

An assessment of this article took place along with other articles about Natural disasters during the week starting 20 February 2006.

Archives

1

Contents 1 Philcha's notes (for use in article) 2 Nature article 3 Marine losses 4 Dubious 5 WP:CITET 6 linkage and foil 7 GA Review 8 Not inconsistent 9 Recovery 10 1 extinction or 2? Other timing considerations 11 Dead / useless links to extinct insects 12 Structure of "Causes" section 13 Fungal spike 14 Out of place sentence in "Dating the extinction" 15 The apparent fungal spike 16 Methane hydrate gasification 17 "Tropical distribution of continents" 18 "Triassic takeover" 19 ppt 20 Apparently irrelevant ref 21 Out-of-place sentence 22 P-Tr and early Tr C13/C12 fluctuations - "hunting" oscillation? 23 Fungal spike - relegate details to footnote? 24 Carbon Isotopes 25 i was just passing though this article... 26 Bryozoan Die Off 27 Extinction patterns

[edit] Philcha's notes (for use in article)

• [3] - Dorritie's very comprehensive account; explains poor fossil record; lots of refs.
• [4] - Benton
• [5] - "How to kill almost all life"
• [6] - links
• [7] - C13 oscillations: good if it had date estimates
• [8] - Ward & co argue for press/pulse model
• [9] - plants!
• [10] - late P dry, early Tr wetter; Lystrosaurs' tolerance for low O2 and high CO2
• [11] - coal gap, correlated to wetter climate.
• [12] - insects!
• [13] - fungal spike eases correlation problems
• [14] - White (Leeds) covers a lot of ground.
• [15] - dating of final extinction and Siberian Traps
• [16] - more volcanism (non-basaltic) in China!
• [17] - Isozaki on non-basaltic volcanism's contribution to double whammy and superanoxia
• [18] - Wignall examines linkage (not 100%) between FBs/LIPs and extinction
• [19] temporal link bet Emeishan and Guadalpian extinction.
• [20] useful links and analysis.
• [21] - Siberian Traps extended into sea.
• Hypercapnia and hypoxia: [22], [23], [24], [25],

[26] Philcha Philcha (talk) 14:52, 18 January 2008 (UTC)

• High CO2 in sea: [27] Philcha (talk) 13:20, 21 January 2008 (UTC)

[edit] Nature article

This recent article also provides a good review that could usefully be incorporated into this article. Verisimilus T 07:57, 12 July 2007 (UTC)

Nature articles are only available to subscribers - if you have access, I suggest you add a summary.Philcha 19:00, 13 July 2007 (UTC)

[edit] Marine losses

It also strikes me that the article's review of extinct organisms is very much oriented to the ones that went catastrophically extinct. It doesn't seem to provide a very rounded view of the extinction as a whole, making it look even more severe than it actually was. Could this be addressed? In fact, the table itself isn't thoroughly encyclopaedic and I'm not sure it's in its best position in the text of the article - perhaps it would be more appropriate to float it? Verisimilus T 08:06, 12 July 2007 (UTC)

Everything I've ever read about the P-Tr extinction suggests or states that the slaughter was appalling and the survivors may just have been extremely lucky. Michael Benton even wrote a book "When Life Nearly Died". Other sources I've seen suggest this extinction was the only one which showed evidence of severe losses among land plants and insects (they say this but without giving details, alas - can you help?).

Re the percentage level of extinction, I've seen articles which say that the widely-quoted estimate of marine species lost was calculated from the empirically-supported figures for marine families lost, but that this calculation made some dubious "business as usual" assumptions about the intermediate ratios needed to estimate species-level extinctions from family-level extinctions - that's on my "to do" list.

What do you mean by the table itself isn't "thoroughly encyclopaedic"? If you mean not detailed enough, I suggest adding much more detail would require it to be moved to a separate "List of victims" article. But then the P-Tr extinction article would still have to have some sort of summary.

I'm not sure about floating the "victims" table. The problems are: it makes the text very narrow and therefore harder to read (web usability studies suggest that about 60 characters per line is optimum); and as the table gets longer unrelated paragraphs / sections get caught up in the float, which makes it appear that the table is relevant to them as well (unless you add BR tags as I did for the ankle images in Archosaur, but that has disadvantages too). Philcha 19:16, 13 July 2007 (UTC)

In the "Marine Extinctions" table, placoderms are listed as having gone extinct. But other sources--both within and outside of Wikipedia--date the extinction of the placoderms to the late Devonian (example: the Late Devonian extinction article, http://en.wikipedia.org/wiki/Late_Devonian_extinction; I think they should be removed from the table, unless perhaps there's some debate about the time of their extinction I'm unaware of.

I do like the tables, however, and it would be great to make one for terrestrial extinctions, and also to add them to add them to all the other mass extinction articles and standardize their format. Glyptodon 08:52, 13 November 2007 (UTC)

[edit] Dubious

When are you counting as the start of the history of the oceans? The oceans were almost enitrely anoxic until around 2,700 million years ago... This could use a little re-wording.

Also, excuse me meddling with your prose as you write it... I'm always being told off for writing sentences that are too long and an aversion to them has become ingrained... Verisimilus T 20:47, 13 July 2007 (UTC)

[edit] WP:CITET

OK, this is just my interpretation, and mostly it's what's done in articles. If its a newspaper or magazine, you use the exact date of year-month-day. If it's a science journal, only the year is required, because if you cite correctly, everyone searches by volume and/or issue number, so the exact date of publication isn't useful. Furthermore, you do not have to wikilink the date, the template does it automatically. Orangemarlin 15:13, 14 July 2007 (UTC)

[edit] linkage and foil

This is a very good article with excellent links. Very interesting. I have however a few remarks on the science, firstly, sorry i say it becus i said it before, i remember from the book first posing impact as the cause of the jurassic extinction it said for many if not every major extinction an iridium anomaly is there. It is a bit strange to see it so consistently denied.(esp. since the theory has been denied herself. My guess would be he sampled greenland) Next, the low sea levels preceding the extinction are significant. Generally spoken water does not generate on a planet our size, does it? It will actually more often evaporate from a planet. (any subsequent sealevel rise suggests a high concentration of water in the then atmosphere) A sudden reversal in such a trend is hard to understand, wich makes me interested in radioisotopes of water from around the boundary(i would guess arid places being the best to start looking). Then i wonder why noone notices the possibillity of several impacts of eg. cometary fragments, or even seperate objects. It is also impossible that there are 2 huge craters dating to aprox. the boundary and there would be no Ir- anomaly at all . Have there been attempts to date impacts through the late permian in that way? Lastly i don't quitte well see how the cometary impact theory can be easily discarded, especially that the majority of extinctions was seabased, suggest something to have to do with water. Another reason to look for several impacts is the anoxian phase in the record since it supposedly stems from continued heating of the environs. Perhaps this is weird, but as long at is is not researched how will we know if not several impacts in a row (some of them near simultaneous, and probably in sea) caused the heating. Possibly the confusion is due to the siberic ashlayers. But elsewhere the option that geologic events caused such widespread extinction is made rather improbable. Although there is no clear relation between impacts and vulcanism, there is also no reason why a present pressurized magma chamber would not coincedentually interact, perhaps it is as obscure as that.(has there been an impact in the vulcanous region (siberia) of that period) 77.251.179.188 23:40, 18 October 2007 (UTC)

The evidence is generally against impact(s) being the primary cause, the best records recording plant pollen and spores show that the extinctions occurred over many years, not as one or a few major catastrophes. Also keep in mind that the oceans had been around for a long time before this event occurred and sea level relates more to the placement of the land masses resulting from effects caused by continental drift and how much water is "tied up" in poler ice or glaciers. If you want to look for correlations between impacts and volcanism, look for magma intrusions and/or volcanoes on the opposite side of the plant from were you thick the impact zone is. 00:14, 19 October 2007 (UTC) —Preceding unsigned comment added by Hardyplants (talk • contribs)

[edit] GA Review

I am troubled that an editor with hardly any experience with this article nominated it for WP:GAC. I think the article is close, but a long ways from GA status. Here are a few concerns:

1. The article is about the extinction event (which is biological). It is not about the geological causes of that event. Similar to the two articles, Cretaceous–Tertiary extinction event, an Featured article that focuses solely on the biological extinction, and K–T_boundary, which focuses on the geological event. They are separate, become one did not necessarily lead to the other.
2. The references, though cleaned up, are still a mess. I continue to find errors, use of unreliable sources and websites. Moreover, there are still a few references that have not been standardized to WP:CITET.
3. Several sections need substantial copyediting. Bullet-pointed sections just aren't acceptable.
4. There are a bunch of wiki-links that aren't pointing to real articles.

I am concerned that an uninvolved editor decided to to move to GA status without discussing it with the editing group. I hope any GA reviewer will take this under consideration. OrangeMarlin ^{Talk• Contributions} 02:52, 9 January 2008 (UTC)

Actually, the extinction event and the boundary itself are inextricably linked. Geological boundaries- particularly major ones like the PT and KT - are traditionally discriminated on the basis of faunal and floral change - between Palaeozoic and Mesozoic communities, and Mesozoic and Cainozoic respectively, in these cases. It's not by chance that extinctions are coincident with chronostratigraphic boundaries, and such a boundary is not really an "event" (except in so far as it may be taken to be an arbitrary point in time). As for the rest of your points - I'm surprised. From a brief glance, I think it might pass as a GA. Badgerpatrol (talk) 21:34, 9 January 2008 (UTC)

I know that they are linked, but IMHO, shouldn't we keep the geological stuff separated from biological. Both together, like at K-T made for a HUGE article that was hard to handle. I agree they are linked, but for the purpose of GA, tighter articles go further. Moreover, it is well-understood that GA is not as critical as FA. I think with K-T, I just skipped GA and went straight to FA. This article requires a lot more copy-editing, which I'm trying to do, in between putting up with personal attacks from Creationists. OrangeMarlin ^{Talk• Contributions} 06:27, 14 January 2008 (UTC)

First, Badgerpatrol is right - many scientists treat the fungal spike as the boundary between the Permian and Triassic (yes, I know it's not the international standard definition, see GSSP for the Permian-Triassic Boundary; but that's no good for terrestrial sediments, see PALEOSOL AND VERTEBRATE EXTINCTION ACROSS THE PERMIAN-TRIASSIC BOUNDARY IN THE KAROO BASIN, SOUTH AFRICA; so for practical purposes the fungal spike and the C13/C12 anomaly are treated as markers, see for exmaple An accurately delineated Permian-Triassic Boundary in continental successions).

Second, it would be ridiculous not to discuss the causes of the "mother of all mass extinctions"; and a thorough, balanced dicussion cannot exclude any type of cause just because it is the subject of the "wrong" scientific discipline. You've implicitly conceded that yourself, in I think with K-T (Cretaceous–Tertiary extinction event), I just skipped GA and went straight to FA", as the two most likely causes of that are astronomical and geological. In fact the K-T article (FA!) shows that the whole of objection 1 above ("It is not about the geological causes of that event") is nonsense. Also K–T boundary is not a good example of anything -it's a poorly-scoped mess at present.

Objection 2 above is little better. "I continue to find errors, use of unreliable sources and websites" contains no examples and therefore is: (a) unhelpful; (b) an attempt to avoid scrutiny of the criticism.

Objection 3 above is not based on Wikipedia's stated rules (Wikipedia:Embedded list).

In fact I've just checked Wikipedia:Good article criteria and Wikipedia:Scientific citation guidelines, and the only objection supported by these is objection 2, but that has no value if not supported by examples of each of the alleged faults. Philcha (talk) 13:46, 18 January 2008 (UTC)

Philcha, I didn't know there was a right or wrong around here. Be careful as to how you throw about your adjectives. Any further attacks by you will be dealt with aggressively. And your comments there was a huge attack. OrangeMarlin ^{Talk• Contributions} 18:47, 18 January 2008 (UTC)

Talk about the pot calling the kettle black!

• "I don't actually violate WP:NPA. Civility, all the time, but never NPA" - your own words at (your Talk page
• "Calling those you disagree with "nutjobs" is hardly appropriate or civil, [28], don't do it again" - complaint by another editor at your Talk page
• "OK, per your latest bout of personal attacks, I think I'll leave it to you to edit the article in future" - complaint by a different editor at Extinction_Event your Talk page. Was "I think I'll leave it to you to edit the article in future" what you wanted?
• "Watch your civility when it comes to dealing with other users, specifically ... or you will be blocked for your continued hostile attitude" - warning from another editor at your Talk page
• "This is an incivil edit comment. Please don't do it" by yet another editor at your Talk page

And I notice that you have not answered any of the points I raised. Until you answer them, you're losing the debate. Philcha (talk) 20:46, 18 January 2008 (UTC)

PS check out Wikipedia:WQA and Wikipedia:WQA Philcha (talk) 21:46, 18 January 2008 (UTC)

[edit] Not inconsistent

Someone flagged

It was the Earth's most severe extinction event, with up to 96 percent of all marine species[2] and 70 percent of terrestrial vertebrate species becoming extinct. Because approximately 25 percent of species survived the event,

as being inconsistent. Sorry to blockquote here but,

Wikipedia said (in its species page)"

* 287,655 plants, including: o 15,000 mosses, o 13,025 ferns, o 980 gymnosperms, o 199,350 dicotyledons, o 59,300 monocotyledons; * 74,000-120,000 fungi[3]; * 10,000 lichens; * 1,250,000 animals, including: o 1,190,200 invertebrates: + 950,000 insects, + 70,000 mollusks, + 40,000 crustaceans, + 130,200 others; o 58,808 vertebrates: + 29,300 fish, + 5,743 amphibians, + 8,240 reptiles, + 10,234 birds, (9799 extant as of 2006) + 5,416 mammals.

"

This demonstrates the 25% can't be worked out from the data in the first sentence and is thus not based said data. I see nothing else for it to be inconsistent with. Hence, the flag was removed. Menswear (talk) 10:42, 15 January 2008 (UTC)

I may have missed the point here, but surely the actual reason it's not inconsistent is because it is mixing environments. It is possible for 96% of marine species and 70% of terrestrial vertebrate species to be extinguished and still retain 25% of overall species-level biodiversity. That may be what you are trying to say, in which case I apologise for restating it.(In any case, if the 96% is taken from the Sepkoski curve or some variant thereof, it is a bit misleading. That curve specifically refers to marine shelly organisms. There's no direct evidence (for obvious reasons) for a reduction in diversity of e.g. picoplankton, which are extremely small and have no preservable hard parts.) Badgerpatrol (talk) 12:41, 15 January 2008 (UTC)

The introduction is also inconsistent with the graph. The intro states that 96% of marine species went extinct, but the graph indicates that only about 50 did. Which one is correct? 68.230.161.164 (talk) 04:44, 26 January 2008 (UTC)

No, it isn't. The text refers to species-level diversity, whilst the graph refers to genus-level diversity. A genus is by definition at least as inclusive, and almost always more inclusive, as a species concept. Badgerpatrol (talk) 11:11, 26 January 2008 (UTC)

[edit] Recovery

According to Sahney, Sarda and Benton, Michael "Recovering from a mass extinction" 2008-01-18 the full ecological recovery (measured by the presence of highly specialized niche species) took 30 Ma. LeadSongDog (talk) 16:26, 18 January 2008 (UTC)

Interesting. I'd be happy with "... - in fact some researchers think it took as long as 30M years" - once we can get a ref from a peer-reviewed journal. But I have to admit I find it surprising: that's about 60% of the Triassic; I'd have thought the Signor-Lipps effect would make it hard to measure how long full ecological recovery took. Philcha (talk) 20:54, 18 January 2008 (UTC)

[edit] 1 extinction or 2? Other timing considerations

In a long-ago version [http://en.wikipedia.org/w/index.php?title=Permian%E2%80%93Triassic_extinction_event&diff=144139716&oldid=143359693} I included all the dating evidence I could find, including: mentions of a smaller extinction about 5M years earlier at the end of the Guadalpian: that the fungal spike and carbon isotope anomalies are trearted as P-Tr boundary markers of practical purposes. In the meantime someone removed most of this and stated that the "2 phases" view is obsolete. I'm still finding papers (dated 2006-2007) that mention 2 phases - 1 says that all but one of the surviving dinocephalian genera died out at the end of the Guadalpian (Retallack, Metzger, Greaver, Jahren, Smith and Sheldon; "Middle-Late Permian mass extinction on land"; GSA Bulletin November/December 2006, v. 118, no. 11/12, p. 1398–1411; doi: 10.1130/B26011.1). I think the timing section needs to be restored as it was in the older version referred to above. Philcha (talk) 17:55, 18 January 2008 (UTC)

Undue weight issues. Most articles do not give much credence to the view. Moreover, the fungal spike has been largely discredited too. It's not our job to represent every single theory. OrangeMarlin ^{Talk• Contributions} 18:43, 18 January 2008 (UTC)

How many refs from the last 3 years would be enough to make you think that the issue might just not be entirely decided? Philcha (talk) 19:19, 18 January 2008 (UTC)

I seem to recall a paper last year performing a statistical analysis that offered quite strong support to three extinctions spanning 5Ma, and feel that such a theory is very important in the interpretation of the events and deserves at least a mention. I don't pretend to be up to date with the literature in this area but am not aware of a paper conclusively killing off the idea. Fungal spikes, on the other hand, can be safely omitted from the article; evidence supporting them is crumbling, as I understand it. Verisimilus T 13:53, 21 January 2008 (UTC)

I'm re-incorporating the stuff about 2 extinction pulses, with refs. This will also include the fungal spike, for now. Verisimilus, can you please provide details and refs for: the 3-pulse theory; crumbling support for a fungal spike. If the fungal spike really is a goner, I'll then check the rest of the article and remove mentions of it. Philcha (talk) 09:43, 21 February 2008 (UTC)

[edit] Dead / useless links to extinct insects

"Extinction patterns: Terrestrial invertebrates" contains the sentence "The caloneurodeans, monurans, paleodictyopteroids, protelytropterans, and protodonates became extinct by the end of the Permian" where:

• caloneurodeans links to the extant Exopterygota. A quick google for "caloneurodea" got me no useful info about these insects, in particular nothing about their paleobiology which would be informative in Permian–Triassic extinction event.
• monurans is a red link. Google go me nothing useful in the P-Tr context.
• protelytropterans redirects to the extant Earwig. Google go me nothing useful in the P-Tr context.

We need someone with real knowledge of extinct insects to examine these links and either unlink them or make them link to something that's relevant to the P-Tr extinction. Philcha (talk) 09:12, 20 January 2008 (UTC)

[edit] Structure of "Causes" section

Hi,

I feel that this section of the article has a lot of scope for improvement. The "causes" come across as unrelated events, and the "combination" section is unclear -- it doesn't really draw them together. The article would benefit a great deal from a consideration of the "domino effect" that was almost certainly involved, i.e. spelling out that an impact event (to which too much significance is attached to this article; the idea is now rather unfashionable as there is little evidence to support it -- it certainly shouldn't be presented first) could create the Siberan traps, and that the volcanism may have caused anoxia, as well as a release of sulfates causing a cold snap and sea level drop etc. There's a good diagram of this web of events in Benton (2005) which illustrates how all factors are interrelated -- this is an impression which needs to be made more clearly in this article.

Verisimilus T 13:48, 21 January 2008 (UTC)

I'm surprised you think the "domino effect" is not made clear - that's the intention of "Combination of causes", and the section about each "domino" after the first says it was cause by the previous one. 82.34.73.184 (talk) 18:59, 22 January 2008 (UTC)

[edit] Fungal spike

In response to Philcha's comment on my talk page, I thought it more appropriate to respond here.

The "Fungal Spike" hypothesis still has its adherents, but the more it is examined, the more it seems to fall apart.^[1] A particularly embarassing blow came when palynologists looked at Reduviasporonites, the predominant "fungal spore", and realised that it was actually algal.^[2][3]

The theory lost further weight when it transpired that it wasn't global in extent,^[4][5][6] and - worse still - that in many places, it didn't fall on the P-T boundary.^[7]

This has led to the suggestion that there may not in fact be a direct relationship between the extinction and the "spike" - if there even is a spike.^[8]

The most sceptical review I found in my brief search was that of Retallack, who believes that the spikes probably represent a transition to a lake-dominated Triassic world.^[9]

There does seem to be a lot of literature out there taking the spike as canon, though; but most of it accepts it as a fact without addressing the problems highlighted. So while it's probably a bit too POV to remove all mention of it from the article, it is worth explaining the controversy. Verisimilus T 18:09, 21 February 2008 (UTC)

Why isn't all the material above edited into the article, along with the footnotes? --Wetman (talk) 21:11, 21 February 2008 (UTC)

Because Verisimilus is a very polite person. Don't worry, it'll be done within 2 days. Philcha (talk) 21:38, 21 February 2008 (UTC)

Now done. I've also removed the "Fungal spike" sub-section from "Post-event biotic recovery". Philcha (talk) 12:51, 23 February 2008 (UTC)

[edit] Out of place sentence in "Dating the extinction"

The final sentence of section "Dating the extinction" (which I am about to edit re the fungal spike theory, see preceding discussion) says,

“

Further evidence for environmental change around the P-T boundary suggests an 8°C rise in temperature,[5] and an increase in CO2 levels by 2000ppm (by contrast, the concentration immediately before the industrial revolution was 280ppm).[5] There is also evidence of increased ultraviolet radiation reaching the earth, and causing the mutation of plant spores.[5]

”

This is out of place in a section about timing. It is relevant to causes of the extinction, but the same points are already covered in various sub-sections of "Causes of extinction event". It may be an environmentalist attempt to hijack the article (as happened in April 2007 with Extinction event). I will comment it out for now, and will delete it if no justification for including it in "Dating the extinction" is provided within 2 weeks. Philcha (talk) 09:41, 22 February 2008 (UTC)

I wasn't sure where best to put this data; a separate section is probably warranted, but there's no obvious place for it in the current article structure. It fits in well with the explanation of the δ¹³C anomaly, and seems out of place in the "causes of the extinction event" section. These are environmental responses to the causes: while they undoubtedly had an effect on the biology, the cause of the the temperature and CO₂ concentration increases may be intimately related to the cause of the extinction - or be a result of the extinction, with the removal of a CO₂ draw down. I thought that the ability to detect a higher mutation rate in the increased abundance of meiotic failure in spores was fascinating, and certainly ought to be mentioned somewhere in the article! The source is also a very up to date (2007) review paper, so probably supersedes the data already in the article (which I didn't spot at first glance). I think any environmentalist attempting to draw an analogy between fossil fuel oxidation and the P/T extinction will have a tough time! Verisimilus T 10:29, 22 February 2008 (UTC)

First off, I didn't notice at the time that you had added the material I commented out - I don't suspect you of being an environmentalist hijacker! But I'd still rather not offer them a handle - in the last year some of them have started to use the P-Tr extinction as ammo, arguing that human activity is causing the fastest rise in CO2 since P-Tr and that clathrate dissociation could cause a similar catastrophe now (for an early and well-argued version see Dorritie's [http://www.dcn.davis.ca.us/GO/dorritie/ "Killer in our Midst"]). At present I still think the commented-out material is covered later: Siberian Traps -> clathrate dissociation (¹³C excursion) -> severely anoxic oceans -> euxinia -> H₂S emissions -> ozone layer damaged -> increased UV -> deformed spores. Or am I missing something? Philcha (talk) 12:24, 23 February 2008 (UTC)

[edit] The apparent fungal spike

suppressing the section is not as sensible as discussing how it came to be examined and why it was finally(?) dismissed. Could someone better equipped recast the deleted text in the form of a suggestion that didn't pan out, please?--Wetman (talk) 21:24, 23 February 2008 (UTC)

Section "Dating the extinction" covers it, because for a while the alleged spike was used as a boundary marker where no others were available. Philcha (talk) 08:54, 25 February 2008 (UTC)

[edit] Methane hydrate gasification

I've merged in an older presentation of this section and made some other changes, for the following reasons:

• It's very technical and numerical for a paleo topic. In particular we can't expect non-specialist readers to know much more than therapsids and perhaps archosaurs.
• I've added notes to explain the terminology. In addition to consideration for non-specialist readers, there's a guideline somewhere that requires articles to be as free-standing as possible.
• The ‰ notation is both unfamiliar and easily misread as % (even on a good monitor like the one I've just got).
• The δ¹³C notation strictly means change or variation from normal in the ¹³C/¹²C ratio. The previous text sometimes misused it to refer to the actual value of the ¹³C/¹²C ratio. Although this (mis)usage is common in the literature, where fellow-specialists will understand it easily enough, a deviation from the strict definition will confuse non-specialist readers.
• I hope I've clarified the reasoning about the PETM δ¹³C (strict sense!), and have removed the "clarification" tag.
• I've presented all the "insufficient" causes as bullets because each would merit a paragraph if they were not subordinate to "A variety of factors ... insufficient" (see examples at Wikipedia:Embedded list).
• I've changed the intro to the hydrate gasification para because:
  • It was first raised several years before any attempt at modelling the P-Tr carbon cycle, and was essentially a last-resort hypothesis (I remember seeing the phrase "default hypothesis" in the literature).
  • Modelling cannot tell us what happened, it can only tell us whether a hypothesis is consistent with our current understanding of natural laws and of the relevant maths. Philcha (talk) 15:48, 28 March 2008 (UTC)

Philcha, you own the article. It's all yours. OrangeMarlin ^{Talk• Contributions} 22:27, 28 March 2008 (UTC)

δ¹³C refers to variation from a given set standard, not really from "normal", which somehow kind of implies to me the average background value. ‰ is correct notation (see below) and should be used. Badgerpatrol (talk) 02:25, 30 March 2008 (UTC)

[edit] "Tropical distribution of continents"

The section "Methane hydrate gasification" includes the sentence "With the more tropical distribution of continents at the time, the oxic or anoxic state of estuarine environments had the potential to result in a rapid release or burial of large amounts of (light) organic carbon." This needs a lot of explaining:

• Was the % of the world's land around the equator much higher than to-day? If so, by how much?
• What's so special about estuarine environments?
• Why should this have affected either the oxic / anoxic state of estuarine environments or or the impact that changes in these states had on amounts of (light) organic carbon buried / released? —Preceding unsigned comment added by Philcha (talk • contribs)

I don't have any specific knowledge of this- as a guess though this may have something to do with run off. Tropical continents = increased (liquid) precipitation per unit area (during humid intervals) = increased run off into estuarine and nearshore environments = potential for anoxic or dysoxic settings = increase in organic carbon sequestration. That is off the top of my head, I'm not presenting it as gospel, and it is quite possibly completely incorrect. I see that the assertion does have a reference, although unfortunately I can't get access to Science at present. Badgerpatrol (talk) 02:41, 30 March 2008 (UTC)

Can you provide title and authors? Does not have to be word-for-word accurate, just enough to get googling. Philcha (talk) 16:57, 12 April 2008 (UTC)

[edit] "Triassic takeover"

Since the article linked as a source for [http://en.wikipedia.org/w/index.php?title=Permian%E2%80%93Triassic_extinction_event&diff=201602168&oldid=201592639 this section] does not mention fur or metabolic rates, the statement that competition forced these adaptations seems unsupported. I've removed it for now until a source that directly addresses this question can be found. Tim Vickers (talk) 21:34, 28 March 2008 (UTC)

Reinstated with better ref. Dunno how that ref got into the the other article from which I summarised a para to produce this sentence - I must have had a brain failure. Thanks for drawing my attention to the problem. I'll fix the other article now as well. Philcha (talk) 22:42, 28 March 2008 (UTC)

[edit] ppt

As explained at parts per notation: ppt is "parts per trillion" and you should avoid using "ppt" to mean "parts per thousand" which should either be written out, labeled as "permille", or ‰. Personally, I would prefer it be labeled ‰ as this is the scientific standard with a parenthetical explanation on the first use. Dragons flight (talk) 02:46, 29 March 2008 (UTC)

Thanks for pointing out the problem with "ppt". It seems there's less consensus than parts per notation claims about the meaning of "ppt", see for example [http://www.seagrant.umn.edu/pubs/ggl/p.html Minnesota Sea Grant - Glossary of the Great Lakes] and [http://filaman.uni-kiel.de/Glossary/Glossary.cfm?TermEnglish=parts%20per%20thousand Term: parts per thousand], which use "ppt" in the sense with which I'm familiar. That suggests we should avoid using "ppt" for either meaning.

But I really don't like ‰ as it's too easily confused with %. It seems "ppth" is widely used to mean "parts per thousand" (http://www.google.co.uk/search?hl=en&q=ppth+thousand&btnG=Search&meta= Google search) and it avoids the ambiguity, so I'll change all occurrences accordingly. Philcha (talk) 15:45, 29 March 2008 (UTC)

‰ is the correct notation for parts per mille. First occurrence can be wikified as ‰ I suppose, if there is any possibility of confusion. Badgerpatrol (talk) 02:06, 30 March 2008 (UTC)

"Widely used" seems unlikely given that I've never seen "ppth" and it occurs in what is rather tiny number of webpages compared to ppm, ppb, etc. For example, [http://www.google.com/search?q=permille permille] gets many times more google hits than [http://www.google.com/search?q=ppth ppth]. Dragons flight (talk) 04:28, 30 March 2008 (UTC)

[edit] Apparently irrelevant ref

The end of section "Terrestrial vertebrates" refers to Tanner, Lucas & Chapman (2004). But this is about extinctions within and at end of Tr; an dfocuses more on geological phenomena rather than patterns of extinction. I've commented out the ref for now. It would be a good idea to check all other refs to Tanner, Lucas & Chapman (2004). Philcha (talk) 15:38, 29 March 2008 (UTC)

[edit] Out-of-place sentence

"Extinction patterns - Marine organisms" contains the sentence "It is more difficult to produce detailed statistics for land, river, swamp and lake environments, as rock strata from these environments are extremely rare — the Karoo basin in southern Africa is the most complete" which now looks like it's in quite the wrong place. I wrote it when the "Extinction patterns" section was much shorter and simpler. If no-one can suggest a good home for it, I'll remove it. Philcha (talk) 17:02, 12 April 2008 (UTC)

Done. Philcha (talk) 11:09, 20 April 2008 (UTC)

[edit] P-Tr and early Tr C13/C12 fluctuations - "hunting" oscillation?

The fluctuations described by Payne et all (Payne, J.L.; Lehrmann, D.J.; Wei, J.; Orchard, M.J.; Schrag, D.P.; Knoll, A.H. (2004). "[http://www.sciencemag.org/cgi/content/abstract/305/5683/506 Large Perturbations of the Carbon Cycle During Recovery from the End-Permian Extinction]". Science 305 (5683): 506. doi:[http://dx.doi.org/10.1126%2Fscience.1097023 10.1126/science.1097023]. ) remind me of " hunting" oscillations in systems that are seeking to re-establish equilibrium but where causes and effects are separated by time lags. Does anyone know of any relevant publications that relate the P-Tr and early Tr C13/C12 fluctuations to "hunting" oscillations? Philcha (talk) 10:56, 20 April 2008 (UTC)

[edit] Fungal spike - relegate details to footnote?

The discussion of the fungal spike and why the idea is busted takes almost 1/3 of the "Date and timing" section. I suggest it would be a good idea to replace this with a 1-sentence paragraph, "It used to be thought that there was a sharp increase in the abundance of fungi at and for some time after the P-Tr boundary, but this 'fungal spike' hypothesis is now discredited" and move the details and citations to a footnote. Philcha (talk) 11:02, 20 April 2008 (UTC)

[edit] Carbon Isotopes

Hi Philcha- do you have any experience with geochemistry? You are using terminology which I am not familiar with, but I am not a geochemist by trade, and you may be, in which case I cede to your better judgement. In particular, you keep using the word "normal", which, in my view, is inappropriate. The delta notation means that any change is being quoted relative to a given fixed standard - usually the Pee Dee Belemnite- it does not strictly speaking mean a change from any kind of background level, as implied. I've never seen the word "normal" used in this way, but as I say I am not an expert in this specific area. "variance" is a statistical term describing the square of the standard deviation of a sample- I don't think this is what you mean, although I can't remember the exact C isotope calculation off the top of my head (I can look it up, but I don't remember it incorporating any measure of dispersal- this would be more likely be signified separately by error bars derived from iterative measurement).

My, that was quick! Thank you.

Mathematically δ or Δ means change in, as I learned in my first few calculus lessons. I'm also familiar with it from astronautics, where Δv or "delta-vee" means change in velocity. I suspect at least a few other readers may remember that. In geochemistry (something I only started paying attention to fairly recently) it seems to mean "difference from some expected value", and "variance" is a standard term for this in many fields. Non-statisticians are more likely to be familiar with that use of "variance" than with "the squared distance of its possible values from the expected value (mean)" (in Variance, which considers only its meaning as a tech term in statistics; typipcal of the parocialism of many Wikipedia articles). But I suspect "variance" should be avoided because of the ambiguities.

Your comment above about Pee Dee Belemnite is corroborated by [http://www4.nau.edu/cpsil/isotopes.htm Colorado Plateau Stable Isotope Laboratory], so I'll assume for now that that's the baseline used in all the references for the P-Tr article. Thank you for enlightening me. Philcha (talk) 18:03, 20 April 2008 (UTC)

yes- difference from some expected value = level of departure from the standard. That's what the delta notation signifies- the actual "real" differences in absolute terms are minute and not particularly informative, so it's better to calibrate them to a reference value. "Variance" really means "difference from the mean value" - a changeable quantity - rather than "difference from the (fixed) reference value", but I take your point that it's ambiguous. As you say, I think we can come up with a better term. Yes, the PDB is used almost exclusively for carbonate I think, there are some other standards, but that is the key one. I am fairly certain that is indeed the baseline for this work- and although I haven't read them all, I am nearly 100% certain that any paper quoting such figures will specify somewhere (probably in the methods, which for Science and Nature papers may be in supplementary online repositories rather than the main text), that they are relative to the PDB (or whatever). If they don't specify this, I would almost go as far as to say that it can be taken as the default. Badgerpatrol (talk) 20:17, 20 April 2008 (UTC)

In general, I would recommend that we ditch these explanations, which I don't feel are appropriate for this article. The material (with references) would be better incorparated into the related geochem articles perhaps, which we can then link to from here. That is the standard for high quality articles, as this is I'm sure shaping up to be. But this is about the Permo-Triassic mass extinction, not Introductory Stable Isotope Geochemistry. It seems a bit long winded at present to me, but perhaps I am in a minority? Badgerpatrol (talk) 12:02, 20 April 2008 (UTC)

I've just looked up Isotope geochemistry and it does not mention any of the ratios that are important in paleontology, which is pathetic. I'm beginning to see your point about the need to improve linked articles. But a person can do only 1 thing at a time (especially with the time it takes to find and incorporate references).

Even if the relevant articles were adequate, I would still think it useful to have short description of the relevant tech terms here. First (to get it out of the way, not because it's foremost) per Wikipedia:Summary_style#Levels_of_desired_details the average reader does not want a full article on any aspect of geochemistry, just enough to understand "Methane hydrate gasification". In fact I thought there was a guideline that said articles should be as self-contained as possible, but I can't remember where (I thought) I saw it. More importantly, the average reader who knows nothing about geochemistry will be put off if he / she has to read and remember the relevant parts of at least 2 more articles in order to start reading "Methane hydrate gasification". It's far better to define the relevant terms here, with wikilinks to other relevant articles in case we score a real hit and whet his / her appetite. Defining the terms also makes it possible to introduce them in the right order, so that the explanation of the 2nd builds on the explanation of the 1st and therefore reinforces the reader's ability to remember the 1st, etc. (I've developed and presented technical courses, and this is a standard teaching technique). And if the reader gets hazy about one of these terms halfway through, he / she will know where to look for a brief, relevant explanation. I don't want to rely on wikilinks because as far as I've seen the usual approach is to wikilink only the first occurrence of a term in a section; but that would leave the reader looking for the first wikilinked occurrence, then reading the linked article,, then coming back to the wikilink, then trying to find where he / she left off, and then possibly forgetting what it was all about and having to re-start the section. Philcha (talk) 18:03, 20 April 2008 (UTC)

I take your point to an extent, but I think that's the Wikipedia way- jumping back and forth between articles, forming chains and links between articles, and expanding one's knowledge in that way. I'm not sure that a full explanation of things like parts per mille etc. is needed here- that kind of information is only very tangentially related to the P-T boundary episode. Isotope geochemistry indeed concentrates more on radiogenic systems- it's not a great article. Isotopes of Carbon is not great either, although that's probably the place we should put this material (with refs). I see your point about articles being as aself-contained as possible (even if it's not formalised, it's common sense) but I think there is room for wikipfying and drawing in other articles, and I think this is recognised as part of the FA process.

Can I just say that I hate to nitpick because I am not a very dedicated writer or editor myself, where as you certainly are- you are putting a lot of effort into this article and I bet it will wind up very nicely indeed as a result. Please don't think that I'm being pedantic for the sake of it, and nor do I expect you to update all the other, related, articles- I'm just giving my input, and thanks for the sensible and constructive discussion. Badgerpatrol (talk) 20:17, 20 April 2008 (UTC)

[edit] i was just passing though this article...

and id like to congratulate the editors on a well written article! i found it very informing and understandable keep up the good work!216.96.164.199 (talk) 04:00, 29 April 2008 (UTC)

[edit] Bryozoan Die Off

The following was reverted earlier to-day - not by me - on the grounds that it's "not very encyclopedic" and gives undues weight to a specific theory.

Doctoral student Catherine Powers at the University of Southern California has found evidence that the Permian extinction started in the deep oceans, spread to shallow waters and then onto the land.

This conclusion was gained from studying bryozoans, (a family of marine invertebrates). The species of bryozoans adapted for deep water started to decline 270 million years before the end of the Permian. However, 10 million years before the end, there was a sharp increases in deep water extinctions followed by shallow water extinctions. Shoreline species were affected last. This pattern is the opposite of the types of deaths found in impact extinctions. In those, the land species are hardest hit with marine species having a much larger chance of surviving.

The full article can be found in the November, 2007 issue of the journal Geology.

I also notice that "270 million years before the end of the Permian" would make it an early Cambrian extinction, which would make it even more difficult to explain the Cambrian explosion. But it might be worth seeing what Powers' paper really says. If she found that the bryozoan extinction started 2.7 My before the end of the Permian, it could be very relevant. Philcha (talk) 01:11, 5 May 2008 (UTC)

Bryozoa didn't emerge until the Ordovician (or at least the first fossils are found at that time) so they'd be struggling if any species started to decline 270 million years before the Permo-Triassic extinction... that's a long time. If memory serves, they're the only major phyla that did not originate in the Cambrian. [http://www.gsajournals.org/perlserv/?request=get-abstract&doi=10.1130%2FG23858A.1 This] is the abstract of that paper, certainly worth mentioning I suppose. Badgerpatrol (talk) 07:59, 14 May 2008 (UTC)

Good point. Merlin must have evolved into the Bryozoa (remember "Sword in the Stone"). Philcha (talk) 08:25, 14 May 2008 (UTC)

Correction: it was Doctor Who's fault - he exterminated them before they appeared. This must have been his 2nd attempt at this trick (in his own subjective timeline) , as he failed with the Daleks. Philcha (talk) 09:56, 14 May 2008 (UTC)

Perhaps the editor meant "270 million years ago, before the end of the Permian"?

Anyway, The WP article doesn't currently do a very good job of differentiating what I understand to be the three major patterns: the long-term declines apparent in some phyla (bryozoa, ammonoids?); the end-Guadalupian pulse, caused by environmental change; and the end-Permian pulse, with a catastrophic cause. (At least, that's my understanding of the current state of affairs!) Smith609 Talk 11:35, 14 May 2008 (UTC)

[edit] Extinction patterns

This now contains the introductory para:

The extinction event multiplied background extinction rates, and therefore caused most damage to taxa that had a high background extinction rate (by implication, taxa with a high turnover).^[1][2] In general, the taxa most likely to survive were small, rare members of a diverse community.^[3]

The ref for the last sentence (Leighton & Schneider, 2008) deals only with brachiopods, so I don't see how it tells us much about extinction patterns in general. All of the information in the intro para applies only to marine invertebrates, so I would have thought it should be in that section. I would be inclined to delete the 3rd sentence of the para and and move the rest to follow the para beginning "The groups with the highest survival rates generally had active control of circulation, ..." Philcha (talk) 17:57, 13 May 2008 (UTC)

I've moved and re-worded the second paragraph as per your suggestions. I think the first is fine where it is; as I interpret the paper, Stanley is trying to make a general point based on ecological principles, rather than just referring to the marine realm from which he draws most of his data. That said, the lead is now structurally a little thin and could use bulking up a little - but this article remains a work in progress and I'm sure I'll come across more general points to pad it out with in the future! Smith609 Talk 07:18, 14 May 2008 (UTC)

I'm sorry, I still disagree. The titles of both refer to marine organisms. Stanley's 2007 paper is abour marine organisms over the whole Phanerozoic, and briefly mentions the 2 P-Tr extinctions as an exaggerated instance of the long-term pattern. The first para of the 2008 paper explicitly says twice that it applies to benthic organisms and finishes "what particular species or group of species occupies a particular microhabitat is often simply a matter of time of arrival," a point that only applies to sessile marine animals, as the later analysis makes clear. The last para of the intro says, "The degree to which competition structures terrestrial communities is not my subject here," and finishes, "I will suggest here that some carnivorous marine taxa are exceptions to my basic assertion that competition plays a relatively weak role in the marine realm." The selection of quotes from other works lists mainly mobile benthic grazers; the 2nd last of these quotes mentions grazing fish, and that is the only example of marine vertebrates I can find in the article. The only para in the whole 2008 paper that mentions the Permian mass extinctions is exclusively about marine animals. Philcha (talk) 09:01, 14 May 2008 (UTC)

You're quite right: the paper restricts itself to benthic marine organisms. Thanks for checking this out! Smith609 Talk 17:52, 14 May 2008 (UTC)