My Research!

[Ordovician_Odyssey]

http://www.scribd.com/doc/116484398/The-Ordovician-Silurian-Extinction-Event

Hey guys!

After about 14 months of research, I finally have some research to present to the community!

I am continuing my research, but to date this is what I have!

The research is on the cause of the Ordovician extinction..

Please give feed back!

Thanks guys!

Cheers

Shamus

[KansasFossilHunter]

Congratulations- that's very cool!

[Ordovician_Odyssey]

Congratulations- that's very cool!

Thank you!

[TMNH]

Nice job Shamus...what a great project!

[Ordovician_Odyssey]

Thanks Joe!

[Auspex]

I have to commend you for your effort and dedication to this project! I am impressed!

[FossilDAWG]

Hi Shamus,

You have obviously worked hard on this, and have clearly learned a lot in the process. You should be commended. You have my sincere congratulations.

Since you ask for feedback, I do have several comments. I hope you find them constructive, because that is how they are intended.

First, if you are going to conclude that the prevailing ideas about the end-Ordovician extinction event are wrong, you should discuss the evidence that has been used to support those ideas and show how they can be interpreted another way. You shouldn't just ignore the evidence of an ice age at the end of the Ordovician, you need to discuss it.

Second, you should be aware that there are no rocks that record the actual Ordovician-Silurian boundary in Ontario or upstate New York, there is a major unconformity at the top of the Ordovician section there. The "Cincinnatian" is not the latest stage of the Ordovician; that would be the Gamachian in the old terminology. Rocks of that age are present in Manitoba and on Anticosti Island, to name two places adjacent to Ontario, but Richmondian rocks are the last Ordovician in Ontario and New York. Strata that record the actual interval of the hypothesized ice age are found in only a few areas around the world, due to a major drop in sea level that resulted in an unconformity at the boundary in almost the whole world. Indeed, the drop in sea level is thought to be due to so much water being locked up in ice, as also happened during the Pleistocene.

You should discuss more the influence of local tectonic events on the environment represented by the rock formations. In Southern Ontario and New York the Gull River and correlative strata record fairly shallow water deposition, with ripple marks and even mud cracks at some levels, and with carbonate (limestone) suggesting warm conditions. Altogether, the evidence suggests the Gull River was largely intertidal or shallow subtidal Water levels deepened as the Ordovician progressed, with the Bobcageon, Verulam, and Lindsey being subtidal but still within the photic zone, so faunas are highly diverse. In the Verulam, limestone beds alternate with calcareious shale; the limestone in many cases represents turbidity flows where storm events caused carbonate (and fauna)-rich mud to slump off of shallower slopes into deeper water. After the Lindsey, water levels rapidly deepened in a restricted basin, giving rise to the black shale Billings Formation and equivalents nearby. Pyrite nodules and pyrite replacement of fossils indicates anoxic conditions, but that is plausibly explained by deep water and poor water circulation in a restricted basin. Age-equivalent strata in the Cincinnatti area, Manitoba, and the Canadian Maritimes as well as elsewhere around the world indicate that conditions were very favorable to very diverse organisms, including brachiopods, corals, etc. The deep basin in Ontario probably resulted from the beginning of the Taconic mountain-building event, when the North American tectonic plate started to collide with Europe/Africa, forcing the North American plate down and under the European/African plate. As the basin filled in, waters again became shallow enough for lots of organisms and some thin limestone beds, but mostly this was shale with the sediment derived from the eroding land mass to the East. This is the Georgian Bay Formation in Southern Ontario, the Carlsbad Formation in the Ottawa Valley, and the Lorraine in the St. Lawrence Valley. Mud is a poor environment for corals and crinoids, so those organisms are limited at this interval, but brachiopods, bivalves, trilobites, and some other types of fauna were diverse and abundant. As the basin continued to fill in with sediment from the eroding mountains that were rising to the East (Taconic Mountains), delta type deposits depositied in brackish water came to predominate; this is the Queenston Formation. Fossils are virtually absent here, because of the rapid deposition of sediment and (likely) low salinity. The rocks are also conspicuously red due to iron oxidation, suggesting an abundance of atmospheric oxygen. So, perhaps a lot of the faunal differences you have in your paper could be explained by local water depth conditions.

It is great that you sampled local faunas, and I'm sure you learned a lot by doing that. I suspect you know a lot more than I did when I was your age. I would just suggest that, because your paper is about a world-wide phenomena (Ordovician-Silurian extinction), you should try to see how your findings based on local rocks compare with patterns elsewhere in the world.

Lastly, it would be nice if you were to include a map indicating roughly where your collecting sites were, and a stratigraphic column showing the starigraphic position of the sites. I can't tell from your paper how many sites you sampled, or what formations you are calling "Cincinnatian". Did you find some Carlsbad Formation exposed around Ottawa? I saw it a few times, but only in construction sites, never in natural outcrops as the rock erodes so easily.

I enjoyed reading your report, and I hope you find my comments helpful.

Don

[erose]

Thanks Don. Glad you filled in some information I was also concerned about, namely the missing Gamachian in much of North America. I am very impressed with the work by Shamus. It is the kind of thing all of us want to do at some point. I think I am happy with smaller projects like collecting local faunas to look for the "unknowns." A whole extinction event is one big project.

For what it matters, I have always believed in the idea that these events are not singular. Combinations of factors, cascading to cause more harm than any single thing.

[FossilDAWG]

I predict that we'll be hearing good things from Shamus for a long time. He's got an excellent attitude and a ton of promise for someone his age.

I also agree that combinations of factors make a huge difference in the effect of challenges to the Earth's biosphere. The worst mass extinction of all, that ended the Permian and the Paleozoic, involved adding a runaway global warming event (due to a supervolcanic eruption through a massive coal deposit, releasing huge amounts of CO2 and methane) on top of an ecosystem that was already stressed because all the continents had collided into a single huge land mass, producing extreme continental climates and greatly reducing the extent of shallow seas. Similarly, there is evidence that ecosystems were already stressed at the end of the Cretaceous, so the comet/asteroid impact was especially devastating. There are other times when similar stresses produced a milder extinction event, because there was only one stress on the biosphere, not several added together.

Don

[ashcraft]

From the other side, I think that mass extinctions are the result of a massive change caused predominantly by one event, and it occurs in a very short (minutes) period of time. Otherwise life will adapt. Ecosystems are always under stress. As humans, we see the world around us and assume as it is, it always has been, and we should know better. The area I live in is a modern day coastal forest, changing from a massive swamp complex, changing from a prairie/desert, changing from a boreal forest/ changing from permafrost. All within less then 15,000 years. That is some pretty serious stress, and there were no true mass extinctions, closest being the loss of the mega fauna, and what happened then? We see the survivors (deer and buffalo) adapting and rapidly speciating (the number of white-tailed deer subspecies has been said to be as high as 20, although I think that is a bit high).

I don't keep up with research as much as I used to, but I don't think we really understand the end of the Permian. As suggested a warming planet is not good for all life, but the dominant land animals at this time were reptiles and mammals like reptiles. These organisms would thrive in a long term high temperature enviornment, such as a desert, just as they do now. Not to mention the warming during the Cenozoic (showing my age- Eocene maybe?) where temperatures in this area were on average 10 degrees warmer then now, there was no polar ice, and Europe existed as a series of islands. No true mass extinction accompanied that event.

As far as the cretaceous, many fights and shed blood has been spilled on the actual cause of dino death. I can not add anything to it except this, every organism that is alive today will be dead within one hundred years, which is not discernible in the fossil record. My point is, how can you have a mass extinction event, and expect the fossilization rate to go up? Just a pet peeve of mine.

Anyway, my soap box for the day. Feel free to chop at it with an axe.

Brent Ashcraft

[Auspex]

...I think that mass extinctions are the result of a massive change caused predominantly by one event, and it occurs in a very short (minutes) period of time. Otherwise life will adapt...

Rate of change is a singularly important factor. Another is how deep the adaptive change must be in order to result in viable organisms.

For terrestrial Permian critters, whose basic architecture evolved in an oxygen-rich atmosphere, there was no way to reboot for an oxygen-poor atmosphere; they'd have had to devolve first.

[ashcraft]

You are referring to Dr. Ward's work. His theories are certainly interesting, and maybe even correct. But what I recall from what reading I have done of his work, he assumes that early dinos had evolved the system of oxygen exchange that birds use, which is certainly more efficient then a mammals'. That is a big assumption to make some hundred plus million years before birds evolved.

I have also wondered that such a drop in oxygen levels wouldn't kill all gill based life. Water is not a particularly good solvent for oxygen, and becomes poorer as it warms. Gills are much more efficient then any land based oxygen removal system, but there are still limits. I wonder if such a large drop in oxygen levels in the atmosphere wouldn't be mirrored in dissolved oxygen levels in water, and simply wouldn't leave enough oxygen for aquatic organisms to survive. Of course, many of them didn't.

Also, organisms can adapt to a low oxygen enviornment (within bounds). Humans who live at high altitudes develop blood with higher levels of hemoglobin, not so that they can carry more oxygen, but to become more efficient in capturing every bit of oxygen they come in contact with.

That's why they call it a theory though, testing and study will resolve these issues.

Brent Ashcraft

[AgrilusHunter]

Also, organisms can adapt to a low oxygen enviornment (within bounds). Humans who live at high altitudes develop blood with higher levels of hemoglobin, not so that they can carry more oxygen, but to become more efficient in capturing every bit of oxygen they come in contact with.

Just to quibble, adaptation in a species and adaption in an individual are not equivalent. Evolution does not act at the individual level, i.e. giraffes did not evolve long necks because individuals stretched them in search of food. If the topic of conversation is mass extinction, only species level adaptation is of import.

[FossilDAWG]

Hi Brent,

Your point is well taken that species will adapt given a chance, but there are constraints on that. For example, the merging of tectonic plates to produce Pangea resulted in a gradual but substantial loss of coastline and continental shelf area. Less area will inevitably result in a loss of species diversity, that's basic island biogeography, and no amount of physiological adaptation will overcome that. As far as the end of the Permian is concerned, my understanding (and I admit that's mainly based on Irwin's book "Extinction" and a few more recent papers) is that the marine record indicates a series of smaller extinctions at intervals of perhaps tens of thousands of years, possibly correlating with episodes of volcanic activity in the Siberian Traps. Each eruption racheted up the level of CO2 (and so the temperature), and decreased O2 levels, quite abruptly. Susceptible species dropped out at each event, then the next event hit before the survivors could diversify much, taking out the next set of susceptible species. Apparently by the time it was all said and done, CO2 levels reached 2,000 ppm (high enough to have toxic effects), oxygen partial pressures were similar to what we have today at 8-10,000 feet elevation, and ocean surface temperatures were in the vicinity of 40 degrees C. Now, if those changes had happened gradually over a few million years the effect might have been less dramatic. If the changes happened as a series of very rapid jumps, on the other hand, it's not surprising that organisms had a hard time adapting. If those jumps hit in the midst of a longer-term trend of loss of habitable area, it's not hard to see how they could have been catastrophic.

Another point is that multiple end-Permian physiological stresses could have exerted selection pressures in different directions at the same time, making adaption especially difficult. For example, plants might have coped with increasing temperatures by dispersing to higher (and so cooler) elevations, and the animals that depended on those plants could have followed. However, falling oxygen levels at the same time would have been worse with increasing elevation, perhaps constraining the ability of animals and even plants to track temperature zones to higher elevations. In comparison, temperature changes during the Pleistocene were more gradual (as opposed to jumps of several degrees in perhaps just a couple of decades), and were not accompanied by drastic changes in oxygen levels, so plants and the associated fauna were able to disperse and follow climactic zones as they moved around over time. For plants to be able to do this, climactic zones have to change slowly enough that seeds can be dispersed into favorable zones, grow up, produce new seeds that disperse a little farther, and so on. If climate changes so fast that the habitable zone for some species moves faster than the species can disperse, that species will probably go extinct. The sedimentology of river deposits worldwide indicate the loss of plant communities that normally stabilize river bands and reduce erosion rates, suggesting that whatever happened eradicated forests worldwide.

Regarding your comment about deer and buffalo diversifying, that is true but the level of diversity is not something we would be able to see in the fossil record. Since we would only have skeletal elements as fossils, we would not be able to recognize subspecies that are based on color varieties etc.

"I can not add anything to it except this, every organism that is alive today will be dead within one hundred years, which is not discernible in the fossil record. My point is, how can you have a mass extinction event, and expect the fossilization rate to go up? Just a pet peeve of mine."

I'm sorry but I don't understand this comment. Who expects the fossilization rate to go up? Can you elaborate on this? Thanks.

Don

[AgrilusHunter]

I can not add anything to it except this, every organism that is alive today will be dead within one hundred years, which is not discernible in the fossil record. My point is, how can you have a mass extinction event, and expect the fossilization rate to go up?

Periods of extended volcanism, increased atmospheric CO2 and increased ash deposition.

Edited December 14, 2012 by AgrilusHunter

[AgrilusHunter]

Don,

I greatly enjoyed reading your post; it is well crafted, highly informative, and logically inductive.

Bravo sir!

Edited December 14, 2012 by AgrilusHunter

[ashcraft]

Just to quibble, adaptation in a species and adaption in an individual are not equivalent. Evolution does not act at the individual level, i.e. giraffes did not evolve long necks because individuals stretched them in search of food. If the topic of conversation is mass extinction, only species level adaptation is of import.

My point was that individuals have the ability to adapt to lower oxygen levels (within bounds of course), so lowering of oxygen levels itself may not necessarily be the cause of an extinction.

Brent Ashcraft

[ashcraft]

Hi Brent,

Your point is well taken that species will adapt given a chance, but there are constraints on that. For example, the merging of tectonic plates to produce Pangea resulted in a gradual but substantial loss of coastline and continental shelf area. Less area will inevitably result in a loss of species diversity, that's basic island biogeography, and no amount of physiological adaptation will overcome that.

I don't know if you can make that correlation. A coral reef is an isolated area, yet they have the largest amount of species diversity on the earth.

As far as the end of the Permian is concerned, my understanding (and I admit that's mainly based on Irwin's book "Extinction" and a few more recent papers) is that the marine record indicates a series of smaller extinctions at intervals of perhaps tens of thousands of years, possibly correlating with episodes of volcanic activity in the Siberian Traps. Each eruption racheted up the level of CO2 (and so the temperature), and decreased O2 levels, quite abruptly. Susceptible species dropped out at each event, then the next event hit before the survivors could diversify much, taking out the next set of susceptible species. Apparently by the time it was all said and done, CO2 levels reached 2,000 ppm (high enough to have toxic effects), oxygen partial pressures were similar to what we have today at 8-10,000 feet elevation, and ocean surface temperatures were in the vicinity of 40 degrees C. Now, if those changes had happened gradually over a few million years the effect might have been less dramatic. If the changes happened as a series of very rapid jumps, on the other hand, it's not surprising that organisms had a hard time adapting. If those jumps hit in the midst of a longer-term trend of loss of habitable area, it's not hard to see how they could have been catastrophic.

That was my point, these events had to be sudden and catastrophic, leaving no time for adaptation.

Another point is that multiple end-Permian physiological stresses could have exerted selection pressures in different directions at the same time, making adaption especially difficult. For example, plants might have coped with increasing temperatures by dispersing to higher (and so cooler) elevations, and the animals that depended on those plants could have followed. However, falling oxygen levels at the same time would have been worse with increasing elevation, perhaps constraining the ability of animals and even plants to track temperature zones to higher elevations. In comparison, temperature changes during the Pleistocene were more gradual (as opposed to jumps of several degrees in perhaps just a couple of decades), and were not accompanied by drastic changes in oxygen levels, so plants and the associated fauna were able to disperse and follow climactic zones as they moved around over time. For plants to be able to do this, climactic zones have to change slowly enough that seeds can be dispersed into favorable zones, grow up, produce new seeds that disperse a little farther, and so on. If climate changes so fast that the habitable zone for some species moves faster than the species can disperse, that species will probably go extinct. The sedimentology of river deposits worldwide indicate the loss of plant communities that normally stabilize river bands and reduce erosion rates, suggesting that whatever happened eradicated forests worldwide.

You make an excellent point. Were (to your knowledge) plant species decimated as much as animal species at the end of the Permian? I know there were a few extinctions post Cretaceous, but fairly small hit in relation to animal extinctions.

Regarding your comment about deer and buffalo diversifying, that is true but the level of diversity is not something we would be able to see in the fossil record. Since we would only have skeletal elements as fossils, we would not be able to recognize subspecies that are based on color varieties etc.

Given enough time, (and without European intervention), the speceis diversity would have recovered after the loss of the mega fauna. With "elephants" and "sloths" replaced by deer and buffalo descendents. If the extinction of the mega fauna had occured 200 million years ago, it wouldn't even have been a blip, just a replacement of species due to what ever cause.

"I can not add anything to it except this, every organism that is alive today will be dead within one hundred years, which is not discernible in the fossil record. My point is, how can you have a mass extinction event, and expect the fossilization rate to go up? Just a pet peeve of mine."

I'm sorry but I don't understand this comment. Who expects the fossilization rate to go up? Can you elaborate on this? Thanks.

Can't you read my mind? I was off on a tangent dealing with the Cretaceous extinction. Impactor naysayers always say "no fossils found in the impact zone and few immediatly before it" The impact layer is extremely small, a slice of a few minutes in time, statistically speaking, you wouldn't expect to find any fossils. Look randomly at any two inch layer of sediment from a land environment, almost none will have fossils.

Brent Ashcraft

[AgrilusHunter]

My point was that individuals have the ability to adapt to lower oxygen levels (within bounds of course), so lowering of oxygen levels itself may not necessarily be the cause of an extinction.

Brent Ashcraft

That was my point, these events had to be sudden and catastrophic, leaving no time for adaptation.

Hi Brent,

A lower concentration of atmospheric/oceanic oxygen may not kill that individual but it could absolutely be enough to cause the species to go extinct in the long run. Extinction does not have to be a sudden process. In fact, it can be long and drawn out, even if the reason for the extinction is a singular event far in the past. It's called extinction debt and it is well documented in bird species in the Amazon. A single logging event can destroy just enough habitat that a species is no longer sustainable. That species will sometimes carry on for many generations, but eventually, slowly, it will die out.

Edited December 14, 2012 by AgrilusHunter

[AgrilusHunter]

I don't know if you can make that correlation. A coral reef is an isolated area, yet they have the largest amount of species diversity on the earth.

The species-area relationship is a solid ecological concept. MacArthur and Wilson laid out the bones of the concept 45 years ago in The Theory of Island Biogeography. A more recent text tome on the subject would be Quammen's The Song of the Dodo: Island Biogeography in an Age of Extinctions. I wholeheartedly recommend both.

If you are really ambitious you might dive into Hubbell's The Unified Neutral Theory of Biodiversity and Biogeography. Hubbell built on themes from both MacArthur and Wilson, and Quammen to generate his theory. He uses many palaeontological examples throughout the work. The unified neutral theory of biodiversity and biogeography is still pretty controversial but it holds real promise as a way to better link palaeontological evidence and modern ecological theories.

Edited December 14, 2012 by AgrilusHunter

[AgrilusHunter]

Shamus,

I just wanted to say how impressed I am with your knowledge, enthusiasm, and drive. Keep up the good work! Too many people, my self included, work on parts of things. The level of focus you display at your age is very impressive and is a real testament to your passion and ability. Best of luck with your continued research!

There is a deeper debate here as well. Darwin clearly saw biotic factors as the most important elements in determining the ultimate fate of a species/lineage. This view has been championed by many ecologists and evolutionary biologists since his time. Palaeontologists, geologists, and planetary scientists, on the other hand, often place more merit with environmental variables. The fate of a species is obviously impacted by large scale environmental events. But to what relative extent? Global climate change or an asteroid impact leave traces we can measure. The evolution of a new pathogen, the extiction of a keystone species, and the introduction of a superb invasive often leave little or no record. Are we sure we have the right culprit? The linkage of cause and effect is often difficult to unravel. To be honest I'm not sure where I stand on this, but I love the debate. I recomend this article by Gene Hunt for more info, its a great read full of crisp beautiful charts and graphs all produced using the program R, you can tell because they are crisp and beautiful.

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... brain dump complete

Edited December 15, 2012 by AgrilusHunter

[ashcraft]

The species-area relationship is a solid ecological phenomenon. MacArthur and Wilson laid out the bones of the concept 45 years ago in The Theory of Island Biogeography. A more recent text tome on the subject would be Quammen's The Song of the Dodo: Island Biogeography in an Age of Extinctions. I wholeheartedly recommend both.

If you are really ambitious you might dive into Hubbell's The Unified Neutral Theory of Biodiversity and Biogeography. Hubbell built on themes from both MacArthur and Wilson, and Quammen to generate his theory. He uses many palaeontological examples throughout the work. The unified neutral theory of biodiversity and biogeography is still pretty controversial but it holds real promise as a way to better link palaeontology evidence and modern ecological theories.

Read! How dare you make me want to learn, much easier to spout without facts!

I would ask though, is it truly a speceis/area relationship, or is it a species/niche relationship? The old ecological study where two speceis of flour beetles are placed into two separate containers of flour. One of the containers has glass and flour in it, the other only flour. The first container will support only one beetle species, the second two. The difference being that the second container allows partioning of resources through the formation of a niche around the broken glass. (I assume beetle one larvae are hard bodied, allowing contact with the glass, while species 2 is soft bodied and gets eviscerated when bumping up against the shards.).

In the case of islands, I think the speceis number is limited because the number of niches is limited, not necessarily due to size, but due to lack of diversity at the abiotic and even the biotic level.

Brent Ashcraft

[Auspex]

Niches are delineated, in part, by the species that occupy them, and are dynamic pseudo-organisms in themselves. Non-biotic environmental change is the sliding baseline which stresses the fabric.

[ashcraft]

It has also been strongly argued that a niche doesn't exist until something occupies it. I don't agree with this, as a niche is more human defined then organism defined. But nobody would pay to hear my opinion.

Brent Ashcraft

[Auspex]

...But nobody would pay to hear my opinion.

I would, especially if the fee was lunch.