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Tuesday, April 21, 2015

Capitanian: A Sixth Major Extinction 262 Million Years Ago?

      One of the first things geologists learn about is the major extinction at the end of the Permian Period (and Paleozoic Era) 250 million years ago. 96 percent of all species died during that mass extinction.






       Now geologists have discovered new evidence that may point to another extinction during the mid-Permian, 262 million years ago, just 12 million years before the major Permian-ending event. An April, 2015, Geologic Society of America (GSA) paper (Lead author David Bond) notes that the "Capitanian" saw the extinction of 87% of all brachiopod species.




        The Capitanian was named 20 years ago based on research in tropical to sub-tropical areas in China and elsewhere and believed originally to be more localized. Newest research in northern Norway suggests that this extinction may actually be more global (though several dissenters have commented on the publication in the well-respected GSA paper).



      
          Dr, Bond et al  write that the Capitanian extinction was likely triggered by the eruption of the Emeishan Traps, located in the southwestern Chinese province of Sichuan. Volcanic eruptions release large amounts of carbon dioxide, causing ocean acidification. Seafloor oxygen depletion may also have played a role.

             The major shift after the acidification and oxygen depletion was from domination of brachiopods to domination by bivalves after the Capitanian extinction:




      Brachiopods and bivalves differ in the number of adducting muscles, the way they eat, in their very classification, and in the symmetry of their shells. The two shells of bivalves are mirror images of each other; they are not in brachiopods.

          So, why were bivalves better suited than brachiopods for life after the Capitanian? Any guesses?




Shellfishly (and sleepily),

Steph


29 comments:

  1. Steph,

    So, why were bivalves better suited than brachiopods for life after the Capitanian?
    They survived by dint of smoke and mirror (imaging)?
    Somewhat more seriously, perhaps the dorsal ligament bivalves possess, along with their adductor mussels (haha!) gave bivalves more flexibility than their brachiopod cousins to weather the ocean’s acidity (to “clam up,” so to speak) yet to open wide when necessary to access the limited oxygen?

    El Capitan!

    Foiled again by Zorro, El Capitan is about to become extinct!

    LegoBlowin’ScientificSmokeWhileLookin’AtHisRefractionInTheMirror

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    Replies
    1. Hey, Lego, that explanation seems quite plausible.

      I am on the fence about the videos though. ;-)

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    2. Steph,
      Noosie, my late great tabby cat might have said, "That explanation gives me paws."

      LegoNoosieMightHaveAdded"Don'rClamsGetClawstrophobicInsideOfThere?"

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  2. Replies
    1. Sure. But the issues were less clear then (we weren't up to worrying about nuclear winter yet, let alone global warming), and the Vietnam War and suppression of protest against it loomed larger.

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    2. Besides “environment,” the word “ecology” also gained currency post-Rachel and post-Gaylord. (Incidentally, where is “Gaylord” on the list of top baby boy names of 2015?) Also, Gaylord Nelson and Bill Proxmire (he of Golden Fleece fame) were “my guys” from the Badger state. They were the Jagger and Richards of politics in the land of cheese.

      The article mentions Jimi, The Fab Four, and S&G. Here is what else was on our “transistor radios” back in the Paleozoic Era.

      LegozoicError

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    3. Reading "Silent Spring" in junior high school and Earth Day really changed everything for me.

      Great set of tunes, Lego. I remember them all.

      Too bad we've not made more progress, but we have made some.

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    4. As jan noted, the global warming/climate change realty was not on our front burner in 1970. But it seems to me that that “debate” (whether our behavior is affecting climate change) has been conceded by the sayers of “Nay, we are not at all to blame. ‘Tis just the sun’s normal fluctuations!” Those holdouts perhaps have now been relegated to lunatic fringe status. Al Gore may not have become prez, but he did help accomplish this.

      The trajectory of the climate change debate has mirrored that of the smoking debate. People funally realize that polluting their skies, waters and soil – or their lungs – is not wise. But it is just so darn difficult to break that addiction!

      LeGorelAmbda

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    5. It's a couple of days late, but I liked this NPR segment on the guy who named Earth Day. (He was the father of Sarah Koenig, of This American Life and Serial fame.)

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    6. Yes, I like it, too.Thanks, jan.

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  3. Replies
    1. Deep Basalt (great band name) feeding Shallower Rhyolite--great double chambers of liquid magma. Thanks for the share.

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  4. Replies
    1. I had to read all that to get to no. Well, now I know. Put that in your pipe and smoke it. ;-)

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  5. Corollaries to "ascetic" from today's "A Word A Day" site. I especially enjoyed the last one:

    Ascotic: Wearing one’s scarf really tight
    Copascetic: Avoiding the Copacobana
    Bascetic hound: A dog that doesn’t eat all his food at once
    Cascettic: Refusing to upgrade to a CD player
    Videocascettic: Refusing to upgrade to a DVD player
    Amasscetic: Avoiding any contact with Donald Trump

    Enjoy. (no !, you'll notice, Lego)

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    Replies
    1. Glacial ascetic: Refusing to acknowledge evidence of global warming or acid rain.

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    2. I do know a few glacial erratics like that.

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  6. There are some great Nepal earthquake plate tectonics illustrations here.

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    1. Every time I see pictures like that, I'm tempted to suggest drilling some deep holes and squirting in some WD-40 to smooth things out.

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    2. Interesting. I just learned WD-40 stands for Water Displacement-40th try. Trying to fit that in with your deep hole idea. . .

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    3. Well, there's no stopping plate tectonics. Those plates are gonna move. Earthquakes happen when friction tries to slow them down. Just like a frozen nut on a rusted bolt. Enough WD-40, and they'll just slide smooth as silk down into their subduction zones, and we'll all sleep better at night.

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    4. Or, if you don't like that idea, maybe we can keep all those plates from sliding around after all, with enough duct tape.

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    5. Maybe it should be We'll Dream-40 then since we'll all sleep better.

      Subduct tape--perfect!

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  7. New post on "Fluoride and Fluorite: First Change since 1962: Decreased Levels of Recommended Fluoride in Drinking Water by the United States" is now up.

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  8. New post on "Fluoride and Fluorite: First Change since 1962: Decreased Levels of Recommended Fluoride in Drinking Water by the United States" is now up.

    ReplyDelete