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Wednesday, April 15, 2015

Exquisite Dating Tool: Zircons as Indicators of Earlier Closing of the Land Bridge Between North and South America

          New research indicates that the connection between North and South America was created 13-15 million years ago rather than 3-5 million years as previously thought. The age of zircons was the main indicator of the much older closing age. Here's an image of a  zircon (greenish elongate diamond) in crossed nichols polarization:



           Zircons are crystals that form when magma cools. Newly-formed zircons contain some uranium, but no lead.  Therefore, any lead found in an old zircon must have originated in the radioactive decay of uranium. Thus, zircons are a favorite tool for dating in geology. (as well as dinner and a movie ;-)).

          Zircons found in streams in Colombia and Panama have dated the closing of the gap and formation of the "land bridge" at 13-15 million years.




           The biggest mystery is why animals, especially mammals like this racoon ancestor, 
Chapalmalania




did not make the mass movement across the land bridge until 3-5 million years ago (as seen in the fossil record). Perhaps the "land bridge" was more like a series of volcanos with shallow waters in between so it took ten million years for a solid, continuous land bridge to form. 

            This research was performed by Camilo Montes et al. This article also contains a link to terror birds (if you dare). [And a new terror bird species has just been discovered as reported on April 13, 2015.]



             Any ideas as to what was going on in the 10 million years between the possible closing of the North and South American continents and the mass mammal migration (say that 5 times fast!)?

Zirconly,

Steph










38 comments:

  1. The closest living bird to the extinct clade of terror birds or Phorusrhacids are the South American Seriemas.

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  2. I think those mammals were busy picking bits of lead out of zircons just to confound future geologists. Even today, when we want someone to quit dawdling and start moving, whether across land bridges or not, we say, "Get the lead out!"

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    Replies
    1. Perfect.

      Now, how about the origin of Pb and Jay sandwiches?

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  3. I think headlines like "Exquisite Dating Tool" are termed "clickbait." Thought you were referring to the AhleyMadison IPO.

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    1. Wow, never knew such an IPO existed.

      I was being a bit "encouraging," I suppose. Clickbait if you will ;-).

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  4. I have always found cubic zirconia to be a pretty effective dating tool.

    Forget the Chapalmalania. I'll bet peeps coulda migrated across those intervolcanic waters by simply floating over them.

    LegoPeepsBobSquarePants

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    Replies
    1. Peeps floating at the speed of light, Lego?

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    2. I could see Maizie enjoying hanging out with a Chapalmalania, too.

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  5. Perhaps you will be a fan of this fire vortex video.

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    1. Yes, I will be a fan of this tor(ch)nado. But, don't try this at home, kids! At any moment, I expected a satanic genie to emerge from its apex and grant me three deals with the devil. Good corkscrew, though, for uncorking a bottle of firewater.

      LegoChubbyCheckerMustaBeenFilledWithTheHolySpirit

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    2. All that fussing with the fans!

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    3. I saw your posting right after getting home from a much too long training session on EMS operations on firegrounds, with too many videos of flashovers and backdrafts. (Are all firefighters pyromaniacs?) I, too, expected a CGI genie to appear. What if they filmed a fire tornado at the site of the ice volcano that was posted here a few months back? Some say the world will end, he said Frostily....

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    4. Let's try it! Hope today holds no more long training sessions.

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  6. Replies
    1. This USGS page seems vaguely Onionesque to me. Perhaps my shaken faith has turned me into an unsettled cynic?

      LegoCan'tTakeAnythingSeriouslyAnymore

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    2. Interesting. Are you crying Onion tears?

      It's a legitimate USGS site, all tears aside.

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    3. Nice idea. Even 30 seconds of warning gives time to turn off gas and get out of buildings. Once it's ready for general rollout, they should get Taylor Swift to make a PSA video. Or, if she's not available, that Delaware cop.

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    4. Agreed. "Shake it off" works for me, too.

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    5. My brother-in-law, who works for BART (not the one who says "Don't have a cow, man", see below) says that they and Muni (the San Francisco transit system) are plugged into the ShakeAlert system.

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    6. That's cool. I wonder how sensitive the ShakeAlert equipment is.

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  7. Replies
    1. Moor's Law: Don't trust that Iago!

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    2. Shaking something here too, I see!?

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    3. Moore's

      But don't let that bother you.

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    4. Mooer's Law: Don't have a cow, man.

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    5. Moorer's Law: Whatever floats your boat.

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    6. Moore's Law: that's an invertebrate fossil.

      Welcome back Kotter, er, moore appropriately, Paul.

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  8. Replies
    1. I'm afraid tea time usually finds me knapping.

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    2. I really don't know; I never looked.

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    3. I was going for flint-faceted/faced. That may or may not be understood this kalpa.

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    4. I meant to imply that I have never observed my facial expression whilst napping. We'll find the same page eventually -- right now I'm at Isaiah 50:7.

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    5. I've never observed it whilst knapping either.

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    6. The k threw me off at the knees. Farther than a knock knock joke. But, I do think we are on the same kpage now.

      Speaking of K cars, do you suppose some Flint, Michiganders use that passage as their motto?

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  9. New post is up (on a Tuesday!):

    "Capitanian: A Sixth Major Extinction 262 Million Years Ago?"

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