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JamieLynn

Canyon Lake odd balls - Texas Cretaceous

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JamieLynn

Found a messload of these odd half rounds but with "edges" that seem to have partially folded in on themselves.....very odd. I first thought they were HUGE porocystic globularis, but they are more rough than any I have found, strictly halves and HUGE. When you look at the underside, it's almost like a rind of a fruit that has contracted in on itself, which still leads me to think it might be some kind of globularis. They were found in an area with thousands of the biggest orbitolina I've ever seen. Any one have any ideas what the heck these might be?? Thanks!! 

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abyssunder

I think, they might be very worn Porocystis globularis, like the ones in the picture below.

 

4319204_orig.jpg.e9d590dc3ce0fa1412d2367913d90d27.jpg

 

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JamieLynn

kind of what I figured. Just never seen them all consistently the same "decay". 

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JamieLynn

Has anyone else found Porocystus bigger than golf ball sized? 

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JamieLynn

Geologic....interesting. I have found many many of these in my area, but always pea to quarter sized and always in full round.. I'v just never found any that looked liked like this. And that pentagonal one is really interesting, to me.  Here is a picture of my porocystis globularis finds from prior huntings.

Porocystus Globularis (2).JPG

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JohnJ
16 minutes ago, JamieLynn said:

Geologic....interesting. I have found many many of these in my area, but always pea to quarter sized and always in full round.. I'v just never found any that looked liked like this. And that pentagonal one is really interesting, to me. 

 

I apologize for not being clear...I was referring to the various sized concretions in your original post.  Porocystis have different surface texture and are not typically found with these concretions.

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JamieLynn

ahhh...I understand. You believe my odd balls are geologic and are not porocystis   Yes, all the porocystis I have found have very different surface textures, so that is what is odd about these new finds. They are rough texture, not full round . and they look like "rinds" that have decayed. . Can you point me to any geologic references to these structures? Thanks so much for your interest and help!! 

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erose

I agree with JohnJ they are mineral concretions. I think they may be a type of gypsum crystal with an originally pentagonal structure. I have been fooled by the shape as well. 

 

The little discs are Orbitolina texana forams (Foramnifera) and an index fossil for most of the Glen Rose. Forams are amazing in being single-celled organisms of "immense" size.

 

Most of the Glen Rose was deposited in fairly shallow waters. imagine shallow salty lagoons. Salts grew forming, layers rich in anhydrite such as gypsum. Later ground water, over all those millions of years, flowed thru those layers disolving the salts and the resulting cavities collapsed. When you read the lithologic descriptions of these formations they call them solution collapse zones.

 

 

 

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JamieLynn

thanks Erich! I definitely knew about the orbitolinas, but not the concretions. Thanks everyone! 

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JamieLynn

so here's another question for y'all. As I am an avid amateur I am trying to learn to identify what formations I am finding stuff. I had understood that if you found orbitolinas that was the zone that sea urchins would be in. I have yet to find that to be true. I have found at least four nice roadcuts with loads of orbitolina and nary a single sea urchin.  Am I just particularly unlucky? 

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abyssunder

This one looks strange to me just being a geological wonder. :headscratch:

I could be wrong, also.

 

5cbf0d4582989_PorocystusGlobularis(2).JPG.fcdbaf55ff7360af87ca8920ee19481c.JPG.0d1729355e35f603d2779f5b27676183.JPG

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JamieLynn

That is from the picture i  posted of my Porocystis globularis finds to contrast with the round ball geologic finds. That one is definitely from something organic (algeal fruit or whatnot) That picture of all the globularis is to contrast with the original posting picture of the geological round thingies.

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erose
1 hour ago, JamieLynn said:

so here's another question for y'all. As I am an avid amateur I am trying to learn to identify what formations I am finding stuff. I had understood that if you found orbitolinas that was the zone that sea urchins would be in. I have yet to find that to be true. I have found at least four nice roadcuts with loads of orbitolina and nary a single sea urchin.  Am I just particularly unlucky? 

Maybe...

 

The presence of Orbitolina is not always a guarantee of echinoids. For example one of the thickest beds of Orbitolina at the base of GR Unit 2 in the Lower Member is devoid of almost anything else. But directly below it is the "micro zone" rich with echinoids.  At the other extreme the "Loriolia beds" in units 6 & 7 of  the Upper Member have no Orbitalina at all. 

 

Orbitolina occurs throughout the Lower Member and up into about the bottom half of the Upper Member. It then disappears.  And some of the echinoids are only found at specific levels while others show up almost top to bottom.  I also know a few layers that produce at one location and a mile away zip. 

 

So don't be discouraged. They are still a good indicator you are on the right track for echinoids. Be patient.

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JamieLynn

thanks!! I'll keep looking! 

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