Jump to content


Photo

Here's A Strange 'un


79 replies to this topic

#21 geodan03

geodan03

    Advanced Member

  • Regular Members
  • PipPipPip
  • 41 posts
  • Gender:Male
  • Location:St. Louis, Missouri, USA

Posted 20 July 2009 - 06:07 AM

They are slickensides or calcite crystal growth within the limestones. I see them alot in the limestone of my area. On a previous post of mine i uploaded similar pictures of this kind of limestone. They are not fossils, but still very interesting.

#22 grandpa

grandpa

    Advanced Member

  • Regular Members
  • PipPipPip
  • 257 posts
  • Gender:Male
  • Location:Austin, Tx

Posted 20 July 2009 - 06:09 AM

Looks like vertosol = "Clay soils with shrink-swell properties that exhibit strong cracking when dry and at depth have slickensides and/or lenticular structural aggregates. "

A slickenside in this usage is "a surface of the cracks produced in soils containing a high proportion of swelling clays", i.e. a vertosol. ;)

In other words: Yea, what JB and them said. :D

#23 jpbowden

jpbowden

    Advanced Member

  • Regular Members
  • PipPipPip
  • 804 posts
  • Gender:Male
  • Location:Almost near Mathis, Texas

Posted 20 July 2009 - 06:11 AM

As I understand it, this forms along a single fissure?

This rock is entirely composed of these parallel structures, sort of like a big honeycomb.

Glad the experts are as stumped as I! Now I feel a little less dumb :blink:


Experts? It's not that hard to understand, just follow the construction companies building the road systems here in Central Texas and and you figure it out.

#24 tracer

tracer

    Member of the Month 02/09

  • Regular Members
  • PipPipPip
  • 9,639 posts
  • Gender:Male
  • Location:N.W. Gulf of Mexico area

Awards

 

Posted 20 July 2009 - 06:18 AM

if you look carefully, "zoomed in", at the third hi-res picture, you will note that the "bottoms" of the striations look faint as if the impressions are just beginning, and the top of the striations look deeper and "gouged" into the rock, with little lips of material that were pushed outward. to me this is indicative that there was pressure against the rock in question as it slipped downward or the rock pressing against it slipped upward. carefully examined, i see every reason to believe the impressions were mechanically created and no reason to believe that they were organically or chemically created.
Posted Image

#25 Frank Menser

Frank Menser

    Advanced Member

  • Regular Members
  • PipPipPip
  • 2,572 posts
  • Gender:Male
  • Location:Ayden, North Carolina USA

Posted 20 July 2009 - 06:33 AM

its the entire rock, not just a single line... that is what is throwing me off. haha.

auspex... ive never seen gypsum do that. haha. then again... it has done some pretty weird things...



In S. Florida we occasionally run into Gypsum seams- lines of needlike xls that look similar to that. on the specimen below you can see that (in real life) by looking at the edge (unfortunately, my camera doesn't do well on things this small).


Parkland_fossil.JPG
Be true to the reality you create.

#26 Guest_solius symbiosus_*

Guest_solius symbiosus_*
  • Guests

Posted 20 July 2009 - 07:17 AM

slickenside

more

This is very common in Texas, Hyway 35 going into Bell County from the south has some and over in Killeen also. You may also find these forming in clay here, mainly when Calcite fills in the cracks. Common in the Garyson Formation again along 35. What am I talking about, I had to clean the stuff out of my water heater once a month when living there!


Slickedsides are indicative of movement, usually along a fault plane, but also associated with mass wasting. It results in the polishing of the surface. It is for these reasons that I don't think this is stone displays that kind of structure.

While not familiar with the geology of your area, the area above, and below, the lineations exhibit classic styolites structure. The lineations are along the axis of the plane of one of the styolites, and orthogonal to the stress that caused it.

styolites

styolites (see the bottom of page 20)

Look at the photo in THIS link. Now, imagine the structure along one of the lines that is perpendicular to the bedding plane... viola!

#27 jeepinthemud

jeepinthemud

    Advanced Member

  • Regular Members
  • PipPipPip
  • 402 posts
  • Gender:Male
  • Location:Houston, Texas

Posted 20 July 2009 - 07:40 AM

In S. Florida we occasionally run into Gypsum seams- lines of needlike xls that look similar to that. on the specimen below you can see that (in real life) by looking at the edge (unfortunately, my camera doesn't do well on things this small).


Parkland_fossil.JPG



alright, frank, I am always glad to be corrected and to learn!


and personally, i do not think it is a slickenside or a styolite... it doesnt quite fit the definition of either..

my theory is that the limestone, while forming, was two different temperatures/density... and so the wamer particles rose straight up, cooling off as they went, until theyve cooled enough to stop moving....
(its just a guess.)
"To do is to be." -Socrates
"People are Stupid." -Wizard's First Rule
"Happiness is a warm Jeep." -Auspex

#28 Guest_solius symbiosus_*

Guest_solius symbiosus_*
  • Guests

Posted 20 July 2009 - 07:47 AM

and personally, i do not think it is a slickenside or a styolite... it doesnt quite fit the definition of either..


Why not? I explained why I think that it is not slickenside, why do you not think styolites?

#29 jeepinthemud

jeepinthemud

    Advanced Member

  • Regular Members
  • PipPipPip
  • 402 posts
  • Gender:Male
  • Location:Houston, Texas

Posted 20 July 2009 - 07:51 AM

the links for the styolites you gave all mentioned something having to do with pressure... this does not at all look like it formed by pressure... it is too even/straight for that.
same with the slickenside.. "formed by one rock against another"... i do not think this has to do with physical happenings after the rock was formed... this rock was originally created like this, not deformed after being formed.
"To do is to be." -Socrates
"People are Stupid." -Wizard's First Rule
"Happiness is a warm Jeep." -Auspex

#30 Shamalama

Shamalama

    Member of the Month 01/10

  • Regular Members
  • PipPipPip
  • 3,416 posts
  • Gender:Male
  • Location:Norristown, Pennsylvania

Awards

   

Posted 20 July 2009 - 10:04 AM

I agree with Solius, looks like a Styolite of some sort. Slickenslides are way smoother and look like a smooth surface with just some scratches while styolites often have some structure. I doubt it's a coral as the rock just doesn't look right. Can you see any cross sections of the chambers? I could see it being a gypsum mold as that is a fairly common mineral in the type of formations in Texas. Since you had the ebb and flow of the sea over time Gypsum may have formed in lens shaped ponds at times and maybe this is just a remnant of a now dissolved lens.

-Dave

 

__________________________________________________

Geologists on the whole are inconsistent drivers. When a roadcut presents itself, they tend to lurch and weave. To them, the roadcut is a portal, a fragment of a regional story, a proscenium arch that leads their imaginations into the earth and through the surrounding terrain. - John McPhee

If I'm going to drive safely, I can't do geology. - John McPhee

Check out my Blog for more fossils I've found: http://viewsofthemah...o.blogspot.com/


#31 tracer

tracer

    Member of the Month 02/09

  • Regular Members
  • PipPipPip
  • 9,639 posts
  • Gender:Male
  • Location:N.W. Gulf of Mexico area

Awards

 

Posted 20 July 2009 - 01:22 PM

what about styoslickenesque? compromise is the essence of diplomacy when what's at stake is your brain exploding from trying to understand semi-fluid dynamics in geology.

p.s. - that was a rhetorical comment. i'm abandoning this topic for less stressful ones. (hah!)
Posted Image

#32 Guest_solius symbiosus_*

Guest_solius symbiosus_*
  • Guests

Posted 20 July 2009 - 01:30 PM

the links for the styolites you gave all mentioned something having to do with pressure... this does not at all look like it formed by pressure... it is too even/straight for that.


Click the high resolution pic.


The pressure involved in the formation of styolites can be due to the over burden, and not always tectonic stresses. The area above, and below, the linear feature appear to be classic styolitic structure resulting from pressure dissolution.

#33 Ron E.

Ron E.

    Advanced Member

  • Regular Members
  • PipPipPip
  • 772 posts
  • Gender:Male
  • Location:Bentonville, AR

Posted 20 July 2009 - 02:39 PM

Here's another hi-res pic, showing more detail not seen in the originals.
100_2263.jpg

#34 Dave Bowen

Dave Bowen

    Advanced Member

  • Regular Members
  • PipPipPip
  • 413 posts
  • Gender:Male
  • Location:Plano, Texas

Posted 20 July 2009 - 02:52 PM

Here's another hi-res pic, showing more detail not seen in the originals.
100_2263.jpg

That changes everything. You can now see the same pattern in the bottom of the recess. That used to go all the way across the rock.

I still have no clue what it was, but it definitely negates my theory. Now it does resemble some sort of coral formation.
Dave Bowen
Collin County, Texas.






Paleontology: The next best thing to time travel.

#35 tracer

tracer

    Member of the Month 02/09

  • Regular Members
  • PipPipPip
  • 9,639 posts
  • Gender:Male
  • Location:N.W. Gulf of Mexico area

Awards

 

Posted 20 July 2009 - 03:23 PM

i tole ya'll from the start that it's obviously a styolite. why are ya'll being so hard-headed?

"Do I contradict myself?
Very well then I contradict myself,
(I am large, I contain multitudes.)"

Whitman
Posted Image

#36 tracer

tracer

    Member of the Month 02/09

  • Regular Members
  • PipPipPip
  • 9,639 posts
  • Gender:Male
  • Location:N.W. Gulf of Mexico area

Awards

 

Posted 20 July 2009 - 04:15 PM

p.s. - that last picture convinced me that i was dealing with forces i'd never before seen or experienced, which is so often the case whenever i find myself not in abject, genuflective concurrence with all the RKIs on the forum. seems sometimes that my ole cap and bells just tees me to a fit!

love,

tracer, the exspurt


(p.s. - an "ex" is a has-been, and a "spurt" is a drip under pressure, so there you have it)
Posted Image

#37 jpbowden

jpbowden

    Advanced Member

  • Regular Members
  • PipPipPip
  • 804 posts
  • Gender:Male
  • Location:Almost near Mathis, Texas

Posted 20 July 2009 - 06:09 PM

Click the high resolution pic.


The pressure involved in the formation of styolites can be due to the over burden, and not always tectonic stresses. The area above, and below, the linear feature appear to be classic styolitic structure resulting from pressure dissolution.


First, they are not formed by pressure, they are formed by calcite crystals forming in clay, calcium carbonate comes down with water and really can grow large slabs of these crystal structures under ground, some get so thick that people who find them think they are fossil wood. They always follow the cracks, no tectonic stresses and no pressure, just a bunch lime clay. Come down here and look in these local caves and see some of the things hanging from the from them they are still growing. The name they used for this action is called "slickenside" and is referenced to the marks it leaves, this term cover a lot of territory and is general in it's meaning.

#38 jeepinthemud

jeepinthemud

    Advanced Member

  • Regular Members
  • PipPipPip
  • 402 posts
  • Gender:Male
  • Location:Houston, Texas

Posted 20 July 2009 - 06:15 PM

the way JP just explained it seemed to fit.... except I cannot imagine where the 'cracks' would be that it follows..

Ive been in plenty of caves, and that was my first thought.. but I cant imagine this thing forming in a cave...

Ron, look at the little holes... do they seem like air bubbles, weathering, little fossils, other chunks of (missing) limestone/calcite crystals, etc...
"To do is to be." -Socrates
"People are Stupid." -Wizard's First Rule
"Happiness is a warm Jeep." -Auspex

#39 Ron E.

Ron E.

    Advanced Member

  • Regular Members
  • PipPipPip
  • 772 posts
  • Gender:Male
  • Location:Bentonville, AR

Posted 20 July 2009 - 06:24 PM

Ron, look at the little holes... do they seem like air bubbles, weathering, little fossils, other chunks of (missing) limestone/calcite crystals, etc...


If you're referring to the holes beginning about 1/4 the way down, not air bubbles, not weathering, more like cleanly missing chunks.

#40 jeepinthemud

jeepinthemud

    Advanced Member

  • Regular Members
  • PipPipPip
  • 402 posts
  • Gender:Male
  • Location:Houston, Texas

Posted 20 July 2009 - 06:53 PM

If you're referring to the holes beginning about 1/4 the way down, not air bubbles, not weathering, more like cleanly missing chunks.


same with the larger holes, too?
"To do is to be." -Socrates
"People are Stupid." -Wizard's First Rule
"Happiness is a warm Jeep." -Auspex



Reply to this topic



  


0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users