Why Do Pennsylvanian Rock Formations Appear as Strips?

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Evo
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A number of people have said they are interested in this topic.

Please posts any pictures, information or questions about rocks or fossils here.

I'll start off with some odd formations in rock here from the Pennsylvanian period (318.1 to 299.0 mya).

They appear to be strips of wood, but why do they always appear as strips, no depth? I can't find anything online. I'm dating them by the fossils found in the rock with them.
 
Attachments
  • Close-up photo of reddish-brown elongated fossil strips with fine parallel ridges embedded in grey and cream rock, partly in shadow.
    wood like objects 5.jpg
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  • Close-up of a weathered grey rock surface with several elongated, strip-like brownish fossil impressions running across it, partly shaded by overhanging green leaves.
    wood like strips.jpg
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  • Two elongated reddish-brown, flattened streaks embedded in grey lichen-speckled rock, one tapering to a point at the left, the other angled diagonally below it.
    wood-like objects 3.jpg
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Discussion

Sorry, I need to upload these to a webhosting site and resize them.
 
Ok, more.

This is a block of wood in stone from the same era as above.
 
Attachments
  • Photo of a rough, brownish-tan rock specimen resting on white paper towels, with a cylindrical, bark-like woody fragment embedded at the upper left and layered, fractured stone surfaces.
    front of wood block 59.jpg
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  • Close-up photo of a brownish-gold rock lying on white paper towel, with layered, banded surfaces and a rough, broken edge.
    back of block 58.jpg
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  • Photo of a rough, weathered rock specimen, tan and brown, with a cylindrical woody-looking fragment embedded at upper left, resting on white paper towel.
    front of wood block 59 big.jpg
    39.9 KB · Views: 863
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Small fossils, including what appears to be a fern leaf I found in an ancient river bed.

Photo of small pale fossil fragments on a black background: a fragmented ribbed shell-like piece in the centre, plus small rounded and tubular fragments around it.
 
Attachments
  • Photo of small fossil fragments on a black background: a ribbed, fan-shaped fossil in the centre, a small cylindrical segment at upper left, a short ridged rod at left, and two small rounded shells at upper right and bottom.
    brachipods fern leaf.jpg
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  • Rock slab with small fossils beside a US nickel for scale: a ribbed fossil on the left, two small bivalve shells on the right, and a short segmented fossil and a small cylindrical fragment in the middle.
    058 misc fossils w nickel.jpg
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Interesting thread!
So that is from the period when the variscean orogenesis took place?
 
DrDu said:
Interesting thread!
So that is from the period when the variscean orogenesis took place?
Yes, in Kansas , we had many periods at and below sea level, and we were below the equator at the time.
 
Just a note, I know pretty little about fossils, but I believe it is standard practice to put a "scale bar" into pictures. Rocks can be notoriously 'self-similar', meaning that it can be very difficult at times to know from pictures whether you are looking at an angular pebble, or an angular mountain top! That is, unless of course, there is a sense of scale. A simple coin, or other well known object usually suffices for fossils.
 
billiards said:
Just a note, I know pretty little about fossils, but I believe it is standard practice to put a "scale bar" into pictures. Rocks can be notoriously 'self-similar', meaning that it can be very difficult at times to know from pictures whether you are looking at an angular pebble, or an angular mountain top! That is, unless of course, there is a sense of scale. A simple coin, or other well known object usually suffices for fossils.
HEY! *I* know how big they are!

Good idea. Ok, so I just got back from risking my life hanging off the edge of a cliff while holding a camera just so I could place a nickel next to the odd wood-like strips. Ok, I wasn't hanging, but I did have to lean in an awkward position on the boulder and it IS on the edge of an overhang.

Close-up photo of several parallel ridged, rust-brown rock strips lying on a grey rock surface in shadow, with fine grooves running along their length.
 
Attachments
  • Close-up photo of rock with two elongated, parallel-striped rusty brown strips embedded in grey stone, with a US nickel placed alongside for scale.
    050 odd wood like nickel e.jpg
    87.3 KB · Views: 853
  • Close-up of several parallel-ribbed, rust-brown strips lying on grey rock in shadow, with fine grooves running lengthwise along each strip.
    odd wood like strip.jpg
    76.5 KB · Views: 1,521
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These "strips" are everywhere, what are they?
 
Most of the fossils in this area contain simple bivalves from when this place was under sea-water, however I still have my anti-gravity fossil rock from the Alpha Centauri system.

Close-up photo of a dark, rough rock with many small white and grey rounded shell-like fossils embedded in a brown matrix against a pale background.
 
Evo said:
HEY! *I* know how big they are!

Good idea. Ok, so I just got back from risking my life hanging off the edge of a cliff while holding a camera just so I could place a nickel next to the odd wood-like strips. Ok, I wasn't hanging, but I did have to lean in an awkward position on the boulder and it IS on the edge of an overhang.

Close-up photo of rust-coloured, ribbed fossil-like strips lying on weathered grey rock in shadow, with parallel grooves running along each strip.

*Much* better. :smile:

I still don't know what they are though :redface:
 
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This one is a real shame, what a nice brachiopod specimen it would have been.
 
Attachments
  • Close-up of a fossil shell fragment embedded in tan rock, with a US nickel placed beside it for scale; the shell is weathered and broken.
    044 brachiopod nickel e.jpg
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turbo said:
Most of the fossils in this area contain simple bivalves from when this place was under sea-water, however I still have my anti-gravity fossil rock from the Alpha Centauri system.

Photo of a dark brown rock specimen with a rough, pitted surface studded with rounded, whitish and grey fossil-like shells or nodules set in a rusty matrix against a pale background.
I love your "anti-grav" rock!
 
Evo said:
A number of people have said they are interested in this topic.

Please posts any pictures, information or questions about rocks or fossils here.

I'll start off with some odd formations in rock here from the Pennsylvanian period (318.1 to 299.0 mya).

They appear to be strips of wood, but why do they always appear as strips, no depth? I can't find anything online. I'm dating them by the fossils found in the rock with them.

Do you think they look like these Calamites?
 
Some rocks.

Close-up photo of a small rough rock fragment on a white textured background, with brown and rust-colored mineral surfaces, pitted cavities, and pale grainy patches.


Small rock fragment with irregular edges, cream and tan surfaces, brown weathered patches and a glassy white mineral area, on a white textured paper towel.
 
Attachments
  • Photo of a small brownish rock specimen on a white textured background, with rough, pitted surfaces and pale, grainy patches.
    045 rock e.jpg
    52.3 KB · Views: 1,331
  • Close-up photo of a small, irregular rock fragment with pale cream and tan surfaces, brown weathered edges and a glassy, crystalline area in the centre, resting on a white textured surface.
    048 rock e.jpg
    33.1 KB · Views: 1,528
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austinuni said:
Do you think they look like these Calamites?
That's it! Thank you!
 
This is what I call "swimming yams". Any guesses?
 
Attachments
  • Close-up of a weathered sedimentary rock surface with numerous elongated, reddish-brown oval clasts or fossil-like fragments scattered through a pale grey matrix.
    swimming yams.jpg
    64 KB · Views: 823
Evo said:
That's it! Thank you!

That's exciting! You gave a lot of good information to help track it down. Any more info on the swimming yams?
 
austinuni said:
That's exciting! You gave a lot of good information to help track it down. Any more info on the swimming yams?
Notice the empty indentations? That's where yams fell out.

Normally, the fossils are the usual hard white substance. But I have found a large number of rocks recently where the fossils are of a soft, crumbly orange substance. These are all from this area, both the white and the orange. I'm wondering what the orange yam like fossils could be.

Here's an orange fossil of possibly a crinoid?
 
Attachments
  • Close-up of a grey sedimentary rock with a yellowish-orange, crumbly fossil fragment sitting in a hollow, with a silver coin partly visible at the top edge for scale.
    060 crinoid maybe.jpg
    54.4 KB · Views: 823
Can anyone identify this type of rock and what caused the pits?
 
Attachments
  • Close-up of a rough, knobbly rock with many round pits and cavities across its surface, beside a nickel coin on white paper.
    071 pitted rock e.jpg
    41.9 KB · Views: 1,441
Evo said:
Can anyone identify this type of rock and what caused the pits?

A guess, maybe those are calcite etch pits

Calcite (if it's that) will dissolve slowly in rain water (chemical weathering) which is slightly acid (due to carbonic acid - dissolved carbon dioxide) and little dents may grow out to pits. There is not a lot of literature about it.

http://www.limestone-pavements.org.uk/geology.html
http://www.essc.psu.edu/~brantley/publications/dislocations.pdf[/URL]
 
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Evo said:
Can anyone identify this type of rock and what caused the pits?

A coral may be?
 
Thanks, both of you. I've been reading that similar holes are formed in rocks when iron ore they contained dissolved. Iron might also explain the reddish discoloration on the rock surface. I'm still searching, the rock is heavy, solid, and very hard, so far, I've ruled out calcite.

I have more rocks I need to post so please keep the ideas coming.
 
Okay. I finally bought a "point and shoot". Here's my first two photos.

http://imageshack.us/a/img442/3152/arrowheads1.jpg

http://imageshack.us/a/img18/2004/arrowheads2.jpg

All of these where found in Arkansas with the exception of the middle one on the bottom row of the first picture, which was found in Kansas.
 
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Evo said:
Can anyone identify this type of rock and what caused the pits?

This looks like a textbook example of 'tafoni' weathering in rocks. This type of weathering pattern occurs in 'case hardened' rock where the hardened outer surface is somewhat more reisitant to weathering than the softer interior. Nice example.
 
chemisttree said:
This looks like a textbook example of 'tafoni' weathering in rocks. This type of weathering pattern occurs in 'case hardened' rock where the hardened outer surface is somewhat more reisitant to weathering than the softer interior. Nice example.
Oooh. Now I will have to photograph the huge rock slabs that are pockmarked, I'll post some tomorrow, it's getting dark.
 
Evo,
You taking a geology course? I sure hope we're not doing your homework for you.:biggrin:
 
chemisttree said:
Evo,
You taking a geology course? I sure hope we're not doing your homework for you.:biggrin:
LOL! No, I've always had a love of rocks and fossils and now find myself sitting on top of an enormous fossil bed.
 
This gives you an idea of the density of the fossil layers.
 
Attachments
  • Close-up of a sedimentary rock surface densely packed with fossil shells and fragments set in a pale cemented matrix.
    fossils tons 1.jpg
    92.1 KB · Views: 651
  • Close-up of a sedimentary rock surface densely packed with fossil shell fragments and rounded bioclasts cemented in a pale tan matrix, lit by low sun from the upper left.
    fossils tons.jpg
    112 KB · Views: 644
  • Close-up photo of a rough, tan sedimentary rock packed with fossil shells and shell fragments, many of them broken and set in a fine matrix.
    021 fossils.jpg
    92.7 KB · Views: 618
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