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Some kind of trace fossil?


Trickworm

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Hello all, I found this piece about a couple months ago while searching for dinosaur prints in cretaceous siltstone. I'm not sure what it is, it is raised and could potentially be some type of depositional feature or erosion pattern.  What do you think?

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All I see is an erosion pattern. But maybe one of the more experienced members may see something I dont.

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WhodamanHD

Erosion pattern is possible, but it seems not only to be eroded out, but convex, leading me to believe it is a good old worm burrow.

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I agree with a burrow. 

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Three of them in parallel following the contours of the matrix ? I don't think so. 

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ofcourse i am quite new to the subject, but I live in a house with a million unidentified stone and fossil and mineral things, that i gathered and dug out myself, so I will go on and humbly express an opinion: 

 

I also see similar shapes on that stone, (2nd photo) below and on the left side of ur object.  It is probably erosion, I mean if u look at it as a whole, and not fixate on the worm shaped island, where would be the burrows or trace fossils to justify the obvious erosion marks below and on the left? (again 2nd photo) also the 'burrow' fades out in the matrix, so maybe dig a bit there to see if it leads somewhere. if it has a beginning it will have a similar sized ending, that's how I perceive a burrow, maybe I am wrong. 

 

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4 hours ago, Rockwood said:

Three of them in parallel following the contours of the matrix ? I don't think so. 

?

I do not see three parallel structures and the "worm" has a much more pronounced undulation than what I can see in the layers of the rock in general.

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I think we need to know more about this fossil. The formation should be a big help if we have an ichnologist watching. You being from the streets doesn't give us much to go on.:)

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50 minutes ago, ynot said:

?

I do not see three parallel structures and the "worm" has a much more pronounced undulation than what I can see in the layers of the rock in general.

I realize it is an overstatement, but I still feel strongly that one would need prove that it's not just a result of weathering, and perhaps staining to some degree rather than the other way around.

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1 minute ago, Rockwood said:

I realize it is an overstatement, but I still feel strongly that one would need prove that it's not just a result of weathering, and perhaps staining to some degree rather than the other way around.

The thing that makes Me think burrow is the perfect undulation of the raised part. It makes a very uniform sign wave that is a rarity in geologic structures.

There is a distinct layer of heavier mineralization that makes Me think it may be an oxidized iron pyrite replacement or infill.

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2 minutes ago, ynot said:

The thing that makes Me think burrow is the perfect undulation of the raised part. It makes a very uniform sign wave that is a rarity in geologic structures.

There is a distinct layer of heavier mineralization that makes Me think it may be an oxidized iron pyrite replacement or infill.

If it didn't fade so nicely into a similarly shaded contour, and weren't surrounded by a weathered looking layer I would agree completely.

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Kids: It's okay. We are not fighting. 

If disagreement weren't allowed there would be no science. 

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doushantuo

rootless (intrafolial)fold is a slight possibility.

But that belongs in the category "wild guess" 

The rock doesn't appear to be tectonized

 

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WhodamanHD

Patuxent is shallow water, and I'm not sure if this means anything, but burrows are common in the shallow water Gettysburg shale I sometimes collect in Frederick county, MD, although different time. The curvature (squiggliness) says worm to me. Also whenever I find them, because they are infilled, mineral staining often occurs. This is true for your specimen. My hypothesis is erosion was taking place around the fossil, which had a slightly harder composition due to the infilling material, and the material around it eroded and the fossil did not (or at least at a slower rate).

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  • 10 months later...
On 5/30/2017 at 9:23 PM, Trickworm said:

Hello all, I found this piece about a couple months ago while searching for dinosaur prints in cretaceous siltstone. I'm not sure what it is, it is raised and could potentially be some type of depositional feature or erosion pattern.  What do you think?

 

I'm kind of late to this, but I've collected a fair bit in the Patuxent Formation and I agree that it likely is a fossil owing to it's sinusoidal shape. However, I've never found any worm burrows in it. I know a fish was found in the Patuxent further south in Virginia, so is there any possibility this could be undichna (fish swimming trace fossil made by the tail)? 

 

As for the iron, it is my understanding that those concretions of iron hydroxide formed after the deposition of the rocks as the environment remained (and still is to this day, really) a humid near coastal area that is prime territory to induce those kinds of changes within the iron (III) oxide. It could be possible that the fossil merely became engulfed, if you will, in the iron hydroxide after it had been formed and thus give the illusion it is geologic in origin. Also, if it's from where I think it is, then the current environment tends to be an area of erosion and thus could further distort the fossil and rock (not like in metamorphosis through stretching). 

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