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sjbaird

Is this a fossil?

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sjbaird

Hi. I'm new to the Forum, but would like some opinions about this object I found here in Alaska. It was found in a tidal creek in an estuary in southcentral Alaska. The estuary surface is a mix of gravel, mud, and glacial silt. I've shown this to various local experts, and most think it is some kind of broken fossil, but a few think it isn't a fossil at all.

 

Any thoughts would be appreciated.

 

IMG_8055.JPG

IMG_8047.JPGIMG_8046.JPG

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LordTrilobite

Sure looks like a type of bone.

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ynot

Welcome to :tff:!

It does look like a bone, but I think it is a concretion. There is no evidence of bone structure in the areas that should show the coarse marrow structures. These areas look more like a sandstone. (Could be a cast of a bone or something else(?))

 

Tony

 

 

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sjbaird

To me it has always looked like a broken part of a zygomatic arch from a mammal skull. The color is very similar to some mammal fossils I've seen also. It looks too organic to be a concretion to me. However, that interior structure that should look like bone is what has led some to conclude that it is not a fossil. Others, however, are just as sure that it is fossil.

 

Anyone else want to weigh in?

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JohnJ

Sharper images of the broken surfaces will go a long way in assisting an ID.  ;)

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fifbrindacier

Less blurry ones of each end of it also.

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sjbaird

Here are some attempts at sharper photos of the broken edges.  I'm having trouble getting decent depth of field.

 

IMGP9982.jpg

 

IMGP9985.jpg

 

IMGP9988.jpg

 

IMGP9989.jpg

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westcoast

Initially i thought ironstone but looks like bone, particularly the second image in the latest close up images. Not a clue what kind however

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ynot

I still see a concretion. The internal structure is made of spherical objects of varying size and desperation, A bone would have a consistent pattern of irregular shapes. Also the "wall" is way to thin for a bone structure.

Tony

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sjbaird

To me it has always looked like a broken part of a zygomatic arch from a mammal skull. The color is very similar to some mammal fossils I've seen also. It looks too organic to be a concretion to me. However, that interior structure that should look like bone is what has led some to conclude that it is not a fossil. Others, however, are just as sure that it is fossil.

 

Anyone else want to weigh in?

 

Is there anyone I could send this to for some definitive ID? Are there paleontologists who are willing to do such things? We are slowly accumulating evidence that there were Pleistocene mammals on the Kenai Peninsula, mostly from scattered mammoth teeth and some steppe bison remains. It would be interesting to see if this could add to that understanding.

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Fossildude19

I took the liberty of brightening/contrasting your pictures. 

 

IMGP9982.jpg.02289f7fdec57a55738c27fd57f59ee4.jpg   IMGP9988.jpg.e23196cb90fd7dbcaabac08852d58396.jpg


It looks like an oolitic ironstone concretion, to me. :unsure: 

Regards,

 

 

 

   

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Darktooth

I have found many of these in the streambed of Big Brook New Jersey. When I was much less knowledgeable in fossils I fell for the suggestive shape and appearance of these concretions. But like Tony has already pointed out, the internal structure is made up of coarse grains. It is not a bone. The proof is in the structure.

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Darktooth

By the way, I still fall for faux-fossils now and then.

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westcoast

Yeah. Those latest pictures cleared things up. I'm back in the 'mineral that looks like bone' camp. I've had a few. Particularly with ironstone.

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sjbaird

Thanks, all. Glad to have this cleared up.

 

 

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sjbaird

One last question for those of you who have a good understanding of geology: how does the thin rich brown layer on the outer surface form, what is it composed of, and why does the object have such a deceptively organic shape? I guess that was actually three last questions.

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ynot

It forms from iron in the surrounding rock/soil oxidizing around a nucleus, often of some biologic material.

Iron oxides.

Concreations like to take a variety of shapes some that resemble things that We recognize, and Our brains try to fit a shape to an unknown object. (Ever see shapes in the clouds).

Tony

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