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Micro Fossil From Conglomerate Found in East Central FL

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I picked up a nice chunk of conglomerate that had an obvious fossil tooth embedded in it, but became interested in what  small micro fossils might be in it.  I experimented with a small piece of fossil bearing rock and found that the acid destroyed the fossils amost as much as the rock, so as a result I turned to just doing surface scans.  I eventually decided to remove one surface micro fossil that seemed to be pretty much on the surface of the conglomerate.   The results were satsifactory, but I don't know what the micro fossil is.   It is roughly one mm in diameter and maybe half a mm thick.


It is small enough that it stretched my limits and the limits of my imaging system.  I think it could be a fish tooth or scale, but have no idea.  It definitely has some form and detail to it.  I don't think it is just a broken piece.


The first two photos show the item still attached to the conglomerate.  One photo shows a bit of conglomerate still attached to one side.  For size, the one line you see is .5 mm in thickness. 


I consider it a success simply because I was able to extricate one small fossil from conglomerate and get some photos.   If it is actually something identifiable, I'd be doubly happy.   Thanks to all.





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tbr wrote:


"I experimented with a small piece of fossil bearing rock 

and found that the acid destroyed the fossils almost as 

much as the rock,.."


This is an interesting development as paleontologists have been

able to use acid preparation to extract bone from calcareous rocks. 


You might be interested in:


Schiebout, J.A., Ting, S. and Sankey, J.T., 1998. Microvertebrate 

concentrations in pedogenic nodule conglomerates: Recognizing 

the rocks and recovering and interpreting the fossils. Palaeontologia 

Electronica, 1(2), pp.1-54.


Penn State PDF


Another Online PDF


Researchgate PDF


Of course, any acid is hazardous and has to be handle with care

and proper safety measures.


A slightly related paper is:


Cohen, D.R., Cohen, E.J., Graham, I.T., Soares, G.G., Hand, S.J.

and Archer, M., 2017. Geochemical exploration for vertebrate

fossils using field portable XRF. 

Journal of Geochemical Exploration, 181, pp.1-9.




Paul H.

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As with anything, you have to do it correctly, and I seldom do on my first attempt.   In the Penn State paper they used acetic acid.   I suspect it depends not only on the solution, but also the composition of the conglomerate and perhaps also the fossils.   Being a complete newbie  (not to mention ignoramous), I used what I had available at the time and did it wrong.  Whatever percent of Muriatic acid I used ruined visible fossils in my experimental clump.  I didn't mind that much, because I selected a small clump that I didn't care about, just for the learning experience. 


In contrast, here is how the Penn State paper describes their method.


"Current laboratory treatment of the Fort Polk Miocene conglomerates involves soaking pieces, usually between three and forty cm in diameter, in approximately 10% acetic acid to partially dissolve cement, releasing the fossils and nodules as a residue (Movie 1). Calcium carbonate, which is dissolved in weak acetic acid, is the main mineral in the nodules and in the cement holding the rock together. Teeth and bones are composed of apatite and are not dissolved. Sankey and students under her direction have experimented upon Cretaceous conglomerate from Big Bend, Texas, and concluded that up to 40% acetic acid can be used without harm to vertebrate teeth from these conglomerates, but a 10% concentration has been seen to cause erosion of dentine in a few instances on the Fort Polk Miocene specimens, so the largest of our dissolution operations continues at that level of acid concentration."  


So 10% solution of acetic acid causes erosion of dentine.    And higher than 40% could harm vertebrate teeth?


Thanks much for the references.


If I find some acetic acid, I'll give it a try.  


When I said the acid destroyed the fossils, I should have been more specific about my method, but was more in the mode of excited child rather than disciplined academic.


My personal experiment taught me one thing that doesn't work.   Muriatic acid can dissolve the conglomeates I have, but can also dissolve vertebrate fossils.


I'd still like to know if anyone has any idea what the item I freed from the conglomerate might be.   


Thanks again.














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Mark Kmiecik
5 hours ago, tbr said:

If I find some acetic acid, I'll give it a try.  

It's known as vinegar. The acid's reaction speed can be altered by changing the percentage of dilution. Acetic acid is a fairly weak acid, but it can do serious damage in high concentrations. Vinegar is about a 4% solution at the store, but can be purchased in higher concentrations from chemical supply outlets. Most of the time you don't need to spend more money than just buying vinegar at your local food store.

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I managed to get some photos that I think are much better.   The item appears to be around one mm in length and with and perhaps more like .5 mm in height, considering the side with matrix as the bottom.


In the first photo it looks like there is a thin raised ridge that runs between four lumps. 


The bottom of the object was shown in a photo above.  The bottom appears to be flat but is still obscured by some of the original matrix which is still attached and which you can see a bit of in the first and forth photos. 







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