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1090 Views 12 Replies Last post: Mar 29, 2014 5:24 PM by caitycat RSS
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Jan 25, 2014 3:35 PM

Unknown Fossil Imprint??

I picked this up out of a small creek behind my home where I often find common coral fossils. I almost passed it up, but it seemed so peculiar, and upon further examination I realized it looked like some sort of animal-like fossil imprint. I consulted a science teacher and we concluded it may be a segmented creature (like a legged larva, millipede or centipede) of some kind, but I feel I need a further opinion. The width of the segments are roughly the same as the diameter of a dime, and if you look closely you can see what appear to be indentations of legs. I sent the same images to "Discovering Fossils" on facebook. Here is the response.


"Yes this is an intriguing piece. It would be useful to understand a little more about the geology of the area, i.e. how the rock was formed as that will help narrow the options if indeed the marks depict something living/organic. You mention the presence of fossil corals which are marine so it would make sense that other fossils in the same horizon/layer lived in the same environment (true for most instances). All that said I'm unsure whether your specimen is mineral or fossil, I notice a similar raised 3D object on the rock that features similar shapes, it's possible that the hollows you point out are left behind after the mineral formation has eroded/disappeared. If it is fossil then top of my list would be the hollow left behind by a dissolved bivalve shell or other shelled marine organism. I don't think it's crinoid which could potentially present in a similar way. I'll see if I can get a second opinion for you."


       So, here are also some examples of what I usually find, aside from the shells that you can find in just about any small stream around here. The problem is that it's quite possible these have just been washed in from nearby gravel pits, dirt roads, and driveways. They are clearly much lighter and softer, while this piece, and some of the surrounding stone, is very heavy and dark.


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    Jan 25, 2014 4:26 PM (in response to caitycat)
    Re: Unknown Fossil Imprint??

    Not easy!

     

    I feel, in order of probability: animal, vegetable, mineral; just based on experience.

     

    I see the raised structure mentioned above, and I can't see any sign of a 'shell' on either that or the recessed versions. That leads me to suspect trace fossil - specifically, a type of burrow. Those are often filled with much the same sediment as the surrounding rock, being picked out by subtle contrasts in composition (having been passed through an animal's gut, perhaps). Having said that, it is not one I recognize.

    The segmented nature could arise from pulsatory defaecation of the filling sediment.

     

    Since the objects seem to occur scattered through the rock (not just on a plane surface), I think it might be interesting to saw and polish/varnish the specimen, in several directions - to see if any are visible in cross-section - enabling a better idea of their shape in 3D and without vagueness introduced by weathering. If you fancy that, I suggest you take it to a university geology dept., and speak nicely to somebody; or you could try a funeral stonemason, who may have rock cutting and polishing equipment (but might charge for its use).

     

    Mike

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        Jan 25, 2014 5:07 PM (in response to caitycat)
        Re: Unknown Fossil Imprint??

        ...Also try a local museum and geological society, if such exist.

        And please do let us know when you get a confident ID.

         

        Mike

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        Jan 25, 2014 9:26 PM (in response to caitycat)
        Re: Unknown Fossil Imprint??

        Hi caltycat, some very nice finds! have you any more to show us?

        I think your first two images are of a coloinal corral called Synaptophyllum or Emmonsia or Lithostrotion but I don't know.

        Your next three images could be of an ammonite multi block death assemblance, this is were a lot of ammonites have been preserved at the same time.

        My reason on this is because there are what look to be two partial negatives were the ammonites used to be and in the last image is what looks to be whats left of an ammonite just above the middle to the right.

        I recently saw some ammonite track ways for sale in a Whitby fossil dealers shop, this is were the ammonite has rolled along the bottom of the sea and left it's imprint in the sediment, at first I thought you had one of these specimens but I don't think your specimen is the same.

        Once again nice finds.

         

        Tabfish

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          Jan 25, 2014 10:00 PM (in response to Tabfish)
          Re: Unknown Fossil Imprint??

          Have you found similar blocks to the one's in your last three images?

           

          Tabfish

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                Jan 26, 2014 9:24 PM (in response to caitycat)
                Re: Unknown Fossil Imprint??

                Some more nice finds.

                The one that has caught my eye is the third image down, the one with quarts infill.

                The main line of quarts looks to be in separate sections similar to what you find in an ammonite and there are a couple of shapes also similar to an ammonite.

                I have added an image of a cross section from an ammonite for you to compare with your specimen.

                 

                Tabfish

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