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354 Views 2 Replies Last post: Apr 10, 2013 6:25 PM by wolvesjeff RSS
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Apr 10, 2013 3:56 PM

Can anyone ID this fossil?

Hi

 

I found this fossil today on the beach at Hornsea. It appears to have cells with a different material within the cells. Can anyone provide an ID please?

 

 

Regards

 

Wolvesjeff

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    Apr 10, 2013 4:22 PM (in response to wolvesjeff)
    Re: Can anyone ID this fossil?

    Hello Wolvesjeff,

     

    Methinks there is no fossil here, though there is a hint of echonoderm ambulacral plates.

     

    The 'cells' are the rock, possibly an iron-rich siltstone, and the white parts are veins, possibly of calcite (if they were quartz, they would probably stand out from the siltstone more prominently).

    In some places the siltstone has fallen out, leaving a socket rimmed by the vein mineral.

     

    This sort of structure arises either by:

    - the rock fracturing, leaving irregular voids, which later become filled with vein minerals

    - in-situ chemical processes happening as the sediment turns to rock and subsequently, resulting in nodules or concretions.

     

    Some of the latter can have a rather regularly fractured structure, and if there is prominent colour contrast between rock and vein (eg.iron-rich siltstone with white veining), such specimens can be quite eye-catching. The regularity often leads folks to think they are fossils. I remember seeing one in a local museum in the west of Ireland where such a 'septarian nodule' was labelled as a fossil turtle.

    Here's an example - http://commons.wikimedia.org/wiki/File:Septarian_Nodule.jpg

     

    Ref:

    - http://en.wikipedia.org/wiki/Concretion

     

    Regards,

    Mike

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