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651 Views 5 Replies Last post: Sep 20, 2013 9:02 PM by MikeHardman RSS
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Sep 19, 2013 3:23 PM

Any ideas ?

Hi,

I am new to fossil collecting and also to this group. I have left it a bit late to get involved in fossils as I am close to becoming one myself !

I would appreciate any ideas on what the photos show. I have been told that they are not fossils - I had hoped they were some form of encrusting bryozoan. Well there's no harm in hoping !

 

The rocks were picked up in a local, long disused limestone quarry and there were several pieces showing the same thing so it wasn't uncommon there. Other rocks from the same place show plenty of bits of crinoid stems and shells.

 

001-Birkrigg.JPG

No 1 shows the outer face of the rock. To the top left, and below it, centre of left are two "leaf shaped" areas one slightly green and the other slightly yellow. The rock is covered in tiny holes and also seems to have a very thin coating of something white coloured.

 

002-Birkrigg.JPG

No 2 is an edge view of the rock and shows how thick it is between top and bottom surfaces.

 

 

003-Birkrigg.JPG

No 3 shows the inner, clean, face of the rock and is cropped to give an enlarged view. As can be seen the surface is well covered in tiny holes. Like the outer surface there is a very thin coating of something on the rock.

 

 

004-Birkrigg.JPG

 

No 4 is a view of the top ,outer, surface taken at an angle to try and show the thin coating that is present.

 

 

 

005-Birkrigg.JPG

 

No 5 is cropped to enlarge it more and is of the inner, clean, surface.

 

 

 

 

006-Birkrigg.JPG

 

No 6    A change is as good as a rest.... this is a different piece of rock with bits of crinoid stem in it this also has lots of the tiny holes in it.

 

 

 

 

007-Birkrigg.JPG

 

No 7  The same as No6 but rotated 180 degrees. I think the "cigar shaped" piece at the bottom edge is a crinoid stem ???

I have put two small red dots on this photo. Between the dots is a circular pattern of holes. It appears circular rather than random. I found several examples of this and also one eliptical shaped one with slightly larger holes. Any ideas ?

 

 

 

I thought you might like to see these two photos of a Fenestalla Bryozoan. This came from the same place and shows I don't always turn up rubbish !

I only know what it is because someone kindly identified it for me.

 

It's 3 centimetres across with the less visible part extending it out to 4 centimetres or so total.

009.JPG

008.JPG

 

Thanks for any suggestions as to what is going on with these rocks.

 

turnstone

 

 

 

 

Just posted another photo.... this has just been taken using LED lighting and shows the layer (of whatever it is) on the rock with all the holes. The thin coating seems to stand out better under an LED light.

rock.JPG

  • Currently Being Moderated
    Sep 19, 2013 3:35 PM (in response to turnstone)
    Re: Any ideas ?

    turnstone,

     

    Thank you for a very well prepared posting. Nice Fenestella.

     

    The dark "leaf shaped" areas are, I believe, lichen.

     

    The minute holes are due to solution by acid secreted by lichen

    Here are a couple of places where the phenomenon is mentioned:

    - http://www.zetatalk.com/food/tfood17h.htm

    - http://digital.library.okstate.edu/oas/oas_pdf/v05/p147_150.pdf

     

    If there is any significance to circular/elliptical patches of holes, they probably reflect particular patches of lichen, which may have been in that spot for some time and happened to be circular. The lichen has since disappeared; it may have been grazed away by molluscs or the rock may have moved such that it came to lay under water or part-buried in soil. That would change the microenvironment, which could lead to the lichen being decomposed.

     

    Mike

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    • Currently Being Moderated
      Sep 19, 2013 10:00 PM (in response to MikeHardman)
      Re: Any ideas ?

      Hi everyone!

      Thanks Mike, yes the network, net-like fossil is bryozoan. I am interested in the crinoids but cannot see enough detail.I cannot see the location you collected these from - if you can tell us we can approximate an age for your fossils. Struggling to comment on the other specimens, would need to see them in hand specimen. Please visit or post to the Angela Marmont Centre, Identification & Identification Service at the Natural History Museum, London, if you wish them identified further.

      All the best,

      Fiona

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