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Re: Notes from the under-matrix.



David Peters (davidrpeters@earthlink.net) wrote:

<In the case of the Nyctosaurus from the Niobrara chalk I believe that
traces of preservation or "echoes" of the same above and below the bedding
plane are what I am seeing. In Ichnology these are called "underprints" I
think.>

  If I understand the formation of chalk properly, it is not possible to
form any sort of prints as it is a gradualistic, non-layered form of
conglomeration. Material would settle into any depression, and, being so
fine-grained, the chalk would not form layers but intermix; the fossil is
included in more than one plane sometimes, whereas in limestone it is
usually in a single plane, and the sediment is coarser, enabling
impressions to be preserved. If the preparators were removing any sort of
matrix, any underprints possibly and unforeseeably there would be
obscurred by the needles and prep area made by the workers. This is
usually circular in area, as the workers seek to surround the fossil with
their tools to find any more bones. I do not think it is right to refute
Chris Bennett by only saying his observations are old school when in fact
he has worked on these fossils and sediments for quite a few years.

  Cheers,

=====
Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)

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