To whomever could help,
My name is Vadec Lobza and I am a graduate student in geology at the
University of Texas at Arlington. My project involves a detailed study
of trace fossils in very fine grained, terrigenous sediments (mud) of the
Upper Devonian age. I am interested in backtracking such information as
sediment firmness and relative oxygen levels within the water above the
sediment. From observations made thus far I have strong grounds to
believe that those traces were produced mainly by polychaete worms.
Fossil scolecodonts stand as one of the pieces of evidence.
The sequence I study consists of alternating black, brown, and gray
shales. Burrows in my rocks are manifested as traces of mud, lighter in
color, pulled down by the burrowers into a darker in color matrix. Seldom
it is the other way around and I strongly believe it is directly
associated with the amount of oxygen in the substrate. The color of
rocks is directly related to their organic content. I have also
conducted series of experiments to compare substrate density and burrow
morphology as produced by worms moving through sediments of different
densities. Both the experiments and my rocks strongly suggest that, when
considering the overall burrow assemblage of a single layer, some burrows
were produced in very soupy substrate (up to 70% water content) and some
later, when the mud became firmer (currently in press in the Journal of
Sedimentary Research). All of my rocks show a higher degree of
bioturbation by, what I believe were errant worms, then by the sedentary
types. That is, if a freely moving worm has to come out of the mud often,
but does not spend much time in the water. I do not know how such worms
really behave. I could not find any information as to how much time
errant worms spend inside the substrate vs. the time in the water above
it. Also, there are questions as to how fast can errant worms "swim" in
such soupy substrate (cm/s). I realize that the answers are not simple
and more than likely depend on what worm genus is considered.
This is where I am turning to you for help. I really do not want to
produce science fiction and need reliable information to keep me in
check, but unfortunately such data seems to be scarce. Even pointing me
in the direction of proper literature would be of tremendous help.
Please keep in mind that I am interested in the behavior of modern worms!
If you would like to respond, please do so at my e-mail address.
Thank you very much for your time,
University of Texas at Arlington
Arlington, TX 76013
(817) 272 2987
WML at utarlg.uta.edu
home: Plaster9 at mci2000.com
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