From: Darryl Maddox <firstname.lastname@example.org>
> Field trip to a roadcut which exposes a sand/blackshale/sand with marine
> fossils/pure white sand sequence from bottom to top. The basal sand has a
> few dinosaur bones in it within a few miles of here, the shale has lots of
> pelecypods, a few small ammonites and other stuff in it including an
> ocassional shark took. The overlying sand that also contains marine
> has a few sharks teeth in it also. ...
> The teacher said the black shale was deposited in a shallow bay in a
> re-entrant from the open sea and that the overlying sand marked a beach
> sequence etc. ...
> The teacher then replied: "Well if you don't believe my interpretation
> it looks to me like you re left with one of the following: Sharks lived on
> land or I came out here and buried all these fossils to fool you.
There is another interpretation. The bottom sand/shale pair could represent
tsunami/turbidite depositions. (You do not mention what the contact lines
are like.) The fossil contents of the layers represent the load originally
picked up by the tsunami/turbidite then deposited after the wave front
passed by. The shale is black because of the organic material contained in
it at deposition. The other fossils are probably sorted vertcially in the
sand/shale pair according to size and density.
(I am going to have to refrain from responding any further to this, not
because I would not want to, nor because I cannot, but simply because I only
have so much time and there are some more important things I need to get
done. I'll go back into Lurking mode for a while again. See you. It's
This archive was generated by hypermail 2b29 : Wed Feb 13 2002 - 15:29:47 EST