Geoscience Reference
In-Depth Information
Hey, What do you think of this feature in the photo? Yes, it looks somewhat
phallic, but that's not what I'm asking. The central structure ranges from
sandy mudstone to sandstone and crosscuts claystone. Beds dip to the left.
Brush is one inch wide. DV
[Dave Varricchio]
I opened the photo attached to the message and studied it. The top part
showed a red mudstone overlying a gray mudstone. The latter had a big chunk re-
moved—probably byshovelsandpicks—which freshlyexposedadarker-grayrock
underneathitsweatheredsurface.Therewasindeeda“centralstructure”withinthat
gray mudstone (what Dave called a “claystone”), so I focused my attention on that.
It protruded slightly compared to the rock around it, so it was made of more resist-
ant material, and was a lighter gray.
These observations and inferences of mine synced with Dave saying it was a
sandy mudstone or sandstone, which would have contributed to its bas-relief ap-
pearance. It also had a horizontal segment toward its top, which turned abruptly
downward into a vertical segment. In my imagination, I converted this part into
three dimensions, and a spiral shape came to mind. The vertical part connected dir-
ectly to a white oval near the bottom of the photo, which had a piece of shiny metal
pokingfromit.EventhoughIalmostneverworkedwithfossilvertebrate skeletons,
I nonetheless recognized the white oval as a plaster jacket, which must have been
placed around the remains of a fossil vertebrate. The metal was likely aluminum
foilthefieldcrewusedtocoverpartoftherockaroundtheskeletonbeforeslapping
burlap strips soaked in wet plaster of Paris around the fossil specimen, the latter a
time-honored practice in vertebrate paleontology since the 1880s.
And yes, there was a small field brush as the only scale in the photo, off to the
left. Assuming a width of about 2.5 cm (1 in), I used that to extrapolate its length as
about 15 cm (6 in). I then applied this brush length to figure the approximate length
and width of the plaster jacket. Using this seat-of-the-pants reckoning, it came out
to 55 to 60 cm (22-24 in) long and 40 cm (16 in) wide. The central structure kept
