RE: Sauropods in wet versus dry environments... a tip of the hatto some past artists (Was Re. Lost Worlds)

["Tracy L. Ford" <dino.hunter@home.com>]

-----Original Message-----
From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of Ray
Stanford
Sent: Wednesday, January 16, 2002 9:59 PM
To: dino.hunter@home.com; Dinonet (E-mail)
Subject: Re: Sauropods in wet versus dry environments... a tip of the hatto
some past artists (Was Re. Lost Worlds)

    Tracy wrote,"Come on Ray ease up here, I hope your not having a bad
day."

    Thanks, Tracy, but no.  I'm having a good day. The exercise that such
discussion provides is good for the mind and invigorating, at least to me.
You see, I'm an identical twin, and we grew up arguing and enjoying it.<<

Understood and I can relate on how one can get a bit irritated by the list
at times :)

    >>Ford also asked, "Ok, educate us. How could a terrestrial, dry track
be
fossilized without it being covered up by sediment from an aquatic force?
(Had to think how to write that one :) )."


   A geologist friend of mine has a marvelous Permian multi-trackway where
some reptiles were crawling up a sand dune.  One can pretty well calculate
the angle of the dune being climbed, from the push-up by the back parts of
the pedes. Manus impressions were clearly there, too, but with not so much
push-back, informing one of the difference in the way the manus and pes were
utilized in climbing the dune.  There is nothing whatsoever in that trackway
to suggest that the dune was damp at all.  Had it been, one should have seen
some surface breakage in the areas of push-back, but they are perfectly
smooth.<<

Was a book written about this or a paper? I seem to remember something about
this.

>>  Don't ask me to explain exactly how such examples are preserved,
but there are many such examples, which we must accept even if we cannot
understand them, so that some day maybe we can understand.<<

Actually I think I can. The surface of the dune somehow gets hard, and the
animal walks up it 'breaking' through it like one would on thin ice. It
again gets hard (I don't know if the sun itself can 'bake' the surface or if
a little mist or rain would do it). I've walked up some of this kind of
surface.

 >>   I have also seen dinosaur trackways made in very dry environments.

    But, let me proffer a hypothetical but realistic case that will exercise
one's taphonomic grasp to the extreme:  A big sauropod plods along on a
hard, dry surface, but is ever so slightly more damp beneath the surface --
a common situation.  With each step, the animal is compressing the hard
substrate at the grain level, driving the grains closer together for some
respectable depth, although the depression atop the ground where the foot
has been is very shallow.  What happens is not a text-book pretty footprint,
but a column beneath where the foot was, that is more compressed and, thus,
more resistant to erosion that adjacent areas. In time, waters come, eroding
the hard dirt to the sides of the foot's compression area, but being in
great part resisted by the compressed area. In time, what results is a
'stand up and be counted' trackway.  :-)  In turn, this whole amazing thing
is covered by either wind or water-driven deposits.  Ultimately, millions of
years later, however, the covering deposit erodes away.  It was less
endurated than the 'stand up and be counted' trackway.  One looks across an
eroded surface and there is a recognizable sauropod trackway, incredibly
standing higher that the rest of the rock!<<

Hmmm...I wonder how many are out there and just haven't been noticed? I
think it's possible. Heck, even really good footprints can often be over
looked until the sun is just right or even it's noticed. I remember Jim
Kirkland talking about digging at the Utah Raptor Quarry (I think or close
to it, and I've been there to see it) and lying on hard uneven ground. It
wasn't year/months/days after laying on the surface did they look and see
they were laying on a track site!


  >>  Yes, there trackways of such a remarkable nature.  Compressional
preservation (in its various manifestations) is well known.  I simply
describe this one bizarre and rare type with hopes that there are simpler
scenarios for creating and preserving tracks in dry sand or dirt that you
(or anyone who cares to try) might imagine.  For me, analysis of taphonomy
is one of the greatest joys of track study.<<

Nature does tend to through us curves...

Tracy L. Ford
P. O. Box 1171
Poway Ca  92074