[... Snip Example 1 ...]
>At Dinosaur Ridge near Denver, the Dakota Group shows dinosaur tracks
>on 6 different layers separated by 5 meters (16 feet)~Martin Lockley and
>Adrian Hunt, Dinosaur Tracks, (New York: Columbia University Press,
>1995), p. 198
[... Snip Example 1 ...]
>The importance of these examples is that the water was out for layer after
>layerand only a foot or two of sediment was deposited when the floodwaters
>supposedly came in again. The flood was not very deep nor did it
>show a lot of turbulence at these time periods. I think a case
>could be made that the other intervals also were not very rapidly
>deposited.
As a geologist who has spent a lot of time at "Dinosaur Ridge" leading field
trips for Grade School Kids, College students, Natural History Museum
sponsored groups, and church groups, I thought that I might add a few more
details to this terse description and discussion. Dinosaur Ridge is a newly
designated Natural Historic Site and has a volunteer group of people
(Friends of Dinosaur Ridge) that are actively engaged in making the site
accessable, providing interpretive signage and materials, and leading tours.
Because all of the rock layers are tilted at an angle, this is a great place
to see a lot of sedimentary and paleontological features in a small easily
accessable area.
A simplified (and partial) stratagraphic section of the Cretaceous rocks in
the area is shown below (youngest layers on top)
---------------
Denver/Arapahoe Fm. (1200' claystones, sandstones, and conglomerates with
dinosaur bones, petrified trees, and the Cretaceous/Tertiary boundary
---------------
Laramie Fm (500-1100' of nonmarine clays, sandstone, and coal: contains
gorgeous leaf fossils and dinosaur footprints)
---------------
Fox Hills Sandstone (60' of marine sand interpreted as shoreline sands)
---------------
Pierre Shale (6000-8000' of marine shale or mud with occasional marine
reptile fossils and ammonite beds)
---------------
Niobrara Limestone (330' of limestones full of clam shells & rare shark teeth)
---------------
Benton Shale (495' of marine clays, thin limestones, & abundant fish scales)
---------------
Dakota Group (280' sandstones with clay and coal layers generally
interpreted to be marine shoreline in origin. Various layers contain
dinosaur tracks, wood & leaf impressions, worm burrows, stream channels and
ripple marks.)
---------------
Morrison Fm (Jurassic: 270' of nonmarine claystones with sandstone lenses.
Contains dinosaur bones that were first quarried here during the great Bone
Rush of 1879)
---------------
I point out all of this detail in order to make a few simple observations.
The conventional explanation for these layers is that they record the
encroachment of the ocean and re-emergence of land during the Cretaceous
Period (shoreline deposits covered by marine muds and limestones,
subsequently covered by more shoreline deposits). Note that this event (or
alternatively the Flood ;-) ) left almost 2 miles of sediment here and that
we have dinosaur bones and tracks before and after this incursion of the
sea. To explain this all as a single catastrophic event, we have to find a
way to preserve large air breathing dinosaurs while depositing 1000's of
feet of mud.
At a finer scale, the track sites that Lockley refers to in the above quote
show the tromping of numerous dinosaurs. Three distinct types of tracks are
noted and there are several trackways. A set of three parallel tracks have
been tentatively interpreted as a "family group" since they represent
parallel movement of 2 large and 1 small animal of the same species.
Although track making in deeper waters may be remotely possible, this
observation suggests that the water (if there was any) had to be very
shallow. Nearby but on a different layer we have tracks of a similar animal
walking up the center of what appears to be an old sandy stream channel.
The other problem that trace fossils may present to the single catastrophic
flood hypothesis here is the repeated interlayering of the track beds with
individual beds containing undisturbed ripple marks, and then beds with
"worm" burrows.
Now besides the guidebook literature available from the "Friends of Dinosaur
Ridge", there is also an alternative creationist guidebook available. This
makes Dinosaur Ridge a great place to bring people from all sides of the
issue together at the outcrop for discussions.
Steve
[The opinions expressed here are my own
and are not to be attributed to my employer]
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:: ////// Steven M. Smith Office: (303)236-1192 ::
:: |----OO U.S. Geological Survey Message: (303)236-1800 ::
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