Clifford and his Friends // Palmer Park
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Palmer Park // Dawson Arkose
This extensive urban natural park is made of coarse gravels derived
from erosion of the Pikes Peak area. The top of Palmer Park gives
superb views of Pikes Peak and an interestingly diminished view of
the Garden of the Gods, as the peak towers 8,000 feet over the
Garden. Palmer Park contains splendid white bluffs of feldspar-rich
sandstone called the Dawson Arkose (D1 sequence) and is of the Late
Cretaceous age, about 60 million years old. The granular rock is
resistant to erosion and forms the steep-walled battlements and
scarps. If you closely at the rocks you can see that they are made
up of small bits and pieces of granite rock, the same granite that
makes up the towering massif of Pikes Peak to the west. Beneath the
white cliffs are olive-brown mudstone and sandstone beds made up
largely of volcanic debris. The rocks tell us that a cover of
volcanic rocks was eroded off the mountains to the west before the
Pikes Peak granite was exposed.
This sequence of sedimentary rocks, containing coarse gravel,
sandstone, and clay-rich mudstone, bears witness to the uplift and
erosion of the Rocky Mountains. The character of the sedimentary
rock changes dramatically as you move across the Denver Basin. To
clarify the sequence and name it, members of the Denver Basin
project grouped the beds by age. The 900–1,800-foot sequence
represents the first episode of uplift along the Front Range. It is
called D1 and includes rocks known as the Denver Formation,
Arapahoe Conglomerate, and part of the Dawson Arkose.
This material, which consists mostly of quartz and feldspar, is
known to geologists as Arkose. The formation is called the Dawson
Arkose, and it is of the same geologic age as the formations about
Denver that have been called the Denver and Arapahoe
formations.
The Dawson Arkose, derived from the Pikes Peak granite and
associated rocks, was laid down under various continental
conditions, chiefly as wash and stream deposits accompanied by
local ponding. During the accumulation of the Arkose this region
may be conceived of as a piedmont [foot of the mountain] area
having a moist and temperate climate, an area in which the
vegetation was characterized by the presence of many fig trees,
palms, magnolias, poplars, willows, oaks, maples, etc., and which
was occupied by primitive mammals.
The formations into which the sedimentary rocks of the Colorado
Springs region are grouped by geologists and the names of the
geologic periods in which they belong, as it is determined by the
study of their fossils. The term formation is generally applied to
a distinctive bed or a series of distinctive beds of rock, such as
sandstone, shale, or limestone, that were formed continuously or in
close succession during a certain period of geologic time, or to a
group of beds that are of about the same geologic age. It is thus
frequently applied to such an assemblage of beds as may be grouped
together as a unit for convenience in mapping. The deposits made in
a single geologic epoch or period are usually represented by
several formations. In this region the Upper Cretaceous epoch, for
instance, is represented by eight formations, though other periods
are each represented by only one formation. Between the Manitou
limestone and the shale at the base of the Fountain formation there
are no representatives of the rocks that were formed elsewhere
during the Silurian and Devonian periods. Nor is there any rock to
represent the earliest division of the Carboniferous period. The
absence of these beds means either that during these long periods
of time the Colorado Springs region was dry land, upon which no
material was being deposited, or that the rocks then deposited
there were later worn away. Between the Lykins and the Morrison
formations no representative is found of the Triassic period, whose
rocks constitute another of the geologic systems.
Not all the sedimentary rocks of the Colorado Springs region were
laid down on the sea floor. The Dawson Arkose, for instance, at the
top of the column, was spread out on the land by the many
eastward-flowing streams, which brought quantities of disintegrated
granite and gravel down from high lands, on the west. As these
streams shifted from side to side over the country they spread
gravel somewhat evenly over the slope until they had thus deposited
considerably more than a thousand feet of coarse material.
Near Colorado Springs, white bluffs and hoodoos of upper Dawson
Arkose are clearly visible found through out the “Pulpit
Rock” and the “Austin Bluffs” Parks that consists
of debris weathered from Pikes Peak granite. The upper Dawson is so
friable and easily eroded that, according to one local geologist,
"it just melts away" once exposed. Between the upper and lower
Dawson members is a brightly-colored clay paleosol (fossil soil)
developed on the floor of a Paleocene tropical rainforest. The
paleosol once served as a source of pigments for Native Americans
living in the area. (There is a very good example of the brightly
hued rocks found in the “Paint Mines Interpretive Park”
out in Calhan, and Mr. Titocache pointed this out with another
wonderful Earthcache; GC1DR4Y.)
To receive credit for this Earthcache:
1) Post a picture of yourself with your GPS receiver and an example
of the Dawson Arkose in the background, along with the coords. (You
may do this from anywhere in the park.)
2) Update, Ignore question #2 // An example of The Dawson Arkose
found near the posted coords is the thickness of 1,000 feet? (This
info was posted via a sign, near these parking coords, but now the
sign has disappeared: N38 52.273 W104 46.029.
3) Take a measurement (height and width in inches) of the unique
weathering found among of the rocks at these coords: N38 52.289
W104 46.014. (Hint, sometimes the rocks Smile back at
you…)
4) Tell me if you can spot, from these posted coords: N38 52.270
W104 46.057, via the rock formations, the head of a Red Dog. My son
told me he spotted something, and he even nicked-named the rock,
why what else but Clifford. And to keep your imagination running a
little, what other animals can you spot, if you let your
imagination run a little? (My son spotted two others, and I am only
looking for one...)
* Please email the answers to these questions (using my profile
link) - do not post the answers in your log. Enjoy your visit to
this unique park, and have fun caching Along the Way!
The above information was compiled from the following
sources:
The Denver Museum of Nature & Science
http://www.dmns.org/main/minisites/ancientDenvers/park.html#references
USGS (science for a changing world) Geological Survey
Bulletin 707 Guidebook of the Western United States: Part E. The
Denver & Rio Grande Western Route
http://www.nps.gov/history/history/online_books/geology/publications/bul/707/trip2.htm
Additional Hints
(No hints available.)