(Note: This entire paper was (is being)
updated in April/May, 2005. The primary changes involve:
1) Changed the “overflow” date of the Colorado River from
5.5 million years ago to 5.4 million years ago. (Only notations for
this change existed in the old version.)
2) Changed the river reversal date in Wyoming from about 30 million
years ago to 20-25 million years ago. (Only notations for this change
existed in the old version.)
3) Added better illustrations to the various pages.)
This paper is an attempt to model the geologic history of
the Colorado River and its tributaries starting with the Late
Cretaceous through the present. In addition to the large scale Colorado
River system, local features near Durango, CO are also covered.
Several of the conclusions presented here disagree with
currently accepted interpretations. As for the origin of the Grand
Canyon, none of the existing models seems to provide an adequate
explanation and a new model is proposed. Colorado’s Gore Range
and White River Plateau appear to be of recent origin (Miocene) instead
of Laramide time. Also, the ancestral San Juan River has undergone wide
variations before establishing its current path
The model also examines features near Durango, Colorado
(see the appendix). These include: 1) The origin of the Bridge Timber
Mountain gravel deposits (which appear to be much older than the
accepted age); 2) How and why the La Plata River bisects the La Plata
Mountains; and 3) What formed the “Dry Valley” north of
Events are presented in chronological order with general
overviews of river systems for each geological epoch. Where there are
differences from published conclusions, special sections in the
appendix discuss arguments and evidence to support the model. The most
appealing part of the model is the sense that the pieces seem to form a
logical sequence, and components that previously were unexplained seem
to fit together properly.
As the chronology progresses, a pattern emerges where many
locations throughout the southwest have undergone multiple distinct
periods of local uplift. This does not fit the standard models of
mountain building, which classically falls into one of two camps.
Normal mountain building is usually caused by, (1) either plate
convergence and subduction which produces compression and thrusting or,
(2) plate rifting due to doming within the mantle accompanied by fault
block mountain building (a better description is valley dropping). At
the end of the appendix, a theory is presented to explain the
phenomenon of multiple distinct local uplifts in a given location.
Major references include:
1) Dr. Ron Blakey’s historical geology depictions (http://jan.ucc.nau.edu/~rcb7/
2) “Grand Canyon Geology” (1990 Printing) by Beus and
3) “Roadside Geology of Arizona” (1993 Printing) by
4) “Roadside Geology of Colorado” (1992 Printing) by
5) “Roadside Geology of New Mexico” (1995 Printing)
by Halka Chronic
6) “Roadside Geology of Utah” (1994 Printing) by
7) “Roadside Geology of Wyoming” (1998 Printing) by
Lageson and Spearing
8) “Field Trip Guidebook” by The Department of
Geology, Fort Lewis College
9) “Grand Canyon The Story Behind The Scenery” by
10) Geologic maps at: http://geology.about.com/science/geology/cs/geomapsusstates/index.com
11) “Geologic Map of Colorado” Compiled by Ogden Tweto
12) High altitude photos and USGS topographic maps at: http://terraserver.microsoft.com/
13) Additional topographic maps at: http://www.topozone.com
14) 2-D and 3-D computer images and maps generated by Topo USA v.
2.0 by Delorme
15) Detailed USGS topographic maps of Colorado by Delorme’s
3-D Topo Quads
16) Grand Canyon Symposium 2000 abstracts: http://wwwflag.wr.usgs.gov/GCSymposium/
Did rivers exist in
this area during the Cenozoic?
The first question that must be asked concerns the
existence of river systems during this period. The Colorado River Basin
is a dry area today with most river water supplied by runoff from high
mountain systems (which were generally lower during most of the
Cenozoic). It is therefor useful to provide evidence that sufficient
water was present in the past to support river systems; and in
particular, if there was drainage exiting the Colorado Plateau to other
During the Paleocene and Eocene Epochs, a large lake (or
series of lakes) about the size of Lake Ontario developed in southern
and central Utah, and with time it (they) extended northeastward into
Colorado and Wyoming. During the same time span, sediments brought in
from somewhere else buried most of Wyoming’s Laramie Range and
Owl Creek Mountains. This would require a large river system. During
the early Oligocene, the climate was wet enough to support large
Sequoia trees next to a lake just east of the Colorado Plateau at
Florissant Fossil Beds National Monument. During the late Oligocene and
through most of the Miocene it was drier, but rivers still dissolved a
lot of salt from the old Paradox Basin area and deposited it in western
and northwestern Utah. We note that this is the only time period that
had significant salt accumulation; thus any other salt dissolved in
river systems must have exited the area without being left behind in
evaporative basins. Thus, we conclude that major river systems existed
throughout the Colorado Plateau area, and the next problem is to try to
deduce where they were.
Can rivers run uphill
to get across mountains?
There are many locations throughout the western U.S. where
rivers have cut canyons through mountain ranges instead of taking
easier, lower routes around them. For example, the Wasatch Range near
Salt Lake City is of recent origin and is still rising. Yet, rivers
such as the Weber, Ogden, and Provo cut right through the range
producing canyons thousands of feet deep. We can conclude that the
rivers were in place first; and as the mountain range rose, the rivers
as stationary band saws cutting deep groves into the rising block.
There are examples where even arroyos have cut canyons through rising
blocks. For example, east of Albuquerque, NM, highway I-40 uses Tijeras
Canyon cut by Tijeras Arroyo through the Sandia Mountains. This leads
to the following important rule. An established river (or stream or
even an arroyo) is frequently capable of maintaining its path through a
rising mountain range.
Alternately, a river may try to maintain a path through a
rising mountain mass but eventually be forced to abandon this channel.
An example of this phenomenon is Unaweep Canyon
located high on the Uncompahgre Plateau southwest of Grand Junction,
Colorado. An ancient river was here (will be identified later), but
long ago it found an easier route.
It is also possible to have both events occur at the same
location over a period of time if the mountain range has several
distinct periods of uplift. A river may be able to maintain a canyon
during a first uplift and then abandon it during a second uplift. Such
a combination would only happen rarely, but should subsequent events
reactivate this ancient canyon millions of years later, it would be a
geologic grand finale.
What happens to water if it exists on a slope? The obvious
answer is - it runs downhill. More precisely, unless there is some
obstruction, it runs directly downhill at right angles to the contour
lines that appear on topographic maps. This leads to another important
rule. When a river (stream, etc.) first develops, it will take the
easiest downhill path that is available. If a modern river follows a
more illogical course, it is because it (or a related predecessor)
became entrenched in an ancestral easier course, and has resisted
changes produced by subsequent erosion, mountain uplifts, etc. The
illogical course of the river has thus preserved a record of the old
topography. Equally important, if there are stream deposits,
paleovalleys, etc. in areas that are now at higher elevations not
occupied by current rivers; then these areas (and any linked strata)
must have been lower at some time in the past.
If a river uses bits and pieces of an ancestral drainage
established during some earlier topography and then integrates these
with drainage derived from current topography; it can produce some
rather bazaar results. For example, both the Laramie Range in Wyoming
and the Gore Range in Colorado contain streams that start down one side
of the mountain range, and then make 180-degree turns back through the
crest of the range to flow down the other side. In both of these
ranges, the sections of the streams that reverse back through the
crests are remnants of ancestral rivers. This double-back phenomenon
shows up frequently in other locations throughout the southwest.
There are two dominant sequences of events that govern why
current river systems exist in areas that are not favored by present
topographical terrain. Either: (1) The river system was entrenched
BEFORE subsequent tectonic and erosional events produced changes (a
process called “antecedence”); or (2) The earlier
topography was subsequently covered by sediments, a new river course
developed across these sediments, and finally the river eroded downward
into the old terrain BEFORE the surrounding silt/sediments could be
washed away ( a process called “superimposition”). Both of
these processes contributed to current river patterns throughout the
Combinations of these rules can be used to deduce the
relative order of tectonic and erosional events controlling the current
paths of rivers, streams, arroyos, etc. Some examples of present rivers
(and old deposits) not flowing directly downhill (smoothed
topographically and/or stratigraphically) and other unexplained recent
sedimentary formations include: (Illustrations and more details are
provided in the Appendix and “Image Index” pages for many
of these examples.)
a) The Colorado River flows almost parallel to the smoothed
contour lines on the west side of the Kaibab Plateau
b) The Colorado River flows stratigraphically uphill on the east
side of the Kaibab Plateau. For that matter, it flows stratigraphically
uphill for most of its path across southern Utah and northern Arizona.
c) Kanab Creek has cut its own canyon en route to joining the
Colorado in the Grand Canyon. If it established this route based on
current topography, it would have had to flow uphill at least 1,200
d) The Paria
(in northern Arizona) cuts across (and 2,500 feet down
through) the Paria Plateau instead of taking an easier route further
e) Tsaile Creek flows parallel to the smoothed contour lines on
the north side of Canyon de
Chelly National Monument
f) West of Mexican Hat, Utah, the San Juan River cuts through Monument Upwarp
instead of going around it. Thus, we have Cedar Mesa to the north and
Douglas Mesa (capped by old river deposits) to the south.
g) Just to the east of Escalante, Utah, the Escalante River has
carved a 1,000 foot deep canyon through a mesa instead of taking a much
easier route to the southeast.
h) From Dolores, CO to Gateway, CO, the Dolores River
across terrain that no river in its right mind would seek out today.
i) Upstream from Dolores, CO, the Dolores River cuts diagonally
across contour lines from Stoner (the forks) to Carver Canyon.
j) Tributaries entering the West Dolores River from the west flow
stratigraphically uphill. (Also uphill across the smoothed topographic
k) All the major rivers in eastern Utah (Colorado, Dirty Devil,
Escalante, Green, and San Juan) have entrenched meanders (goosenecks)
indicating that at some point in the past they meandered lazily across
l) At some point in the past, a large river formed Unaweep Canyon
across the Uncompahge Plateau in Colorado, yet the canyon is dry today.
There are two other similar high dry valleys crossing the Gore Range
and another parallel to the Colorado River in the southwest section of
the Grand Canyon
m) A deep canyon (used by highway I-70) cuts east to west through
the Wasatch Plateau in Utah. Salina Creek
opportunistically uses this old canyon, but its origin is far more
n) Several rivers including the Price cut across Utah’s San
Rafael Swell (Reef) oblivious to contours that should have directed
o) The Price
slices into the Book Cliffs north of Green River, Utah
instead of taking a much easier route a few miles further to the
southwest. Even more interesting, this illogical course contains
p) The Green River cuts through the Tavaputs
north of Green River, Utah - thus forming the deepest
canyon in Utah.
q) The Green/Yampa river system slices through Split Mountain
the northeast corner of Utah.
r) The Green River cuts through the eastern Uintas to form the Canyon of Lodore
but topographically the river should be somewhere else.
s) The late Miocene age Browns Park Formation covers parts of
northwestern Colorado. The “Roadside Geology of Colorado”
offers no explanation as to how it got there.
t) The Colorado River cuts through the northwest side of the La
Sal Mountains (in Utah) instead of going around them.
u) A resolution to the origin of the Chuska Sandstone. The
“Roadside Geology of New Mexico” and other sources had
noted its existence along with an age estimate of early/mid Tertiary,
but explanations of how it was deposited were not given.
v) The Colorado River has cut deep canyons through the Gore Range
of Kremmling, CO) and across the White River Plateau (Glenwood Canyon
w) Both Colorado’s Gore Range and Wyoming’s Laramie
Range have streams that start down one side of range and then make
180-degree turns to go back through the crest of the range to flow down
the other side.
x) The White River cuts into the north side of the White River
Plateau. Of greater interest, Big Beaver Creek flows stratigraphically
(and smoothed topographically) uphill into the plateau to join the
y) The La
form a north-south range near Durango, CO. The La
Plata River runs north to south bisecting most of the range just where
its crest should be.
z) A lot of “old” salt has been dissolved out of the
Paradox Basin. A lot of “new” salt exists in northwest
Utah. Something transported it.
We will try to fit ALL of these puzzle pieces together in a coherent
A Little Arithmetic
Regarding Erosion Rates
The history of the Grand Canyon indicates a major break
point in river patterns occurred about 5.4 (+/-4%) million years ago
(see Beus and Morales). (Added 8/9/05: Latest evidence (at http://gsa.confex.com/gsa/2005AM/finalprogram/abstract_91054.htm
narrows this further to 5.36 +/-0.06 million years ago) It is
most helpful to do a little arithmetic
regarding erosion rates so that we may run the clock backward to
reconstruct the topography of 5.4 million years ago. The result makes
it much easier to discard preconceived ideas.
Before the Glen Canyon Dam was built, the average sediment
transport rate through the Grand Canyon (measured near Phantom Ranch)
was 391,780 tons per day. (Beal page 10. Beus and Morales give a figure
of 300 tons per day on page 334, but calculations for lava dam fill
rates require the much larger number. It appears the
“thousands” designation was lost somewhere in the pipeline
regarding the page 334 data.).
If we use 391,780 tons per day and a weight of 140
Lbs/CuFt for sandstone (Handbook of Chemistry and Physics), then we get
an average sandstone erosion rate of 5.6 million cubic feet per day for
the Colorado River Basin. Then, we multiply this result by 5.4 million
years and divide by the137,641 sq. miles of contributing drainage
area (USGS station # 09402500 – near Phantom Ranch) to arrive at
2,877 feet of erosion for the entire river basin over the last 5.4
It is probable that this figure is too large for a couple
of reasons. First, erosion rates throughout the southwest seem to have
increased after 1880. Since sediment transport measurements in the
Grand Canyon started after this, the true long-term rate is probably
lower. Second, prior to two million years ago, rainfall rates were
lower due to the pre ice age climate. (Beyond 5.4 million years ago
erosion rates were probably much lower).
However, a ballpark estimate of 1,500 feet of erosion
seems quite reasonable for the last 5.4 million years. If we restore
this sediment to the present landscape, we can fill every canyon in the
entire Colorado River basin and have as much as 1,000 ft. or so left
over to cover up current surface features. For example, the Island in
the Sky area in Canyonlands National Park, the Book Cliffs north of
Green River, Utah, and the Paria Canyon area of Arizona were not
exposed yet as of 5.4 million years ago. Erosion formed and exposed
these features in just the last 5.4 million years. We can thus conclude
they (and other recent features) had no influence on river paths before
this time. This allows much more freedom for the placement of earlier
river systems. For example, imagine marking off the area currently
bounded by the Grand Canyon to the south, the Colorado/Utah border to
the east, Green River, Utah to the north, and the Wasatch to the west.
Prior to 5.4 million years ago, ALL river systems within this area
followed different courses than they do at present.
The sediment that has been eroded during this time has
been deposited in the growing rift along the Arizona/California border
extending southward through Mexico to include the northern quarter of
the Gulf of California. (See Eugene Singer’s monograph at http://web.archive.org/web/19991008060017/www.aloha.net/~esinger/homegeol.htm
section of the rift that has been filled in extends 100 miles
northwestward to include the Salton Sea. These deposits have been
measured at up to six miles thick (in the northern Gulf of California).
Four to five million years ago the Los Angeles Basin would have been
100 to 150 miles southeast of where it is now. It is possible some of
the early Colorado River deposits may have helped to fill it in.
Local uplift within the last few million years is also
significant when reconstructing earlier topography. Everyone knows the
Wasatch has risen during this period. (Later, we will provide a
measurement of how much). Equally important, there is evidence that the
Kaibab Plateau has had three separate uplifts starting with the
Laramide. The most recent uplift is probably still in progress today.
(We will document this later.) These are all components as to how the
Colorado River relocated to its present course in the Grand Canyon.
Continue to Part 2 - Late Cretaceous through
Return to Evolution of the Colorado River
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