Durango Bill's
Paleogeography (Historical Geology) Research



Evolution of the Colorado River and its Tributaries

by
Bill Butler


Evolution of the Colorado River and its Tributaries
including Formation and Origin of the Grand Canyon
Geologic History of the Grand Canyon

Part 1 - Introduction

(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 Durango.

   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 Morales
3)  “Roadside Geology of Arizona” (1993 Printing) by Halka Chronic
4)  “Roadside Geology of Colorado” (1992 Printing) by Halka Chronic
5)  “Roadside Geology of New Mexico” (1995 Printing) by Halka Chronic
6)  “Roadside Geology of Utah” (1994 Printing) by Halka Chronic
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 Merrill Beal
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 areas.

   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 acted 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 Colorado Plateau.

   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 vertical feet.

d)  The Paria River (in northern Arizona) cuts across (and 2,500 feet down through) the Paria Plateau instead of taking an easier route further north.

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 cuts 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 contours.)

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 silt flats.

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 consequential.

n)  Several rivers including the Price cut across Utah’s San Rafael Swell (Reef) oblivious to contours that should have directed them elsewhere.

o)  The Price River 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 entrenched meanders.

p)  The Green River cuts through the Tavaputs Plateau north of Green River, Utah - thus forming the deepest canyon in Utah.

q)  The Green/Yampa river system slices through Split Mountain in 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 (southwest of Kremmling, CO) and across the White River Plateau (Glenwood Canyon, CO).

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 White River.

y)  The La Plata Mountains 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 model.



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 million years.

   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) Another 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 the Eocene

Return to Evolution of the Colorado River Main Page



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