When Was The Colorado River Formed?
Raise of the Colorado Plateau (33-15 MYA), and Formation of the Colorado River & Grand Canyon
The Great Reversal: A Case for the Oligocene Integration of the Colorado River
For over two decades, the geologic community has remained locked in a debate regarding the “Old” versus “Young” Colorado River, often missing the forest for the trees. By hyper-focusing on localized datasets—such as the geochemical signatures of the Grand Wash Trough, the Peach Springs Tuff, or the elusive zircon dating of downstream alluvium—researchers frequently ignore the most significant evidence staring them in the face: the relationship between canyon incision and the regional tectonic upwarps. To understand the Colorado River’s evolution, we must prioritize two diagnostic features: the canyons that cut through massive structural folds and the lacustrine (lake) “fill-to-spill” deposits that inevitably accompany major drainage reversals.
Addressing the former first, its important to remember that in all locations which completely lack ANY evidence of large basin fill deposits suggesting a fill-to-spill scenario of fold overtopping– the fold had to pre-date or “antecede” the upwarps of the Colorado Plateau in order to maintain eroding a coarse & canyon through these massive folds as they formed. Let me repeat that. A river HAD TO PREDATE most the major Laramide folds which the modern rivers currently cut through. There is simply no way around it. (Pun intended!). The Colorado River cuts through the Kaibab, Monument, Circle Cliffs, Uinta/Split Mountain, and Uncompahgre uplifts, and its tributaries cut through the Cockscomb, VRG, San Rafael swell and other upwards, with ZERO evidence of basin fill deposits behind the fold in most cases. This strongly suggesting these watercourses were established BEFORE the upwarps began to rise significantly in the Cretaceous & early Tertiary.
This fact alone helps us to ascertain that the river courses through most large folds on the Colorado Plateau are very old. Older than the very folds themselves.
However, it’s also fairly well established that the general drainage in Utah & the Colorado Plateau throughout the Cretaceous & earliest Tertiary was opposite of present, to the NORTH and EAST from the Nevada & Arizona highlands into the retreating Cretaceous seaway, which causes a bit of a puzzle. Much like the fill-to-spill character of a river crossing a superimposed fold, drainage reversal REQUIRES ponding of a drainage as the continental divide passes perpendicularly across the drainage.
So the question is… where is the ponding evidence for the drainage reversal? Researchers have been looking for ‘reversal deposits’ for decades in regard to the debate on the Colorado River’s evolution. Yet to date, the paltry Bidahochi Formation on the Defiance Upwarp is the only proposed candidate for a Tertiary Lake deposit marking the ‘Great Reversal’. But frankly the obvious answer has been staring us in the face the whole time. The Great Paleocene & Eocene lakes of Utah & Wyoming are the evidence of the reversal & beginning of the Colorado River! It was during the Paleocene & Eocene that drainage reversed from Northeastward flow to Southwestward flow, and the proto-Colorado River established it its outlet to the Pacific Ocean through a pass in the Mountains, much like present Ganges River draining the Tibetan plateau through the front range of the Himalayas. Thus as the Nevadan/Arizonan Arc collapsed in the Mid to Late tertiary, the Colorado River had already established an outlet to the Pacific, allowing it to maintain courses through canyons of the “Navadaplano” and the gentle folds of the Colorado Plateau. Then the river was pushed ‘laterally east & southward’ from the centerline of the Eocene lakes to its present location causing ‘planar denudation’ (see figure) of many folds before it settled into its present location and began canyon incision.
This lateral ‘pushing’ of the river from the west toward the east by eastward migrating Laramide orogenic forces can be clearly seen by the folding of Eocene and Oligocene (and even early Miocene) deposits in central Utah. The steeply folding early Cenozoic deposits on the Wasatch Plateau as well as folding under Thousand Lakes Mountain and Boulder Mountain clearly show that folding persisted at least as late as the Signal Peak volcanic rhyolites (26-25mya) which blanket Boulder Mountain. These eastward migrating fold belts would have pushed the proto-Colorado river from the location of its initial inception (in the center of the filled Eocene lake Unita & Flagstaff) to it its current location between the dates of around 35mya and 21 mya as constrained by period Oligocene lakes STOPPED retaining sediment (~35mya) to the time that the Signal Peak Volcanics and Henry Mountain laccoliths were emplaced.
Oligocene Folding and Volcanism
There is a widespread misconception, even among seasoned geologists, that the elevation differential elevation of the west-facing slopes of plateaus like Markagunt Plateau, Pansagunt Plateau, Wasatch Plateau, and the Aquarius Plateaus have somehow been “uplifted” by the Normal Faults that bound their west sides. To the contrary, however, every one of these plateaus are actually remnants of pre-extensional folds. And as already discussed, because many of these folds deform Eocene & even Oligocene strata, they must post-date the 45-33 Ma deposition of that strata. This evidence necessitates that massive folding must POST-DATE 33 Ma and PRE-DATE the the onset of Basin and Range extension around 17–12 Ma. This “window” is a huge, poorly understood, and poorly taught fact in Western geology! This timeframe basically mirrors the deposition of the Browns Park Formation, which was likely being deposited behind a rapidly raising Uinta Arch. As well as the Rio Grande rift and the Mesquite Basin north of the Grand Wash Trough caused by rotation of the Colorado Plateau which I believe was responsible for the initial uplift of the Platau and obliteration of evidence of the ancient outlet of the pre-extensional Colorado River.
This all fits together because these Colorado Plateau bounding folds are undoubtedly associated with the Plateau’s primary rise and the widespread explosive volcanism of the region. From the massive calderas bounding the Plateau to the intrusive laccoliths and dikes, everything points to a rise dating from 33 Ma to 15–12 Ma when the Basin and Range collapse began. The transition from the marine Cretaceous to the lacustrine Claron and Green River lakes is the biggest clue we have. Furthermore, the age of the massive erosional surface of the clastic apron of Bishop Conglomerate undoubtedly dates the primary initial rise of the Colorado Plateau and its folds. It is well-constrained by ash beds to 34–30 Ma and correlates to the Starr Flat Member of the Duchesne River Formation, marking a massive erosional pulse that followed the plateau’s first great heave.
The Hualapai Limestone and the Grand Wash Trough
The Oligocene “Rim Gravels” of Peach Springs and the Hualapai Plateau are further great evidence of this theory. Why don’t they exist until the Oligocene? Because from the Cretaceous to the Paleocene, rivers flowed unimpeded into the Northern retreated Cretaceous seaway in Canada. In the Paleocene through Eocene the basin became closed and waters and sedements were trapped in the closed lakes of.., these lakes began to rapidly rise, and it was the Oligocene when their filling basins raised to area of the Grand Canyon region, which acted as the structural hinge-point. That is why gravels started accumulating there and why it became the stopping point of the southward migrating river system. [rewrite]
Finally, we must address the Hualapai Limestone, which fills the easternmost and highest basin of the Grand Wash Trough as the uppermost member of the Muddy Creek Formation. Some researchers, like Pearce (2010), suggest that because these layers lack “Colorado River signatures,” the river couldn’t have been there. My argument is that the Colorado flowed through without leaving much evidence until 5 Ma, when it was temporarily blocked from its west exit and redirected south. The layers in that trough are much like the flood deposits of Grand Junction to the north; most of the sediment comes from adjoining Cretaceous hills, but the river backed up occasionally during huge outflow floods from the Rockies. Pearce even mentions that the water chemistry is similar to spring-fed Havasu Creek (high in carbonate). I suggest this is not evidence of a local spring, but rather evidence of an ice-dam break, which caused a short-lived backup, allowing the limestone to form from the carbonate-rich waters of the high plateau.
The Oligocene ‘Rim Gravels’ of Peach Springs and the Hualapai Plateau are another GREAT evidence of my theory. Why dont they exist UNTIL the Oligocene? Because from the Cretaceous to Oligocene rivers flowed unimpeded into the Utah oceans and lakes, but in the end Eocene these lakes began to rapidly raise, and it was the Oligocene when their rise reached the Grand Canyon region which was the hingepoint. Thats why it started accumulating gravels and why it became the stopping point of the southward migrating river!
Also NOTE how the Hualapai Limestone fills the easternmost and highest basin of the Grand Wash Trough. It is the uppermost member of the Muddy Creek Formation.
Be sure to answer the Pearce 2010 paper that suggests that the Grand Wash Trough’s Hualapai Limestone (Miocene) and its layers beneath did NOT have Colorado River signatures. My argument is that the Colorado flowed through without leaving much evidence until 5mya when it was BLOCKED from its west exit and was redirected south. The layers in that trough were MUCH like the flood deposits of Grand Junction to the north, most the sediment in those layers come from the adjoining Cretaceous hills, but the river does back up occasionally during huge outflow floods from the Rockies. IN FACT she mentions that the water chemistry is like spring fed Havasu creek (high in carbonate), I suggest this is evidence of an ice dam break, which caused a short lived backup and limestone formation.
(See. Pearce, 2010) https://digitalrepository.unm.edu/cgi/viewcontent.cgi?article=1047&context=eps_etds
The Muddy Creek layers in the Mesquite Basin say nothing of the age of the Colorado, but instead they infer the date when the upper virgin basin was separated from the Colorado by the traverse fold highlighted in red in the figure above.
THE SALTON TROUGH AS AN ANALOG
A great modern analog of Lake Hualapai and Muddy Creek Lakes depression is the Salton Trough. It also has thick limestone deposits that border on Tufa. I’ll bet it has a similar geochemistry. Deposits on the alluvial fans downstream of Borrego Springs are locally derived and the natural levees of the Colorado River keep it separate from the Trough most the time with small exceptions.
Image of Lake Cahuilla Shoreline, just above Coolidge Springs north-west of the Modern Salton Sea. Ancient shoreline of the short-lived Lake are readily visible. (Image from google earth from user Robert Hyatt. Likely open source-ish)
IMAGINE USING SIMILAR GEOLOGIC UNITS IN THE SALTON TROUGH TO SUGGEST THE COLORADO DIDN’T EXIT TO THE SEA DURING THE LAST ICE AGE?!
CATHEDRAL VALLEY AS AN ANALOG TO HUALAPAI FM
(Image of lacustrine sediments of Cathedral Valley Nevada. replace with my pics)
The thick basel limestone units are a good example of how a trapped lake can form right next to an existing river course.
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Be sure to answer the Pearce 2010 paper that suggests that the Grand Wash Trough’s Hualapai Limestone (Miocene) and its layers beneath did NOT have Colorado River signatures. My argument is that the Colorado flowed through without leaving much evidence until 5mya when it was BLOCKED from its west exit and was redirected south. The layers in that trough were MUCH like the flood deposits of Grand Junction to the north, most the sediment in those layers come from the adjoining Cretaceous hills, but the river does back up occasionally during huge outflow floods from the Rockies. IN FACT she mentions that the water chemistry is like spring fed Havasu creek (high in carbonate), I suggest this is evidence of an ice dam break, which caused a short lived backup and limestone formation.
(Pearce 2010) https://digitalrepository.unm.edu/cgi/viewcontent.cgi?article=1047&context=eps_etds
GRAND MESA & EAGLE RIVER VOLCANICs
The Grand Mesa basalts date to around 10mya and sit about 5,000 feet east above Grand Junction and give some indication of the timing and amount of erosion of the upper Colorado River. They are often used to suggest the 5 Ma age of Colorado River creation. But these can’t be considered without also considering the Miocene Eagle River Collapse Center basalts just upstream (Hinsdale Formation & Servilleta Formations?). These basalts sit on the Weber Sandstone on a surface that feels like eastern Split Mountain. And they date to EARLIER than those of Grand Mesa (as early as 30-20 Ma), and yet they are on a more eroded surface suggesting….
This GSA paper by Lidke et al 2002 details the entire Miocene/Oligocene history of the upper colorado, and there was definitely considerable erosion on the surfaces these 30-20 Ma basalts are deposited on!
https://coloradogeologicalsurvey.org/wp-content/uploads/RT-0061890-i0-8137-2366-3-366-0-101.pdf
DETRIDAL ZIRCONS
The detridal Zircon evidence see page 83, Pearce 2010, ONLY speaks to where most the sediment in those beds was coming from.
Fall of the Nevadaplano (15-0 MYA)
-The beginning of Basin & Range extension is well researched from abundant evidence. (write a summary of it here)
I think the only common misunderstanding I see and read about regarding it, is the fact that nearly EVERY extensional fault and mountain range in the region is a reactivated Mesozoic & early cenozoic feature. And many of the normal faults likely began during compression. I think many geologists forget or dont learn that although compressional faults are rare under extensional forces, extensional (normal) faults are incredibly common during compressional forces.\
In other words, many normal faults that are often supposed to be associated with Basin & Range extension were actually formed during early compression. Likewise, many basin deposits which are believed to be associated with Basin & Range extension were actually deposited in subsiding basins during compression. [AND HONESTLY THIS IS HUGE… WE NEED MORE GEOLOGIST FINDING THESE DEPOSITS BECAUSE THEY WILL FILL IN HUGE GAPS OF OUR UNDERSTANDING.]
The Grand Castle and Canan Peak Formations are late Cretaceious in age, perhaps as early as 100mya suggesting orogenic uplift made its way to central utah around this time
Colorado River Formation References (Papers to Cite)
-Great overview of Green River capture: Revisiting the Classic Conundrum of the Green River’s Integration through the Uinta Uplift. Joel Pederson (use its refs, its in my peleo drive folder)
-Pre-Colorado River Paleogeography and ext along the… James Faulds, Price & Wallace (my folder)
-search through all of these: file:///H:/My%20Drive/%60UtahGeology.com%20Website%20Stuff/paleogeography%20reconstructions/paleogeography%20papers/Tons_Of_Colorado_Platuea_Evolution_Papers.htm
-DRAW SOME ILLUSTRATIONS WITH ALL THESE EVIDENCES ON THE MAP!!
-ALSO DRAW A MAP OF CLARON FM area of the Grand Staircase showing that as soon as the four basins (pinevalley, markugunt, paunsagunt & Aquarius Plateaus) finish filling, they are uplifted and SEPARATED at 33 mya which causes EACH to find an outlet to the south through the paleo-virgin, Kanab creek, Paria and Escalante drainages.
-REMEMBER: knowing from the Bishop Cng and Wasatch Plateau that the folds really took off AFTER 33 mya, is important, because then we can also assume that the Paria/Cockscomb, Kaibab uplift and Virgin River Gorge uplift really take off then too. AND WE KNOW EACH OF THEM MUST HAVE REVERSED BY 33 MYA!
-And the reversal of the Paria drainage has major implication to the formation of the Grand Canyon, It must have been flowing the current direction by not much after 33 mya, and had to have been flowing INTO the claron basins,
-WHEN DOES THE VIRGIN RIVER REVERSE? During the Claron of course! Between 55-33 mya, and all the others are likely the same!
WHEN DO THE COLORADO PLATEAU UPLIFTS OCCUR?
-I think they must be later/more recent than I first thought. It makes sense that they match with the emplacement of the intrusions, AND they have to be late if the colorado river migrated from the early cenozoic lakes, because it had to move across the san rafael swell, circle cliffs AND kaibab, so they must post date 33-25ish mya. Check out this article and quote which backs this up:
“the rise of the Kaibab and Circle Cliffs uplifts. Stockli et al. (2002) hoped to apply the (then) new technique of (U-Th)/He thermochronology to the problem of dating structural deformation of many of the Colorado Plateau uplifts. To that end, they collected and analyzed samples from stratigraphic profiles on the Circle Cliffs, San Rafael, Monument, and Kaibab uplifts. Unfortunately, all of the samples yielded ages from 33 to 11 Ma, consistent with uplift and denudation of the Colorado Plateau, but too young to be referencing the rise of individual Laramide uplifts”
https://www.geo.arizona.edu/sites/www.geo.arizona.edu/files/Colorado%20Plateau%20Structure.pdf
Stop using detrital Zircons!!!
They may work great in a wide variety of cases such as the dating of the Bishop conglomerate and Browns park fms, or Peach Springs conglomerates, but they just don’t work for finding the Colorado because ITS LIKE A FINDING A NEEDLE IN A HAYSTACK trying to find the early signatures for the colorado river in all those extensional basins, and what are you going to match it with? There are no good matches of areas upstream (other than the bishop cng?)
Source: https://www.youtube.com/watch?v=CiyNnu5o0O4
Here’s another bullcrap paper on re-dating the Browns Park Fm with detridal zircon (write a rebuttal to this and the colorado river one..
