Geology of the Grand Canyon
The geology of the Grand Canyon is characterized primarily by one of the geologically from comprehensive rock sequences on the planet. Around 1.5 billion years of the geological development of this part of North America are exposed in the steep walls of the Grand Canyon . For the most part, these are sedimentary rocks . These are around 1200 to 250 million years old and thus cover a period of just under a billion years. If the metamorphic , mostly supracrustal rocks of the Vishnu Basement Rocks are included , then the geological tradition goes back as far as 1750 Ma BP . Most of the sediments have been deposited in warm shelf seas, mostly near the coast. In addition to rocks of marine origin, there are also terrestrial deposits, including dune sediments from a former desert landscape .
In the course of the Laramian mountain formation , which began around 75 million years ago, the Rocky Mountains , which are located much further east, were pushed upwards by steeply falling faults , but also in the vicinity of the Grand Canyon there was a widespread uplift. 17 million years ago ( Miocene ) the uplift process was accelerated and the Colorado Plateaus were formed , which frame the Grand Canyon. All in all, the area encompassing the Grand Canyon should have been pushed up by about 3000 meters; this allowed the forerunner of the current Colorado River to cut into the emerging plateau landscape. However, the actual canyon was not formed until 5.3 million years ago when the Gulf of California opened, reducing the Colorado's erosion base to sea level .
With the onset of the ice ages about 2.5 million years ago, there was an increase in the amount of precipitation and thus a significantly stronger erosion force of the Colorado; the current erosion base was almost reached 1.2 million years ago. The volcanism in the Uinkaret volcanic field , which started 2 million years ago, caused ash and lavas to be deposited. At least 13 lava flows dammed the Colorado River and huge lakes formed that were up to 600 meters deep and 160 kilometers long.
With almost 40 identified rock formations and 14 discordances (layer gaps), the Grand Canyon is one of the best-studied rock sequences in the world.
Polymetamorphic Basement Rocks - Vishnu Basement Rocks
The beginnings of the Vishnu Basement Rocks (Unit 1a in the picture opposite) go back to the Paleoproterozoic . In a backarc basin comparable to the Sea of Japan , a thick sediment package consisting of volcanic ash , clay , silt and sand was deposited between 1750 and 1740 million years BP . The sedimentary basin at that time was located between the continent Laurentia , further northwest of the continent , the forerunner of what is now the North American continent, and a volcanic arch of the island lying southeast , which probably resembled today's Japan .
The oldest radiometrically dated rock of the Vishnu Basement Rocks, however, is the Elves Chasm gneiss , a metamorphosed orthogneiss with a crystallization age of 1840 Ma BP. It shows affinities to the continental Mojave Terran and possibly formed the abutment of the sediment pile.
From 1740 Ma BP, the aforementioned island arc of the Yavapai Province began to collide with the Wyoming Craton in the north and the Mojave Terran in the west. This collision caused by plate tectonics compressed the intervening marine sediment stack and pushed it onto the continental margin of Laurentia. The climax of the dynamo metamorphosis was reached between 1706 and 1697 Ma BP, the accretion process, however, lasted up to 1650 Ma BP, with a second arch of the island added further to the southeast with the Mazatzal province.
The tectonically heavily stressed and metamorphosed sediments are now in the Inner Gorge at the bottom of the canyon. These are the dark, garnet-bearing and generally northeast-southwest trending shale rocks of the Vishnu Basement Rocks, to which the Vishnu Schist , the Brahma Schist and the Rama Schist belong. They are fossil, but occasionally contain marble lenses , which may be due to primitive algae colonies .
From 1740 Ma BP, the Vishnu Basement Rocks were penetrated by rising magma that came from a subduction zone upstream to the southeast. It gradually solidified into the present Zoroaster granite and several other plutons - light layers in the Vishnu Schist (Unit 1b). During these intrusions, however, the tectonic movements did not stop and so the granitic intrusions were later converted to gneiss in places.
The granite intrusions took place in several phases: three during the metamorphosis process of the Vishnu basement rocks between 1740 and 1660 Ma BP and the last before around 1400 Ma BP. This last phase was accompanied by major faults , trench-like fractures occurred on north-trending faults and perhaps even a partial rifting of the continent that was forming.
In the rocks of the Vishnu Basement Rocks, the traces of two mountain-forming events can be read - the Yavapai mountain formation followed by the Mazatzal mountain formation . The mountain ranges that were postponed in the process are likely to have been in no way inferior to the height dimensions of today's Himalayas . As the orogenic movements subsided, erosion started and over the next 400 million years reduced the former high mountains to a flat hilly landscape. What remained was an enormous angular discordance over the eroded mountain stump.
Meso- and Neoproterozoic Sediments - the Grand Canyon Supergroup
In the Mesoproterozoic there was a thinning of the continental crust , caused by the movement of a larger plate (or several small plates ) drifting away from Laurentia . In this expansion process, which should eventually lead to the Midcontinent Rift System around 1100 Ma BP , Laurentia almost broke - large intercontinental rift basins were created along which the sea penetrated. A shallow sea formed on Laurentia, stretching from Lake Superior to Glacier National Park in Montana to the Grand Canyon and the Uinta Mountains .
The sediments deposited during this marine incursion between 1200 and 825 Ma BP form the Grand Canyon Supergroup (Unit 2), which in turn is divided into two larger groups and is composed of nine quite different formations. Their total thickness of sediments and volcanic lava exceeds 3000 meters. It is exposed in places in the Inner Gorge and in some of the deeper side canyons.
The deepest section of the supergroup is the open marine Unkar Group (the geological term group encompasses two or more formations that are connected in a special way). It starts with the
- Bass formation , a gray colored dolomite formation around 1250 million years old . The lower lying Hotauta Conglomerate Member of the Bass Formation is the base conglomerate of the marine transgression from the west over the eroded basement stump , its pebbles were washed up by the surging waves of the slowly penetrating sea. The actual bass formation that follows is a shallow marine sediment close to the coast, which consists alternately of dolomite, sandstone and shale . Its thickness is between 35 and 100 meters. The first fossils are already appearing in it - stromatolites .
- It is followed by the approximately 1200 million year old Hakatai Shale . It is made up of thin- layer claystones , sandstones and shale of non-marine origin. The Hakatai Shale was deposited during a brief regression of the coastal fringe. Its orange to red color gave the Red Canyon its name.
- With the Shinumo Quartzite , full marine conditions were established again. It is an extremely resistant sandstone that was supposed to protrude from the Cambrian Sea like an island during the Cambrian . These islands withstood the surf for a long time; they were only covered with sediment much later, the sandstone was converted to quartzite .
- The Dox Sandstone is around 1190 million years old and is up to 985 meters thick. It is of shallow marine origin and contains intermediate claystone and slate clay layers. The appearance of ripple marks and other structures reveals its near-shore deposition conditions. Outcrops of this red to orange colored formation are located in the eastern sections of the canyon. Stromatolites and algae are found as fossils.
- The Cardenas Lava , the uppermost formation of the Unkar Group , then poured over the sediments that had previously accumulated . the dark brown lava was extruded on the surface, it has a basaltic composition and was dated from 1103 to 1070 Ma BP. It consists of 10 to 12 individual lava flows and reaches a thickness of 300 meters. Basaltic tunnels and corridors that penetrate the lower strata of the Unkar Group are likely to be genetically related to the Cardenas Lava.
This is followed by the 1050 million year old Nankoweap Formation , which does not belong to either of the two groups. It consists of coarse-grained sandstone of shallow marine origin that was deposited along a transgression discordance over the Cardenas Lava. The Nankoweap Formation is only exposed in the eastern part of the canyon. it ends with a hiatus, a geological gap in the layer.
- The Chuar Group starts with the green colored Galeros Formation , which consists of an alternation of sandstone, limestone and shale. Some of the slate layers are colored, the hues vary from red to purple. Stromatolites also occur in the Galeros Formation.
- The overlying Kwagunt formation consists of black shale and red to purple colored clay stones, limestone is subordinate. Isolated red sandstone pockets can be found on the carbon butte. Stromatolites also occur in the Kwagunt Formation.
- The sixtymile formation follows at the end . It consists largely of brown sandstone that contains little slate.
In the Grand Canyon mountain formation , which took place at around 800 Ma BP , the Grand Canyon Supergroup was adjusted by 15 ° and broken into individual clods. This fracture tectonics mainly took place on north-south trending faults and created a rocky rock formation. In the following 100 million year interval, most of the Chuar Group and part of the Unkar Group were eroded again, with the erosion reaching down to the Shinumo Quartzite in places (see above). The chains of broken clods were leveled, and in places the entire Grand Canyon Supergroup was eroded away, so that the Vishnu Basement Rocks underneath come to the fore again.
John Wesley Powell called this phenomenon Great Unconformity - one of the world's best examples of an enormous angle discordance . A total of 250 million years of regional geological history were lost in it.
The Great Canyon Supergroup and the Great Unconformity are easy to see in the eastern part of the Inner Gorge.
Cambrian - Tonto Group
- Below is the 545 million year old Tapeats Sandstone . This dark brown, thin-layer sandstone formation consists of medium to coarse-grained sands and conglomerates that originate from the surf area (unit 3a). Ripple marks are often found in the upper layers of the stratum, while brachiopods and crawling tracks of trilobites are fossil preserved in Tapeats Sandstone. The formation reaches a thickness of 75 to 90 meters, it is resistant to weathering and therefore forms steep walls in the Grand Canyon.
- The transgressive base unit of the Tapeat Sandstone is followed by the approximately 530 million year old Bright Angel Shale , a shale in which subordinate layers of sandstone, marl and thin dolomite are embedded. It was deposited as mud not far from the coast and contains brachiopods, trilobites and worm tracks (Unit 3b). The Bright Angel Shale reaches a thickness of 100 to 120 meters, is usually greenish in color with brownish and gray interlayers. It weathers very easily and therefore forms gently sloping slopes over the steep walls of the Tapeats Sandstone.
- Finally, the approximately 515 million year old Muav Limestone (unit 3c), which consists of gray, thin-banked limestone. It was deposited in deeper, more coastal areas and is relatively poor in fossils, only a few brachiopods and trilobites are found. Its thickness fluctuates very strongly (between 250 and 375 meters), in the western part of the Grand Canyon it is much more powerful than in the eastern part. The Muav Limestone also forms steep walls.
The three formations of the Tonto Group were deposited over a period of around 30 million years (Lower Cambrian-Middle Cambrian). Trilobites and worm burrows are relatively common in these sediments. The sedimentological sequence documents a gradual transgression from the west onto the Transcontinental Arch , the southern foothills of what was then the North American continent. The Tonto Group now forms the so-called Tonto Platform above the Colorado River. In contrast to the Grand Canyon Supergroup, its layer members lie horizontally and in their original position. The slope-forming Bright Angel Shale in the Tonto Platform is a good water reservoir , groundwater remains in the Muav Limestone above and then escapes at several springs in the Inner Gorge - vital in this arid landscape.
Lower Devon to Upper Carboniferous - Temple Butte Formation, Redwall Limestone and Surprise Canyon Formation
The next two periods of the geological timescale , the Ordovician and the Silurian , left no debris in the Grand Canyon. It is not clear whether sediments were sold during this period and then eroded away again or whether sedimentation had ever occurred at all. Anyway, the hiatus lasted around 165 million years.
What is certain is that during this period deep gullies were cut into the surface of the Muav Limestone. The cause of this is very likely river erosion, but submarine currents are also conceivable. From around 350 Ma BP these depressions were then filled again in the Central Devon . It formed the
- Temple Butte Formation (also known as Temple Butte Limestone - Unit 4a), the total thickness of which varies between 80 and 120 meters. The purple-colored channel backfills consist of freshwater lime and can be seen well in the Marble Canyon in the eastern part of the national park . In the western part of the park, the limestone changes into a very resistant gray to cream-colored dolomite that forms steep walls. Vertebrate finds have been made, in the eastern part bone plates of freshwater fish, in the western part numerous marine fish. The Temple Butte formation ends in a discordance.
- The next formation in the Grand Canyon sedimentary sequence is the 140 to 160 meter thick Redwall Limestone (Unit 4b). It consists of thick, dark brown to blue-gray limestone and dolomites with embedded chert tubers . The Redwall Limestone formed about 335 million years ago (Lower to Middle Lower Carboniferous) in a receding tropical sea near the equator. It contains petrified crinoids , brachiopods , bryozoans , horn corals , nautiloids and sponges , as well as trilobites and other marine organisms. The limestone or dolomite rock is quite massive, sometimes forming overhanging steep walls, rock arches and caves. After the Redwall Limestone was deposited, the Grand Canyon area was slowly uplifted so that the upper parts were eroded again in places during the Upper Lower Carboniferous. The red color of the rock is purely external, it comes from the overlying red sediments of the Supai Group and the Hermit Shale.
- The Surprise Canyon Formation consists of reddish-purple clay slates that stand in disjointed layers over the Redwall Limestone (Unit 4c). They were formed in the tidal area of estuaries during the very late Lower Carboniferous, possibly also during the very early Upper Carboniferous. In isolated sediment lenses, it reaches a thickness of up to 12 meters. The Surprise Canyon formation was only discovered in the 1980s and can only be approached by helicopter. Above it is a discordance that has removed most of its former stratification and exposed the Redwall Limestone below.
Upper Carboniferous to Lower Permian - Supai Group
The Supai Group is predominantly of siliciclastic origin and was deposited in swamps and floodplains during the Upper Carboniferous and Lower Permian; its mean age is 285 million years BP. Limes also appear in the western part of the national park - an indication of a warm shallow sea. The sedimentation area in the eastern part may have been a muddy river delta. It essentially consists of red siltstones and shale, overlaid with brownish sandstones. Their overall thickness varies between 180 and 210 meters. The sub-permeable slate layers have been oxidized to a bright red shade . In the eastern part of the park, fossil footprints of amphibians have been preserved, and fossils of reptiles and plants can also be found (very common). In the western part, however, fossils of marine origin predominate. The Supai Group is made up of the following formations (from old to young):
- Watahomigi Formation (Unit 5a): A slope-forming gray limestone formation in which chert bands, sandstone layers and a purple layer of silestone are interposed. It becomes 30 to 50 meters thick.
- Manakacha Formation (Unit 5b): It consists of pale red resistant sandstone and red slope-forming slate, its thickness varies between 60 and 85 meters.
- Wescogame Formation (Unit 5c): A pale red resistant sandstone, which alternates with a pale red slope-forming siltstone, the thickness is between 30 and 70 meters. At the top finally follows the
- Esplanade Formation (Unit 5d): In its sedimentological structure, it is a repetition of the Wescogame Formation, only twice as thick (70 to 90 meters).
Each of these formations is closed by a discordance.
Permian - Hermit Shale, Coconino Sandstone, Toroweap Formation, and Kaibab Limestone
- Like the Supai Group before, the Hermit Shale, which is 265 million years old on average, was deposited in a swampy environment (unit 6a). It is made up of thin-bank, iron oxide-containing alternating layers of slate and siltstone ; the sediments were transported by rivers into a semi-arid basin. The deep red sediment package, between 49 and 53 meters thick, is very soft and therefore forms slopes in the canyon. The receding erosion in the Hermit Shale often undermines the layer associations above, so that house-sized blocks detach from their association and fall down onto the Tonto Platform. The Hermit Shale also contains fossils - wing insects, cone-bearing plants and ferns have been found so far. The formation also ends with a discordance.
- The following Coconino Sandstone (Unit 6b) reflects continental, desert-like environmental conditions. The sandstone was formed around 260 million years ago when dunes consisting of pure quartz sand gradually penetrated into expanding desert areas. The thickness of the sandstone formation varies between 115 and 200 meters and forms white to cream-colored steep walls below the canyon rim. In the fossilized former sand dunes, aeolian (wind-generated) sloping layers can be seen, the dune bodies themselves are made up of myriads of opaque, rounded and well-sorted grains of sand. They also contain fossilized tracks of arthropods and first reptiles as well as their structures. Here, too, there is a discordance.
- Above it lies the 60 to 75 meter thick and approximately 250 million year old Toroweap Formation (unit 6c). It is made up of red and yellow colored sandstone and gray marly limestone containing layers of gypsum . The calcareous sediments come from a warm shallow sea, they reflect oscillating sea levels and in general the slow return to marine conditions. Fossil contents are brachiopods, corals , mollusks and various land plants. The Toroweap Formation comprises the following layers (from old to young):
- Seligman Member : A slope-forming yellowish to reddish sandstone or siltstone.
- Brady Canyon Member : A resistant, steep wall-forming gray limestone with activated chert lenses.
Wood Ranch Member : A slope-forming pale red and gray colored siltstone or dolomitic sandstone.
A discordance ends the formation.
- At the edge of the canyon, finally, the massive, sheer wall-forming, 80 to 110 meter thick Kaibab Limestone (unit 6d). This cream-colored to gray-white limestone formation was formed around 225 million years ago (Middle Permian) in the deeper areas of a warm shallow sea that had already transgressed during the Toroweap Formation. Normally, the Kaibab Limestone is followed by sandy lime on a basal sandstone layer, which, however, can also be replaced by sandstone and clay slate in places in the upper section. At fossils were shark teeth and numerous marine invertebrates such. B. Brachiopods, corals, mollusks, sea lilies and worms found. The Kaibab Limestone covers large parts of the Kaibab Plateau north of the Grand Canyon and the immediately southern Coconino Plateau . This formation is also bound by a discordance.
With the beginning of the Mesozoic Era, uplift began in the area of the Grand Canyon, the dry landscape was again crossed by rivers. Sediment from the nearby hinterland was deposited in wide, deep valleys during the Triassic and created the Moenkopi Formation , which is up to 300 meters thick . It consists of sandstone and slate with layers of plaster in between. The formation is very unstable to weathering and therefore only occurs very sporadically. It is open along the Colorado River in Marble Canyon , on Cedar Mountain , a mesa in the southeast part of the national park and on Red Butte south of Grand Canyon Village . Remains of the Shinarump Conglomerate , a conglomerate that belongs to the Chinle Formation , and a much younger lava flow follow on the Red Butte above the Moenkopi Formation .
During the Mesozoic and the Cenozoic , rock formations over 1,500 meters thick were sedimented in the area of the Grand Canyon, but these were mostly cleared out again by the subsequent erosion in this sector (see following section). Further details can also be found under Geology of Zion National Park and Geology of Bryce Canyon . These layer sequences, which were lost in the Grand Canyon, have been preserved in the so-called Grand Staircase further north and are excellently exposed.
Formation of the Grand Canyon
Uplift and nearby crustal expansion
The Laramian orogeny covered all of western North America and thus contributed significantly to the formation of the Rocky Mountains and the American Cordillera . The orogenic movements began at the end of the Mesozoic around 72 Ma BP and lasted into the earliest Tertiary, i.e. into the Paleogene . A second phase of uplift occurred before 17 million years ago in the Lower Miocene and created the Colorado Plateau (the Colorado Plateau are north of the Grand Canyon, the Kaibab- , Kanab- and Shivits plateau and in the south the Cococino Plateau ). Strangely enough, the strata in the Colorado Plateau remained relatively undisturbed during these two uplift processes and also retained its originally horizontal storage conditions, although it was raised up to 2,700 meters. An attempt to explain it helps to make a clockwise rotation of the plateau crust block, which supposedly kept its stability. Before the uplift, the plateau was only about 300 meters above sea level and was surrounded by high mountain ranges in the south and west.
At about the same time as the second uplift phase, strong crust expansion occurred about 20 Ma BP, old, already existing faults were revived and new fractures were created. This process was accompanied by relatively moderate volcanic activity . Further to the west, however, the effects of the crustal expansion were enormous: the Basin and Range Province emerged - a rift system that differentiated itself into long-drawn fault zones facing north-south into standing clumps (the current mountain ranges) and sacked trenches (the current basin landscapes) allowed a crust elongation of over 100%. The Grand Wash Fault at the west end of Grand Canyon National Park is already under the Basin and Range Province's sphere of influence.
The newly formed Colorado River begins its erosion work
Continuous tectonic movements in the area of the Colorado Plateau created large-scale monoclinal folds in the cover layers and led to a significant gain in height, which caused the flow gradient of the waters in the region to rise sharply. The primeval Colorado River was an inland river with no access to the sea until about 5.3 million years ago . At that time it ended in large inland lakes - in the early Tertiary still within the Colorado Plateau and in the middle Tertiary then in the area of the Basin and Range Province. The great monoclinal fold of the Kaibab Arch gradually began to bulge out six million years ago. According to one hypothesis, this obstacle in the course of the Colorado River was overcome by both a canyon coming from the east and a canyon coming from the west simultaneously eroding and then receding. The other possibility, of course, is that the river behaved in an antecedent manner to the slowly rising obstacle.
The opening of an arm of the Gulf of California 5.3 million years ago changed the direction of flow of the surrounding waters towards the sinking and collapsing rift. The elevation of the catchment areas on the upper reaches and the lowering of the lower reaches of the rivers that flow into the Gulf of California led to a greater gradient and increased erosion , so that the rivers could dig into the landscape more quickly. As a result of regressive erosion, the catchment areas of several rivers were united in a geologically short period of time to form one main drain, today's Colorado River. The most important phase occurred when a separate older river, which drained through the San Andreas Trench into the Gulf of California, seized the Colorado River, which at the time was still an inland river. The cutting of the eastern part of the Colorado River had begun earlier, but was then greatly accelerated and extended to the west.
With the beginning of the ice ages 2.5 million years ago BP in the Pleistocene , the climate in the region became much cooler and more humid. The additional amounts of precipitation caused higher runoff and greater erosion due to increased spring melt water and flash floods in summer. Due to the higher volume, the steeper gradient and the lower erosion base, the river cut into the landscape much faster from two million years BP onwards and almost reached its current depth around 1.2 million years ago.
Volcanic activity dammed the river in the new canyon
During the Quaternary about 725,000 years ago BP, basaltic lava poured into the western Grand Canyon. It came from the erupted ash cones of the Uinkaret volcanic field . In the period between 725,000 and 100,000 years BP, the river was dammed several times. The duration of these huge reservoirs is controversial, often assumed to be 20,000 years, but other researchers doubt this, believing that the volcanic dams were not too long and that if they gave way caused catastrophic floods. The extent of the lava flows themselves is considerable, from river mile 178 they follow the course of the Colorado River for over 121 kilometers!
Actuogeology, anthropogenic influences and the future
With the end of the Ice Age in the Pleistocene and the beginning of the Holocene , the change from a damp and cold climate to the current drier conditions began. The erosive activity of the river decreased due to the lower rainfall and the rocks of the Inner Gorge are more resistant to the current flow rates. Mass movements such as B. landslides therefore gained importance in terms of erosion. This created steeper side walls and the Grand Canyon and its tributaries widened.
Today the construction of dams, such as the Glen Canyon Dam , leads to a further reduction in erosion. Dams reduce the flow speed, at the same time the water flows through the gorge much more evenly. The river also loses its erosive grinding effect due to the reduced sediment load. The additional extraction of water for drinking water supply and for irrigation means that the Colorado River no longer reaches its delta in the Gulf of California in dry years .
The dam has also changed the properties of the river water. If the water was previously muddy and rather warm and thus offered a habitat for fish at the bottom of the water, the river is now rather clear and cold, which created a livelihood for the trout used . This also had an influence on the migration behavior of the bald eagles , which originally used the canyon as a stopover on the way to the fishing grounds downstream, but now use the canyon as a source of food.
During the 1990s, about 45 earthquakes occurred in and around the Grand Canyon , five of which reached an intensity between 5.0 and 6.0 on the Richter scale . Dozens of faults cross the canyon, and many of them have been seismically active for the past hundred years.
The slope of the Colorado River is steep enough to allow another 400 to 600 meters of erosion work. A further elevation of the environment in the geological future has not been taken into account. The human influence is likely to have a slowing effect on the erosion force of the Colorado River.
- WS Baldridge: Geology of the American Southwest. Cambridge University Press, 2004.
- B. Bronze: The Colorado River Super Guide Map of the Grand Canyon. Dragon Creek Publishing, Flagstaff, Arizona 1990
- A. Foos: Geology of Grand Canyon National Park. North Rim 1999. ( online (PDF; 1.5 MB), accessed August 11, 2008)
- AG Harris et al. a .: Geology of National Parks. 5th edition. Hunt Publishing, Kendall, Iowa 1997.
- EP Kiver u. a .: Geology of US Parklands. 5th edition. John Wiley & Sons, New York 1999, ISBN 0-471-33218-6 .
- JL Powell: Grand Canyon: Solving Earth's Grandest Puzzle. Pi Press, 2005, ISBN 0-13-147989-X .
- R. Ribokas: Grand Canyon Rock Layers. Grand Canyon Explorer. 2000. ( online , accessed March 20, 2005)
- C. Rudd: Grand Canyon: The Continuing Story. KC Publishing, 1990, ISBN 0-88714-046-7 .
- LS Tufts: Secrets in The Grand Canyon, Zion and Bryce Canyon National Parks. 3. Edition. National Photographic Collections, North Palm Beach, Florida 1998, ISBN 0-9620255-3-4 .
References and footnotes
- For comparison: the age of the earth is approx. 5.9 billion years
- Geology of US Parklands. P 398.
- Pages of Stone: Geology of the Grand Canyon & Plateau Country National Parks & Monuments. P. 100.
- The Geology of the Grand Canyon: When did this all happen? and Grand Canyon Rock Layers , Kaibab.org
- Geology of National Parks. P. 11 and Geology of US Parklands. P. 399.
- The Geology of the Grand Canyon: When did this all happen? , Kaibab.org
- Grand Canyon Rock Layers , Kaibab.org
- Geology of Grand Canyon National Park (PDF; 1.5 MB) National Park Service. P. 23, 3. Archived from the original on October 10, 2008. Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. Retrieved January 4, 2007.
- Archive link ( Memento of the original from October 10, 2008 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- Geology of US Parklands. P. 405.
- The Geology of the Grand Canyon: Why does it look like it does? , Kaibab.org
- Geology of US Parklands. P. 407.
- K. Karlstrom, R. Crow, L. Peters, W. McIntosh, J. Raucci, L. Crossey, P. Umhoefer: 40Ar / 39Ar and field studies of Quaternary basalts in Grand Canyon and model for carving Grand Canyon: Quantifying the interaction of river incision and normal faulting across the western edge of the Colorado Plateau. In: GSA Bulletin. Vol. 119, No. 11/12, 2007, pp. 1283-1312.
- WK Hamblin: Late Cenozoic lava dams in the western Grand Canyon. In: Geological Society of America Memoir. 183, 1994.
- CR Fenton, RJ Poreda, BP Nash, RH Webb, TE Cerling: Geochemical discrimination of five Pleistocene lava-dam outburst-flood deposits, western Grand Canyon, Arizona. In: The Journal of Geology. Vol. 112, 2004, pp. 91-110, doi : 10.1086 / 379694 .
- George H. Billingsley: Geologic Map of the Grand Canyon 30 'by 60' Quadrangle, Coconino and Mohave Counties, Northwestern Arizona US Geological Survey Geologic Investigation, 2000.
- United States Geological Survey
- Jack Share: The Great unconformity of the Grand Canyon and the Late Proterozoic-Cambrian Time Interval: Part I - Defining It (English)