scholarly journals Realignments of the Colorado River by ~2 m.y. of rotational bedrock landsliding: The Surprise Valley landslide complex, Grand Canyon, Arizona

Geosphere ◽  
2021 ◽  
Author(s):  
Jesse E. Robertson ◽  
Karl E. Karlstrom ◽  
Matthew T. Heizler ◽  
Laura J. Crossey
Keyword(s):  
Cross Sections ◽  
Colorado River ◽  
Grand Canyon ◽  
Geologic Mapping ◽  
River Level ◽  
The Past ◽  
The North ◽  
Seismic Triggering ◽  
Depositional Age ◽  
Deer Creek

The Surprise Valley landslide complex is the name used here for a group of prominent river-damming landslides in Grand Canyon (Arizona, USA) that has shifted the path of the Colorado River several times in the past 2 m.y. We document a sequence of eight landslides. Three are Toreva-block landslides containing back-rotated but only mildly disrupted bedrock stratigraphy. The largest of these landslides, Surprise Valley landslide, is hypothesized to have dammed the Colorado River, cut off a meander loop through Surprise Valley, and rerouted the river 2.5 km south to near its present course at the Granite Narrows. Another bedrock landslide, Poncho’s runup, involved a mass detachment from the north side of the river that drove a kilometer-scale bedrock slab across the river and up the south canyon wall to a height of 823 m above the river. A lake behind this landslide is inferred from the presence of mainstem gravels atop the slide that represent the approximate spillway elevation. We postulate that this landslide lake facilitated the upriver 133 Mile slide detachment and Toreva block formation. The other five landslides are subsequent slides that consist of debris from the primary slides; these also partially blocked and diverted the Colorado River as well as the Deer Creek and Tapeats Creek tributaries into new bedrock gorges over the past 1 m.y. The sequence of landslides is reconstructed from inset relationships revealed by geologic mapping and restored cross-sections. Relative ages are estimated by measuring landslide base height above the modern river level in locations where landslides filled paleochannels of the Colorado River and its tributaries. We calculate an average bedrock incision rate of 138 m/m.y. as determined by a 0.674 ± 0.022 Ma detrital sanidine maximum depositional age of the paleoriver channel fill of the Piano slide, which has its base 70 m above the river level and ~93 m above bedrock level beneath the modern river channel. This date is within error of, and significantly refines, the prior cosmogenic burial date of 0.88 ± 0.44 Ma on paleochannel cobbles. Assuming steady incision at 138 m/m.y., the age of Surprise Valley landslide is estimated to be ca. 2.1 Ma; Poncho’s runup is estimated to be ca. 610 ka; and diversion of Deer Creek to form modern Deer Creek Falls is estimated to be ca. 400 ka. The age of the most recent slide, Backeddy slide, is estimated to be ca. 170 ka based on its near-river-level position. Our proposed triggering mechanism for Surprise Valley landslides involves groundwater saturation of a failure plane in the weak Bright Angel Formation resulting from large volumes of Grand Canyon north-rim groundwater recharge prior to establishment of the modern Deer, Thunder, and Tapeats springs. Poncho’s and Piano landslides may have been triggered by shale saturation caused by 600–650 ka lava dams that formed 45 river miles (73 river km; river miles are measured along the Colorado River downstream from Lees Ferry, with 1 river mile = 1.62 river kms) downstream near Lava Falls. We cannot rule out effects from seismic triggering along the nearby Sinyala fault. Each of the inferred landslide dams was quickly overtopped (tens of years), filled with sediment (hundreds of years), and removed (thousands of years) by the Colorado River, as is also the potential fate of modern dams.

scholarly journals Will Earth’s Grandest Canyon Keep Getting Grander?

Eos ◽  
2019 ◽  
Vol 100 ◽  
Author(s):  
Mary Morton
Keyword(s):  
Colorado River ◽  
Grand Canyon ◽  
Geologic Time ◽  
The Past

Living in Geologic Time: Rafting through the past, present, and future of the Colorado River and the Grand Canyon.

scholarly journals Insights into post-Miocene uplift of the western margin of the Colorado Plateau from the stratigraphic record of the lower Colorado River

Geosphere ◽  
2019 ◽  
Vol 15 (6) ◽  
pp. 1826-1845 ◽  
Author(s):  
Ryan S. Crow ◽  
Keith A. Howard ◽  
L. Sue Beard ◽  
Philip A. Pearthree ◽  
P. Kyle House ◽  
...  
Keyword(s):  
Sea Level ◽  
Colorado River ◽  
Grand Canyon ◽  
Lake Mead ◽  
Basalt Flow ◽  
Data Set ◽  
Continental Scale ◽  
The Past ◽  
River Deposits ◽  
Lower Colorado River

Abstract The spatial and temporal distribution of Pliocene to Holocene Colorado River deposits (southwestern USA and northwestern Mexico) form a primary data set that records the evolution of a continental-scale river system and helps to delineate and quantify the magnitude of regional deformation. We focus in particular on the age and distribution of ancestral Colorado River deposits from field observations, geologic mapping, and subsurface studies in the area downstream from Grand Canyon (Arizona, USA). A new 4.73 ± 0.17 Ma age is reported for a basalt that flowed down Grand Wash to near its confluence with the Colorado River at the eastern end of what is now Lake Mead (Arizona and Nevada). That basalt flow, which caps tributary gravels, another previously dated 4.49 ± 0.46 Ma basalt flow that caps Colorado River gravel nearby, and previously dated speleothems (2.17 ± 0.34 and 3.87 ± 0.1 Ma) in western Grand Canyon allow for the calculation of long-term incision rates. Those rates are ∼90 m/Ma in western Grand Canyon and ∼18–64 m/Ma in the eastern Lake Mead area. In western Lake Mead and downstream, the base of 4.5–3.5 Ma ancestral Colorado River deposits, called the Bullhead Alluvium, is generally preserved below river level, suggesting little if any bedrock incision since deposition. Paleoprofiles reconstructed using ancestral river deposits indicate that the lower Colorado River established a smooth profile that has been graded to near sea level since ca. 4.5 Ma. Steady incision rates in western Grand Canyon over the past 0.6–4 Ma also suggest that the lower Colorado River has remained in a quasi–steady state for millions of years with respect to bedrock incision. Differential incision between the lower Colorado River corridor and western Grand Canyon is best explained by differential uplift across the Lake Mead region, as the overall 4.5 Ma profile of the Colorado River remains graded to Pliocene sea level, suggesting little regional subsidence or uplift. Cumulative estimates of ca. 4 Ma offsets across faults in the Lake Mead region are similar in magnitude to the differential incision across the area during the same approximate time frame. This suggests that in the past ∼4 Ma, vertical deformation in the Lake Mead area has been localized along faults, which may be a surficial response to more deep-seated processes. Together these data sets suggest ∼140–370 m of uplift in the past 2–4 Ma across the Lake Mead region.

scholarly journals Cenozoic incision history of the Little Colorado River: Its role in carving Grand Canyon and onset of rapid incision in the past ca. 2 Ma in the Colorado River System

Geosphere ◽  
2016 ◽  
Vol 13 (1) ◽  
pp. 49-81 ◽  
Author(s):  
K.E. Karlstrom ◽  
L.J. Crossey ◽  
E. Embid ◽  
R. Crow ◽  
M. Heizler ◽  
...  
Keyword(s):  
Colorado River ◽  
Grand Canyon ◽  
River System ◽  
The Past ◽  
History Of

Ice over Fire: Glaciers Carve the Landscape

2000 ◽  
Author(s):  
Robert B. Smith ◽  
Lee J. Siegel
Keyword(s):  
Grand Canyon ◽  
Ice Age ◽  
Yellowstone Lake ◽  
The Past ◽  
North East ◽  
The North ◽  
Jackson Hole ◽  
Teton Range ◽  
Continental Ice Sheets ◽  
Glacial Periods

Yellowstone, the Tetons, and Jackson Hole were shaped by multiple catastrophes. Huge volcanic eruptions and powerful earthquakes played major roles. Finishing touches were added by another kind of calamity: A rare global Ice Age produced gigantic glaciers that buried the landscape with ice two-thirds of a mile thick in places. The glaciers carved mountains, canyons, and lake basins. They dumped large piles of debris and redirected the flow of rivers. The Yellowstone—Teton region is a world-class example of how land was reshaped by glaciers during what is known as the Pleistocene Ice Age. The Ice Age was not a single glacial period, but many intermittent cold spells interspersed with warmer periods during which the ice melted. The timing of major glacial periods is notoriously uncertain. Although continental ice sheets did not quite reach as far south as Yellowstone, a regional icecap and large glaciers covered the Yellowstone—Teton country during three major episodes of at least the past 300,000 years—and perhaps the past 2 million years. The last of these big glaciers retreated about 14,000 years ago, although some argue they did not recede until 10,000 to 12,000 years ago. Today, small glaciers in the Teton Range are found only above 10,000 feet. During each major episode, most of Yellowstone National Park was buried beneath an icecap as much as 3,500 feet thick, among the largest in the ancient Rocky Mountains. Gigantic masses of ice flowed down from the high Yellowstone Plateau, carving and scouring the Earth’s surface, diverting and damming rivers into their present forms, steepening mountain fronts, and deepening lakes. The ice helped sculpt the Grand Canyon of the Yellowstone. More than anything, the thick ice scraped Yellowstone’s volcanic topography, further smoothing the plateau and helping to excavate the basin occupied by Yellowstone Lake. Jackson Hole became a rendezvous of glaciers converging from the north, north-east, and west. Ice up to 2,000 feet thick scooped out the valley floor. The glaciers left tall ridges of rocky debris now covered by lush conifer forests. Such ridges, called moraines, helped shape Jackson Lake.

Numerical Ages of Holocene Tributary Debris Fans Inferred from Dissolution Pitting on Carbonate Boulders in the Grand Canyon of Arizona

1998 ◽  
Vol 50 (2) ◽  
pp. 139-147 ◽  
Author(s):  
Richard Hereford ◽  
Kathryn S. Thompson ◽  
Kelly J. Burke
Keyword(s):  
Debris Flow ◽  
Colorado River ◽  
Grand Canyon ◽  
Linear Rate ◽  
Blue Green Algae ◽  
Relative Age ◽  
The Past ◽  
Pit Depth ◽  
Flow Activity ◽  
Depth Ranges

Carbonate boulders transported down steep tributary channels by debris flow came to rest on Holocene debris fans beside the Colorado River in Grand Canyon National Park. Weakly acidic rainfall and the metabolic activity of blue-green algae have produced roughly hemispheric dissolution pits as much as 2-cm deep on the initially smooth surfaces of the boulders. The average depth of dissolution pits increases with relative age of fan surfaces. The deepening rate averages 2.4 mm/1000 yr (standard error = 0.2 mm/1000 yr), as calculated from several radiometrically dated surfaces and an archeological structure. This linear rate, which appears constant over at least the past 3000 yr, is consistent with field relations limiting the maximum age of the fans and with the physical chemistry of limestone dissolution. Dissolution-pit measurements ( n= 6973) were made on 617 boulders on 71 fan surfaces at the 26 largest debris fans in Grand Canyon. Among these fan surfaces, the average pit depth ranges from 1.2 to 17.4 mm, and the resulting pit dissolution ages range from 500 to 7300 cal yr B.P. Most (75%) surfaces are younger than 3000 yr, probably because of removal of older debris fans by the Colorado River. Many of the ages are close to 800, 1600, 2300, 3100, or 4300 cal yr B.P. If not the result of differential preservation of fan surfaces, this clustering implies periods of heightened debris-flow activity and increased precipitation.

The Pleistocene Succession in the Lower parts of the Thames Valley

1936 ◽  
Vol 2 (1-2) ◽  
pp. 52-76 ◽  
Author(s):  
W. B. R. King ◽  
K. P. Oakley
Keyword(s):  
Cross Sections ◽  
Present Knowledge ◽  
Present Communication ◽  
River Level ◽  
Main Valley ◽  
The North ◽  
Composite Section ◽  
The One ◽  
North And South ◽  
As If

The object of the present communication is to demonstrate the relationships which, in the light of present knowledge, appear to exist between the various Pleistocene and Holocene deposits in the Lower and Middle Thames Valley. For this purpose two cross-sections of the valley have been drawn indicating the relative positions of the deposits which occur at various localities as though they were all present in two localities, one in the Lower, and one in the Middle Thames.As many of the more important deposits in the Lower Thames are represented to the north and south of the river in the Dartford area, we have drawn the one section as if our ideal locality occurred in that neighbourhood. In this section, therefore, the relative altitudes of the various beds above and below present river level are those which are found in that part of the Thames basin. In tributary valleys, or in other parts of the main valley these altitudes are not of course necessarily maintained. In cases where deposits belonging to a particular stage have not been preserved in the Dartford area, but occur in a neighbouring part of the valley, or in a tributary valley, their position in the composite section has been roughly gauged by a process of extrapolation. Similarly when dealing with the Middle Thames, we have drawn our ideal section as though all the deposits occurred in one section of the valley in the neighbourhood of Iver.

scholarly journals Detrital sanidine 40Ar/39Ar dating confirms <2 Ma age of Crooked Ridge paleoriver and subsequent deep denudation of the southwestern Colorado Plateau

Geosphere ◽  
2021 ◽  
Vol 17 (2) ◽  
pp. 438-454
Author(s):  
Matthew T. Heizler ◽  
Karl E. Karlstrom ◽  
Micael Albonico ◽  
Richard Hereford ◽  
L. Sue Beard ◽  
...  
Keyword(s):  
Colorado River ◽  
Grand Canyon ◽  
San Juan ◽  
Potential Importance ◽  
Late Oligocene ◽  
San Juan Mountains ◽  
Black Mesa ◽  
Younger Age ◽  
San Juan River ◽  
Depositional Age

Abstract Crooked Ridge and White Mesa in northeastern Arizona (southwestern United States) preserve, as inverted topography, a 57-km-long abandoned alluvial system near the present drainage divide between the Colorado, San Juan, and Little Colorado Rivers. The pathway of this paleoriver, flowing southwest toward eastern Grand Canyon, has led to provocative alternative models for its potential importance in carving Grand Canyon. The ∼50-m-thick White Mesa alluvium is the only datable record of this paleoriver system. We present new 40Ar/39Ar sanidine dating that confirms a ca. 2 Ma maximum depositional age for White Mesa alluvium, supported by a large mode (n = 42) of dates from 2.06 to 1.76 Ma. Older grain modes show abundant 37–23 Ma grains mostly derived ultimately from the San Juan Mountains, as is also documented by rare volcanic and basement pebbles in the White Mesa alluvium. A tuff with an age of 1.07 ± 0.05 Ma is inset below, and hence provides a younger age bracket for the White Mesa alluvium. Newly dated remnant deposits on Black Mesa contain similar 37–23 Ma grains and exotic pebbles, plus a large mode (n = 71) of 9.052 ± 0.003 Ma sanidine. These deposits could be part of the White Mesa alluvium without any Pleistocene grains, but new detrital sanidine data from the upper Bidahochi Formation near Ganado, Arizona, have similar maximum depositional ages of 11.0–6.1 Ma and show similar 40–20 Ma San Juan Mountains–derived sanidine. Thus, we tentatively interpret the &lt;9 Ma Black Mesa deposit to be a remnant of an 11–6 Ma Bidahochi alluvial system derived from the now-eroded southwestern fringe of the San Juan Mountains. This alluvial fringe is the probable source for reworking of 40–20 Ma detrital sanidine and exotic clasts into Oligocene Chuska Sandstone, Miocene Bidahochi Formation, and ultimately into the &lt;2 Ma White Mesa alluvium. The &lt;2 Ma age of the White Mesa alluvium does not support models that the Crooked Ridge paleoriver originated as a late Oligocene to Miocene San Juan River that ultimately carved across the Kaibab uplift. Instead, we interpret the Crooked Ridge paleoriver as a 1.9–1.1 Ma tributary to the Little Colorado River, analogous to modern-day Moenkopi Wash. We reject the “young sediment in old paleovalley” hypothesis based on mapping, stratigraphic, and geomorphic constraints. Deep exhumation and beheading by tributaries of the San Juan and Colorado Rivers caused the Crooked Ridge paleotributary to be abandoned between 1.9 and 1.1 Ma. Thermochronologic data also provide no evidence for, and pose substantial difficulties with, the hypothesis for an earlier (Oligocene–Miocene) Colorado–San Juan paleoriver system that flowed along the Crooked Ridge pathway and carved across the Kaibab uplift.

Interrogating the Constitutionality of Federal Character Principle in Nigeria

2018 ◽  
Vol 9 (07) ◽  
pp. 20492-20498
Author(s):  
Aborisade Olasunkanmi ◽  
Christopher Agulanna
Keyword(s):  
Ethnic Groups ◽  
Research Work ◽  
National Unity ◽  
The Past ◽  
The North ◽  
Inhibiting Factors

This work interrogates federal character principle (FCP) in Nigeria. The FCP was designed to fundamentally address the striking features of Nigeria politics of intense struggles for power among the different ethnic groups in the country between the elites from the North and their Southern counterparts and the various segments, but the practice of FCP in Nigeria so far raises curiosity and doubts. Given the outcome of the interrogation, this research work discovered and conclude that federal character has not indeed achieve its objective in the Nigeria, the study finds that Ethnocentrism, Elitism, Mediocrity, Mutual suspicion amongst others accounts for some inhibiting factors of the FCP in Nigeria. Like many other provisions of the Constitution, the Federal Character principle was meant to correct some imbalances experienced in the past, but it has created more problems than it has attempted to solve. Rather than promote national unity, it has disunited Nigerians. There is an urgent need to use more of professionals and result oriented Nigerians to carry out national tasks, than to use unprogressive people due to this "Federal character" issue. Nigeria should be a place where one's track records and qualifications are far greater than just "where they come from" or their lineage if Nigerian truly want to progress.

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