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Source-linked reports with geographic coverage including Grand Canyon.

69 records · Page 4Linked to original sources
USGS1999

Physiographic rim of the Grand Canyon, Arizona: A digital database

This Open-File report is a digital physiographic map database. This pamphlet serves to introduce and describe the digital data. There is no paper map included in the Open-File report. The report does include, however, PostScript and PDF format plot files, each containing an image of the map. For those interested in a paper plot of information contained in the database or in obtaining the PostScript plot files, please see the section entitled "For Those Who Don't Use Digital Geologic Map Databases" below. This physiographic map of the Grand Canyon is modified from previous versions by Billingsley and Hendricks (1989), and Billingsley and others (1997). The boundary is drawn approximately along the topographic rim of the Grand Canyon and its tributary canyons between Lees Ferry and Lake Mead (shown in red). Several isolated small mesas, buttes, and plateaus are within this area, which overall encompasses about 2,600 square miles. The Grand Canyon lies within the southwestern part of the Colorado Plateaus of northern Arizona between Lees Ferry, Colorado River Mile 0, and Lake Mead, Colorado River Mile 277. The Colorado River is the corridor for raft trips through the Grand Canyon. Limestone rocks of the Kaibab Formation form most of the north and south rims of the Grand Canyon, and a few volcanic rocks form the north rim of parts of the Uinkaret and Shivwits Plateaus. Limestones of the Redwall Limestone and lower Supai Group form the rim of the Hualapai Plateau area, and Limestones of Devonian and Cambrian age form the boundary rim near the mouth of Grand Canyon at the Lake Mead. The natural physiographic boundary of the Grand Canyon is roughly the area a visitor would first view any part of the Grand Canyon and its tributaries.

Arizona↗
USGS1996

Tributary debris fans and the late Holocene alluvial chronology of the Colorado River, eastern Grand Canyon, Arizona

Bouldery debris fans and sandy alluvial terraces of the Colorado River developed contemporaneously during the late Holocene at the mouths of nine major tributaries in eastern Grand Canyon. The age of the debris fans and alluvial terraces contributes to understanding river hydraulics and to the history of human activity along the river, which has been concentrated on these surfaces for at least two to three millennia. Poorly sorted, coarse-grained debris-flow deposits of several ages are interbedded with, overlie, or are overlapped by three terrace-forming alluviums. The alluvial deposits are of three age groups: the striped alluvium, deposited from before 770 b.c. to about a.d. 300; the alluvium of Pueblo II age deposited from about a.d. 700 to December 1900; and the alluvium of the upper mesquite terrace, deposited from about a.d. 1400 to 1880. Two elements define the geomorphology of a typical debris fan: the large, inactive surface of the fan and a smaller, entrenched, active debris-flow channel and fan that is about one-sixth the area of the inactive fan. The inactive fan is segmented into at least three surfaces with distinctive weathering characteristics. These surfaces are conformable with underlying debris-flow deposits that date from before 770 b.c. to around a.d. 660, a.d. 660 to before a.d. 1200, and from a.d. 1200 to slightly before 1890, respectively, based on late-19th-century photographs, radiocarbon and archaeologic dating of the three stratigraphically related alluviums, and radiocarbon dating of fine-grained debris-flow deposits. These debris flows aggraded the fans in at least three stages beginning about 2.8 ka, if not earlier in the late Holocene. Several main-stem floods eroded the margin of the segmented fans, reducing fan symmetry. The entrenched, active debris-flow channels contain deposits <100 yr old, which form debris fans at the mouth of the channel adjacent to the river. Early and middle Holocene debris-flow and alluvial deposits have not been recognized, as they were evidently not preserved adjacent to the river or are buried by younger deposits.

Arizona↗
USGS1990

Origin, structure, and evolution of a reattachment bar, Colorado River, Grand Canyon, Arizona

In a channel expansion, flow can separate from the bank, creating a zone of relatively weak recirculating current. Bars that accumulate in this weak flow near the point where flow reattaches to the bank are called reattachment bars. As a reattachment bar evolves, the recirculation zone may fill with sediment and restrict flow from the main channel. The increasingly restricted flow over the bar causes ripples to replace dunes and causes the sediment size to fine; the resulting vertical sequence resembles that of point bars. Seasonal and daily flow fluctuations in the Grand Canyon complicate this idealized sequence. Changes in discharge alter the geometry of recirculation zones, flow within the recirculation zones, the location of depositional and erosional sites, the kind of bedform and migration direction of bedforms on the bar, and the transported sediment size. Dunes and ripples within a recirculation zone migrate in a rotary pattern in response to the recirculating flow. Ripples near the reattachment point often resemble oscillation ripples in morphology and dynamics. The reversing flow that creates these ripples is caused by fluctuations in location of the reattachment point. These fluctuations cause flow near the reattachment point to reverse in an upstream-downstream direction, thereby producing symmetrical, reversing ripples with crests that trend normal to the bank. Low rates of ripple migration in the reversing flow, accompanied by rapid deposition, cause these ripples to climb at a high angle. At increasing distances from the reattachment point, the reversing flow is less balanced, and the ripples climb at lower angles as they migrate upstream and downstream. Although these observations were made in a bedrock canyon, the same processes operate in alluvial and tidal channels and are important in adjusting the shape of channels on point bars and concave benches and behind bedforms that become emergent at low stage. Reattachment bars can be recognized by the rotary flow patterns and by symmetrical, reversing, vertically climbing ripples.

Arizona↗
USGS1982

Use of packrat middens to determine rates of cliff retreat in the eastern Grand Canyon, Arizona

Packrat midden data can be used to calculate rates of cliff retreat by relating midden age to the distance between cliff face and midden. Regression analysis using 14 radiocarbon-dated packrat deposits from the Mississippian Redwall Limestone in the eastern Grand Canyon suggests that the Redwall has been retreating at an average rate of 0.45 m/10 3 14 C yr. This rate of cliff retreat, which is comparable to other cliff-retreat rates reported from arid environments, implies that the Colorado River cut through the Redwall Limestone in the vicinity of Horseshoe Mesa about 3.7 m.y. B.P.

Arizona↗
USGS1977

Uranium, radium, and selected metallic-element analyses of spring water and travertine samples from the Grand Canyon, Arizona

Samples for this report were collected from springs and travertine deposits along the Colorado River in the Grand Canyon, Arizona. Sampling was done in April and May of 1976. Data obtained from these samples will be used by R. A. Cadigan and J. K. Felmlee as part of a project designed to determine the value of subsurface waters in prospecting for uranium deposits. Sample sites were preselected at approximately equal intervals, but river conditions and accessibility forced some modification of the sampling plan at each spring visited, a 2-liter untreated water sample was collected to be analyzed for uranium and radium. At two of the sample locations, an additional 4-liter water sample was collected, filtered, acidified, and later analyzed for the 24 additional elements listed in table-2. A more detailed description of the sampling technique is presented in Brown and others, 1970. All samples were placed in full, tightly capped plastic containers. Temperature and conductivity were measured in the field. Measurements of the pH of the non-acidified samples were made in the laboratory a few weeks after the samples were collected. An effort was made to collect the freshest possible travertine samples, but the freshness of the samples varied, as noted in the descriptions of the sample sites. Analyses were performed by laboratories of the U.S. Geological Survey. Radium values were determined by radiochemical methods; uranium, by extraction fluorometry; eU (equivalent uranium), by beta-gamma count; and other elements, by semiquantitative emission spectrography. Table 1 is a description of the sample sites. The analytical results for spring water are presented in table 2. Table 3 gives the analyses of the travertine samples.

Arizona↗
USGS1968

K-Ar age of lava dam in Grand Canyon

The K - Ar age of the basal basalt flow at the bottom of the "Lower Canyon group" of lavas near Toroweap fault is 1.16 ± 0.18 standard deviation (sd) m.y. This represents a minimum age of Grand Canyon , for at the time the lava formed, the canyon was essentially as deep as it is today. Since that time the Colorado River has cut through the 550-ft lava dam at the mouth of Toroweap Valley, an additional 50 ft of Paleozoic strata below, and through one or more younger lava dams in the area; downstream it has cut through 100 feet of younger intracanyon lavas.

Arizona↗
USGS1923

A section of the Paleozoic formations of the Grand Canyon at the Bass trail

The thick series of horizontal strata of Paleozoic age which makes the greater part of the wall of the Grand Canyon is probably broadly familiar to more people than the strata exposed in any other area in the western United States. Each detail of form or color in the wall is so definitely associated with a bed or set of beds in the series that these strata are the very elements of the canyon landscape. Consequently they have been described not only by geologists but by many writers who have been interested in the Grand Canyon chiefly as a scenic spectacle.

Arizona↗
USGS1882

Tertiary history of the Grand Canon District, with atlas

This work is chiefly devoted to a description of the methods and results of EROSION upon a grand scale. Since erosion depends for its efficiency principally upon the progressive elevation of a region, and upon its climatal conditions, these collateral subjects are also discussed in their relations to the principal theme. And in general such an erosion influences and is in turn influenced by the whole train of phenomena of which physical geology takes account. I have endeavored to show in what manner and to what extent the most important of these events and groups of events are correlated. In the analysis and synthesis of these processes may be found the materials for reconstructing the history of the evolution of the physical features of the region. This history is indeed but an outline, but in it appear many things which would not readily be discerned without such a comparison.

Arizona, Utah↗