Grand Canyon Area Research Articles

Determination of Semivolatile Organic Compounds in Particles in the Grand Canyon Area

Several diffusion denuder-filter-sorbent bed and filter-sorbent bed sampling systems with varying selectivity for the collection of different classes of organic compounds have been used for the collection and determination of atmospheric organic material present at Hopi Point in the Grand Canyon. The data show that the amount of semivolatile organic compounds in particles in the atmosphere in the Southwest United States has been underestimated by sampling with only a filter. The collection of gas-phase organic compounds by the filter causes a small positive artifact. However, a much larger, negative error results from the loss of 40%–80% of the organic material in the particles collected by the filter. The concentration of organic particulate matter present at the Hopi Point site is probably about 2 μg/m3 larger than inferred from previous data.

Airflow and air quality simulations over the western mountainous region with a four-dimensional data assimilation technique

We apply a three-dimensional meteorological model with a four-dimensional data assimilation (4-DDA) technique to simulate diurnal variations of wind, temperature, water vapor, and turbulence in a region extending from the west coast to east of the Rockies and from northern Mexico to Wyoming. The wind data taken during the 1985 SCENES ( S ubregional C ooperative E lectric Utility, Dept. of Defense, N ational Park Service, and E nvironmental Protection Agency S tudy on Visibility) field experiments are successfully assimilated into the model through the 4-DDA technique by ‘nudging’ the modeled winds toward the observed winds. The modeled winds and turbulence fields are then used in a Lagrangian random-particle statistical model to investigate how pollutants from potential sources are transported and diffused. Finally, we calculate the ground concentrations through a kernel density estimator. Two scenarios in different weather patterns are investigated with simulation periods up to 6 days. One is associated with the evolution of a surface cold front and the other under a high-pressure stagnant condition. In the frontal case, the impact of air-mass movement on the ground concentrations of pollutants released from the Los Angeles area is well depicted by the model. Also, the pollutants produced from Los Angeles can be transported to the Grand Canyon area within 24 h. However, if we use only the data that were obtained from the regular NWS rawinsonde network, whose temporal and spatial resolutions are coarser than those of the special network, the plume goes north-northeast and never reaches the Grand Canyon area. In the stagnant case, the pollutants meander around the source area and can have significant impact on local air quality.

Devonian Paleogeography and Paleoenvironments in Northern Arizona: ABSTRACT

Devonian strata in the northern half of Arizona are mostly early Upper Devonian (Frasnian) carbonate rocks up to 160 m thick but include some terrigenous clastics of latest Middle Devonian (Givetian) and Frasnian age. Devonian sediments were deposited on a shallow-marine cratonic platform bordered by the Defiance lowland area to the east and by the continental shelf adjacent to the Cordilleran geosynclinal belt to the west. The Beckers Butte Member of the Martin Formation accumulated as fluvial to subtidal sands in a small embayment End_Page 676------------------------------ southwest of the Defiance area during latest Givetian or earliest Frasnian time. In early Frasnian time, the Aneth Formation and unit 1 of the Jerome Member, Martin Formation, were deposited as fine-grained intertidal carbonates in northeastern and central Arizona, while the lower Temple Butte Formation carbonates formed in a more open circulation subtidal marine environment in northwestern Arizona. Between these two areas the Marble Canyon-eastern Grand Canyon area was a positive feature (here called the Grand Canyon shelf) that remained very near sea level and received little or no sediment. By late Frasnian time depositional environments in northeastern Arizona had changed from intertidal-supratidal conditions to those of a shallow subtidal sea with restricted circulation in the east (the Elbert Formation pelleted carbonate rocks) and more open-marine circulation toward the south and west (the fossiliferous carbonate rocks of the upper Jerome Member and western Temple Butte Formation). The Grand Canyon shelf received carbonate sediments in intertidal channels and on a shallow subtidal platform to form the thin Temple Butte Formation. End_of_Article - Last_Page 677------------

One hundred years of Earth science in the public service

For a century the USGS has mapped and studied the rocks and water of the nation by means of both classical and newly developed techniques.The U.S. Geological Survey was founded on March 3, 1879, to consolidate some of the functions of the several federal surveys that were conducted in the West after the Civil War. The newly organized Survey continued to study the Grand Canyon area to answer questions posed by John Wesley Powell's exploration of the Colorado Plateau country begun in 1869. Under Clarence King, its first director, the Geological Survey continued investigations of significant mining districts, an interest King had pursued as head of the earlier U.S. Geological Exploration of the Fortieth Parallel. King also extended the new agency's work nationally by gathering mineral statistics for the 1880 census.

Late Cenozoic Alkali-Rich Basalt from the Western Grand Canyon Area, Utah and Arizona: Isotopic Composition of Strontium

Twenty samples of Pliocene-Holocene basanite, hawaiite, and quartz-bearing basaltic andesite from the western Grand Canyon district have Sr 87 /Sr 86 ratios that range from 0.7028 to 0.7069. Sixteen of these are lava flows that have Sr 87 /Sr 86 (0.7028 to 0.7041), K/Rb (500 to 790), and Rb/Sr (0.016 to 0.047) ratios, which suggest a probable mantle origin. These data are typical of many late Cenozoic basaltic flows from the southern Great Basin and southern Colorado Plateau. In the remaining four Grand Canyon samples (3 hawaiites, 1 basaltic andesite) Sr 87 /Sr 86 , K/Rb, and Sr concentrations are suggestive of possible crustal contamination. Correlation coefficients for chemical and isotopic compositions of the Grand Canyon basalt are significant at the 95 percent level for covariances between Sr 87 /Sr 86 and only TiO 2 , Rb/Sr, and Sr. The latter two correlations are mainly influenced by data for the four possibly contaminated basalt samples and are insignificant when those samples are omitted. The isotopic and chemical data are compatible with the model proposed by Best and Brimhall (1974) in which the Grand Canyon basalt flows are derived by variable degrees of partial melting of mantle material over a range in depth and modified by polybaric crystal fractionation during ascent to the surface. Small variations in isotopic composition in the bulk of these samples probably reflect heterogeneities in their mantle source regions rather than the effects of crustal contamination. It is inferred that the mantle underlying the western Grand Canyon district is similar in its isotopic characteristics to typical oceanic-type mantle regions.

A Historical Analysis and Synthesis of Grand Canyon Archaeology

AbstractThis historically oriented description of the development of archaeological research and conceptualization in the area of Grand Canyon National Park begins with the contributions of the earliest Spanish explorers of the area and proceeds to research completed in 1964. Three periods of research are identified: discovery and exploration, 1540 to 1900; general investigation, 1900 to 1950; and concentrated analysis, 1951 to 1964. By the end of the first period the historic tribes and the presence of Pueblo ruins in the Grand Canyon area had been recognized. During the next 50 years many details were added to the understanding of the Pueblo material, including a sound temporal framework, the postulation of a second prehistoric group in the area, the Cohonina, and additional information on the ethnographic groups of the area accumulated. In the years between 1951 and 1964 there developed an increasingly complete description of the Cohonina branch, an analysis of Havasupai culture history, an examination of the Anasazi occupation within the depths of the Canyon, and the discovery of a Canyon occupancy some 2000 years earlier than had been known previously. Finally, a summary of the current conception of the area's culture history is presented, along with an indication of possible directions for future research.

Plant Communities of the Grand Canyon Area, Arizona

Plant Communities of the Grand Canyon Area, Arizona

Stratigraphy of Pennsylvanian, Permian, and Lower Triassic Rocks of Confusion Range, West-Central Utah

Work by the United States Geological Survey in the Confusion Range of west-central Utah during the past few years has resulted in the accumulation of considerable data regarding the stratigraphy of rocks ranging in age from Late Mississippian through Early Triassic. These rocks are here discussed as six formations, whose physical limits more or less coincide with the boundaries selected by earlier workers in the area, although considerable changes in stratigraphic nomenclature have been made. The Ely limestone of Late Mississippian, Early and Middle Pennsylvanian, and Permian age consists of 1,850-2,000 feet of alternating resistant thick-bedded limestone and slabby slope-forming limestone. The upper 100-350 feet of the formation contains an early Permian fauna and is generally more massive and less cherty than the remainder of the formation, which contains a fauna characteristic of the lower half of the Pennsylvanian and locally Late Mississippian. A hiatus representing Late Pennsylvanian time separates Middle Pennsylvanian and Permian faunas. The Arcturus formation, which conformably overlies the Ely limestone, consists of poorly indurated yellowish gray calcareous sandstone with thin, ledge-forming interbeds of dark gray to tan limestone and dolomite. The few fossils found in the Arcturus formation, and its stratigraphic position, suggest that the formation is early to middle Permian in age. The total thickness of the formation is uncertain, but a minimum thickness of 2,700 feet has been measured. The succeeding three formational units, the Kaibab limestone, the Plympton formation (new name), and the Gerster limestone, all of Permian age, have been included in the Park City group. The Kaibab limestone overlies the Arcturus formation and consists of 480 feet of somewhat cherty bioclastic limestone. The lithologic character of the Kaibab is in sharp contrast to the succeeding unit which is here named the Plympton formation and is predominantly dolomite and chert. The Plympton formation is 690 feet thick and contains phosphatic beds believed to be lithologic correlatives with parts of the Park City formation of northwestern Utah. The overlying Gerster limestone consists of 1,100 feet of very fossiliferous cherty bioclastic limestone and argillaceous limestone. The Gerster limestone is the youngest Permian unit in the Confusion Range. Like the Kaibab, it is differentiated from the Plympton formation by its high limestone content and lack of dolomite. The contact be ween the Plympton and the Gerster limestone is conformable throughout the area. The Kaibab limestone, the Plympton formation, and the Gerster limestone are believed to be correlative with units within the Park City and related formations of nearby areas in northern and northwestern Utah and northeastern Nevada. In areas south of the Confusion Range, the younger Permian units, the Plympton formation, and the Gerster limestone, are absent and only the Kaibab limestone is present in the Grand Canyon area. The Thaynes formation of late Early Triassic age consists of thick beds of predominantly greenish gray calcareous clay shale interbedded with thin beds of gray to chocolate brown limestone, and is more than 1,900 feet thick in the Confusion Range. It is unconformably overlain by Tertiary and Quaternary strata, and no younger Mesozoic rocks crop out in the area. The contact of the Thaynes formation with the underlying Gerster limestone appears conformable; however, faunal evidence indicates a considerable hiatus between the two formations.

Woodchuck Remains in Northern Arizona Caves

Woodchucks, Marmota flaviventris, have been recorded twice in northern Arizona; these were from skeletal remains at archeological sites in the northeastern part of the state (Keet Seel and Woodchuck Cave). Woodchucks are known to be living today no closer than Kane County, Utah. Recent investigations of caves in north-central Arizona, particularly in the Grand Canyon area, have brought to light the remains of woodchucks in five other places and considerably extend the known range of Marmota flaviventris southward, indicating that the species was rather widespread in northern Arizona a few hundred years ago. The dated material found in the archeological sites has been placed as recently as A.D. 1300 and some as far back as A.D. 200 ± one hundred years. The woodchuck localities of Grand Canyon and the Navajo country lie in desert canyons of the Lower Sonoran Life-zone bordering on the Upper Sonoran. Woodchucks today tend to...

Paleozoic Stratigraphy of Part of Northwestern Arizona

Eleven stratigraphic sections were measured along the southwestern margin of the Colorado Plateau, from north-central Arizona to southeastern Nevada. The northwestern sections are thick and consist dominantly of limestones. The southeastern sections are thin and contain much clastic material. The Cambrian rocks, which are almost 2,200 feet thick in extreme southeastern Nevada, wedge to extinction southeastward. They have complex facies relationships resulting from diverse shifting environments during a Lower-Middle Cambrian transgression and a Middle-Upper(?) Cambrian regression. The deposition of primary dolomitic limestones in two types of shallow-water environment is clearly demonstrated. The Ordovician(?) is represented by a thin wedge of dolomitic limestones which occurs only at the northwest. The Upper Devonian Muddy Peak and Martin limestones form a continuous limestone series across the area. In the southeast the Martin truncates the Middle Cambrian Tapeats sandstone and contains basal clastic beds. In the western Grand Canyon area the Martin limestone contains soft, argillaceous limestone beds of Temple Butte lithologic character. The Rogers Spring and Redwall limestones, western and eastern equivalents, are remarkably uniform in thickness and in general lithologic character. They are of Kinderhookian and Osagian age and consist of thick-bedded, light gray, fine-grained, and oolitic limestones with persistent zones of bedded chert. End_Page 503------------------------------ Fig. 1. Outline map of northwestern Arizona showing location of stratigraphic sections. End_Page 504------------------------------ The Callville limestone, as restricted in this study, is entirely Pennsylvanian. It forms an eastward tapering wedge of two members, which intertongues and intergrades with lower Supai redbeds. The limestones were formed during a Late Pennsylvanian, Virgilian, transgression that extended almost across the area. A new formation, the Pakoon limestone, is proposed for the dolomitic limestones conformably overlying the Callville limestone. These dolomitic limestones were deposited in a Wolfcampian regressive phase, which followed the Late Pennsylvanian transgression. They are overlain conformably by cross-bedded sandstones of Supai lithologic character. The pink and gray, cliff-forming, cross-bedded sandstone overlying the Pakoon limestone is designated the Queantoweap sandstone. This formation is not present in the southwestern part of the area, where the Supai is undifferentiated. The southwestern Supai contains many thin limestone beds between red sandstones. The repetition of these limestones with redbeds suggests simple types of cyclothems. The dominant direction of dip of cross-bedding in all formations between the lower Callville limestone and the Coconino sandstone is south and southeast. This suggests that the source of clastic material was on the northwest or north. The possibility is presented that the Supai redbeds were deposited in a wide mud-flat marginal to a clearer-water environment on the north, and that the repeated subsidence of the mud-flat allowed marine water to spread out cross-bedded sandstones, and at times to precipitate thin limestones. The Coconino sandstone is the only formation which thins northwestward. The consistent dominant southward dip of the eolian, wedge-shaped, cross-beds in the formation indicates that the source of the sand was north of the area. The Toroweap formation consists of two gypsiferous members separated by a middle limestone member. It is Leonardian in age. The aridity or semi-aridity of Coconino time persisted during the deposition of the evaporite members of the Toroweap formation. The Kaibab limestone contains many chert-bearing beds and forms steep cliffs above the less conspicuous cliffs of the Toroweap formation. The Kaibab limestone is overlain by redbeds of the Triassic Moenkopi formation.