Elk Mountain Research Articles

Guenther Boden, MD (1935-2015): A Pioneer in Human Studies of Nutrition and Obesity-And the Mystery of Insulin Resistance for Handling Glucose.

Professor Guenther Boden, MD, was drawn to the field of diabetes research through an unconventional route, but in that journey he brought a perpetually fresh set of eyes to help unravel the relationships between nutrition, obesity, and defects in insulin action. A delighted Guenther Boden in ski gear, Elk Mountain, PA, 1980 Guenther Boden was born on 8 January 1935 to Dr. Alwin Boden, an internist who practiced from a home office, and Irma Boden ( nee Godelmann), a homemaker who had trained as a medical technologist. During his early years, the family lived in Ludwigshafen am Rhein, an industrial city in southwestern Germany. The place and time would leave Guenther with vivid memories of a childhood spent during, and immediately after, World War II. Guenther once wrote that when Allied bombing of key industrial sites in Ludwigshafen began, the bombs were, from an 8-year-old child’s perspective, “more a matter of excitement than threat for me[,] and together with my friends, we would rush out of the cellar after the air raids to look for bomb shards, which we boys considered a valuable collection item. This lost much of its attraction as the air raids became more frequent… .” When his father was drafted as a medical officer in the Luftwaffe (Air Force), Guenther’s mother took him and his two sisters to the relative safety of her parents’ home in Heidelberg. Young Guenther Boden with mother Irma and two sisters, Marianne and Ilse, in Durkheim, Germany, 1950 Early life promoted an independent spirit, a healthy skepticism of authority, and remarkable resourcefulness. Rough lessons came at a personal level, from the “sadist” who taught his 3rd and 4th grade classes—using frequent corporal punishment—and from Guenther’s childhood experiences of hunger—today called food insecurity. Hard lessons also came from learning of the genocidal war criminals …

The Morrison Formation and its bounding strata on the western side of the Blanding basin, San Juan County, Utah

In 2016 and 2017, the Utah Geological Survey partnered with the U.S. Bureau of Land Management to conduct a paleontological inventory of the Morrison Formation south and west of Blanding, Utah, along the eastern margin of the Bears Ears National Monument. The Morrison in this region is critical to understanding Upper Jurassic stratigraphy across the Colorado Plateau because it is the type area for the Bluff Sandstone, Recapture, Westwater Canyon, and Brushy Basin Members of the Morrison Formation, which are the basis for nomenclature in New Mexico and Arizona as well. Researchers have disagreed about nomenclature and correlation of these units, which transition northward in the study area into the Tidwell, Salt Wash, and Brushy Basin Members. Numerous vertebrate localities make inclusion of the Bluff Sandstone and Recapture Members in the Middle Jurassic San Rafael Group, as suggested by some previous workers, unlikely. The Salt Wash Member does not separate the Bluff Sandstone and Recapture Members at Recapture Wash, but sandstone lenses of Salt Wash facies occur higher in northern Recapture exposures. Northward, along the outcrop belt east of Comb Ridge, the Bluff-Recapture interval thins, interlenses, and pinches out into the Tidwell and lower Salt Wash, with the main lower sandstone interval of the Westwater Canyon merging northward into the upper Salt Wash Member.
 The partly covered, 1938 type section of the Brushy Basin Member is identified along Elk Mountain Road at the southern end of Brushy Basin. We describe a detailed, accessible Morrison Formation reference section about 11.2 km (7 mi) to the south along Butler Wash. There, 81.68 m (268 ft) of Brushy Basin Member is well exposed along a road between the top of the Westwater Canyon Member and the base of the Lower Cretaceous Burro Canyon Formation. We informally call the upper sandstone bed(s) of the Westwater Canyon Member that cap mesas and benches in the region “No-Mans Island beds.” Smectitic mudstones between the No-Mans Island beds and the main sandstone body of the Westwater Canyon suggest that the Salt Wash-Brushy Basin contact to the north may be somewhat older than the base of the Brushy Basin Member as originally defined in its type area. Determining whether the No-Mans Island beds pinch out to the north or are removed by erosion below the regional basal Brushy Basin paleosol requires further research. Several significant fossil vertebrate and plant sites have been documented in the Brushy Basin type area. Newly identified volcanic ashes provided zircons for U-Pb ages of 150.67 ± 0.32 Ma from near the top of the Brushy Basin Member and of 153.7 ± 2.1 Ma and 153.8 ± 2.2 Ma for two zircons in lower part of Recapture Member. At the top of the Brushy Basin Member, ferruginous paleosols commonly overlying conglomeratic sandstone are speculated to be of Early Cretaceous age (detrital zircon age pending) and are assigned herein to the Yellow Cat Member of the Burro Canyon Formation. These iron-rich paleosols suggest wetter climatic conditions during the Jurassic-Cretaceous transition in the Blanding basin.

Is something happening to our supply of Supercooled Clouds?

On October 19, 1977, on a flight from Albany, New York to Reno, Nevada, I spent most of the trip on the sunny side of the jet aircraft watching the world go by.... The flight route from Chicago to Reno went past Cheyenne, Elk Mountain, Flaming Gorge Reservoir, just north of the Bingham Copper Pit, and then across the Bonneville Salt Flats into Nevada. Much of the region west of Chicago was cloudless but shortly afterwe crossed the Nevada state line,the first batch of cumulus clouds appeared as we approached the Ruby Mountains. Proceeding west southwest, convective clouds increased in concentration until they obscured the ground. The sky above our plane was cloudless and therewere no middle clouds.....

Population Dynamics of a Bighorn Sheep (Ovis canadensis) Herd in the Southern Black Hills of South Dakota and Wyoming

Abstract Bighorn sheep (Ovis canadensis) were re- introduced to the Black Hills of South Dakota and Wyoming beginning in 1965. Various pneumonia outbreaks caused populations to decline periodically, resulting in little to no lamb recruitment. An isolated population of bighorn sheep resides on Elk Mountain along the South Dakota-Wyoming border in the southern Black Hills. We estimated population size, survival, and recruitment rates of bighorn sheep on Elk Mountain by radio-collaring adult and neonatal sheep from 2012 to 2014. Overall annual ewe survival was 88.1% (se = 0.05), ram survival was 85.1% (se = 0.10), and 26 wk lamb survival was 44.7% (se = 0.09). Recruitment through 26 wk averaged 35% (SD = 0.02) across years. Population estimates for the 3 y were 80 (se = 0.58), 100 (se = 2.42), and 115 (se = 6.89) individuals, respectively. The Elk Mountain bighorn sheep herd experienced lamb survival and recruitment during 2012-2014; coupled with minor predation losses and a lack of deadly pneumonia, this he...

Late Laramide tectonic fragmentation of the eastern greater Green River Basin, Wyoming

Today9s greater Green River Basin is limited to the southwestern quarter of Wyoming. From late in the Cretaceous into late Paleocene time, however, sedimentary accumulations within that basin continued uninterruptedly much farther to the east, connecting areas now occupied by the isolated Hanna, Carbon, Pass Creek, and Laramie basins. Field-based research resulted in three contiguous geologic maps that focus on modern basin margins and boundaries among those eastern elements. Analyses of derived cross sections and restored stratigraphic columns suggest that active subsidence and rapid sedimentary accumulation persisted with only minor interruptions until very late in the Laramide Orogeny. That led to a generally symmetrical north–south cross-sectional configuration of the original Hanna Basin, with its true depositional axis set well south of its apparent position of today. The Hanna Basin9s present strong asymmetry developed only secondarily. That basin9s modern configuration reflects Paleogene influences of: (1) late Laramide (early Eocene and probably younger) basement-involved contractional tectonics and associated uplifts; (2) out-of-the-basin thrusting passively responding to stratigraphic crowding; (3) prodigious syntectonic erosion; and (4) resulting basin fragmentation. North–south dimension of the late Paleocene (i.e., pre-fragmentation) greater Hanna Basin sedimentary sequence was roughly twice that of today, and near-sea-level topographic conditions persisted until late Eocene time. As expected, remnants of basin margins universally show major thinning of stratigraphic sequences. Principal thinning was from tectonic causes, however, exhibiting erosional angular unconformities only rarely. Out-of-the-basin, younger-on-older faulting (in which fault planes cut down-section) accompanied by massive erosion was the rule at all basin margins. Uplift of Simpson Ridge Anticline postdated deposition of upper Paleocene strata in direct continuity between what is now the separated Hanna and Carbon basins. The basement-involved fault system responsible for westward relative tectonic transport (and ca. 8 km of elevation) by Simpson Ridge also led to raising the attached Carbon Basin. Original Hanna Formation of the Carbon Basin was beveled away by erosion and soon thereafter became replaced by shallow-slope sliding of a long-runout allochthon, the Carbon Basin Klippe. The klippe9s original site of deposition probably was to the northeast, above what later became Flat Top Anticline. Uplift of Flat Top and Simpson Ridge anticlines was essentially synchronous (latest Paleocene or, more probably, early Eocene), establishing a lengthy, faulted-synclinal separation of the Hanna/Carbon Basin from the Laramie Basin. That syncline also bifurcated Simpson Ridge Anticline into western and eastern segments. A second allochthon, the Dana Klippe, rests upon southern parts of the Hanna Syncline (of Hanna Basin). That klippe9s site of deposition probably was above the area that later elevated as Elk Mountain, thus causing origin of Pass Creek Basin. Elk Mountain9s ca. 12 km uplift could not have occurred prior to the early Eocene, and that event contributed to tight folding of the Hanna Syncline. Coal Bank Basin is a giant footwall syncline ahead of the out-of-the-basin, thrust-faulted (with relative tectonic transport to the southwest) Dana Ridge Anticline. That fault–fold complex represents a common structural style seen at all scales across the Hanna Basin.

Ephemeral work group formation of Jenu Kuruba honey collectors and late 19th Century Colorado silver prospectors

Humans frequently form short-lived cooperative groups to accomplish subsistence and economic tasks. We explore the ecological and cultural factors behind ephemeral work-group formation in two disparate cultural contexts: groups foraging for wild honey in present day South India and groups prospecting for silver ore in the Elk Mountain Mining District of Colorado in the late 19th century. Contrary to traditional economic foraging predictions, we find little evidence that per capita yields are the most important factor in determining size and composition of ephemeral work groups. We explore factors in each of these cultures that may be of importance for group formation such as kinship, reputation, and pleasure. Models that only incorporate economic parameters will make poor predictions of how humans interact with their environments.

Multi-step TIMS and CA-TIMS monazite U–Pb geochronology

Multi-step chemical abrasion thermal ionization mass spectrometry (CA-TIMS) methods were developed for monazite using six samples that vary in composition and age—Amelia, Jefferson County, Burke, Elk Mountain, 554 and Madagascar. To evaluate whether the multi-step CA-TIMS approach reveals complexities in either age or composition that might be masked by single-step analysis, this study presents a side-by-side comparison of monazite samples dated via multi-step TIMS (not annealed) and CA-TIMS (annealed), and measurement of rare earth element ratios for each dissolution step. The data demonstrate three important contributions. First, annealing reduces solubility—after one partial dissolution step, not-annealed fractions were 3.3–4.1 times more digested than the annealed fractions. The difference in solubility suggests that monazite does not fully self-anneal at low temperatures. Second, multi-step TIMS analyses yielded high-precision U–Pb plateau ages for the Burke and Amelia monazites; CA-TIMS analyses yielded high-precision U–Pb plateau ages for Madagascar and Amelia monazites. Jefferson County, Elk Mountain and 554 yielded more complex results and no U–Pb plateau ages. Third, chemical analysis of partial-dissolution steps reveals heterogeneous age and compositional data for annealed samples. Because not-annealed samples yielded more consistent age and compositional data, high-temperature annealing is not recommended for monazite. Instead, optimal TIMS results are provided by slow, partial dissolution of monazite in weak acid.

Structural and seismic-reflection evidence for development of the Simpson Ridge anticline and separation of the Hanna and Carbon Basins, Carbon County, Wyoming

The eastern border of the Hanna Basin, Wyoming, is defined by Simpson Ridge anticline, a Laramide structure that separates the Hanna Basin from the more easterly Carbon Basin. New geologic mapping along with interpretation of well logs and seismic-reflection data suggest that this structural feature was created through a combination of thick- and thin-skinned deformation during the contractional Laramide orogeny. Major west-directed, basement-involved faulting occurs beneath Simpson Ridge, suggesting that this structural feature is not related to the eastvergent Elk Mountain anticline. Although major basement-involved thrusts underlie Simpson Ridge, the development of the anticline also involved thin-skinned, out-of-the-basin thrusting related to the deeply rooted basement faults by a trishear deformational zone. An unconformity between the Cretaceous–Paleocene Ferris Formation and Paleocene Hanna Formation marks initiation of fault-controlled uplift along the Simpson Ridge anticline. On the eastern side of Simpson Ridge, the Hanna Formation was faulted westward onto the Lewis Shale, thereby yielding a younger-on-older structural relationship. Palynological data suggest that the age of the Hanna Formation in the southwestern Carbon Basin is late Paleocene. These data thus provide a maximum age for later deformation along Simpson Ridge anticline and for the consequent definition of the western edge of Carbon Basin.

Effects of increased nitrogen deposition on soil nematodes in alpine tundra soils

Summary Because of anthropogenic activities, atmospheric deposition of nitrogen has increased on some high elevation ecosystems in North America. On Elk Mountain in SE Wyoming, USA, we found that ice, formed by the impaction of supercooled cloud droplets, contains nitrogen levels (NH 4 + = 58 ± 47 μmole/1, NO 3 − = 52 ± 40 μmole/1) significantly higher than snow (NH 4 + = 7 ±5 μmole/1, NO 3 − = 14 ± 7 μmole/1). At this site the impaction process (riming) occurs on krummholz and is an important mechanism of water and nutrient deposition. We sampled nematodes in alpine soil for two seasons under this rime ice deposition and in adjacent meadow and krummholz soil with only snow deposition. No significant difference was found in nematode density and trophic composition between snow and rime ice deposition zones in krummholz; and nematode densities were significantly higher in meadow soil than in the krummholz rhizosphere. Densities of active nematodes were highest immediately after snow melt and a positive correlation was found between nematode density and percent soil moisture. With subsequent soil drying, nematodes gradually entered anhydrobiosis and this process began earlier in the exposed meadow than under the krummholz canopy. In a subsequent microcosm experiment we exposed nematodes in two alpine soils to four different nitrogen treatments [ammonium nitrate (NH 4 NO 3 ) at 0, 20, 40 and 80 kg N/ha/yr] and two temperatures (5 and 25°C). None of the three variables had a significant effect on nematode density. But at the first sampling (1 month) the interaction between soil type and nitrogen level was significant, and at the second and final sampling (6 months) the interaction between soil type and temperature was significant. Nematode response to increasing nitrogen deposition rates varied in a complex way with soil type and temperature. Under the microcosm conditions, nematode community composition shifted to opportunistic rhabditid species. Our work indicates that higher levels of nitrogen deposition (>80 kg N/ha/yr) were necessary to produce detectable effects on nematode density in this alpine region.

95-GHz Polarimetric Radar Measurements of Orographic Cap Clouds

The use of millimeter-wavelength radars for cloud microphysical research was investigated in experiments at the Elk Mountain Observatory near Laramie, Wyoming, between April 1990 and March 1992. The 95-GHz polarimetric radar used in these experiments is a portable, high-power, dual-polarization radar capable of characterizing the complex scattering matrix in two pulses. The scatterer's polarimetric response is characterized in terms of the Mueller matrix, a form that is seen to be convenient for computing the response of a scatterer for any arbitrary combination of transmit and receive antenna polarizations. This paper summarizes the results of recent experiments carried out at the Elk Mountain Observatory. Polarimetric data from orographic cap clouds are found to be sensitive to ice-particle orientation and composition. Comparison of radar-observed reflectivities with those computed from in situ images shows good agreement if the volume fraction of ice in ice-air mixtures is taken into account.

Duplex development and abandonment during evolution of the Lewis thrust system, southern Glacier National Park, Montana

The westernmost duplex (Brave Dog Mountain) includes the low-angle Brave Dog roof fault and Elk Mountain imbricate system, and the easternmost (Rising Wolf Mountain) duplex includes the low-angle Rockwell roof fault and Mt. Henry imbricate system. The geometry of these duplexes suggests that they differ from previously described geometric-kinematic models for duplex development. Their low-angle roof faults were preexisting structures that were locally utilized as roof faults during the formation of the imbricate systems. Crosscutting of the Brave Dog fault by the Mt. Henry imbricate system indicates that the two duplexes formed at different times. The younger Rockwell-Mt. Henry duplex developed 20 km east of the older Brave Dog-Elk Mountain duplex; the roof fault of the former is at a higher structural level. Field relations confirm that the low-angle Rockwell fault existed across the southern Glacier Park area prior to localized formation of the Mt. Henry imbricate thrusts beneath it. These thrusts kinematically link the Rockwell and Lewis faults and may be analogous to P shears that form between two synchronously active faults bounding a simple shear system. The abandonment of one duplex and its replacement by another with a new and higher roof fault may have been caused bymore » (1) warping of the older and lower Brave Dog roof fault during the formation of the imbricate system (Elk Mountain) beneath it, (2) an upward shifting of the highest level of a simple shear system in the Lewis plate to a new decollement level in subhorizontal belt strata (= the Rockwell fault) that lay above inclined strata within the first duplex, and (3) a reinitiation of P-shear development (= Mt. Henry imbricate faults) between the Lewis thrust and the subparallel, synkinematic Rockwell fault.« less

A “Cloud Gun” Primer

Abstract The cloud gun is a direct-impaction instrument for determining cloud droplet size distributions and number concentrations. The instrument was designed for airborne use. Procedures are detailed for operating the instrument at the surface. The Langmuir crater-to-diameter ratios are used for reducing the data. Liquid water contents from cloud-gun data collected at Storm Peak Laboratory (SPL), Steamboat Springs, Colorado are found to be similar to those reported from a replica cloud gun operated at Elk Mountain Observatory (EMO), 129 km to the north. This consistency in the SPL and EMO data is evidence that the procedures reported produce reliable results.

Soil, archaeological, biotic, and climatic relationships for the late holocene of the Wyoming basin: The case of the Garrett Allen (Elk Mountain) site (48CR301)

AbstractSoils at the Garrett Allen (Elk Mountain) site (48CR301) along Quealy Spring in Carbon County, Wyoming, indicate nearly continuous, although episodic, meadow soil formation during much of Neoglacial or post‐Altithermal time at a mountain‐basin edge (elev. 2237 m) of the Wyoming Basin. Seven relict and buried meadow soils now under sagebrush (Haplaquents or Fluvaquents, Haplaquolls, and Argiaquolls) of the T1 terrace date less than 200 B.P. as well as around 200, 600, 900, 1700, and two soils at greater than 3100 B.P. Composite‐superposed soils of two or more of the individual soils are common. Some soils have E horizons and the older ones have intensely gleyed cambic or argillic subsoils. Development of meadow soils and deposition of their respective parent materials seem to coincide with glacial episodes in the region when the climate may have been somewhat humid. Occupations of the meadow by Archaic and younger cultural groups, whose artifacts occur mainly in A(O?) horizons of meadow soils, appear to coincide with these humid–glacial climates when the meadow grew and flourished. Changes in subsistence and settlement of these peoples may have been partly influenced by humid climates during glacial episodes when rangeland and habitat were able to support large human and animal populations. However, four major erosional unconformities separate some soils. These unconformities may coincide with times of lessened glacial activity when the climate may have become drier and the meadow decreased in size. During these times, human groups may have abandoned the meadow, left the region, or only sparsely occupied the plains and basins. The youngest unconformity developed when Quealy Spring cut from T1 to the T0 level in the last century. This appears to coincide with sagebrush invasion across portions of the meadow, although a small relict meadow still exists. Sagebrush invasion and downcutting of the drainage may relate to climatic drying in the last century. Fluvents are now forming in alluvium of the T0 level along the Quealy Spring drainage.

Observations of Liquid Water in Orographic Clouds over Elk Mountain

Abstract The relatively simple orographic clouds forming in winter over Elk Mountain, Wyoming provided useful opportunities for field studies of cloud formation and of ice crystal development. In this paper, the observations of cloud droplet populations spanning a range of five consecutive years are summarized. Date are presented which describe the climatology of the cloud droplet spectra. Selected cases are described in detail to illuminate the process at work and to allow comparisons with theoretical predictions. Droplet concentrations are mostly around 300 cm−3 in accordance with the weak updrafts of the clouds and with the mid-continental, unpolluted cloud condensation nucleus concentrations prevailing in the region. In general, the data are in agreement with one-dimensional microphysical model calculations.

Foreland Deformation--A Critique of Cause: ABSTRACT

The cause of foreland deformation has been argued for nearly 100 years, and despite definitive stratigraphy, superb exposure, and extensive seismic and well data, mechanism and geometry remain elusive. It is necessary to separate arguments for cause from arguments that only support a particular geometric interpretation. The following statements are presented for discussion and are not advanced as the answer. (1) Foreland deformation is caused by end-load buckling in a plate tectonic setting driven by abnormally shallow subduction. (2) The crust is active (competent) unit, and plastic subcrust is a passive cushion allowing great vertical component, though a slight slope forced on it by subducting slab may have aided telescoping of crust above. (3) No strictly vertical cause can allow basins to go down as much as they did, and active (causal) intrusion under uplifts only is not likely. (4) While reverse faults and modest shortening predominate, fault attitudes can End_Page 1353------------------------------ have greater diversity than in thin-skinned regime because plastic substratum allows easy vertical motion; nearly vertical faults are allowable. (5) The basement does fold, but with difficulty and in broad wavelength. (6) Because of broad arching, a exists well within basement over uplifts, allowing high-level features, such as Rattlesnake Mountain, to be bounded by high-angle normal faults. (7) This same neutral surface forces out-of-the-basin crowding, causing steep flanks of most basin folds to face toward adjacent uplift. (8) The Hafner approach illustrates diversity of curved faults that can be generated in a vertically sinusoidally loaded beam, and which can be generated equally well in an end-loaded sinusoidally buckled beam, as long as it sits on a passive plastic substratum. (9) The Sanford model is excellent for depicting fault configuration generated in sediments above a high-angle fault. (10) Faults such as Dinosaur Monument can be seen to steepen downward, but my models suggest that they go listric at their lower transition with plastic substratum. (11) The COCORP trace of Wind River fault indicating a nearly planar 35° dipping fault most of way through crust is probably real; arguments that you cannot see a fault of granite against granite do not apply. (12) Gravity highs over uplifts, models, and later collapsed uplifts speak for a flexed and slab configuration and against a buoyant root configuration. (13) Thrusting from several different directions appears not to be a when viewed in context of jostled slabs. (14) Blocky corners do place limits on amount of thrust and strike-slip translation. (15) The argument for pure verticality to solve a presume space problem in Piney Creek structure loses validity as soon as bounding tears are allowed to stray from a perfectly vertical dip. (16) The argument at Elk Mountain that dip of bounding structure must be at least as low-angle as degree of overturning of sedimentary panels is wrong (proven by Five Springs). (17) Sales' eastward crowding of Colorado Plateau and development of a Wyoming couple north of it still seems cogent. (18) The Chapin and Cather, and Gries subdivision into movement phase also appears to be correct. (19) If horizontal compression is a reality, Stone must be correct in principle; there have to be logical connecting structures. (20) The crust can transmit stress over great distances because it is weak enough; southeast Asia tectonics require greater distances of stress transmittal than Laramide foreland tectonics. End_of_Article - Last_Page 1354------------

Foreland Detached Deformation: ABSTRACT

In an area having perhaps more relief on the top of the Precambrian surface than any other structural province in the world, attention understandably has been focused on the basement-cored structures of the Rocky Mountain foreland. Deep-seated compression interpreted as responsible for the shortened basement features has also created detached structures in the overlying sedimentary cover. These latter structures have never been the object of systematic study, yet they provide important additional evidence of a compressional origin for the Rocky Mountain foreland and other forelands, and are also prospective for oil and gas. Detached structures can be attributed to at least two types and stages of deformation. First, compression operating early in the development but prior to the differentiation of the foreland created small-scale fold and thrust structures. Probable examples of early compressional structures include those formed on what are now the gentle tilted flanks of the Owl Creek Range in Wyoming and the Cara Cura Range in Argentina. Second, after differentiation of the foreland into blocks, the flexural slip mode of folding in competent sedimentary layers dictates that space problems in both anticlines and synclines be accommodated by the creation of decollement surfaces and associated detachment structures. Examples have been documented from virtually every Rocky Mountain foreland basin. Specific lly cited are the North Park basin in Colorado, Elk Mountain area, northwestern Wind River basin, and Big Horn basin in Wyoming, and the Cara Cura mountains in Argentina. Prominent detachment horizons in the Rocky Mountain foreland are shales of Cambrian, Triassic (Chugwater), and Cretaceous (Mowry, Cody, and equivalent) age. Oil and gas have been produced from detached folds. A negative aspect is that otherwise prospective beds beneath a completely detached structure do not have closure unless they are affected by deeper faults. More optimistically, closures related to local detachment are prospective. End_of_Article - Last_Page 1349------------

Three-Dimensional Numerical Model Simulations of Airflow Over Mountainous Terrain: A Comparison with Observations

Abstract Numerical simulations of airflow over two different choices of mountainous terrain and the comparisons of results with aircraft observations are presented. Two wintertime casts for flow over Elk Mountain, Wyoming where surface heating is assumed to be zero and one case for airflow over Mt. Withington, New Mexico where surface heating is strong are considered. In the Elk Mountain simulations the flow becomes approximately steady state since the upstream conditions are assumed to be constant and the surface heating is assumed to be zero. The response is significantly different in the two cases. In one case (dynamic Elk) strong lee waves formed with a horizontal separation of ∼10 km whereas in the second case (microphysical Elk) mainly weak untrapped waves formed with a vertical wavelength of ∼2.5 km. Because of the presence of the lee waves in the first case it is shown that the ridges south of Elk Mountain affect the flow near Elk Mountain. In the second case where there were no strong lee waves, ...

Electrification experiments on Elk Mountain

During the winter of 1976, along with the continuing studies of ice crystals in the cap cloud on Elk Mountain, measurements were made of ice crystal charges and the atmospheric electric field strength. The electric field was, in general, found to be of the same sign as the fair weather field. The net particle charges were predominantly positive with mean values of the order of ±10−14 C with fairly symmetrical distributions of positive and negative charges. The ‘mirror image’ effect was seldom observed perhaps because of the small extent and short lifetime of the cap cloud. The absence of large negative charges suggests that the particles and particle charges do not originate from blowing snow. A mechanism of charging which may explain the symmetrical charge distributions is inductive charge transfer between particles which contact and then separate in random directions relative to the electric field.

Cystopteris bulbifera in the Southwestern United States

(Wagner, 1972). Anderson (1974) discussed the distribution of this species in the Great Plains but not in the Southwest. Cystopteris bulbifera (L.) Bernh. is known in Texas only in the Guadalupe Mountains, Culberson Co. (Correll & Johnston, 1970). New Mexican collections have been made in these same Guadalupe Mountains, Otero or Eddy Co. (Blasdell, 1963, p. 67); in the White Mountain wilderness, northern Otero Co. (C. R. Hutchins, pers. comm.); and north of Taos, Taos Co. (Dittmer, et al., 1954, p. 28). In Utah, Flowers (1944) reported the species from Zion National Park, Washington Co.; Elk Mountain, San Juan Co.; and Brighton and Little Cottonwood Canyon, Salt Lake Co. There are no reports of this species from Colorado, Nevada, or farther north. In Arizona, C. bulbifera has previously been known only from the West Fork of Oak Creek Canyon, Coconino Co. (Kearney, et al., 1960, p. 44). I have recently collected specimens of it in Walnut Canyon, Coconino Co., at a site about 40 km northeast of the Oak Creek locality. A recent floristic study of Walnut Canyon by Joyce (1974) does not mention the occurrence of C. bulbifera, but my examination of his collections has revealed one specimen of this species (Joyce WC634, ASC) misidentified as C. firagilis (L.) Bernh. Blasdell (1963, p. 28) stated that C. bulbifera usually grows on neutral soils associated with limestone, whereas Anderson (1974) indicated that in Nebraska it occurs on sandstone. In Arizona, I have collected this species on both substrates. Cystopteris bulbifera is abundant in the lower portion of the West Fork of Oak Creek Canyon (1550 m), occurring in large colonies on the red sandstone talus and cliffs capped by Kaibab limestone. Associated fern species are Adiantum capillus-veneris , A. pedatuim, and Polypodium hesperium. At higher elevations in the canyon (2000 m), where Cystopteris fragilis, Dryopteris filix-mas, and Polystichulmio lonchitis are found, the Bulblet Fern occurs on limestone outcrops and boulders. At Walnut Canyon, C. bulbifera occurs in a few small colonies at 1800 m in the narrow gorge to the southwest of the Walnut Canyon National Monument Headquarters. Here, the plants grow in shaded seepage sites on vertical cliffs of Kaibab limestone. Associated species are Cheilanthes feei, Cystopteris fragilis, and Selaginella underwoodii. Putative hybrids between C. bulbifera and C. fragilis from Walnut Canyon are currently under investigation. Since the only previously reported chromosome counts for C. bulbifera were based on specimens from eastern North America, an attempt was made to obtain

FORM AND STRUCTURE OF SILLS NEAR PANDO, COLORADO

Research Article| May 01, 1951 FORM AND STRUCTURE OF SILLS NEAR PANDO, COLORADO OGDEN TWETO OGDEN TWETO U. S. GEOLOGICAL SURVEY, 460 NEW CUSTOM HOUSE, DENVER 2, COLORADO Search for other works by this author on: GSW Google Scholar Author and Article Information OGDEN TWETO U. S. GEOLOGICAL SURVEY, 460 NEW CUSTOM HOUSE, DENVER 2, COLORADO Publisher: Geological Society of America Received: 11 Apr 1949 First Online: 02 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Copyright © 1951, The Geological Society of America, Inc. Copyright is not claimed on any material prepared by U.S. government employees within the scope of their employment. GSA Bulletin (1951) 62 (5): 507–532. https://doi.org/10.1130/0016-7606(1951)62[507:FASOSN]2.0.CO;2 Article history Received: 11 Apr 1949 First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation OGDEN TWETO; FORM AND STRUCTURE OF SILLS NEAR PANDO, COLORADO. GSA Bulletin 1951;; 62 (5): 507–532. doi: https://doi.org/10.1130/0016-7606(1951)62[507:FASOSN]2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Four varieties of early Tertiary quartz monzonite and quartz latite porphyries: the Elk Mountain, Lincoln, and Eagle River porphyries, and one here named the Pando porphyry, form numerous sills in the Pennsylvanian and Permian(?) clastic rocks of the southern part of the Gore Range, Colorado. The major sills are 50–400 feet thick and 1–10 miles across. The sills fall into two groups on the basis of form and structure. Sills of the Pando and Elk Mountain porphyries, the more widespread and uniform although they show local irregularities in form and are locally discordant, are in general tabular in cross section and irregular in ground plan. Near the contacts, the porphyry of the sills shows folds, intrusive-stage faults, platy parting produced by differential movement between thin laminar plates of magma during intrusion, and linear mineral orientation at right angles to the orientation in the inner part of the sill and to the direction of magma flow.Sills of the Lincoln and Eagle River porphyries are less extensive and more irregular in shape. They do not show intrusive-stage folds and faults except locally and poorly, and their linear mineral orientation is normally uniform from contact to contact and parallel to the direction of magma flow.The structural features of the sills of Pando and Elk Mountain porphyry suggest high magmatic viscosity; absence of these structures in sills of Lincoln and Eagle River porphyries suggests that these were more fluid magmas, a conclusion that is supported by the difference in contact metamorphism produced by sills of the two groups. Contrary to what should be expected, the most uniform and widespread sills thus seem to have been formed by viscous magmas, and the most irregular sills, some of which grade into laccolithic bodies, by relatively fluid magma. Emplacement of the viscous Pando and Elk Mountain magmas in uniform and widespread sills may have been aided by the lifting action of laterally compressed competent beds. The Lincoln and Eagle River sill magmas apparently were capable of making room for themselves by lifting the load; in doing so they compacted the host rocks, which being lenticular yielded unevenly, causing smallscale knobs, domes, swellings and constrictions to form in the sills. Large-scale or laccolithic doming occurred near the supply vent, probably as a result of rapid introduction of magma. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.