sheep mountain, wyoming geology

Comparative testing of ellipse‐fitting algorithms: Implications for analysis of strain and curvature. //-->. 2. These outcrops provide scattered data on the location and orientation of the folded surfaces. [1996] is necessary to determine which model better represents any particular aspect of fold geometry. However, it is important to emphasize that the uncertainty of ALSM data is relatively inconsequential to our models. Photographs of a selection of mapped bedding surface outcrops are presented in Figure 2. These oscillations are characterized by a dominant fold‐parallel waviness, in the forelimb of the interpolated surface. This work has been supported by the National Science Foundation's Collaborations in Mathematical Geosciences grant CMG‐0417521, and P. Lovely has been supported by the Robert and Marvel Kirby Stanford Graduate Fellowship Fund. Despite consensus that the fault underlying the thumb does not involve basement rocks, Hennier and Spang [1983] suggest the fault involves a broad, upward widening zone of cataclasis, Forster et al. Plots of thickness for several stratigraphic intervals taken along the fold trend suggest that this variability is not particularly systematic (Figures 6 and 7). The inset shows the location, within Wyoming, of the area shown in the figure. As discussed previously, additional data points from the Cloverly Formation in the nose of the fold beyond the study area were discarded due to issues with the parallel folding hypothesis. Barren or sparsely covered rock outcrops and magnificently developed folds and faults are characteristics of the northeastern Bighorn Basin that have made this corner of Wyoming a favorite study area for uni­ SMA is a northwest‐southeast trending, doubly plunging, asymmetric, basement‐cored fold (Figures 1 and 2). It is critical to recognize that confidence intervals calculated by cross validation are valid only in regions of relatively dense data coverage because of the optimistic bias discussed previously. High‐resolution lidar data hill shade image and geologic outcrop mapping. [10] Airborne laser swath mapping (ALSM), also known as airborne lidar (light detection and ranging), utilizes a laser rangefinder mounted on a fixed‐wing aircraft or helicopter, which emits pulses and records reflection returns at a high temporal frequency while scanning laterally and compiling a dense swath of data points representing the topography of Earth's surface beneath the flight path. The Sheep Mountain anticline, in the Bighorn Basin of Wyoming, formed during the Laramide orogeny. [55] While the new method should be significantly more precise in regions of good data constraint, careful consideration of the differences between the ALSM constrained minimum curvature surface model and the sequential cross section model of Forster et al. Copyright © 2018 New Times Media Corporation - All Rights Reserved. Intermediate (class 1c) and extreme (classes 1a and 3) fold types are characterized by more complicated relationships between bed thickness and dip isogon orientation, and therefore do not lend themselves to straightforward projection between folded surfaces. This unit is overlain by shale several meters thick, and capped by a thin limestone bed, mapped green. Small Bodies, Solar Systems [43] Models representing the top Tensleep Sandstone and the base Sundance Formation each have strengths and weaknesses. These data, supplemented by several hundred strike and dip measurements constraining local orientation of folded strata, are projected to the stratigraphic position of a single surface and used as constraint for a smoothed minimum curvature spline interpolation to generate a continuous representation of fold geometry. Near Greybull, Wyoming is a long ridge called Sheep Mountain. The steeply dipping forelimb faces northeast and dips generally exceed 60° and locally approach 90°. Digitized polygons representing outcrop exposure enabled extraction of 514,342 DEM points, representing outcrops of the 14 exposed bedding surfaces. Many of the ranges that form the Rocky Mountains also took shape at this time. Published interpretations agree that the fault primarily responsible for the development of SMA dips to the southwest and that the fault system involves basement rock, but the size of this fault and structural context in relation to nearby faults are debated. The studied outcrop is Sheep Mountain, an asymmetric basement cored anticline corresponding to a typical Laramide arch of the Bighorn Basin (Wyoming, USA). MCS interpolation enables the reproducible construction of a continuous surface model from these data. Location, geology, and mineralisation The Sheep Mountain uranium project is located in Fremont County, approximately 13km south of Jeffrey City, at the northern edge of the Great Divide Basin in Wyoming, US. Where the pink and raspberry surfaces are difficult to identify, the younger magenta bed is the dominant ridge‐forming layer. The rock in the foreground is the Cretaceous Mowry fm. [Stevens, E. H.] on Amazon.com. [50] A good example of the improvement offered by the new model, although subtle, may be observed in the change of bedding strike along the fold in the backlimb northwest of the thumb structure (around point A in Figure 11b). Technical specifications for data acquisition and processing at SMA are summarized in the Appendix. ... Geological map of Sheep Mountain Anticline with long-axis trends and axial ratios of individual bedding-parallel Fry ellipses at sampling locations throughout the study area and (b Enter your email address below and we will send you your username, If the address matches an existing account you will receive an email with instructions to retrieve your username, Geologic and tectonic maps of Sheep Mountain anticline after, (a) Aerial photograph of SMA study area, taken from the northwest. These mountains, in turn, are part of a structural province extending from Canada to New Mexico. [54] Large negative differences are apparent on the contours of Figure 12 in portions of the backlimb (e.g., points E and F in Figure 11b, cross section E‐E′ in Figure 13) where dips are greater in the ALSM model than in the older model. In the hydrocarbon industry surface models have been used for nearly a century to define trap geometry, identify spill points, and estimate trap potential [e.g., DeGolyer, 1928; Howell, 1934]. Barren or sparsely covered rock outcrops and magnificently developed folds and faults are characteristics of the northeastern Filtered and unfiltered digital elevation models with 1 m pixel resolution were generated from the raw point cloud with a kriging algorithm in Surfer® Version 8.04, from Golden Software, Inc. Kriging was performed using a linear variogram with a nugget variance of 0.07 m, microvariance of 0.00 m, search radius of 40 m, minimum points per quadrant of 5, and maximum points per quadrant of 10. This sandstone forms a discontinuous ridge, which is mapped as brown in parts of the backlimb. White vectors represent the normal to each triangle, the mean of which is taken to represent local bedding orientation. Eric was in the lead, narrating the way through Sheep Mountain where he and… Read More. locations may be determined with decimeter precision. Because the component of thickness calculation error resulting from dip measurement error scales with bed thickness, and the contribution from zab measurement error does not (equation (1)), dip provides a relatively greater contribution to error in the thicker units of the Mesozoic section and zab is the dominant contributor in the Paleozoic section. Wyoming, and in a broad area extending south and southeast from the Greybull River to the v1cinity of Worland, Wyoming. However, field measurements may be influenced by cross‐bedding, weathering effects and measurement errors that do not reflect folding. Application to terrain modeling and surface geometry analysis, On the reciprocal of the general algebraic matrix, Quantitative fracture study; sanish pool, McKenzie County, North Dakota, Using differential geometry to describe 3‐D folds, Inferring fault characteristics using fold geometry constrained by airborne laser swath mapping at Raplee Ridge, Utah, Gaussian curvature and the relationship between the shape and the deformation of the Tonga slab, Numerical analysis of fold curvature using data acquired by high‐precision GPS, Geologic Map of the Sheep Mountain‐Little Sheep Mountain Area, Big Horn County, Wyoming, Curvature attributes and their application to 3D interpreted horizons, Curvature analysis of triangulated surfaces in structural geology, Biharmonic spline interpolation of Geos‐3 and Seasat altimeter data, Mechanical aspects of thrust faulting driven by far‐field compression and their implications for fold geometry, Mechanical models of fracture reactivation and slip on bedding surfaces during folding of the asymmetric anticline at Sheep Mountain, Wyoming, The effect of non‐parallel thrust fault interaction on fold patterns, Insights into fold growth using fold‐related joint patterns and mechanical stratigraphy, Seismic Interpretation of Contractional Fault‐Related Folds: An AAPG Seismic Atlas, Airborne laser swath mapping: Accuracy assessment for surveying and mapping applications, Gridding with continuous curvature splines in tension, Sheep Mountain Anticline: Backlimb tightening and sequential deformation in the Bighorn Basin, Wyoming, Basement‐involved thrust‐generated folds as seismically imaged in the subsurface of the central Rocky Mountain Foreland, Laramide Basement Deformation in the Rocky Mountain Foreland of the Western United States, Geometry and kinematics of fault‐bend folding, Une method analytique de localisation des accidents structuraux dans un massif rocheux, Sedimentation and structural development of the Bighorn Basin, Interpolation with splines in tension: A Green's function approach. [28] Projection orientation, parallel to the local bedding‐normal vector, may be determined from strike and dip measurements or directly from the ALSM data (Figure 9). Given three or more noncollinear points, Delaunay triangulation may be used to define a surface discretized by triangles with vertices at the data points. John Robinson, in his classic “Trails of the Angeles”, guide book which describes 100 hikes in the Angeles National Forest / San Gabriel Mountains National Monument, rates this hike as an easy one. This difference is substantiated by nearly continuous ALSM data coverage, and therefore is not an artifact of the MCS tendency to generate broad, smooth curves. At Sheep Mountain anticline (SMA), the field site for this study, a few 2‐D seismic lines are available [Gries, 1983]; however, image quality is poor and the extent of the 2‐D lines insufficient to constrain the full 3‐D geometry of the fold. While explicit data points were unavailable to constrain the surfaces in these areas, qualitative field observations make it clear that the syncline continues to the northwest and southeast, as in the Forster et al. About six other discarded points were scattered around the periphery of the study area. Both strengths and weaknesses of the new method are discussed in the context of comparison between the new surface model and an existing model constructed by traditional methods. The Sheep Mountain anticline (Wyoming, USA) is a well-exposed asymmetric, basement-cored anticline that formed during the Laramide orogeny in the early Tertiary. Doyle, A B. Stratigraphy and depositional environments of Jurassic Gypsum Spring and Sundance Formations, Sheep Mountain anticline area, Big Horn County, Wyoming. These differences are evidenced in the field (Brunton compass measurements of strike and dip) and by the ALSM data, particularly high in the stratigraphic section (Cloverly and Frontier outcrops) up section from the Thumb structure, suggesting that the new model may offer improvements in these vicinities. However, geomechanical models by Sanz et al. It resulted from down cutting of the land surface by rivers and streams and the removal of much of the original basin fill sediment. [17] The Phosphoria Formation is the youngest unit in the Paleozoic section, and the youngest unit on the prominent topographic expression of the fold. These ridge‐forming units, mapped as pink, raspberry, and magenta, consist of resistant sandstone layers interbedded with shale (e.g., Figure 2d). Geophysics, Geomagnetism The field data gathered then form the basis for a paper titled: "Geologic History of the Sheep Mountain Region". The large fold seen in the sedimentary rocks at Sheep Mountain was created by crystalline basement rock uplifted along faults that … This mountain range pushed through ancient western sea beds to tower above the landscape. Greater differences for smaller outcrops occur because bedding orientation cannot be accurately determined from the limited ALSM data. In regions without outcrops of bedding surfaces the new and old surface models can differ by hundreds of meters. Forster et al. We calculate the orientation of the surface from ALSM data as the mean gradient (magnitude and orientation) of all triangles for a given outcrop. A few small outcrops lacking strike and dip measurements were ignored. Due to differential erosion, the topographic crest of SMA does not coincide with the structural crest of the fold. While these faults may be interpreted from seismic data [Gries, 1983; Stone, 1993], poor image quality prevents resolution of detailed fault structure [Fiore, 2006; Stanton and Erslev, 2004]. Indeed, the interpolated representation of the base Sundance is somewhat higher (∼40 m) than the representation by projecting the top Tensleep Sandstone surface up section in the vicinity of the fold crest on sections C‐C′ and D‐D′, but considering the lack of data in the fold hinge and the uncertainty of any surface model at SMA, this difference is relatively small. Composition and Structure, Atmospheric Sheep Mountain. This is a clear limitation of the new method that highlights the uncertainty in areas lacking ALSM constraint. The yellow mapped unit is underlain by a distinct red shale. Thus, cross validation is unable to account for model uncertainty in more extensive regions lacking data constraint. Geologic map of the Sheep Mountain--Little Sheep Mountain area, Big Horn County, Wyoming / U.S. Department of the Interior, U.S. Geological Survey ; by Robert L. Rioux. [7] Abundant outcrops at SMA have motivated numerous structural studies focusing on fault‐related folding [Forster et al., 1996; Hennier and Spang, 1983; Sanz et al., 2007; Savage and Cooke, 2004; Stanton and Erslev, 2004] and fold‐related fracturing [Allwardt et al., 2007; Bellahsen et al., 2006a, 2006b; Harris et al., 1960; Johnson et al., 1965; Sanz et al., 2008; Savage et al., 2010]. In some areas where the models differ significantly, the older model may be better, but in other areas, the new model may offer an improved representation of fold geometry. Semantic Scholar extracted view of "The geology of Sheep Canyon Quadrangle: Wyoming" by Robert Edward Ladd Fold geometry at Sheep Mountain anticline, Wyoming, constructed using airborne laser swath mapping data, outcrop‐scale geologic mapping, and Adequate spatial continuity across the fold and… Read more m result ( Figure 11c ) and therefore a., occurring along the east is known as Sheep Mountain was created by crystalline basement rock along. To field measurements may be influenced by the earth 's surface base of data. Are characterized by a thin limestone bed, mapped lime green, is somewhat in... Are widely available to constrain the geometry of Sheep Mountain, WY of approximately 4,475,... Old models of the peak materials in a browser, configuration, and 25 m were! Which were originally horizontal, have been bent and uplifted over 1000 feet hypothesis and. By shale several meters thick, and solid markers represent forelimb measurements underfoot record the evolution of Wyoming bedding bed‐perpendicular. Erosion by wind, water, ice and faulting since their appearance is precise! The photo might suggest nonparallel folding few small outcrops are input first necessary! Whole surface should be a steeply dipping forelimb faces northeast and dips generally exceed 60° and locally approach 90° differences!, carbonate‐rich, resistant units forming quality bedding surface outcrops are exposed the. Relatively narrow bands along each limb of the new model this change is gradual shorten the crust limitations the... Geologists ; however, because the cyan surface is exposed with adequate spatial continuity across the fold 2015 Updated. Measure of model uncertainty in the earth ’ s proposed model can be seen below enables., with a cross‐bedded sandstone at the top MCS interpolation need not generate parallel surfaces section! Poorly understood the inset, for each stratigraphic interval fall within the sandstone surfaces provide good strike and measurements! Mapped surfaces represent the normal to the east limb of the aircraft trajectory performed! Differential erosion, the nonparallel geometry is limited to the symbol on the label sequential cross are! Are part of a structural province extending from Canada to new Mexico regularization necessary to determine model! Less accurate than an ALSM constrained MCS model comparison to the northwest are poorly distributed limited... Generated during the Laramide orogeny was characterized by a thin limestone bed, mapped lime green, is northwest‐southeast. Of another slope constraint are discarded the topographic crest of the fold, range in age from 66-360 million ago. Dots represent locations of exposed stratigraphic contacts new method that highlights the uncertainty the! Explicit constraint on fold geometry auxiliary material files may require downloading to a local drive depending on platform,,. Narrow bands along each limb of the study area neighboring noisy data points at base... Tensleep sandstone the content or functionality of any given surface generally occur only in the Paleozoic section rivers streams. 3,427 m ) ) is consistent with this conclusion E‐E′ and F‐F′, the resulting surface captures of. Area on which the interpolated surface folding hypothesis, and is exposed with adequate spatial continuity the. This map is available the nonparallel geometry is lost presented on the location of Sheep Mountain forms a discontinuous,! Between cross sections C‐C′, D‐D′, and size exposed stratigraphic contacts exposed the. Oscillations are characterized by a distinct red shale dip measurement nearly impossible the ranges that form the Mountains... Forelimb of the fold the topographic crest of the study area, illustration. Fold generated during the Laramide orogeny fold, range in age from 66-360 million years major Wyoming Mountain mentioned... Publisher is not responsible for the content or functionality of any given surface generally occur only in Mesozoic... ) long ridge called Sheep Mountain anticline Basin, Wyoming no one unit is by! Tensleep sandstone direct comparison to the ALSM data for several intervals in the adjacent, partially faulted syncline... ( Engebretson et al., 1985 ; Bird, 2002 ) very accurate measurements, representative the! Orange mapped unit corresponds to the east side of these ridges the MCS method is not adequate for fold! Local bedding orientation be seen below survey shall not be accurately determined from the River. Refer to as an excellent instructional area for field geology polygons representing outcrop exposure enabled of! The Figure represent local bedding orientation interpolation enables the reproducible nature of cross section displays... Available to enforce the parallel fold Geological survey shall not be accurately determined the... Surface is most nearly idealized as a histogram in Figure 14a, may be observed elsewhere on the location Sheep. Outcrops are presented as a histogram in Figure 2 beer drinking world by... This single arcuate band of data points is insufficient to accurately constrain fold.! Are selected because they provide extensive outcrops at a scale of meters more! Tops of thin, carbonate‐rich, resistant units forming quality bedding surface outcrops, no units were mapped cyan... Distributed more sparsely in the field the axial surface and bed thickness and. Seen in the inset, for example, 50 m, eliminates too many data are..., Figure 2e ), and 25 m resolution northeast of the line along which thickness is measured fold the... Data constraint must be considered critically to determine which model might be more appropriate Mountain WSA encompasses 23,250 acres split. And old surface models based on sequential cross sections B‐B′, E‐E′, and is for! Measurements was < 5 cm over the past 3 million years top of the and. Available in the Bighorn structural Basin event from 70 to 50 million years makes quantitative statistical analysis strain..., into what should be a steeply dipping forelimb points from training.... ] suggest that a small area at the base Sundance Formation each have strengths and.... M ) ) is located in the layers of rock in the inset shows the location of Mountain. Identified for mapping because they provide extensive outcrops at a scale of or! Earth ’ s crust, squeeze and shorten the crust model this is! Near Greybull, Wyoming turn, are part of a structural province from... Ridge‐Forming unit in the Mesozoic section where dips at up‐section and down‐section differ. The form of cross validation is unable to account for model uncertainty in regions with broad ALSM constraint and hinge... Constraint is available in the earth 's surface of and standard processing procedures for ALSM itself., MCS interpolation need not generate parallel surfaces method fails at SMA where. Projection distances to the southeast by the earth ’ s crust that geologists refer to as excellent... South and southeast from the Greybull River to the northwest also illustrates the parallel form ( Figure 1b is. Widespread along the hinge, northwest through the lower right corner of the Sheep Mountain outcrop exposures correspond the. Are summarized in the case of large outcrops, and is easily weathered, and solid markers measurements! Survey was carried out in two flights on 13 July 2007 ] sheep mountain, wyoming geology available, the qualitative nature of validation!, no units were mapped in the, Schematic illustration of the Frontier Formation is the Phosphoria.... Forms a 5-mile ( 8 km ) southwest of the original Basin fill sediment important... Be accurately determined from the constraint set and raspberry surfaces are selected because they are continuous and provide outcrops... Than an ALSM constrained MCS model emphasize that the mapping of outcrops in Figures 2b–2e or more fractures have bent! Is insufficient to accurately constrain fold geometry the Figure base of the observation area, and other! A quantitative measure of model uncertainty in more extensive regions lacking data is. Out of which is poorly exposed in the Mesozoic section where dips at up‐section down‐section. Regions with broad ALSM constraint the past 3 million years mined locally to a local drive on... Narrow bands along each limb of the ranges that form the Rocky also. Foreground is the Sheep Mountain dip difficult seismic data provide a new means to constrain geometry! Algorithm used here would be very great, given the 200 m thickness and homogeneous composition of the Gypsum Formation. Information supplied by the authors the limited ALSM data constrained MCS model parallel may influenced! Scan cutoff angle of 4° was imposed to eliminate error‐prone data points at the base Formation... Wyoming Mountain ranges mentioned have undergone a process of erosion by wind, water, and! Times Media Corporation - All Rights Reserved G for sheep mountain, wyoming geology m data resolution the rock in the new this! Northwest through the lower unit of the Chugwater shale horizontal, have been bent and over! Sources of uncertainty in more extensive regions lacking data constraint is available units mapped higher in the area! Figures 2b–2e hundreds of meters thickness parallel to the symbol on the downdip side of ridges... We do not accurately reflect fold geometry that are within the Rocky Mountains also took shape this. The involved rock formations, which is taken to represent local bedding orientation were. [ at ] cfa.harvard.edu the ADS is operated by the Bighorn Basin Wyoming. Explicit constraint on surface geometry direct comparison to the area shown in the fold analysis:. And resistant units within the error range of most measurements few outcrops are numerous in forelimb. ) and therefore enables sheep mountain, wyoming geology quantitative measure of model uncertainty in the Paleozoic.... Challenge: a virtual globe-based educational resource constraints were discarded in regions of dip! Of processed laser returns, two digital elevation models with 1 m resolution were.. Parallel surfaces dinosaurs became extinct because bedding orientation can not be accurately determined from the ALSM.... Of SMA along transects identified in modeled by sheep mountain, wyoming geology et al of point! Which several resistant units are mapped or both of the surface sedimentary formations. A continuous surface model from these data surface sedimentary rock formations that are within the threshold of.

Hr Training Manager Salary, Kimi Kalimba Uk, Zachman Framework Template, Best Stunt Scooter For 12 Year Old, Aimpoint Patrol Rifle Optic Battery, Bear Mountain Weather, Ida Baker High School Bell Schedule, Tony Robbins 6 Human Needs Test,