Geology Commons^™

Evolution Of A Late Cenozoic Supradetachment Basin Above A Flat-On-Flat Detachment With A Folded Lateral Ramp, Se Idaho, A. N. Steely, Susanne U. Janecke, S. P. Long, S. C. Carney, R. Q. Oaks Jr., V. E. Langenheim, P. K. Link

Geosciences Faculty Publications

Uplift and exposure of the Bannock detachment system and the synextensional basin fill deposits of the Salt Lake Formation provide a unique exposure of the three-dimensional geometries of a low-angle normal fault system and the stratal architecture of the overlying supradetachment basin. Within this system, structural and stratigraphic analyses, outcrop patterns, tephra geochronology, and geological cross sections document several important relationships: (1) the Bannock detachment system developed above the Sevierage Cache-Pocatello culmination and resembles the Sevier Desert detachment in its geometry, structural setting, and kinematic evolution; (2) the Bannock detachment system initiated and slipped at low angles; (3) flat-on-flat, ramp-flat, …

Geologic Map Of The Bachelor Mountain 7.5' Quadrangle Beaverhead County, Montana, Susanne U. Janecke, R. J. Dorsey, J. C. Kickham, J. P. Matoush, W. Mcintosh

Geosciences Faculty Publications

Geologic Map of the Bachelor Mountain 7.5’ Quadrangle Beaverhead County, Montana Geologic Summary The Bachelor Mountain quadrangle is located in the Horse Prairie Creek drainage basin of southwest Montana and contains exposures of Middle Proterozoic metasedimentary rocks and eighteen map units of Eocene to Oligocene basin-fill deposits assigned to the Medicine Lodge beds. Locally, overlying upper Oligocene to lower Miocene(?) Everson Creek beds and late early to early late Miocene Bannack Pass beds are also preserved as basin-fill deposits. The Medicine Lodge beds were deposited in an early basin, the Grant protobasin (Fig. 1a), during slip on the Muddy-Grasshopper detachment …

Great Plains Workshop Held To Prepare For Usarray Deployment, Mary S. Hubbard, S. S. Gao, K. H. Liu, K. E. Nicolaysen, C. G. Oviatt

Geosciences Faculty Publications

Relative to most parts of North America, the Great Plains region, which is bordered by the Rocky Mountain Front on the west and the Mississippi River on the east, has been understudied in terms of the structure, formation, and evolution of the underlying crust, mantle, and core. The anticipated arrival of the USArray portable seismic stations, which will cover the entire United States regardless of surface geology and tectonic activities, and the deployment of the accompanying flexible array stations and the permanent seismic stations in this area, will fill this gap and address numerous problems related to the structure and …

High Altitude Himalayan Climate Inferred From Glacial Ice Flux, Joel T. Harper, Neil Humphrey

Geosciences Faculty Publications

Glaciological processes are modeled to investigate precipitation patterns and the resulting mass flux of snow and ice across Himalayan topography. Our model tracks the accumulation and ablation of snow and ice and the transport of snow and ice across the topography by glacier motion. We investigate high elevation precipitation on the Annapurna Massif by comparing the existing ice cover with model-simulated glaciers produced by a suite of different precipitation scenarios. Our results suggest that precipitation reaches a maximum level well below the elevation of the highest peaks. Further, essentially no snow accumulates on the topography above an elevation of 6200–6300 …

Hydrologic Properties And Structure Of The Mozumi Fault, Central Japan, Craig B. Forster, James P. Evans, Hidemi Tanaka, Ronald Jeffreys, Tsuyoshi Nohara

Geosciences Faculty Publications

Analyses of rocks from the Active Fault Survey Tunnel (AFST) provides insight into the structure and hydrogeology of the northeast-trending Mozumi-Sukenobu fault, an active strike-slip fault with 125 to 500 m of right-lateral slip in central Japan. Interlayered regions of sub-vertical permeability zones formed by cataclasis and slip on clay-rich foliated zones. Core samples range from 10⁻¹⁹ m² to almost 10⁻¹³ m². CFC analyses of waters from the fault zone show that water entering the tunnel is 27–36 years old, yielding a bulk fault permeability of 10⁻¹⁴ to 10⁻¹⁵ m². The …

Extensional Folds Associated With Paleogene Detachment Faults In Se Part Of The Salmon Basin, Susanne U. Janecke, J. C. Blankenau

Geosciences Faculty Publications

No abstract provided.

Late Miocene-Pliocene Detachment Faulting And Pliocene-Recent Basin-And-Range Extension Inferred From Dismembered Rift Basins Of The Salt Lake Formation, Se Idaho, Susanne U. Janecke, S. M. Carney, M. E. Perkins, J. C. Evans, P. K. Link, R. Q. Oaks Jr., B. P. Nash

Geosciences Faculty Publications

Geologic mapping, basin analysis, and tephra correlations in the Clifton and Malad City East 7.5-minute quadrangles in southeastern Idaho indicate that the modern Basin-and-Range topography is only a few million years old and was superimposed on unrelated rift basins associated with the ~12 to < 4 Ma Bannock detachment system. The Miocene-Pliocene Salt Lake Formation in the greater Cache Valley area was deposited during three sub-episodes of west-southwest extension on the Bannock detachment system.

Depositional systems within the Salt Lake Formation (>10.27 ± 0.07 Ma to < 5.1-4.4 Ma) evolved in response to the changing structural configuration of rift basins in the hanging wall of the Bannock detachment system. Early alluvial fans derived from the underlying Paleozoic rocks were replaced by broad, saline/alkaline lakes during the translation phase on the detachment fault. Later, as the hanging wall broke up internally, freshwater lakes and deltas occupied newly created NE-tilted half graben, and eventually filled them with braided streams. The Bannock detachment system collapsed the Cache-Pocatello Culmination of the dormant Sevier fold-and-thrust belt, much like the Sevier Desert Detachment collapsed the Sevier Culmination and the Wasatch Fault collapsed the Wasatch Culmination.

Deposition and tilting of the Salt Lake Formation ceased in the middle to late Pliocene (< 2 >Ma?) before uplift of the Clifton Horst along a new system of Basin-and-Range normal faults. This later episode of normal faulting uplifted and exposed metamorphic rocks in …

High Plains To Rio Grand Rift: Late Cenozoic Evolution Of Central Colorado, E. M. Leonard, Mary S. Hubbard, S. A. Kelley, E. Evanoff, C. S. Siddoway, C. G. Oviatt, M. Heizler, M. Timmons

Geosciences Faculty Publications

No abstract provided.

Dextral Shear Along The Eastern Margin Of The Colorado Plateau- A Kinematic Link Between Laramide Contraction And Rio Grande Rifting (Ca 75 Ma To 13 Ma), T. F. Wawrzyniec, J. W. Geissman, M. D. Melker, Mary S. Hubbard

Geosciences Faculty Publications

Kinematic data associated with both Laramide‐age and ‐style and Rio Grande rift‐related structures show that the latest Cretaceous to Neogene interaction between the Colorado Plateau and the North American craton was dominantly coupled with a component of dextral shear. Consistent with earlier studies, minor‐fault data in this study yielded results of varied kinematics. Inverted to a common northeast‐oriented hemisphere, the mean trend of kinematic shortening associated with Laramide‐age structures is 056∘±6" role="presentation" style="box-sizing: border-box; display: inline; line-height: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px …

C-Band Sar Backscatter Characteristics Of Arctic Sea And Land Ice During Winter, Konrad Steffen, John Heinrichs

Geosciences Faculty Publications

Synthetic Aperture Radar (SAR) data has become an important tool for studies of polar regions, due to high spatial resolution even during the polar night and under cloudy skies. We have studied the temporal variation of sea and land ice backscatter of twenty-four SAR images from the European Remote Sensing satellite (ERS-1) covering an area in Lady Ann Strait and Jones Sound, Nunavut, from January to March 1992. The presence of fast ice in Jones Sound and glaciers and ice caps on the surrounding islands provides an ideal setting for temporal backscatter studies of ice surfaces. Sample regions for eight …

Normal Faults And Extensional Folds Of Southwest Montana And Eastern Idaho, Susanne U. Janecke, J. J. Blankenau, C. J. Vandenburg, B. S. Van Gosen

Geosciences Faculty Publications

No abstract provided.

Geologic Map Of The Lima 30' X 60' Quadrangle, Southwest Montana, J. D. Lonn, B. Skipp, E. T. Ruppel, Susanne U. Janecke, W. J. Perry, J. W. Sears, M. J. Bartholomew, M. C. Stickney, W. J. Fritz, H. A. Hurlow, R. C. Thomas

Geosciences Faculty Publications

No abstract provided.

Stratigraphy And Tectonics Of Tertiary Strata Of Southern Cache Valley, North-Central Utah, R. Q. Oaks Jr., K. A. Smith, Susanne U. Janecke, M. E. Perkins, W. P. Nash

Geosciences Faculty Publications

Southern Cache Valley occupies one of several large north-trending valleys in the northeastern part of the Basin and Range Province. It lies between the Wellsville Mountains in the west and the Bear River Range in the east. Paleozoic rocks exposed in the two mountain ranges dip easterly adjacent to the north part of the study area and in a narrow horst along the valley center in the south, but curve to a northerly dip in the southwest. A complex depositional and tectonic evolution of Tertiary strata in southern Cache Valley was determined in this study. Detailed photogeologic and field mapping, …

Folded And Faulted Salt Lake Formation Above The Miocene To Pliocene New Canyon And Clifton Detachment Faults, Malad And Bannock Ranges, Idaho: Field Trip Guide To The Deep Creek Half Graben And Environs, Susanne U. Janecke, J. C. Evans

Geosciences Faculty Publications

Previous studies identified a major detachment terrane in southeast Idaho in the Oxford Ridge area of the Bannock Range. This study shows that these top-to-the-WSW detachment faults are late Cenozoic in age, not Mesozoic to early Tertiary as previously inferred. Provenance and facies patterns in the Miocene-Pliocene Salt Lake Formation in the Deep Creek supradetachment basin show that deposition was syntectonic to slip on the detachment faults. The highly extended Bannock detachment terrane likely persists north to the Snake River Plain and south into Utah. The breakaway for this system lies in the Portneuf Range to the east. At least …

Geologic Map Of The Logan Quadrangle, Cache County, Utah, James P. Evans, James P. Mccalpin, David C. Holmes

Geosciences Faculty Publications

No abstract provided.

Constraints On Unroofing Rates In The High Himalaya, Eastern Nepal, Mary S. Hubbard, L. H. Royden, K. V. Hodges

Geosciences Faculty Publications

Thermobarometric data for samples across the Main Central thrust zone in eastern Nepal show an inversion in temperature but not in pressure. These data have been interpreted to represent a portion of the paleogeotherm at the time of Main Central thrust deformation. A 40Ar/39Ar age on hornblende (closure temperature (Tc)=500±50°C) constrains the timing of this deformation to be ∼21±0.2 Ma. The 40Ar/39Ar ages of other minerals (muscovite, Tc=350°C, age (t)=12.0±0.2 Ma; K-feldspar, Tc=220°C, t=8.0±0.2 Ma) from the same location further constrain the cooling history of this region. Together the geochronologic and thermobarometric data yield an average unroofing rate of 1.2±0.6 …

Hydrogeology Of Thrust Faults And Crystalline Thrust Sheets: Results Of Combined Field And Modeling Studies, Craig B. Forster, James P. Evans

Geosciences Faculty Publications

Field, laboratory, and modeling studies of faulted rock yield insight into the hydraulic character of thrust faults. Late‐stage faults comprise foliated and subparallel faults, with clay‐rich gouge and fracture zones, that yield interpenetrating layers of low‐permeability gouge and higher‐permeability damage zones. Laboratory testing suggests a permeability contrast of two orders of magnitude between gouge and damage zones. Layers of differing permeability lead to overall permeability anisotropy with maximum permeability within the plane of the fault and minimum permeability perpendicular to the fault plane. Numerical modeling of regional‐scale fluid flow and heat transport illustrates the impact of fault zone hydrogeology on …

40ar/39ar Age Constraints On Deformation And Metamorphism In The Maine Central Thrust Zone And Tibetan Slab, Eastern Nepal Himalaya, Mary S. Hubbard, T. M. Harrison

Geosciences Faculty Publications

No abstract provided.