Open Access. Powered by Scholars. Published by Universities.®
- Discipline
- Keyword
-
- Precambrian (2)
- Ruby Range (2)
- Basin and Range (1)
- Big Sky Orogeny (1)
- Big Sky orogeny (1)
-
- Centennial shear zone (1)
- Craig Anticlinorium (1)
- Crustal velocity (1)
- Fault slip (1)
- Fractured aquifers (1)
- GPS geodesy (1)
- Geologic mapping (1)
- Geology (1)
- Geophysics (1)
- Groundwater (1)
- Kinematics (1)
- Monazite (1)
- Montana Geology (1)
- Montana Petroleum Exploration (1)
- Montana Structural Geology (1)
- Montana Triangle Zone (1)
- Montana stratigraphic record of the Precambrian-Cambrian transition (1)
- Neotectonics (1)
- Petrochonology (1)
- Petrogenesis (1)
- Petrology (1)
- Phase equilibria (1)
- Phase equilibria modeling (1)
- Rocky Mountain Front (1)
- Southwestern Montana Late Neoproterozoic to Early Cambrian stratigraphy (1)
Articles 1 - 9 of 9
Full-Text Articles in Tectonics and Structure
Petrogenesis And Tectonic Implications Of Cordierite-Orthoamphibole Gneisses (Cog) In The Nw Wyoming Province, Brianna K. Crenshaw Ms
Petrogenesis And Tectonic Implications Of Cordierite-Orthoamphibole Gneisses (Cog) In The Nw Wyoming Province, Brianna K. Crenshaw Ms
Graduate Student Theses, Dissertations, & Professional Papers
Studying cordierite orthoamphibole gneisses (COG) from five different mountain ranges across the Montana Metasedimentary Terrane (MMT) of the Wyoming Province offers a unique opportunity to elucidate the enigmatic origins and petrogenesis of the lithology in addition to gaining a further understanding of Precambrian crustal assembly processes. Geochemical analyses suggest that COG originates from a basalt that underwent metasomatic alteration, likely via seawater, prior to metamorphism. Moreover, COG is considered to represent oceanic crust that was part of the epicontinental sea adjacent to the Wyoming Province before collision with the Medicine Hat Block. Field observations of associated lithologies such as marbles, …
Quantifying Bedrock Recharge In Two Paired Mountainous Watersheds, Kimberly Bolhuis
Quantifying Bedrock Recharge In Two Paired Mountainous Watersheds, Kimberly Bolhuis
Graduate Student Theses, Dissertations, & Professional Papers
This study focuses on 1) estimating the magnitude of bedrock recharge and 2) mean transit time as a function of bedrock permeability in two paired catchments underlain by different lithology. Networks of bedrock wells and stream gauges were installed in two adjacent catchments of approximately the same size in west central Montana. Fracture network properties for both lithologies were characterized from borehole core logging and scan lines on exposed outcrop. Recharge was evaluated using the Water Table Fluctuation (WTF) method on bedrock well hydrographs installed in both catchments. Stable water isotope samples, collected approximately monthly, from precipitation and stream water …
A Record Of The Precambrian-Cambrian Transition In Sw Montana: A Late Neoproterozoic To Early Cambrian Stratigraphic Window, Fortunian Biostratigraphic Assemblage And Treptichnus Pedum, R. Reid Trippe
Graduate Student Theses, Dissertations, & Professional Papers
This study documents a Late Neoproterozoic through Early Cambrian stratigraphic record in the Humbolt anticline of southwestern Montana. The Precambrian-Cambrian transition includes a Fortunian-aged biostratigraphic trace-fossil assemblage with the ichnofossil Treptichnus pedum. The Humbolt anticline represents an inverted paleo-graben that exposes a stratigraphic window interpreted to be a record of rifting along the Cordilleran miogeoclinal margin, linked with the breakup of the Rodinia supercontinent. The graben subsided and captured sediment during late-stage rifting and final-stage dissociation along the rift margin. Its structural axis paralleled the rift margin. Sevier/Laramide orogenic thrusting inverted the graben into the Humbolt anticline. The Late …
Determining The Precambrian Structure And Thermotectonic Evolution Of The Central Ruby Range, Southwest Montana, Sara Vivienne Stotter
Determining The Precambrian Structure And Thermotectonic Evolution Of The Central Ruby Range, Southwest Montana, Sara Vivienne Stotter
Graduate Student Theses, Dissertations, & Professional Papers
The Ruby Range in southwestern Montana is a fundamental location within the Archean Wyoming craton for examining Precambrian crustal architecture and determining the thermotectonic evolution of the region. Monazite, zircon, and garnet geochronology from each of the three major units within the Ruby Range reveal two distinct metamorphic age populations: an older population ca. 2.55-2.45 Ga (the Tendoy orogeny) and a second, younger population ca. 1.78-1.72 Ga (the Big Sky orogeny). Phase equilibria modeling for the Big Sky orogeny within the confines of the Mine Gulch 7.5’ quadrangle reveal discrete pressure-temperature (P-T)histories for each of the three major …
Structural Analysis Of A Triangle Zone Culmination, Comb Rock, Lewis And Clark County, Montana, Shane S. Fussell
Structural Analysis Of A Triangle Zone Culmination, Comb Rock, Lewis And Clark County, Montana, Shane S. Fussell
Graduate Student Theses, Dissertations, & Professional Papers
A triangle zone is a structure commonly found at the leading edge of a thrust belt, characterized by a triangular cross-section of thrust faults. In the Montana triangle zone, west-dipping thrust faults intersect east-dipping ones above a regional detachment fault. Most studies of triangle zones focus on the structure in a cross-sectional sense, but little work addresses variations along the trend. The Canadian Rocky Mountain triangle zone has long been a productive petroleum province, so understanding the southern extent of this zone, where it enters Montana, is of interest for economic purposes as well as geologic understanding. Previous studies have …
Tectonic Alteration Of A Major Neogene River Drainage Of The Basin And Range, Stuart D. Parker
Tectonic Alteration Of A Major Neogene River Drainage Of The Basin And Range, Stuart D. Parker
Graduate Student Theses, Dissertations, & Professional Papers
Depositional characteristics of the ‘Divide unit’ of the Cretaceous Beaverhead Group within the southern Beaverhead Mountains challenge previous interpretations. This study reassigns the Divide unit to the Neogene. This revised age assignment highlights a major influx of immature sediment at the onset of Basin-Range normal faulting. Syntectonic deposition in an active half-graben continued from Middle Miocene to the Pliocene, attaining a thickness of 800 m. Local clasts of carbonate, siliciclastic and orthoquartzite entered the channel from the immediate west through large mass-wasting events. Dacitic fluvial cobbles dated herein to 98 Ma were transported from an unknown southwesterly source. Clasts of …
Kinematic Constraints On Tectonics Of The Northern Basin And Range, Dylan Schmeelk
Kinematic Constraints On Tectonics Of The Northern Basin And Range, Dylan Schmeelk
Graduate Student Theses, Dissertations, & Professional Papers
We derive surface velocities relative to North America, using data from 1989 through 2014 in the interior northwest, to investigate kinematics from the Snake River Plain (SRP) to the Canadian border. The Centennial Tectonic Belt (CTB) exhibits similarities to the main Basin and Range Province (BRP) that suggest the CTB is an extension of the BRP, including range and fault orientation, increasing velocity magnitudes westward, and a distinct high rate of strain across the Madison Range. Calculations of fault spreading rates and orientations from geodetic data show that several faults are more active than previously assumed when compared to seismic …
Spatial Scaling Of Crustal And Lithospheric Deformation In The Western United States, Cody W. Bomberger
Spatial Scaling Of Crustal And Lithospheric Deformation In The Western United States, Cody W. Bomberger
Graduate Student Theses, Dissertations, & Professional Papers
Deformation of continental lithosphere can extend great distances laterally from tectonic plate boundaries. This extent has been used to argue for a variety of constitutive laws for continental materials, based on the underlying principles in continuum mechanics that identify a relationship between characteristic spatial scale and material properties. Although the relationship between observed deformation and material models is always non-unique, quantifying one or more characteristic scales of deformation in a region can rule out some models of how the lithosphere deforms. In the western United States active deformation occurs at the plate boundary between North America and either the Pacific …
Proterozoic Tectonometamorphic Evolution Of The Ruby Range, Sw Montana, Usa: Insights From Phase Equilibria Modeling And In Situ Monazite Petrochronology, Martin Cramer
Graduate Student Theses, Dissertations, & Professional Papers
Phase equilibria modeling and monazite petrochronology reveal a complex history for the Ruby Range, SW Montana, which provides insights into the reactivation and growth of the northwestern Wyoming craton. Metapelites and orthoamphibolites from three areas were investigated. Stone Creek, the structurally highest area along the western flank, records a clockwise P–T path with peak conditions of ~6.5 kbar and ~760 °C and post-peak conditions of ~6.0 kbar and ~680 °C. Monazite growth in this area occurred at 1790–1723 Ma, with monazite inclusions in garnet at 1757 ± 8 Ma. Structurally deeper rocks at Elk Gulch in the south-central part …