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Earth Sciences

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2002

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Seasonal Biogeochemistry And Mineral Cycling Of The Middle Rio Grande Alluvial Aquifer, New Mexico, David Stewart Vinson Dec 2002

Seasonal Biogeochemistry And Mineral Cycling Of The Middle Rio Grande Alluvial Aquifer, New Mexico, David Stewart Vinson

Earth and Planetary Sciences ETDs

The Rio Grande in central New Mexico flows through a semi-arid, historically aggrading Quaternary rift basin. Flow regulation measures include dams, irrigation diversions, levees, and bank stabilization. These have caused severe impairment including incision, lowered water tables, and less overbank flooding; disrupted groundwater - surface water interactions; altered seasonal organic carbon dynamics; and declining native biota. Previously dynamic flowpaths in the shallow alluvial aquifer (hyporheic corridor) have become are less reversible due to parallel drain ditches with lower beds than the river. These ditches impose relatively static hydraulic gradients on the alluvial aquifer that force water to flow from the …


Integrated Geophysical Examination Of A Former Refinery Site, Carson City, Michigan, Kennedy Opiyo Mwanda Dec 2002

Integrated Geophysical Examination Of A Former Refinery Site, Carson City, Michigan, Kennedy Opiyo Mwanda

Masters Theses

Integrated geophysical surveys, including electromagnetic (EM-31), magnetic, dc resistivity, and ground penetrating radar (GPR) methods and soil borings were used to investigate part of a former refinery site in Carson City, Michigan, which has more than a 50-year history of hydrocarbon contamination.

Although not readily evident on the magnetic anomaly maps, the EM-31 conductivity map clearly revealed many sections of buried pipes of various lengths and orientations. Also evident on the EM maps are extensive near surface conductivity anomalies. Soil borings in zones of anomalous conductivities to the west suggest the presence of shallow clays with pooled hydrocarbons at depths …


Inorganic And Organic Chemistry Of The Former Lakeside Refinery In Kalamazoo, Michigan, Kurt W. Carlson Dec 2002

Inorganic And Organic Chemistry Of The Former Lakeside Refinery In Kalamazoo, Michigan, Kurt W. Carlson

Masters Theses

The focus of this investigation of the Lakeside Refinery site is the inorganic geochemistry because previous investigations concerned organics and heavy metals. Because little nitrate is in native groundwater, high dissolved ammonia immediately downgradient from a petroleum body suggests the source is the petroleum and/or associated byproducts. Iron reduction is most prominent immediately upgradient from the known and measurable petroleum while manganese reduction occurs mostly downgradient. Sulfate reduction occurs mostly towards the southern portion of the light petroleum LNAPL. Based on concentrations of nitrate, manganese, iron and sulfate along a groundwater flow path, there appears to be a sequential use …


Martian Xenon Components In Basaltic Shergottite Meteorites, Katherine Delene Ocker Stone Dec 2002

Martian Xenon Components In Basaltic Shergottite Meteorites, Katherine Delene Ocker Stone

Doctoral Dissertations

Analyses of Chassigny, Nakhla, and ALH84001 reveal, in addition to a Xe component from the martian atmosphere, a second component loosely attributed to the martian "interior." This appears to be a mixture of solar- and fission- (244Pu) derived xenon components. The proportions are consistent in each meteorite but vary from meteorite to meteorite. The working hypothesis is that this variation reflects different contributions of solar (mantle-derived) and fission (crustal-derived) xenon to each parent melt.

This study focused on mineral separates from two basaltic shergottites, Shergotty and EETA79001 Lithology-B (EETA), chosen to reflect, as far as possible, the extremes …


Microbial Community Structure In Hydrocarbon Impacted Sediment Associated With Anomalous Geophysical Signatures, Joseph W. Duris Dec 2002

Microbial Community Structure In Hydrocarbon Impacted Sediment Associated With Anomalous Geophysical Signatures, Joseph W. Duris

Masters Theses

The Crystal Refinery is a former refinery site in Carson City Michigan that has had historic releases of refined and unrefined crude oil dating back to the late 1940's. The contamination of soil with light non-aqueous phase liquids (LNAPL) has had a dynamic impact on the subsurface environment in adjacent Carson City Park. Very little is known about the complex interactions between microbial communities, geochemistry and geophysics. In order to investigate possible connections between these parameters a multidisciplinary study was undertaken to investigate the hypothesis that the degradation of LNAPL by resident microbial communities causes a local increase in organic …


Geoelectrical Response Of An Aged Lnapl Plume: Implications For Monitoring Natural Attenuation, Douglas D. Werkema Jr. Dec 2002

Geoelectrical Response Of An Aged Lnapl Plume: Implications For Monitoring Natural Attenuation, Douglas D. Werkema Jr.

Dissertations

The geoelectric stratigraphy at a site impacted with light non-aqueous phase liquids (LNAPLs) is investigated for its link to natural biodegradation, its contribution to the conductive model for aged (i.e. mature) LNAPL contaminated sites, and the relationship to the natural hydrologic regime. The highest conductivities (lowest resistivities) were observed in portions o f soils where LNAPL was in residual and free phase. Corroborating evidence from bacteria enumeration from soil close to the vertical resistivity probe (VRP) installations show orders-of-magnitude increase in both heterotrophic and oil degrading microbes at the depths where the conductivity was at a maximum. The coincidence o …


Geochemical And Isotopic Characteristics Associated With High Conductivities In A Shallow Hydrocarbon-Contaminated Aquifier, Franklyn D. Legall Dec 2002

Geochemical And Isotopic Characteristics Associated With High Conductivities In A Shallow Hydrocarbon-Contaminated Aquifier, Franklyn D. Legall

Dissertations

In-situ vertical resistivity probes (VRPs) deployed at a hydrocarboncontaminated site in SW Michigan showed high soil conductivities within the contaminated zone. Within this zone, different phases of hydrocarbon impact were recognized, namely, zones with residual and dissolved phase hydrocarbons (RDH) and zones where these phases coexist with free product (RDFH). Bulk soil conductivities were highest ( 12 to 30 mS/m) in the zone with RDFH compared to the RDH zone (10 to 25 mS/m). Groundwater chemistry and stable carbon isotope data from closely spaced vertical samples within the anomalous conductive zones were used to provide evidence for biodegradation and to …


Formation And Age Of Raised Marine Beaches, Northern Scott Coast, Antarctica, Nathan Gardner Dec 2002

Formation And Age Of Raised Marine Beaches, Northern Scott Coast, Antarctica, Nathan Gardner

Electronic Theses and Dissertations

The stability of the West Antarctic Ice Sheet (WAIS) is a key problem because of its potential effect on global sea level and climate. Some geologic evidence suggests that the ice sheet has collapsed in the past, which, if correct, implies that future disintegration is possible. Isolation of the mechanism(s) that have affected WAIS behavior since the last glacial maximum (LGM) may yield information about factors that control it today. Previous studies have indicated thatrecession of the WAIS from the LGM position occurred in the middle to late Holocene. However, the data come fiom points too far south to assess …


The Effect Of Nitrogen Loading On An Estuarine Faunal Community: A Stable Isotope Approach, Rachel A. Keats Dec 2002

The Effect Of Nitrogen Loading On An Estuarine Faunal Community: A Stable Isotope Approach, Rachel A. Keats

Electronic Theses and Dissertations

Coastal ecosystems worldwide face increased nutrient enrichment from shoreline and watershed development and atmospheric pollution. To gain an understanding of the effects of nitrogen loading on the natural faunal community of Ruppia maritima beds in Northeast Creek estuary (Acadia National Park, Maine, USA), we (1) assessed the response of the faunal community to increased nitrogen loading using an in situ enrichment experiment during the summer growing season of 2001 (Chapter I), and (2) completed a description of the natural macroinvertebrate community in the estuary in 2001 with qualitative (May-July) and quantitative (August-October) monthly sample collections (Chapter 2). This study formed …


Determining The Mobility Of Metals Through Coal Combustion Byproducts In Surface Impoundments By Analyzing Leachate From Modified Saturated Hydraulic Conductivity Tests, Michael Joseph Trofinoff Dec 2002

Determining The Mobility Of Metals Through Coal Combustion Byproducts In Surface Impoundments By Analyzing Leachate From Modified Saturated Hydraulic Conductivity Tests, Michael Joseph Trofinoff

Theses and Dissertations

Surface impoundments are used extensively throughout the utility industry to store the combustion byproducts, or ash, from coal-fired generating facilities. Following combustion, the metals, naturally contained within coal at low concentrations, may become highly concentrated within the ash. These combustion byproducts are then piped out in a water-ash slurry to the surface impoundments where the ash weathers to- a clay- like substance after approximately 10 years. It is feared that these metals that are contained within the ash could possibly leach into the ground and contaminate the local groundwater. Utilizing a open column percolation test to determine the hydraulic conductivity …


Relationships Between Stream Geomorphology And Fish Community Structure And Diversity In Maine, Emily Gaenzle Aug 2002

Relationships Between Stream Geomorphology And Fish Community Structure And Diversity In Maine, Emily Gaenzle

Electronic Theses and Dissertations

Predicting patterns in species distribution and abundance for resource management and conservation is a major focus of applied ecology. The primary objective of this study was to determine if there is a predictable relationship between stream geomorphology and fish community structure, native species richness, and native salmonid abundance in Maine. Specifically, I examined relationships between fish assemblages and geomorphic stream types, as delineated by the Rosgen classification system (Rosgen 1996). Fifty-three stream reaches in Maine were classified, and fish communities within the reaches were characterized using backpack electrofishing. Species richness was lowest in A-type streams (i.e., steep, entrenched, confined), which …


Late Holocene Sea-Level Change Around Newfoundland, Julia Daly Aug 2002

Late Holocene Sea-Level Change Around Newfoundland, Julia Daly

Electronic Theses and Dissertations

Analysis of basal salt-marsh peats and tide-gauge data from several locations around Newfoundland yield high-resolution late Holocene sea-level reconstructions and constrain differential sea-level change. The transition between rising and falling local sea levels and the influence of glacioisostasy on relative sea-level change around Newfoundland through the late Holocene are not well known fiom previous research. The patterns of local relative sea-level change during this time have important implications for constraining numerical models of sea-level change, and therefore inferences about ice sheet thickness and the response of the lithosphere to deglaciation. I investigated the stratigraphy of salt marshes at four locations …


Availability Of Organochlorides And Accumulation In Populations Of Tadarida Brasiliensis (Free-Tailed Bat) And Eptesicus Fuscus (Big Brown Bat), Michelle Lee Smith Aug 2002

Availability Of Organochlorides And Accumulation In Populations Of Tadarida Brasiliensis (Free-Tailed Bat) And Eptesicus Fuscus (Big Brown Bat), Michelle Lee Smith

Theses and Dissertations

Organochlorides were historically effective in controlling a wide range of pests. However, organochlorides have proved to present many problems to the health and welfare of other organisms. Due to these problems, especially declines in wildlife populations, organochlorides were restricted in the 1970's and a majority of them were banned in the mid to late 1980's. The effects of organochlorides on bats such as Tadarida brasiliensis and Eptesicus fuscus have been intensively studied. The effects can range from problems with reproduction to mortality. My analysis of populations of T. brasiliensis and E. fuscus showed that organochlorides are still present in the …


Using The Index Of Biotic Integrity Of Fish Communities To Evaluate Habitat Quality In Middle Chattahoochee River Tributaries, Theodor W. Roever Aug 2002

Using The Index Of Biotic Integrity Of Fish Communities To Evaluate Habitat Quality In Middle Chattahoochee River Tributaries, Theodor W. Roever

Theses and Dissertations

An ichthyological survey was conducted within the lower Piedmont and upper Coastal Plain physiographic regions of the middle Chattahoochee River drainage basin between August 1998 and September 2000. Sampling was conducted by Columbus State University (CSU) under contract to Columbus Water Works for the purpose of obtaining biological measurements of watershed health. Objectives of the survey were the establishment of a data baseline of IBI scores for this ecoregion and to ascertain if there was a correlation between the IBI score and human influence. The thesis to be tested is: 'Fish community IBI scores of different watersheds within the Middle …


Genesis And Morphology Of Soil Pendants In Quaternary Landforms Of Pahranagat Valley, Nevada, Amy Lynn Brock Aug 2002

Genesis And Morphology Of Soil Pendants In Quaternary Landforms Of Pahranagat Valley, Nevada, Amy Lynn Brock

UNLV Theses, Dissertations, Professional Papers, and Capstones

Five geomorphic surfaces present in the northern Pahranagat Valley, Lincoln County, Nevada range in age from Early Pleistocene to Recent (Q1-Q5) and vary in clast lithology from dolomite to volcanic tephras. Two chronosequences and 5 lithosequences were compared to evaluate micro and macromorphic characteristics and development of soil pendants. This study presents a new interpretation for soil pendant development. Key features observed in the Pahranagat Valley pendants provide evidence for precipitation at the clast-pendant contact suggesting that newer deposits are not always found at the pendant terminus as other studies have assumed. These features include a void at the clast-pendant …


Biogeochemistry Of The Middle Rio Grande Bosque: Links Among Surface Water, Groundwater, And Sediments, Susan E. Block Jun 2002

Biogeochemistry Of The Middle Rio Grande Bosque: Links Among Surface Water, Groundwater, And Sediments, Susan E. Block

Earth and Planetary Sciences ETDs

The potential for water contamination is great in areas where land use is both urban and agricultural. Such land uses can load the surface water and groundwater with nutrients and toxic trace metals. Water pollution can be further increased when natural watersheds have been altered by human activities. The surface and groundwaters of the Middle Rio Grande, NM, USA are part of one such ecosystem.

Because redox processes are important controls on nutrient cycling and contaminant transport, it is vital to understand the redox zonation of an aquifer. This research has been conducted to address such biogeochemical zonation in the …


The Role Of Groundwater And Surface Water Interaction In The Development Of A 1,4-Dioxane Plume In Scio Township, Washtenaw County, Michigan, James W. Brode Jun 2002

The Role Of Groundwater And Surface Water Interaction In The Development Of A 1,4-Dioxane Plume In Scio Township, Washtenaw County, Michigan, James W. Brode

Masters Theses

The purpose of this study was to examine the hypothesis that groundwater and surface water interaction resulted in the development a 1,4-dioxane plume in a glacial aquifer in Scio Township, Washtenaw County, Michigan.

An industrial solvent, 1,4-dioxane, was detected in the groundwater in the area of study in 1986. This area, referred to in this investigation as the Western Plume, is one of several 1,4-dioxane plumes associated with the Pall/Gelman Sciences Inc. (P/GSI) site, an extensively investigated site of groundwater contamination.

1,4-Dioxane in the Western Plume area was initially believed to be the result of contaminated groundwater transported from a …


Multiple Isotopic Investigation Of Lake Sediments From Northern India, Alice Mwanda Jun 2002

Multiple Isotopic Investigation Of Lake Sediments From Northern India, Alice Mwanda

Masters Theses

Stable isotopes ratio of lake sediments can provide valuable environmental information. This possibility has been investigated using radiocarbon dated fossil lake sediments from the Himalayan region of Northern India. The chronology was established using Radiocarbon dating of both organic and inorganic fractions using (AMS). Inorganic ages are older than organic ages. Organic ages are expected to increase stratigraphically, however several anomalous old ages are found in the younger part of the sediments. Final chronology, determined using selected sensible ages identified two periods of sedimentation. The high sedimentation period is characterized by sedimentation rate of 0.8cm/yr and it fairly coincides with …


Communicator-In-Chief: Presidential Use Of Television Past, Present, And Future, Jenna Wasson May 2002

Communicator-In-Chief: Presidential Use Of Television Past, Present, And Future, Jenna Wasson

Honors Theses

This thesis seeks to determine how television has changed as a communication medium for presidents over the past half century. An evaluation of the evolving ways presidents use television to communicate with and to build support from the American people has been conducted. Presidential communication strategies have been identified by drawing primarily from primary sources written by presidents and White House staff. Television technology and the television audience have changed over the years. Presidents have taken a more pro-active, aggressive role in their efforts to harness television for their own purposes. Why have these changes occurred? What impact have these …


Evolution Of Seabed Pockmarks In Penobscot Bay, Maine, Allen M. Gontz May 2002

Evolution Of Seabed Pockmarks In Penobscot Bay, Maine, Allen M. Gontz

Electronic Theses and Dissertations

Seafloor depressions, called pockmarks, have been known to exist in Penobscot Bay, Maine since the mid 1980's (Knebel and Scanlon, 1985). Earlier workers (Ostericher, 1965) recognized "channels" on sonoprobe records that are in the sanle area as the pockmarks recognized by Knebel and Scanlon (1985). Their origins and pathways of evolution are unknown. Much speculation about the sources of pore fluids, levels of activity, and evolutionary pathways has occurred since their discovery. Two surveys of Belfast Bay, in 1998 and 1989, have shown differences in the pockmark field population. Over the course of a decade, 36% of the field's 1998 …


Application Of Biophysical Data To An Unsupervised Classification To Map Ecoregional Boundaries In The Desert Southwest, Paxton R. Mcclurg May 2002

Application Of Biophysical Data To An Unsupervised Classification To Map Ecoregional Boundaries In The Desert Southwest, Paxton R. Mcclurg

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

An unsupervised classification was applied to continuous biophysical variables in an attempt to delineate ecoregional boundaries in the desert southwest. Output was then compared with ecoregions delineated by the Natural Resources Conservation Service (NRCS), the Environmental Protection Agency (EPA), and the Forest Service at the national level. An attempt was made to use the same biophysical variables for input into the unsupervised classification as was emphasized by the various agencies with their ecoregional classifications at the desert level. Major constraints included data availability at such a large study area, data resolution, and data that were continuous. This eliminated categorical data …


A Macroterrain Landtype Association Classification Model For The Great Basin, Frank L. Dougher May 2002

A Macroterrain Landtype Association Classification Model For The Great Basin, Frank L. Dougher

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Three Macroterrain Landtype Association classification models were developed to stratify and categorize Utah's West Desert. These models approached terrain segmentation using an energy-flow paradigm from erosional to transitional to depositional landscape. One model was developed as a slope-backed deterministic model that used slope-threshold limits to discriminate between Landtype Associations. A second model was developed as a stochastic, training-data driven supervised classification, using comparative t-values to classify the landscape to the most similar landtype class. The third model was a probabilistic algorithm, which classified the landscape to the most probable class based on multiple iterations of the stochastic model. These …


Stratigraphy And Paleoecology Of The Morrison Formation, Como Bluff, Wyoming, Melissa V. Connely May 2002

Stratigraphy And Paleoecology Of The Morrison Formation, Como Bluff, Wyoming, Melissa V. Connely

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The Morrison Formation at Como Bluff, Wyoming, has been historically known for containing a rich source of Late Jurassic vertebrate fossils. However, when collected, most of these fossils were not positioned into a stratigraphic or sedimentologic framework. Research shows that the Morrison Formation at Como Bluff can be divided into three members. These members can be identified by lithologic and paleontological characteristics. The lower Morrison members include the Windy Hill Member and the recently described Lake Como Member. The Windy Hill Member primarily contains near-shore marine sandstone. Megavertebrate fauna is lacking. The Lake Como Member contains illitic clay in red …


Geology Of The Cuesta Ridge Ophiolite Remnant Near San Luis Obispo, California: Evidence For The Tectonic Setting And Origin Of The Coast Range Ophiolite, Cameron A. Snow May 2002

Geology Of The Cuesta Ridge Ophiolite Remnant Near San Luis Obispo, California: Evidence For The Tectonic Setting And Origin Of The Coast Range Ophiolite, Cameron A. Snow

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The Cuesta Ridge ophiolite is one of the best-preserved remnants of mid-Jurassic ophiolite in California. Geologic mapping and petrologic studies show that it comprises (1) harzburgite mantle tectonite, (2) dunite-rich mantle transition zone (MTZ), (3) wehrlite and pyroxenite, (4) isotropic gabbro, (5) sheeted dike/sill complex, (6) volcanic rocks (7) late-stage dikes and flows, and (8) tuffaceous radiolarian chert.

The sheeted dike/sill complex is dominated by quartz diorite, with significant modal quartz and hornblende. The volcanic section is dominated by arc tholeiite and boninitic lavas. Boninites, with high MgO, Cr, and Ni comprise 40% of the volcanic rocks. Latestage dikes and …


Sedimentology, Facies Architecture, And Reservoir Characterization Of Lacustrine Rocks, Eocene Green River And Colton Formations, Uinta Basin, Utah, Andrew W. Taylor May 2002

Sedimentology, Facies Architecture, And Reservoir Characterization Of Lacustrine Rocks, Eocene Green River And Colton Formations, Uinta Basin, Utah, Andrew W. Taylor

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Outcrop and petrographic studies of the Eocene Green River and Colton formations in the Uinta basin, Utah, document the facies architecture and heterogeneity characteristic of lacustrine reservoirs. A southwest-northeast transect of Eocene strata in the Uinta basin records three main marginal lacustrine depositional environments: fluvial, deltaic, and wave-dominated. Heterogeneity exists between and within individual depositional systems.

Reservoir rocks of Outcrops One and Two (the flu vial facies of the Colton Formation and the deltaic facies of the Green River Formation, respectively) consist of 2 to 18 m thick lenticular, tabular, or undulatory channel-fill, distributary channel, and distributary mouth bar deposits …


Evolution Of A Miocene-Pliocene Low-Angle Normal-Fault System In The Southern Bannock Range, Southeast Idaho, Stephanie M. Carney May 2002

Evolution Of A Miocene-Pliocene Low-Angle Normal-Fault System In The Southern Bannock Range, Southeast Idaho, Stephanie M. Carney

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Geologic mapping, basin analysis, and tephrochronologic analysis in the Clifton quadrangle of southeast Idaho indicates that the modern Basin-and-Range topography is only a few million years old and that the bulk of Cenozoic extension was accommodated by slip on an older low-angle normal-fault system, the Bannock detachment system. The detachment system was active between ~12 and < 4 Ma and accommodated ~50 % extension.

Cross-cutting relationships show that the master detachment fault, the Clifton fault, is the youngest low-angle normal fault of the system, was active at a low angle, and has not been rotated to a low-dip angle through time. Map patterns and relationships indicate that the …


Geometry And Physical Properties Of The Chelungpu Fault, Taiwan, And Their Effect On Fault Rupture, Richard V. Heermance May 2002

Geometry And Physical Properties Of The Chelungpu Fault, Taiwan, And Their Effect On Fault Rupture, Richard V. Heermance

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Rupture of the Chelungpu fault during the September 21, 1999, 7.6 Mwearthquake in Taiwan caused a 90-Jr,m-long surface rupture with variable displacement along strike. Analysis of core from two holes drilled through the fault zone, combined with geologic mapping and detailed investigation from three outcrops, define the fault geometry and physical properties of the Chelungpu fault in its northern and southern regions. In the northern region, the fault dips 45-60° east parallel to bedding and consists of a narrow (1-20 cm) core of dark-gray, sheared clay gouge at the base of a 30-50 m zone of increased fracture …


Relationships Between Tributary Catchments, Valley-Bottom Width, Debris-Fan Area, And Mainstem Gradient On The Colorado Plateau: A Case Study In Desolation And Gray Canyons On The Green River, Caroline M. Elliott May 2002

Relationships Between Tributary Catchments, Valley-Bottom Width, Debris-Fan Area, And Mainstem Gradient On The Colorado Plateau: A Case Study In Desolation And Gray Canyons On The Green River, Caroline M. Elliott

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The alluvial forms of the rivers that drain the Colorado Plateau are a product of the water and sediment load that tributaries deliver to the trunk streams. Where the Green and Colorado Rivers cross structural barriers, narrow canyons have been incised. In the steep terrain adjacent to many of these canyons debris flows occur in the catchment basins of tributaries and deliver coarse sediment to the mainstem river corridor. Over time, debris flow deposits have aggraded in trunk stream valleys and created landforms known as debris fans. The sizes of these debris fans are related to the accommodation space available …


The Stratigraphic, Sedimentologic, And Paleogeographic Evolution Of The Eocene- Oligocene Grasshopper Extensional Basin, Southwest Montana, Joseph P. Matoush May 2002

The Stratigraphic, Sedimentologic, And Paleogeographic Evolution Of The Eocene- Oligocene Grasshopper Extensional Basin, Southwest Montana, Joseph P. Matoush

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Grasshopper basin, located in southwest Montana, is an east-tilted graben bounded by the listric Muddy-Grasshopper fault and the Meriwether Lewis fault on the eastern and western margins of the basin, respectively. This basin contains a complex stratigraphy of intertonguing facies comprised of five unconformity-bounded sequences of Tertiary alluvial, flu vial, deltaic, and lacustrine sedimentary and volcanic rocks. Sequence 1 consists of the Challis volcanic Group (Middle Eocene). The sedimentary rocks of the Medicine Lodge beds (Late Eocene-Late Oligocene) represent sequence 2 and approximately 90% of the basin-fill within Grasshopper basin. Sequence 3 consists 11 of the Sedimentary Rocks of Everson …


Structural And Kinematic Evolution Of Eocene-Oligocene Grasshopper Extensional Basin, Southwest Montana, Julie C. Kickham May 2002

Structural And Kinematic Evolution Of Eocene-Oligocene Grasshopper Extensional Basin, Southwest Montana, Julie C. Kickham

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The Grasshopper basin of southwest Montana is a complex east-dipping graben containing five unconformity-bounded sequences of Tertiary sedimentary rocks. The Eocene-Oligocene basin lies within the northern Rocky Mountain Basin and Range province. Geologic mapping in five and a half 7.5 minute quadrangles indicates that at least three distinct phases of extension characterize the Cenozoic tectonic evolution of Grasshopper basin from approximately 46 Ma to < Ma.

The significant phases of extension in Grasshopper basin were phases 1 and 3. During the first phase of extension (46-27 Ma) the nonplanar Muddy-Grasshopper fault was initiated and 90% of the basin fill was deposited. At …