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Geology

University of Wisconsin Milwaukee

Theses/Dissertations

2018

Articles 1 - 7 of 7

Full-Text Articles in Physical Sciences and Mathematics

Analyzing Ductile Shear Zone Network Geometries In The Grassy Portage Sill, Rainy Lake Region, Northwestern Ontario, Canada, Ernest John Thalhamer Dec 2018

Analyzing Ductile Shear Zone Network Geometries In The Grassy Portage Sill, Rainy Lake Region, Northwestern Ontario, Canada, Ernest John Thalhamer

Theses and Dissertations

The Grassy Portage Sill (GPS) is a ~2.7 Ga metagabbroic sill located in the Rainy Lake region of northwestern Ontario. The Rainy Lake region is located in the Superior Province between the metavolcanic Wabigoon subprovince to the north and the metasedimentary Quetico subprovince to the south. Two regional faults bound the region and intersect to the east, forming a wedge which defines the Rainy Lake zone. This area was regionally deformed due to oblique transpression, resulting from the Kenoran Orogeny (~2.7 Ga). The GPS is approximately 20 km long and 1-2 km wide, and has undergone heterogeneous strain along its …

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The Geochemistry And Mineralogy Of Surface Hydrothermal Alteration At Nesjavellir, Sw Iceland, Chase Glenister Aug 2018

The Geochemistry And Mineralogy Of Surface Hydrothermal Alteration At Nesjavellir, Sw Iceland, Chase Glenister

Theses and Dissertations

Abundant sulfates have been detected by the Mars Exploration Rover Spirit in the Columbia Hills of Mars, consistent with extensive alteration of basalt by hydrothermal processes. This study uses Iceland’s Nesjavellir geothermal system as an analogue for Columbia Hills hydrothermal alteration. This terrestrial site is home to a variety of acidic and near-neutral waters that are actively altering the Mars-like basalt of host volcano Mt. Hengill. Hydrothermal features heated by H2S gas and phase-segregated steam created oxidizing acid-sulfate conditions at the surface with pH values varying between 3.0 and 2.0 and near-boiling temperatures. Mobilization of cations (FeO, MgO, CaO, Na2O, …

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Invertebrate Paleoecology Of High Paleo-Latitude Carboniferous Strata Of The Tepuel-Genoa Basin, Argentina, Kate M. Gigstad May 2018

Invertebrate Paleoecology Of High Paleo-Latitude Carboniferous Strata Of The Tepuel-Genoa Basin, Argentina, Kate M. Gigstad

Theses and Dissertations

The Late Paleozoic Ice Age (LPIA), which began in the latest Devonian and ended in the Late Permian, was a time of active environmental changes. During this time, glaciers waxed and waned over the ancient continent of Gondwana that was situated over the southern pole. This time of transition from icehouse to greenhouse in the Permian is our closest analogue to our current environmental conditions and increased knowledge of our planetary past will greatly influence our future. Much of the previous research on marine invertebrate paleoecology during the LPIA occurs in far-field or low paleolatitude localities, but less is known …

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Characterizing The Geochemical Changes Across A Strain Gradient In The Beja-Acebuches Metabasites Due To Retrograde Metamorphism And Fluid Flow Along The Southern Iberian Shear Zone, Sheryl Stephenson May 2018

Characterizing The Geochemical Changes Across A Strain Gradient In The Beja-Acebuches Metabasites Due To Retrograde Metamorphism And Fluid Flow Along The Southern Iberian Shear Zone, Sheryl Stephenson

Theses and Dissertations

The Southern Iberian Shear Zone (SISZ), SW Spain, provides an ideal location to study the effects of syntectonic fluid on rock chemistry, deformation, and metamorphism. The SISZ is a 60km long, 300-500m wide shear zone, striking 115 and dipping approximately 50 degrees to the NNE, that follows the contact between metamorphosed MORB-derived Acebuches metabasites (AB) of the Ossa-Morena zone and the metamorphosed Pulo do Lobo (PdL) accretionary prism. Both units underwent two deformational events: 1) a HT/LP event that reached amphibolite facies and significantly dehydrated the rocks, and 2) a retrograde metamorphic event from amphibolite-greenschist facies that required the addition …

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Depositionally-Induced Magnetic Frequency Variations Of A Sandstone Facies Of The Copper Harbor Conglomerate From The North American, Mid-Continent Rift At Union Bay, Michigan, Elizabeth Anne Borucki May 2018

Depositionally-Induced Magnetic Frequency Variations Of A Sandstone Facies Of The Copper Harbor Conglomerate From The North American, Mid-Continent Rift At Union Bay, Michigan, Elizabeth Anne Borucki

Theses and Dissertations

The Mesoproterozoic, Copper Harbor Conglomerate Sandstone Facies of Union Bay, Michigan was investigated to determine whether fluvial red beds from deep time can maintain magnetic variations related to deposition. Additionally, the possibility that magnetic variations represent astronomically forced climate cycles was also explored at this site. The study utilized environmental magnetism and cyclostratigraphic techniques. The magnetic mineralogy was characterized using temperature dependent susceptibility, isothermal remanent magnetization, and anisotropy of magnetic susceptibility to determine composition, approximate grain size, abundance, and magnetic shape and orientation. For a partial cyclostratigraphic study, sequential, outcrop based magnetic susceptibly measurements were taken stratigraphically every 0.47 m …

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Paleobiology And Taphonomy Of Exceptionally Preserved Putative Macroalgae From The Ediacaran Zuun-Arts Biota, Zavkhan Province, Mongolia, Keenan Hassell May 2018

Paleobiology And Taphonomy Of Exceptionally Preserved Putative Macroalgae From The Ediacaran Zuun-Arts Biota, Zavkhan Province, Mongolia, Keenan Hassell

Theses and Dissertations

The first unequivocal evidence of complex multicellular life appears in exceptionally preserved Ediacaran (635-541 Ma) fossil deposits. The newly discovered Ediacaran Burgess Shale-type (BST) Zuun-Arts Biota of Zavkhan Province, Mongolia, contains putative macroalgae fossils. Morphological measurements of 821 individual specimens including length, width, and branching angle obtained using ImageJ software were used to calculate morphological parameters including median thallus length (16.75 mm), filament width (0.50 mm), branching angle (63.63⁰), and surface area/volume ratio (8.19 mm -1). The Zuun-Arts biota contains fossils of six distinct morphotypes: non-branching, dichotomous branching, monopodial branching, fan-shaped, shrub-like, and small non-branching, all morphologies are similar to …

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Hydrothermal Alteration At Devil's Kitchen In The Lassen Volcanic National Park: A Mars Analogue, Andy Wanta May 2018

Hydrothermal Alteration At Devil's Kitchen In The Lassen Volcanic National Park: A Mars Analogue, Andy Wanta

Theses and Dissertations

The Devil’s Kitchen hydrothermal site, within the Lassen Volcanic National Park, has hydrothermal features that cover a wide range of pH conditions (2-7). Analysis of mineral precipitates, hot spring mud, unaltered substrate rock, and hot spring and meteoric water reveal a wide variety of alteration minerals, geochemical conditions, and water chemistry. Mineral suites included primary igneous phases, silica phases, clay minerals, and sulfate phases. Aluminum sulfates are the dominant sulfate species present with abundant Na+, Fe3+, and Ca2+ sulfate phases and less common K+ sulfates. Amorphous silica precipitates were observed in three samples from a near-neutral hot spring and one …

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