Earth and Environmental Sciences Dissertations, Theses, and Plan B Project Papers
Persistent link for this collectionhttps://hdl.handle.net/11299/212256
This collection contains some of the final works (dissertations, theses, and Plan B project papers) produced by master's degree and doctoral students in the Department of Earth and Environmental Sciences (or its predecessors) as part of their requirements to graduate. Specific master's degree programs over the years have included Master of Science in Geology, Master of Science in Geological Sciences, Master of Science in Earth Sciences, and Master of Science in Earth and Environmental Sciences (the current iteration as of spring 2024).
To see final works for specific degrees, click the links below. NOTE: Newer dissertations and theses from roughly 2007 on (including all theses from the Master of Science in Earth Sciences program) will not appear in the lists linked below, though some do appear in this collection. (For the most up-to-date new dissertations and theses, see the University of Minnesota Twin Cities Dissertations and Theses collection.) Newer Plan B project papers will appear in the lists.
- Master of Science in Geological Sciences (items date from roughly 2004-2024)
- Master of Science in Geology (items date from roughly 1971-2021)
- Doctor of Philosophy (PhD) (items date from roughly 1976-2011)
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Item Macrofabric Analysis of Glacial Till(1971-12) Saremba, Scott PPrevious studies on till fabrics of glacial tills indicate that the fabric elements are oriented in preferred directions. The long axes of elongated fabric elements are statistically oriented parallel or transverse to the directions of ice flow. Published studies on the mechanisms by which stones in till become oriented reveal that there is no one set mechanism by which a fabric element obtains a preferred orientation. A study of the till fabrics of the Twig, Independence, and Alborn quadrangles of northeastern Minnesota shows that the glacial tills usually have two preferred orientations, a major and minor orientation. The directions of the two preferred orientations of the till fabric are approximately at right angles to each other. In most cases the major preferred orientation is parallel to the direction of the known ice flow, but in some till fabrics the major preferred orientation is transverse to the direction of known ice movement. The long axes of elongated stones usually plunged up-glacier in the drumlin till, but there was no consistency to the pattern of plunge in the ground moraine till. It is advisable to limit as many variables of the till fabric element such as size, shape, and axial-ratio to obtain accurate results. The positive correlation obtained between the results of the author's till fabric analysis and Wright's and Watt's (1969) interpretation of the studied area support the use of preferred orientation of till fabric as a meaningful indicator of ice movement.Item The Petrology and Sedimentation of the Basal Keweenawan Sandstones of the North and South Shores of Lake Superior(1972-03) Mattis, Allen FrancisThe Puckwunge Formation of northeasternmost Minnesota is intermittently exposed for a 25-mile stretch beneath the Keweenawan North Shore Vo1canic Group. The formation consists of a basal conglomerate and an overlying orthoquartzite, with the maximum estimated total thickness of the formation being 300 feet. Its composition, texture, and structures indicate that the formation was derived from pre-Keweenawan rocks to the North, and was deposited in a high-energy, near-shore environment. The formation disconformably rests on the Middle Precambrian Rove Formation, and is disconformably overlain by Keweenawan lava flows. The Puckwunge Formation is inferred to be correlative with the nearby Sibley Formation of Ontario. The Sibley Formation is disconformably overlain by sedimentary rocks and lava flows of the Osler Formation, also Lower Keweenawan in age. Sedimentary rocks correlating with the Osler Formation are not present in northeasternmost Minnesota. At Nopeming, just west of Duluth, Minnesota, 28 feet of orthoquartzite and interbedded conglomerate are exposed beneath Keweenawan lava flows. Quartzite is the dominant lithology present, with minor metasiltstone interbedded with the quartzite just below the lava flows. The sediments were principally derived from pre-Keweenawan rocks of the area, and deposited by northward-flowing currents, with minor amounts of volcanic detritus being deposited in the metasiltstone. The sedimentary rocks overlie the Middle Precambrian Thomson Formation with an angular unconformity, and are conformably overlaid by Keweenawan lava flows. Deposition of the sediments took place in a high-energy, shallow water environment. The Bessemer Formation of Michigan and Wisconsin is intermittently exposed beneath Keweenawan lava flows along a 55-mile stretch. The dominant lithology is orthoquartzite; however, minor amounts of interbedded siltstone and a basal conglomerate are also present. The formation was principally derived from pre-Keweenawan rocks to the north, with deposition again having taken place in a shallow water, near-shore environment. The formation disconformably overlies the Middle Precambrian Tyler Formation, and is conformably overlain by Keweenawan lava flows. South of the Lake Superior Region, several lower Upper Precambrian quartzite formations are exposed, and may be correlative with some of the Lower Keweenawan formations to the north. Three orthoquartzites, the Barron, Baraboo, and Sioux Formations are very similar in composition, lithology, and sedimentation, and appear to have been deposited during the northward transgression of a sea into a stable region. The Sioux, Baraboo, Barron, Puckwunge, and Sibley Formations were deposited in a shallow water, near-shore, tectonically stable environment, before the outbreak of Keweenawan igneous activity in their depositional areas; while deposition of the Osler, "Nopeming," and Bessemer Formations, which contain minor amounts of volcanic rock fragments, was interrupted by extrusion of the Keweenawan lavas. The Sioux, Baraboo, Barron, Puckwunge, Sibley, and Bessemer Formations are inferred to be correlative with each other, while the Lower Keweenawan sediments at Nopeming and the Osler Formation appear to be younger in age.Item Petrology, Structure, and Correlation of the Upper Precambrian Ely's Peak Basalts(1972-05) Kilburg, James AThe Upper Precambrian Ely's Peak basalts crop out in a north-south trending, wedge-shaped belt in the area around Nopeming, southwest of Duluth, Minnesota. These Lower Keweenawan flows overlie the basal Upper Precambrian quartzite in the southwestern portion of the Lake Superior basin. There are at least 20 individual flows with a total thickness of about 1,200 feet. The thickest flow is about 125 feet thick while the thinnest is less than 10 feet thick. Many of the flows show considerable lateral continuity; for example, one flow is traceable for about three miles along strike. Chemically, there are two main types of flows as classified by MacDonald and Katsura (1964); these are alkali basalts and tholeiite basalts. The alkali basalts, which have a low silica content, are fine- to medium-grained and form flows which vary in thickness from about 15 to just over 100 feet. Plagioclase, small, anhedral olivine pseudomorphs, and actinolite after augite form a subophitic to poikilitic texture. The opaque minerals ilmenite and magnetite form phenocrysts up to 1.5 mm in diameter in some rocks but are usually found as interstitial microlites in the groundmass. Textures and structures within the flows suggest a low viscosity. Structures within these flows include level, ropy surfaces, bent and straight pipe vesicles, straight vesicle cylinders and vesicular tops. Crude columnar joints were observed in one flow. The tholeiitic basalts are usually fine- to medium-grained, but some thicker flows are coarse-grained. These flows are usually from 30 to 90 feet thick. They include porphyritic, subophitic, and poikilitic types. Augite occurs as phenocrysts in the porphyritic flows and as poikilitic oikocrysts and as intergranular grains in the others. Olivine pseudomorphs are occasionally present, and magnetite and ilmenite generally occur as evenly distributed microlites in the groundmass. Structures within the flows include pillows (only in the basal flow), stretched amygdules, and vesicular tops. The augite-porphyritic basalts which lie at the base of the sequence are distinctive and very rare in the North Shore Volcanic Group. The whole sequence of lavas has undergone hydrothermal metamorphism to the high zeolite-low greenschist facies. Minerals present which demonstrate this are actinolite, chlorite, and epidote. The only zeolite present is wairakite which has been discovered here apparently for the first time in the Lake Superior region. It is the highest-temperature zeolite. Intrusion of the Duluth Complex is thought to be responsible for elevating the geothermal gradient and thus, permitting the formation of wairakite. The gabbro intrusion also contact-metamorphosed the lavas to a medium-grained pyroxene hornfels for a distance of up to one-fifth of a mile from the contact. Pressures of metamorphism are thought to have been between 2,000 and 2,500 bars. This pressure was produced by the weight of up to 30,000 feet of overlying Upper Precambrian lavas and Duluth Complex which underlie the North Shore of Lake Superior. Temperatures are estimated to have been between 290° C and 370° C during the hydrothermal metamorphism. Based on their distinctive petrology and reversed magnetic polarity (Green and Books, 1972), the Ely's Peak basalts appear to correlate with the basal flows at Grand Portage, Minnesota. This implies that the time of deposition at these localities was approximately the same, and the source from which these lavas were derived and the physical conditions of magma generation were the same.Item Development of a Copper-Nickel Industry in Northeastern Minnesota(1973-06) Saremba, Scott PMany factors and problems must be considered in the developing of a copper-nickel operation in the Duluth Complex of Northeastern Minnesota. Exploration studies in the Complex reveal large volumes of low-grade copper-nickel sulfides (65 billion tons) and relatively small quantities of high-grade material (in excess of one percent). The Duluth Complex has not been extensibly explored and large areas of the Complex remain to be studied for their mineral potential. The known copper-nickel deposits are in a favorable geographic location with respect to labor, transportation, electrical power, water resources, and needed ancillary operations. The known deposits are found along the base of the Duluth Gabbro, and it is believed that most of the mineralized material will be found along the base. The deposits are found on Federal, state, and private lands, and therefore, the acquisition of these lands to prospect and permit to mine is different in each case. Federal and state mineral rights are leased, but private mineral interests may be bought or sold. Mineral land environment must be considered, as exploration and mining will affect the land, water, and air in varying degrees. Exploration can be carried out with no lasting effect on the environment, but actual mining can produce lasting effects. The degree to which the environment will be affected will depend on advanced planning, statutory authority to regulate the impact of mining on the environment, mineland reclamation plans, and the extraction method used or not used. Because most of the copper-nickel deposits are within the Superior National Forest, prospecting and mining must follow the rules and regulations of the Forest Service and Department of Interior. Part of the Duluth Gabbro is in the Boundary Waters Canoe Area, but a court decision has terminated all attempts to explore the area and prevents future mining in the BWGA. Public opinion is against mining in the BWCA because of the effects that are feared it will have on the wilderness character. Although, geological studies could be carried out without having any detrimental effect on the area. At the present, there is an oversupply of copper and nickel on the world market, but a projected demand is expected to substantially exceed supply in the future (10-20 years). Therefore, the United States will become more and more reliant on foreign sources. The prediction clearly indicates that additional U.S. copper-nickel operations will be needed. This report indicates the probability of success of such an operation in Northeastern Minnesota.Item The Ore Petrology and Structural Geology of the Lower Precambrian Deer Lake Mafic-Ultramafic Complex, Effie, Itasca County, Minnesota(1973-06-30) Ripley, Edward MichaelThe Deer Lake Complex is a 13 km long by 3 km wide belt of Lower Precambrian ultramafic and gabbroic rocks located near the town of Effie, Itasca County, Minnesota. Two layered sills, averaging 200 m in thickness, a 122 m gabbroic sill, and two ultramafic lenses ranging in thickness from 15 to 40 m have been investigated by detailed mapping and drill core investigation. The igneous bodies are intrusive into a sequence containing metagraywackes, slates, argillites and mafic metavolcanic rocks. The volcanogenic sequence overlying the sills is on the order of 400 m in total thickness. Metamorphism of the Complex and associated host rocks has produced mineral assemblages of the greenschist facies. The layered sills contain a succession of basal chilled margin, peridotite, orthopyroxene clinopyroxenite, porphyritic two-pyroxene gabbro, nonporphyritic gabbro, quartz diorite cap rock, and upper chilled margin. The general structure of the sills and their petrographic and chemical characteristics indicate that they are differientiated from a basaltic magma by in situ gravitational mineral accumulation and subsequent nonaccumulative crystallization. Phase chemistry studies utilizing mineral and trace metal compositions from the layered sills of the Conplex indicate that their initial temperature of crystallization was near 1010 C. Sulfide and primary oxide phases are disseminated throughout the layered sills. Textural evidence and phase relations indicate that sulfide and oxide minerals within basal chilled margins formed from an immiscible sulfide-oxide liquid which segregated prior to sill emplacement. Nickel-rich sulfide minerals are concentrated in the lower portions of basal chilled margins with copper sulfide and oxide minerals located in overlying chilled units. Phase relations indicate that sulfide-oxide crystallization began at approximately 1070° C and ended about 960° C. Re-equilibration within sulfide phases occurred at temperatures below 600° C. The primary sulfide phases in the differentiated portions of layered sills range from nickel-rich in peridotite units through copper-rich at intermediate levels to iron-rich in upper layered units. Textural evidence and phase relations suggest that sulfides in peridotite and clinopyroxenite units crystallized from an immiscible sulfide-oxide liquid which segregated during silicate differentiation, whereas sulfides and oxides in upper gabbro units within the layered intrusives crystallized directly from the silicate magma in response to an increased oxygen activity. Textural features in quartz diorite cap rocks indicate that sulfides replaced silicate phases. The Complex has undergone Lower Precambrian isoclinal folding, with a maximum principal stress orientation of N45W. Gravity faulting followed as a result of stress relaxation producing grabens. Subsequent strike-slip faulting along a N40E trend resulted in 1100 m right lateral separation of Complex units. The final phase of observed deformation in the Deer Lake area is evidenced by an additional 100 m of movement of Middle Precambrian dikes along the strike-slip faults. Five characteristics commonly used to evaluate Ni-Cu sulfide ore bearing ultramafic rocks indicate that the Deer Lake Complex has little ore potential. These characteristics are: 1) the presence of layering in the differentiated sills; 2) the Fe-rich, Mg-poor nature of the parent magmas which produced the Deer Lake layered sills and ultramafic lenses; 3) the low nickel content of peridotite units and olivines at Deer Lake; 4) the absence of pyrite in sulfide assemblages of chilled margins and peridotites and 5) the low metal content of sulfide phases in ultramafic zones and chilled margins.Item Differentiated Mafic-Ultramafic Sills in the Archean Vermilion District, Northeastern Minnesota(1974-02-01) Schulz, Klaus JurgenDetailed mapping of part of the Newton Lake Formation north of Ely, Minnesota has shown the presence of numerous sill-like mafic-ultramafic intrusions in the Archean volcanic sequence. Three types of intrusions have been found: layered, differentiated mafic-ultramafic sills ranging from 400 to 1500 feet thick and at least 4 miles long; gabbroic sills of variable thickness and e xtent; and ultramafic lenses ranging from 75 to 300 feet thick and up to 3000 feet long. The layered sills were studied in detail. They have a well-developed internal stratigraphy which consists of a lower chilled-margin, peridotite, pyroxenite, bronzite gabbro, and gabbro units and an upper chilled-margin. Petrographic studies indicate that the units formed by gravitational accumulation of mineral grains, The stratigraphic succession reflects the general order of crystalization: 1) chromite, 2) chromite + olivine, 3) clinopyroxene + orthopyroxene, 4) clinopyroxene + orthopyroxene + plagioclase, 5) clinopyroxene + plagioclase. Microprobe analyses of cumulus pyroxenes has shown cryptic variations exist between units. The gabbroic sills are generally similar to the upper gabbroic parts of the layered sills. The ultramafic lenses consist of a central peridotite unit surround by a complex chilled-margin. Textural and structural features of the ultramafic lenses suggest intrusion of an olivine bearing liquid, with flowage differentiation forming the peridotite unit and rapid chilling of a crystal free liquid forming the chilled-margin. Differentiation trends of whole rock samples and calculated liquid compositions of the layered intrusions are generally in close agreement and show a general iron but minimal alkali enrichment with differentiation. Chemical analyses of chilled-margins are low in Al2O3 (10 wt%) and high in MgO (11 wt%) with a high CaO/Al2O3 ratio (0.85). The calculated bulk composition is distinctly ultrabasic in nature (MgO = 17 wt%). Mixing calculations utilizing least square methods suggest that the magma was partially differentiated at the time of intrusion. The bulk composition for the layered sills is very similar to high-MgO basalts from the Archean of Western Australia. An inital magma temperature for the layered intrusions of between 1200°C and 1100°C is inferred from element partitioning between coexisting mineral phases. Textural relations and phase equilibria suggest that crystallization of both sills and lenses probably did not take place under pressures greater than about 1 kb. (2.7 km) and may have been even lower. Metamorphism of the lower grades of the greenschist facies has affected all rocks of the Newton Lake Formation. The ultramafic rocks are serpentinized to varying degrees with olivine often the only altered phase. Serpentinization appears to have occurred along small microfractures which cut the peridotite. The mafic rocks typically have actinolite, sausseritized plagioclase, chlorite, epidote, and rare sphene. Relict grains are common in both ultramafic and mafic units suggesting that metamorphic reactions were retarded perhaps by low H2O and CO2 availability and pressure, The layered sills and lenses of the Newton Lake Formation apparently formed penecontemporaneously with the surrounding basic volcanic rocks. The layered sills probably formed as high level synvolcanic intrusions, some of which may have also acted as magma chambers for gabbroic liquids which formed sills and/or flows. The ultramafic lenses could be smaller injections of the same magma which formed the larger layered sills.Item Geology of a Sulfide Deposit in Lower Precambrian Metavolcanic-Metasedimentary Rocks near Birchdale, Koochiching County, Minnesota(1974-02-22) Listerud, William HaroldThe Birchdale area lies near the southern edge of the Superior Province of the Canadian Shield. The rocks are felsic-intermediate metatuffs, metasediments, granite, and mafic intrusives. The rocks are part of a northwest dipping, northeast trending monocline which is on the southern margin of a small granitic pluton, the Birchdale Granite. The greenstone rocks have been metamorphosed twice, first to upper greenschist or lower amphibolite facies during the regional metamorphism, and then to albite-epidote hornfels facies as a result of the intrusion of the Birchdale Granite. The two metamorphic events have obscured much of the original textures and structures of the rocks and made the origin of the sulfides more difficult to determine. The sulfides of the Birchdale anomaly area are pyrrhotite, pyrite, chalcopyrite, sphalerite, pentlandite, and marcasite. The main sulfide horizon is in a series of interbedded metatuffs and graphitic metasediments, although disseminated sulfides are found throughout the section. Pyrrhotite is the principal sulfide, with only minor amounts of the other phases. The main sulfide horizon thickens, increases in sulfide content, and increases in graphitic material northeastward along strike. Trace element work shows apparent increases in cobalt and nickel, and an enrichment of copper over zinc northeastward. The sulfides appear to be syngenetic, based on their position in the sequence and their relationships with the enclosing rocks. The sulfides now show mineralogy, textures, and structures related to the metamorphic episodes.Item A Testing of the Prediction of Floating or Settling of Phenocrysts in a Magma by Mathematical Models(1974-06) Saremba, Scott PPrevious work on densities of liquid silicate systems suggest that it is mathematically possible to determine whether phenocrysts in a magma should settle or float based on the density difference between the magma and phenocrysts. The density of most magmatic liquids can be ca1culated from the equation: dmelt = εiXiMi/ViM1, where Xi is the mole fraction of component I, vi its partial molar volume, and Mi its gram formula weight. Mathematically derived results of density difference compare favorably with 4 out of the 5 field observations made on lavas and sills of the North Shore Volcanic Group. The good correlation between the results of the author's mathematically derived results and the field observation support the use of the mathematical model as a meaningful indicator of floating or settling of phenocrysts in a crystallizing melt. The single inconsistency (1 out of 5) suggest that factors other than density difference such as viscosity, affects density, crystal shapes, and convection in magmatic melts may have an effect on the settling or floating of phenocrysts. [See item for proper illustration of mathematical formula]Item The Quaternary Geology of the Lake Johanna Region West-Central Minnesota(1974-09-01) Reid, David ForbesThe lake Johanna Region, encompassing an area of 625 square miles in west-central Minnesota, includes major portions of Swift, Pope, Kandiyohi and Stearns counties. The area has experienced a complex glacial history; all of the surficial deposits are ascribed to depositional events of the Wisconsin stage of the Pleistocene Epoch. If deposits of older glaciations exist in the area, they have eluded recognition. Bedrock is not exposed because of the thick mantle of glacial sediments. The landscape of the Lake Johanna Region is composed of three major elements: a rolling-ground moraine of low relief to the south, that is separated from an extensive outwash plain to the north by a long, linear, hummocky, stagnation moraine complex that runs diagonally in a northwest-southeasterly trend through the area. Numerous hypotheses have been presented during the past century in an attempt to interpret the depositional history of the drift in the Lake Johanna Region. All previous workers have based their interpretations on the spatial distribution of the various drift units throughout the entire state of Minnesota. . This study provides detailed stratigraphic and lithologic descriptions of all drift units in the Lake Johanna Region. Two different tills and outwash ranging from thick bedded, boulder gravels to laminated silts, constitute most of the surface and subsurface drift of the area. Numerous exposures show a variety of drift types in superposition including: outwash over till, till over outwash, till over till, and silt over all other sediment types. These stratigraphic relationships, coupled with topography, provide the key to an interpretation of the geologic history. The two tills, both calcareous; are distinguishable on the basis of rock fragment content and texture. Generally, the lower till is a buff, calcareous, sandy, shale-poor till (less than 5 percent contained shale fragments) having a textural compositon of 58 percent sand, 30 percent silt and 12 percent clay (average of 10 samples), whereas the upper till is a buff, calcareous, silty, shale-rich unit (more than 5 percent contained shale fragments) with a textural composition of 51 percent sand, 30 percent silt and 19 percent clay (average of 36 samples). Regionally, on the basis of composition and texture, the lower till of the Lake Johanna Region is correlated with the till exposed in the Wadena drumlin field to the north. The upper till is correlated with the drift that is the surface deposit over a large area in the Minnesota River Valley to the south. The lower till was deposited by the Wadena lobe, which made its way from its source in the Winnipeg lowland down through north-central Minnesota to its final terminus south of the Lake Johanna Region. The upper till was deposited by the Des Moines lobe, which originated further west and followed the Red and Minnesota River Valley lowlands to its terminus in central Iowa. This divergence in paths accounts for the difference in lithologies of the two types of till. Ice stagnation played an important role in molding the major geomorphic features of the Lake Johanna Region. Controlling factors included: the amount of debris carried by the ice, the position of the debris in the ice, the volume of meltwater produced, the rate of melting and differential erosion and deposition. The major stagnant ice features include an extensive kame complex, perched lake plains, ice walled outwash plains, the Blue Mounds Ridge System (a perched drainageway), and an extensive esker system. Flanking the linear ice stagnation complex are ground moraines, outwash plains, and proglacial lake-beds. The origin of all these features is intimately related to the activity of two ice lobes and their final disintegration. The Wisconsin history of the Lake Johanna Region consists of five phases. During the first phase, Wadena lobe ice completely inundated the Lake Johanna Region, depositing a buff to yellow, sandy, calcareous, shale-poor till. The material from the lithologically distinctive upper Cretaceous Pierre Formation was incorporated into this ice, because it flowed along a course east of the Pierre outcrop belt. In phase two, the Wadena lobe wasted back across the region to a point northeast of the study area, leaving massive blocks of dead ice in pronounced topographic lows which are probably the remains of a pre-Wisconsin drainage system. Meltwater from these large areas of ice swept great volumes of outwash material to the north and south of the ice masses until mantling by this debris slowed the ablation process. The main sheet of ice to the north continued to melt, back through Minnesota, leaving a complex mixture of outwash material and ablation till. In phase three, the Lake Johanna Region, including the buried dead ice, was covered by an advance of the Des Moines lobe. Because the Des Moines lobe crossed the eastern edge of the Cretaceous Pierre Formation, it deposited, in the study area, a ground moraine comprised of buff to yellow, calcareous, clayey, shale-rich till. During phase four, both the thin Des Moines lobe and the buried Wadena lobe ice gradually wasted. Water from this melting ice ponded to produce numerous small proglacial lakes along the northeastern margin of the stagnant ice. Large volumes of water poured through an ice-walled gorge south of Starbuck (the Blue Mounds Sluiceway) along a drainage line produced by a crevasse system or a sag in the continental ice sheet along this linear topographic low. This water eventually drained into Glacial Lake Benson which occupied a low-lying area in the southwestern portion of the Lake Johanna Region. In the last episode of the Quaternary history, the Des Moines lobe had completely wasted, except for a large block of ice that occupied the Lake Minnewaska basin. Meltwater from this ice initially flowed north, but as lower outlet levels were found, the waters flowed south and west into the Lake Emily system. The Wadena dead ice complex was also in its final stages of melting, which caused it to lower a complicated melange of stagnant ice features onto an older stable till surface. Extensive river systems draining this complex again swept copious volumes of debris onto the Bonanza Valley outwash plains. Lake Benson continued to expand until it finally breached an ice-cored morainic dam near Redwood Falls, and then it was quickly drained. As all ice melted, the drainage channels were deprived of their discharge; they have since been gradually filling with paludal deposits.Item Petrology and Structure of Precambrian Gneisses at Big Falls, Eau Claire County, Wisconsin(1975-02) Cummings, Michael LeviPrecambrian amphibolite gneisses and schists at Big Falls County Park in Eau Claire County, Wisconsin, include four main lithologic units: banded amphibolite gneiss, amphibolite schist, transition gneisses and feldspathic gneiss. Structural and petrologic investigation indicate three deformational phases accompanied by recrystallization. The first deformational phase is represented by coarse garnet porphyroblasts that were shattered and flattened in the plane of younger schistosity. Rootless intrafolial folds of compositionally banded rocks are relics of this first deformational phase. Inferred medium pressures and temperatures suggest metamorphism in the amphibolite facies. The second deformational phase resulted in folding of the banded amphibolite gneiss into open folds whose isogon pattern and layer geometry suggest formation as flattened flexural slip folds that were later deformed by inhomogeneous strain. Fold axial plunges are to the north and are coincident with the plunge of the earliest definable lineation. Folds in the amphibolite schist are tight, often isoclinal, isogon patterns suggest formation by inhomogeneous compressive strain. Mineral lineations cross-cut the south plunging fold axes. Folds in both units developed between subparallel slip planes with folding occurring between the slip surfacese Faults, with apparent left-lateral displacements, developed in the banded amphibolite gneiss prior to final recrystallization. Garnet, hornblende and plagioclase were the main phases crystallized under medium temperatures and pressures in the amphibolite facies. The third deformational phase resulted in development of shear zones and cataclastic deformation. A major fault developed between the banded amphibolite gneiss either prior to, or during the third deformational phase. A second schistosity cross-cuts the schistosity formed during the second deformational phase. Crystallization of epidote, cummingtonite, and sphene as well as blue-green hornblende and plagioclase indicate low load pressures and low to medium temperatures. The third recrystallization resulted in disequilibrium textures and incomplete mineral reactions and represents retrograde metamorphism in the epidote-amphibolite facies. Late faulting and jointing were not accompanied by major recrystallization, however alteration is associated with one of three fault sets. Whole rock chemical analyses and individual phase chemistry indicate that the amphibolite schist is more magnesian than the banded amphibolite gneiss. High weight percent of Al2O3 is typical of the banded amphibolite gneiss and the feldspathic gneiss. The chemistry of the rocks indicate the protolith to be a differentiated mafic intrusive. The banded amphibolite gneiss represents a plagioclase cumulate while the amphibolite schist and feldspathic gneiss represent a gabbro grading to an anorthosite or anorthositic gabbro. Traces of vanadium, nickel and chromium in hornblende further suggest a mafic igneous protolith. Isotopic age dates on zircons from an intrusion one mile east of Big Falls were 1900 m.y. The main structural elements of the region are considered coincident with this intrusion. The 1900 m.y. date is interpreted as the age of the second deformation at Big Falls, suggesting intrusion of the Big Falls rocks into the "Chippewa Amphibolite Complex" in early to middle Precambrian time.Item Paleoecology of the Late Cretaceous Upper Frontier and Henefer Formations (Wanship) near Coalville, Utah(1975-04-07) Goodner, David CharlesThe late Cretaceous upper Frontier and Henefer Formations exposed near Coalville, Utah were deposited in a fluctuating set of freshwater, brackish, and marine environments. Sediment was derived from a western source area elevated during the Sevier and Laramide orogenies, pulsations of which are evidenced by unconformities within the Frontier and Henefer Formations in the Coalville area. A series of 6 marine transgressive-regressive sequences during deposition of the Upton Sandstone Member of the Frontier Formation is hypothesized based on a Simpson species diversity study within the benthonic community of ostracodes and foraminifers. The Simpson diversity index ranges from 1.7 to 9.2 for the beds of the Upton Sandstone Member of the Frontier Formation.Item Geology of the Cretaceous-Tertiary(?) Rocks of the Southwest Quarter of the Monte Guilarte Quadrangle, West-Central Puerto Rico(1976-04) Curet, Angel FranciscoThe southwest quarter of the Monte-Guilaerte quadrangle in west central Puerto Rico covers an area of about SO square kilometers. It is located about 8 kilometers south of the southern Puero Rico fault zone. This shear zone is a northwest-southeast trending lineament which divides the central block of the island from the southern block. The oldest rock unit in the area is the Rio Loco Formation which consists mainly of pillowed basaltic lava flows, flow breccias, hyaloclastite deposits, volcaniclastic breccias and conglomerates, and minor calcareous sedimentary rocks and limestone lenses. The rocks are Upper Cretaceous and were deposited subaqueously. The Maricao Basalt, which is in fault contact with the Rio Loco Formation, comprises about 1,300 meters of massive augite-rich volcaniclastic breccias and conglomerates, sandstones, and subordinate calcareous sedimentary rocks, basaltic lava flows, and limestone. The unit is Campanian to Maestrichtian in age. The principal sources of the volcaniclastic material were pre-existing rocks which were exposed subaerialy and were being eroded. The sediments were rapidly buried preventing further reworking. The Yauco Mudstone, which unconformably overlies the Maricao Basalt, consits of about 360 meters of thin- to medium-bedded calcareous volcaniclastic sandstones and siltstones, claystones, limestones, and minor calcareous conglomerates and breccias, and. tuffs. The unit is Campanian to Maestrichtian, but maybe possibly in part as old as Turonian. The principal source of the Yauco volcaniclastic material was pre-existing volcanic and hypabyssal rocks. The sediments were deposited in a shallow-water marine environment which was tectonically unstable; this resulted in widespread accumulations in southwestern Puerto Rico. The Yauco Mudstone is conformably overlain by an unnamed hornblende breccia unit in one part of the area and by the Sabana Grande Formation in another area. The unnamed hornblende breccia unit consists mainly of hornblende-rich volcaniclastic breccias and conglomerates with minor interbeds of calcareous volcaniclastic sedimentary rocks. The unit is Campanian, probably Turonian, to Maestrichtian in age. The source of the sediments was pre-existing rocks which were exposed to the east and/or north. The overall tectonic environment of this unit is similar to that of the Yauco Mudstone. The Sabana Grande Formation consists mainly of amygdaloidal, massive, basaltic, lava flows with minor flow breccias, and pyroxene-rich sandstones. It has been assigned a Turonian to Campanian age but based on paleontological data obtained during this investigation, the unit may be as young as Maestrichtian. The unit was extruded subaerially and since it is con cordant within the Yauco Mudstone it indicates that the basin of Yauco deposition in this area was extremely shallow with periods of exposure above sea level. The entire volcanic-sedimentary sequence was intruded in late Cretaceous to early Tertiary time by augite porphyry and hornblende porphyry bodies. During or after Maestrichtian time the area was deformed into large open folds. Later, faulting became the predominant type of deformation. Vertical faults are apparently more common than other types. The small amount of lava flow, except in the Rio Loco Formation and Sabana Grande Formation, and little pyroclastic material in the sedimentary units strongly indicates that little explosive volcanic activity was going on during deposition of the units. The abundance of volcanic, hypabyssal, and igneous rock fragments in the sediments indicates that the main sources of the sediments were pre-existing rocks. The presence of unpillowed lava flows within the sedimentary units suggests that the sediments were deposited in a shallow water area with periods of exposures above sea level. Paleogeographic evidence indicates that the overall source of the sediments was probably to the north and/or east. The presence of felsic rock fragments in the upper part of the sequence is evidence that felsic source rocks were exposed. Apparently the island arc was mature by Late Cretaceous time with andesite and dacite the dominant rock types.Item Petrology and Structure of the Late Precambrian Mafic Sills East of Silver Creek, Lake County, Minnesota(1976-05) Pope, Neil MarkThe 200 foot (60 meters) thick Silver Creek Cliff sill and the 600 foot (183 meters) thick Lafayette Bluff sill intrude the Keweenawan lava flows of the North Shore Volcanic Group, about 4 - 6 miles northeast of Two Harbors, Lake County, Minnesota. The sills are mainly ophitic olivine diabase, consisting of plagioclase, olivine, pyroxenes, opaques, apatite, and secondary interstitial material. The Lafayette Bluff sill also contains plagioclase phenocrysts and amygdaloidal minerals. The Silver Creek Cliff sill contains minor amounts of olivine-free diabase and pegmatitic diabase in discontinuous lenses and layers. Geologic relations and whole-rock analyses and microprobe analyses of individual minerals indicate the olivine-free diabase crystallized from a residual liquid of the olivine diabase and. the pegmatitic diabase crystallized from a still later residual liquid. The Lafayette Bluff sill contains xenoliths of anorthosite along the shore of Lake Superior, northeast of Crow Creek, and a granodiorite unit at the base of the sill at Lafayette Bluff. No evidence was found to indicate a definite genetic relation between the granociorite or anorthosite and the olivine diabase. The regional attitude of the flows is a northeasterly strike and a gentle dip of about 8 - 10° to the southeast. The Silver Creek Cliff sill appears to be nearly flat-lying and conformable with the lava flows except in the vicinity of Encampment River where it cross-cuts the flows and is here interpreted as the feeder zone. The Lafayette Bluff sill forms a syncline - anticline structure. The lava flows in the trough of the syncline strike NW to NE and dip up to 50°. Faulting at the contacts of the diabase with the lava flows suggest the sill has moved downward relative to the flows. Chemically the sills are similar to one another. The minor amount of differentiation in both sills suggests slight Fe-enrichment toward the center of the sill from the top and base. Very little alkali-enrichment is evident. The sills are chemically compared to several other Late Precambrian intrusives and extrusives of northeastern Minnesota, and the Keweenaw Peninsula, and to the Tertiary Skaergaard intrusion in Greenland. Of the two general mafic magma types in northeastern Minnesota, both sills appear to be similar to the high-alumina olivine diabase type rather than the Logan type.Item Sedimentation of the Middle Precambrian Tyler Formation of Northcentral Wisconsin and Northwestern Michigan(1976-06) Alwin, Bevan WilliamThe Tyler Formation crops out in a northeasterly-trending belt in Northcentral Wisconsin and Northwestern Michigan along the Gogebic Iron Range. Good exposures are found along several of the major streams draining the area, road cuts and railroad right-of-ways. The Tyler is considered Late Middle Precambrian in age, the Wisconsin equivalent of the Baraga Group of Michigan's Marquette Range Supergroup. The formation was warped and slightly metamorphosed during the Penokean Orogeny (1.7 b. y.). Primary sedimentary structures have been generally preserved. The sedimentologic aspects of seven outcrops in the Hurley, Wisconsin area were studied in detail and a measured stratigraphic section was established. Three distinct lithologies are present, sandstone (graywacke), siltstone and shale in varying degrees of metamorphism. Forty-one percent of the beds measured are argillites or slates and fifty-nine percent are sandstones or siltstones. Volumetrically, the sandstones and siltstones are more abundant than the shale units. A thinning-upward trend in the shale beds suggests a decreasing rate of sedimentation up section which in turn suggests increasing tectonic stability in the source area relative to the depocenter. Alternatively, the thinning-upward trend in the shales may reflect increased periodicity of the events which deposited the coarser-grained elastic beds. A corresponding volumetric increase in sandstones and siltstones up section is explained by the peculiarities of local basin bottom topography. Primary sedimentary structures including alternation of sand-mud units, laterally extensive bedding, graded bedding, rnicrocross-bedding, sole marks, rip-up clasts and Bouma sequences suggest a turbidity current mechanism for sediment transport and deposition in a realtively deep water environment. Twenty-four percent of the beds studied in detail are recognizable turbidites while thirty-five percent do not contain specific telltale sedimentary structures. A grain-flow origin for at least some of these latter beds is suspected. Because of the similarity between the lithologies and facies of the Tyler Formation and the ideal facies sequences of submarine fans, it is suggested that that part of the Tyler Formation which was studied in detail was deposited as part of a submarine fan complex. Indicators of current movement found in the rocks of the Tyler are of several types including both interstratal and intrastratal. Sole marks and cross-bedding are most useful. The currents which deposited the Tyler sediments moved from the east-southeast toward the west-northwest. A new type of sole mark, called a ridge mold or negative groove, is described and a possible method of formation is suggested. Two different methods for estimating current velocity were employed, one based on maximum clast size and one based on spacing of ridge molds. Both methods yielded velocities of a few tens of centimeters per second and primary slope is estimated at 0°10'. Petrology reveals that the major framework constituents of the Tyler graywackes are quartz, plagioclase and rock fragments set in a chlorite- and mica-rich matrix. The "average" graywacke is a lithic graywacke with 28% matrix. Quartz and chert comprise 73% of the framework grains, rock fragments 17% and feldspar 10%. The source terrain was probably mostly granitic with some contribution from older sedimentary, metamorphic and volcanic rocks. The Lower Precambrian rocks to the south and southeast of the Tyler outcrop belt were the probable source. Paleoslope was probably at right angles to current flow. Thus a southern limit to the extent of the Middle Precambrian depositional basin is defined. Similarity of the Tyler and other Middle Precambrian sedimentary rocks in the Lake Superior region suggests a common depocenter in a cratonic basin but at different depositional loci. Reconstruction of current movement and probable source area for the Tyler, Rove and Virginia (Thomson) Formations suggest that the depocenter was landlocked on three sides but may have been open to the northeast.Item Trace Element Geochemistry and Geochronology of Early Precambrian Granulite Facies Metamorphic Rocks near Granite Falls in the Minnesota River Valley(1976-12) Wilson, Wendell EugeneThe Sr isotopic composition and the trace element contents of K, Rb, Sr and Ba have been measured for 27 whole-rock samples and 18 mineral separates taken from four rock units in the Minnesota River Valley near Granite Falls, Minnesota. In addition, 4 whole-rock samples and 1 mineral separate were analyzed from samples of amphibolite xenoliths from the Morton-Sacred Heart area southeast of Granite Falls. The isochron ages obtained from the Rb-Sr data are given below in AE (billions of years); ages determined for metamorphic events are given in brackets. The initial ratios (Ri) given refer to the whole-rock isochrons. Garnet-Biotite Gneiss: 3.54 ± .14 [1.81], Ri=.7008 ±.0009 Hornblende-Pyroxene Gneiss (Outer Unit): 3.31 ± .26 [1.78], Ri=.7011 +.0012 Hornblende-Pyroxene Gneiss (Inner Unit): Geochemical disequilibrium precludes dating but suggests an age greater than 3.8. Metagabbro of Himmelberg: 2.68 +.20 [l.80, 2.41], Ri=.7037 +.0001 Amphibolite xenoliths: 3.52 + .15, R.=.7094 +.0013 The trace element distribution patterns suggest the following interpretations. The hornblende-pyroxene gneiss (inner unit) is older than the Montevideo gneiss (which has been previously dated at 3.7 AE); the closest analog is probably a metamorphosed island arc basalt. The hornblende-pyroxene gneiss (outer unit) is probably analogous to a metamorphosed oceanic alkali basalt. The metagabbro is probably analogous to a metamorphosed ocean floor basalt or low-K tholeiite and the age of 2.68 AE is only a minimum. The garnet-biotite gneiss is probably analogous to a metamorphosed graywacke and the age of 3.54 AE is only a minimum. The amphibolite inclusions analyzed are probably analogous to metamorphosed graywackes and are older than the Morton gneiss, which has been previously dated as being 3.55 AE old. The rocks at Granite Falls therefore probably represent a very old (3.7 AE) layered sequence of basaltic rocks and graywackes which was intruded by the Montevideo gneiss 3.7 AE ago. The rock types are analogous to those of the less metamorphosed. Archean greenstone-granite complexes, and are compatible with formation in an ancient island arc tectonic environment. They are probably the remnants of the original continental nucleus of the North American Craton.Item Late Pleistocene Mammalian Extinctions in North America: Extent, Theorized Causes, and Implications(1977-04) Orlando, Mario EItem A Land Suitability Study for Lakewood Township in St. Louis County, Minnesota(1977-05) Berner, HeinzThe purpose of this paper is to provide opportunity for a practical exercise in regional planning. It must be emphasized that this paper is a report rather than an original planning contribution. Fieldwork other than four reconnaissance trips was not undertaken. Instead, data compilation has been achieved through personal consultation of local planning offices and governmental agencies as well as literature research. However, content and format (including graphical representation) are the result of the writer's work and judgement.Item The Surficial and Environmental Geology of the French River Quadrangle, St. Louis County, Minnesota(1977-05-31) Moss, Carol MarieThe French River quadrangle is located just northeast of the City of Duluth, Minnesota. It is bordered on its southeastern margin by Lake Superior, and except for a residential zone along the lake shore, the remainder of the quadrangle is predominantly forested. Local areas were cleared for agricultural purposes in the earlier part of the century, but most of these are now abandoned or used for hay or pasturage. The present landscape consists of three distinct elements: a hummocky ice disintegration complex in the northwestern part of the quadrangle, a northeast-trending belt of ground moraine paralleling the southern edge of the ice disintegration complex, and an extensive area of exposed lake plain with associated strandline features representing the highest level of Glacial Lake Duluth, a predecessor to Lake Superior. Through the 1940's, only limited reconnaissance work related to surficial geology had been done on a regional scale. Detailed stratigraphic or lithologic studies of the complex Quaternary history of the area had not been attempted. Later studies differentiated glacial sediments and their relationships to advances of distinct ice lobes. This helped provide a more complete picture of relationships between Late Wisconsin events on a statewide basis. This study provides detailed areal, stratigraphic and lithologic descriptions of the Quaternary sediments in the French River region. In addition to the typical geological descriptions of the sediments such as color, texture, stone content and sorting, physical characteristics of each unit have been described in terms of potential constraints or favorable properties related to land-use planning. Compaction, permeability, shrink-swell potential, cohesion and frost action potential are among the most important of these soil properties. Lodgement till related to two distinct advances of Superior Lobe ice are recognized in the French River quadrangle. The lower sandy, silt-rich till has a textural composition of 36% sand, 46% silt and 18% clay (average of 9 samples). The upper, more silt-rich till is composed of 30% sand, 50% silt and 20% clay (average of 28 samples). Both contain abundant rock fragments characteristic of the Lake Superior region bedrock; diabase, gabbro, basalt, red rock differentiates and minor red sandstone. These tills have very low plasticity indices. Permeability is slow to moderate. Shrink-swell potential is usually low, while shear strength and compressibility are moderate. Soils of this type may be suitable for septic systems or sanitary landfill sites provided on-site sampling is conducted. The rolling, hummocky terrain in the northwestern part of the quadrangle represents the southernmost edge of the Highland moraine, and is attributed to the Superior Lobe advance which deposited the upper silt-rich till. Due to the small, local depositional environments which may develop in ice disintegration complexes, texture of the sediment is quite variable, and on-site sampling is imperative for almost any proposed land use. As the Superior Lobe began its final retreat, proglacial lakes formed around its margin, eventually coalescing to form Glacial Lake Duluth which reached an elevation of 1150' in the French River quadrangle. At this time the red lacustrine clays which cover much of the southern part of the quadrangle were deposited. Sand content is typically low in these sediments; an average of 22 samples shows a typical textural distribution to be 5% sand, 26% silt and 69% clay. The clays are very plastic, highly impermeable, and susceptible to large amounts of runoff. They are generally unsuitable for septic systems, show poor workability for excavation and building, and in general do not support a thriving agriculture. Where exposed along stream banks and the Lake Superior shoreline, slumping and accelerated erosion are common. Contemporaneous with the deposition of these clays was the formation of large deltaic sand and gravel deposits along the 1150' strandline. Their chief importance is their present and potential economic value for use as road building and construction materials. A depth to bedrock map was prepared as an aid in land-use planning. Ease of excavation, suitable slopes for placement of foundations, and likely difficulties in use of soil absorption septic systems may be estimated from this map. Except for shoreline erosion and variable seasonal flooding there are few geologic hazards in the area. The region lies in an aseismic area, and although it was the scene of active volcanisn in the Late Precambrian, no volcanic activity has occurred here in the last billion years.Item Municipal Solid Waste Disposal: A Problem in Environmental Geology(1977-06) Berner, HeinzThis paper will discuss some of the aspects of municipal solid waste disposal, particularly the physical and technical problems associated with sanitary landfills. One of its purposes is to see to what extent geologic information can be helpful in solving specific land use problems such as the location of landfill sites. Furthermore, this report is primarily a library research paper, required for graduation.Item Drift Lithology in Relation to Bedrock Geology, Long Island Lake Quadrangle, Cook County, Minnesota(1977-06) Everson, Curtis ILithologic studies in northeastern Minnesota suggest that drift prospecting is a useful tool for mapping drift-covered bedrock. A detailed study of till clasts composition in the Long Island Lake Quadrangle revealed a significant relationship between drift lithology and bedrock geology. The Long Island Lake Quadrangle is a suitable area for this study for the following reasons: (1) outcrops are numerous enough to have allowed the construction of a detailed geologic map; (2) the area contains eight distinctive rock units; (3) the local bedrock experienced glacial erosion, indicated by the existence of glacially abraded and quarried outcrops. The distribution of glacial sediments, mainly till and outwash, were mapped and one hundred and one samples of drift were collected along traverses parallel to ice flow (perpendicular to strike of the bedrock). Both till and outwash contain a large quantity of local bedrock clasts in the size ranges greater than 1mm in diameter. Clasts smaller than 1mm are mainly minerals, and therefore not so diagnostic of local bedrock. As a test, boulders greater than 1 meter in diameter were used in the field for inferring bedrock contacts. These contacts were found to be within 60 meters (200 ft.) of contacts placed by outcrop mapping. Lack of local bedrock clasts in the smaller size fractions indicate either high resistance of local bedrock to crushing, or lack of opportunity for crushing because of short residence time in the glacial system (short distance transport). In either case, the fine-grained fraction therefore represents a contribution to the glacial load from more distant sources and the coarse-grained fraction represents a contribution form local sources.