Department of Earth and Environmental Sciences

Persistent link for this communityhttps://hdl.handle.net/11299/212255

Environmental Science provides an overview of how science affects our environment. We focus on interactions between the solid Earth, its water, its air and its living organisms, and on dynamic, interdependent relationships between these four components. Earth and environmental scientists also consider how these relationships produce environmental change at different timescales. To do this, they combine knowledge, models and methods drawn from geology, biology, physics and chemistry. We also strive to understand past and present environmental processes so that reliable and scientifically based predictions can be made about the future.

Learn more at the Department of Earth and Environmental Sciences website.

Historical note: The Department of Geology was formed in 1950. In 1999 it became the Department of Geological Sciences. It kept that name until 2014, when it became the Department of Earth and Environmental Sciences.

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    A 10,000-year lake-sediment based reconstruction of precipitation isotope values in the Canadian Rocky Mountains and implications for past changes in North American hydroclimate
    (2019-01) Wagner, Zachary
    Hydroclimate change in the Canadian Rocky Mountains is an important area of research, as demand for water resources in the Great Plains has been continuously increasing in recent years. The population of Alberta has one of the fastest growth rates in Canada, and cities like Calgary and Edmonton are dependent on surface and groundwater resources that originate from precipitation in the mountains. Recent increases in petroleum exploration have also amplified demands for water, along with the growing water requirements of industrial agriculture. The application of sound water resource management policies is essential, and historical records span only ~200 years, a time frame too short to capture the full range of climate variability. The development of paleoclimate proxy records from the Rocky Mountains is therefore necessary to attain a thorough perspective on potential changes in climate. Such data can, for example, inform water resource managers of possible shifts in precipitation seasonality and drought/pluvial events on timescales of decades to millennia. To this end, we present a 10,000-year oxygen isotope record as a proxy for precipitation seasonality linked to the Pacific North American pattern (PNA) which adds to a growing body of research in a region of high spatial complexity of hydroclimate. Shark Lake in Alberta, CA (50.8412°N, 115.3990°W; 1857 m above sea level) is a hydrologically open basin lake in the Canadian Rocky Mountains with one large outlet and numerous small inlets and groundwater springs. Winter precipitation is more depleted in the heavier 18O isotope relative to summer precipitation due to equilibrium fractionation from rain-out and phase changes. δ18O and δD values of Shark Lake water samples (collected during the summer) range from -18.9 to -20.0 ‰ and -141 to -150 ‰, respectively. The annual weighted average precipitation isotope ratios are -16.6 and -126 ‰ for oxygen and hydrogen, respectively. This indicates that Shark Lake principally receives water inputs from runoff or shallow groundwater that originated as precipitation during the cold season. We collected 1 m and 1.5 m long sediment cores using a modified Livingstone corer and used loss-on-ignition (LOI), x-ray diffraction (XRD), x-ray fluorescence (XRF) analyses to destermine sediment texture and composition. The sediment was dated using 14C from terrestrial plant fossils, as well as 210Pb and 137Cs for the surface sediment. We analyzed the isotopic composition (δ18O) of authigenic carbonate sediment from Shark Lake using mass spectrometry and applied these results as a proxy for precipitation seasonality. Lake water oxygen isotope ratios are captured by authigenic carbonates, which form during the spring and summer in response to pH changes associated with primary production. These carbonate minerals (calcite) precipitate in isotopic equilibrium and are deposited on the lakebed where they are preserved. The Shark Lake δ18O record demonstrates a transition from lower to higher average δ18O values from the middle to the late-Holocene at around 4500 yr BP. This is consistent with previous findings of changes in PNA-like atmospheric patterns during the middle Holocene, when a gradual shift from a more negative to a more positive mean state phase of the PNA occurred. This produced enhanced zonal atmospheric circulation in the Pacific Basin that led to a reduction in winter precipitation in northwestern North America and drier conditions in the southwestern part of the continent in the late Holocene relative to the middle Holocene. The Shark Lake δ18O record has a positive, significant correlation with other similar records from the Pacific Northwest, specifically those from Lime Lake (WA) and the OCNM (OR) speleothem, and has a negative, significant correlation with records from the southern Rocky Mountains and eastern North America, namely those from Bison Lake (CO), Cheeseman Lake (NL), Grinnell Lake (NJ), and the Buckeye Creek Cave speleothems (WV). Decadally resolved records are useful for tracking changes in PNA state and its interaction with other related climate oscillations such as the El Niño Southern Oscillation (ENSO) and the associated Pacific Decadal Oscillation (PDO). Open-basin lake records can also be combined with hydrologically closed-basin lake records to reconstruct pluvial and drought periods over the Holocene. The Shark Lake record increases the spatial resolution of mid- to late Holocene hydroclimate climate data in the Rocky Mountains and provides a baseline for natural variability in precipitation seasonality in a hydrologically important region.
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    A 2000 Year Sub-annual Record of Climate Change from Lake Malawi
    (2009-08) Petrick, Benjamin Fredericks
    Lake Malawi, in East Africa, provides a rare opportunity to look at a sub-annual record of climate change from a region were there is a lack of good climate records. This is possible because the upper most sediments in the north basin Lake Malawi are varved. The varved record extends from back 1200-2000 years depending on dating differences and is well dated back 800 years. In order to construct an overall sub-annual record of climate change, overlapping sections of two cores from the north basin of Lake Malawi taken during the recent Malawi drilling project were examined on a scanning XRF with a step size of .2 mm. This provided an average of 6 measurements per annual varve couplet. Because of the chemical differences between light and dark varves it was possible to count these varves using a high resolution photograph and x-radiography images in conjunction with the chemical data. Four major chemical elements or ratios of chemical element were used to represent the four major components in the sediments of the core: Fe is a proxy for the clay, Si/Ti is a proxy for the Biogenic Silica (BSi, inc/coh scattering ratio is a proxy for %Total Organic Carbon (TOC), and K/Ti is a proxy for volcanic sediments. Comparing Fe to recent records of lake level fall and rise suggests that Fe be when the planktonic community is dominated by diatoms it reflects changes in year to year fluvial input. However at times of change in the planktonic community, the Fefluvial imput relationship breaks down. Comparisons of both the lake level records and to coral records from the Indian Ocean show that both lake level rise and fall are enhanced by increased ocean temperatures over periods of 5-10 years. This suggests that changes in Indian Ocean temperatures have an affect on Lake Malawi. The lake records show no connection to Zimbabwe rainfall but an opposite relationship with Indian rainfall. The inc/coh shows a strong relationship over the last 150 years with IOD and proportion of diatoms in the planktonic community, which tends to change during times with great IOD variability. These relationships suggest that IOD causes changes in the winds that stimulate production of planktonic during the dry season. Looking further back in the record shows that similar shifts to non-diatom dominated planktonic community occurred twice before in the record and there is some evidence in the record that changes in winds might be responsible for these events as well. 11 year and 3-7 year cycles were also found in the record but their meaning is unclear. The times when the 11 year cycle is strong in the lake are not assonated with the record of sunspots and the 3 to 7 year cycle does not seem to be related to changes in ESNO as would be expected. Therefore the meaning of the cycles is still not understood. The longer record suggests dry periods from the bottom of the varved section to around 1250 AD and from 1550 to 1650 AD, with an interceding wetter period from 1250 to 1650 AD. The record from 1650 AD to current day shows some rises and falls and an overall steady record. Comparing this to other records of African lakes and caves shows that this record has similarities to the records of East African lakes but is in opposite of records from Cold Air Cave in Southern Africa. Lastly it also shows similarities to records of Indian monsoon wind strength which is controlled by Indian Ocean temperatures and Cariaco basin records which are a proxy for the ITCZ. Both of these records show that the migration of the ITCZ and changes in Indian Ocean temperatures are important drivers for Lake Malawi and the findings of this paper may be useful in looking at changes both at longer time scales and in the future as well.
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    210Pb Geochronology in Lake Superior Sediments: Sedimentation Rates, Organic Carbon Deposition, Sedimentary Environments, and Post-Depositional Processes
    (1980-07) Evans, James Erwin
    210Pb geochronology is used to determine sedimentation rates, 210Pb flux rates, and organic carbon deposition rates from 17 sediment box cores in Lake Superior, U.S.A. These data, in conjunction with organic carbon, PCB, trace metal, benthic organism, and sedimentary structure data, are used to investigate depositional and postdepositional processes. Sedimentation rates vary from 0.01-0.20 cm/yr in Lake Superior. A dynamic model is presented which emphasizes: (1) very high (greater than 0.15 cm/yr) sedimentation rates in marginal bays, (2) moderate to very high (0.07-0.19 cm/yr) open lake sedimentation rates in regions adjacent to marginal bays, these regions are affected by plumes of suspended sediment that originate in marginal bays by wave-stirring of bottom sediments, and enter the open lake, (3) moderate to high (0.05-0.11 cm/yr) sedimentation rates adjacent to the Red Clay Area, where shoreline recession rates are high, (4) moderate to high (0.05-0.12 cm/yr) sedimentation rates in the deepest portions of the Lake Superior Troughs region, with downslope sediment movement off the adjacent shoals and into the troughs, (5) low to moderate (0.04-0.05 cm/yr) sedimentation rates from cores with current bedding features in the Keweenaw Current region, and (6) very low (0.01-0.03 cm/yr) sedimentation rates in the central lake basins due to isolation from sediment sources. Organic carbon deposition rates (K) range from 0.0001 to 0.0032 g Carbon/cm2/yr, and K varies as a power function of sedimentation rate W (g/cm2/ yr) such that K = 0.04 W1.03. This result may imply that higher sedimentation rates favor organic carbon preservation with rapid removal from the oxidizing conditions at the sediment-water interface through burial. However, the exponent is very close to 1.00, which implies that a constant proportion of organic matter is deposited with sedimentation at any site. Calculations using primary productivity measurements and average K values indicate that about 77-87% of primary production carbon is oxidized in the water column during deposition. The 210 Pb flux rate P (dpm/cm2/ yr) is directly related to the organic carbon deposition rate, such that K = 4 x 10-4P. This indicates that the main transfer mechanism for 210Pb through the water column is via association with organic particles. Organic carbon concentrations (C) decline exponentially with increasing sediment age from surficial values of 1-5% to "background" values of 0.5% in 9,000 year old sediment. The decay phenomena can be described by C = C0 e-λt, with values for the decay constant (λ) ranging from 0.2 to 1.7 x 10 -2/yr. These decay constants are 2 to 3 orders of magnitude higher than the oceans, probably due to the presence of younger and more chemically reactive organic components in Lake Superior sediments. The sedimentation rate (W) is inversely related to the decay constant (λ), such that λ = 5.33 x 10 -4 w -0.53. This may indicate that rapid burial promotes organic matter preservation. Independent evidence for biological mixing of Lake Superior sediments includes surficial zones of constant 210Pb activity, the presence of PCB substances below the sediment horizon corresponding to its first usage in commercial quantities, benthic organism studies, and lack of lamination in the upper portions of cores on x-radiographs. Oligochaete displacement rates are calculated which equal or exceed sediment accumulation rates in many cores. This indicates that oligochaetes cause significant sediment mixing at some sites. At other sites, additional mixing by burrowing amphipods may increase sediment mixing. Mixing is considered as a mechanistic analogue to diffusion phenomenon, and mixing (eddy diffusion) coefficients are calculated (Db = 0.002-10.54 cm2/yr). The highest of these compare to other studies from lakes and nearshore marine regions, while the lowest compare to rates from abyssal regions. Zones of constant 210Pb activity at depth in the sediment correspond to the time intervals 1900-1910, 1910-1920, and 1940-1950. These are interpreted as storm deposit layers, and may correspond to major storms which occurred in the Lake Superior region during November 27-28, 1905, November 22-24, 1918, and November 10-12, 1940. Diagenetic horizons are described from the sediments, these include 1-2 mm thick black laminations, 1.0-1.5 cm thick orange-colored "crusts", and layers 3-5 cm thick of many 1-2 mm diameter micronodules. The available evidence indicates that the black laminations are Mn enrichments and the orange-colored crusts may be Fe enrichments.
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    A 40,000 year geochemical record from Lake Chalco, Mexico.
    (2012-04) Pierce, Megan Leigh
    Water balances of Southwestern North America and of northern South America are dependent on positions of the North American (Mexican) Monsoon and the ITCZ respectively. The North American Monsoon leads to significant summer rainfall across a broad swath of the continent, and constitutes the major source of annual precipitation over the southwestern United States and northern Mexico. The position of the ITCZ and the strength of the accompanying monsoon are affected by variability in insolation. Northern hemisphere cooling results in a southerly displacement of both the ITCZ and North American Monsoon, whereas northern hemisphere warming results in a more northward position. The Basin of Mexico can be potentially impacted by both of these systems. A new geochemical climate record from Lake Chalco, Mexico, which couples inorganic (X-ray fluorescence) and organic (biomarkers and stable isotopes) geochemical proxies, reconstructs external forcings of volcanism and aridity over the past 40,000 years, as well as ecosystem responses to these forcings. The Basin of Mexico is a high altitude closed lacustrine basin (20ºN, 99ºW; 2240 m.a.s.l.) in the Trans Mexican Volcanic Belt. The relict paleolake, Lake Chalco, is located near Mexico City in the southern sub-basin, and has an area of 120 km2 and a catchment of 1100 km2. Though the present-day lake has been reduced to a small marsh due to historic diversion of its incoming rivers; over longer timescales the lake has been a sensitive recorder of hydroclimatic variations in the neotropics. Low Ca concentrations indicate greater aridity during the late glacial relative to the last interstadial or early Holocene. Peaks in Fe concentrations indicate volcanism and the deposition of tephra throughout the last 40ka, with more frequent episodic volcanism occurring in the most recent 23ka. N-alkane biomarkers, compound specific carbon isotopes, and XRF data provide evidence for ecosystem responses to both aridity and volcanism. The extent to which both of these external forcings affected ecosystem is assessed; and the extent to which global or local external forcings affect the Basin of Mexico is addressed.
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    Achieving Peak Flow and Sediment Loading Reductions through Increased Water Storage in the Le Sueur Watershed, Minnesota: A Modeling Approach
    (2015-09) Mitchell, Nathaniel
    Climate change, land clearing, and artificial drainage have increased the Minnesota River Basin’s stream flows and the rates at which channel banks and bluffs are eroded. Increasing erosion rates have contributed to higher sediment-loading rates, excess turbidity levels, and increases in sedimentation rates in Lake Pepin further downstream. These issues have motivated the discussion of flood management through either wetland restoration or the implementation of simple detention basins. This study uses the Soil and Water Assessment Tool (SWAT) to assess a wide variety of water retention site (WRS) implementation scenarios in the Le Sueur watershed in south-central Minnesota, a subwatershed of the Minnesota River Basin. Projected flows were used in conjunction with an empirical relationship developed from gauging data to assess changes in sediment-loading rates from near-channel features in the lower watershed. The WRS term is used as a general term for depressional storage areas, and sites could be made into wetlands or detention basins. Sites were delineated as topographic depressions with specific land uses, minimum areas (3000 m2), and relatively high compound topographic index (CTI) values. Contributing areas were manually measured for the WRS delineated. These contributing areas were used with existing depression depths, and different site characteristics to create 210 initial WRS scenarios. The contributing areas measured for the initial scenarios were used to create a generalized relationship between WRS area and contributing area. This relationship was used with different design depths, placement scenarios, and K values to create 225 generalized WRS scenarios. Reductions in peak flow volumes and sediment-loading rates are generally maximized by placing sites with high K values in the upper half of the watershed. High K values allow sites to lose more water through seepage, emptying their storages between precipitation events and preventing frequent overflowing. Reductions in peak flow volumes and sediment-loading rates also level off as WRS extent increases. This reduction in cost effectiveness with increasing site extent is due to the decreasing frequencies of high-magnitude events. The generalized WRS scenarios were used to create a simplified empirical model capable of generating peak flows and sediment-loading rates from near-channel features in the lower watershed. This simplified model is being incorporated into a decision-analysis model portraying a wide variety of management options in the Le Sueur watershed. This tool may better enable local stakeholders to evaluate, select, and promote management scenarios that best address the issues faced in the region.
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    Archean Geology of an area between Knife Lake and Kekekabic Lake, eastern Vermilion district, northeastern Minnesota
    (1978-09-27) Vinje, Steven Paul
    Sedimentary and volcanic rocks of the Kekekabic Lake area, which is located within the eastern Vermilion district, northeastern Minnesota, comprise a portion of the Lower Precambrian Knife Lake Group and lie in three of Gruner's (1941) structural segments. The dominant lithology within the Knife Lake greenstone segment is arkose. The arkose is largely composed of plagioclase feldspar, is approximately 250 feet thick, and underlies the Amoeba Lake member of the Knife Lake Group. Interbedded with the arkose is black slate. Rocks within the Knife Lake greenstone segment trend N 74°E and dip 60° to the southeast. The dominant lithology within the Spoon Lake segment is graywacke. The graywacke samples studied are equally divided between the lithic and feldspathic subtypes. Rock fragments within the lithic graywackes are predominantly andesite and dacite. Plagioclase is the predominant feldspar within the feldspathic graywackes. Interbedded with the graywackes are green slates, mafic (basalt or andesite) crystal tuffs, volcanogenic conglomerate, and very minor iron-formation. The rocks within the Spoon Lake segment are approximately 800 feet thick, and have been deformed into a syncline which trends S 45W and plunges 35° to the southwest. The dominant lithology within the Kekekabic Lake segment is graywacke. The graywacke samples studied are equally divided between the lithic and feldspathic subtypes. Lithic and feldspathic graywackes of the Kekekabic Lake segment are similar petrographically to lithic and feldspathic graywackes of the Spoon Lake segment. However, the graywacke samples of the Kekekabic Lake segment, in general, contain more detrital K-feldspar (although it is still a minor component) and hornblende grains than those of the Spoon Lake segment. Interbedded with the graywackes of the Kekekabic Lake segment are green slates, mafic (basalt or andesite) and felsic (trachyte to latite) crystal tuffs, and very minor ironformation. Graywackes and associated interbedded rocks of the Kekekabic Lake segment are approximately 1000 feet thick, and have been deformed into a syncline which trends S 50°W and plunges 30° to the southwest. The graywackes and associated interbedded rocks contained in both the Spoon Lake and Kekekabic Lake segments comprise the Amoeba Lake Member of the Knife Lake Group (Gruner, 1941). The eastern portion of the Kekekabic Lake syncline is occupied by three subaerial flows. The oldest of these flows, stratigraphically, is a porphyritic green augite-hornblende andesite which is exposed at the nose of the syncline and is approximately 225 feet thick. To the west, the augite-hornblende andesite is conformably overlain by a red porphyritic hornblende andesite which is approximately 300 feet thick. The red hornblende andesite is overlain conformably, to the west, by a green porphyritic hornblende basalt which is approximately 300 feet thick. The three subaerial flows apparently plunge under a green hornblende-rich tuff and agglomerate unit. The tuff is composed exclusively of hornblende grains and is bedded and cross-bedded. The agglomerate clasts are accidental lamprophyre rock fragments. The hornblende-rich tuff and agglomerate is approximately 200 feet thick. The tuff and agglomerate and the three subaerial flows comprise the Kekekabic Lake Member of the Knife Lake Group (Gruner, 1941). Turbidite sequences within the Kekekabic Lake area are characteristic of distal turbidites, and correspond to facies associated with the depositional lobe of the mid-fan portion of a submarine fan (Walker and Mutti, 1973). Two periods of deformation have occurred in the Kekekabic Lake area along with broad folding and longitudinal and transverse faulting. The first period of deformation produced isoclinal folds, trending S 45°-50°W, with vertical to overturned fold axes that plunge to the southwest. The second period of deformation produced a pervasive N 62°-70°E cleavage throughout the area. Subsequently, broad folding warped the beds of the eastern Vermilion district on an axis trending N 60°W. Following folding, longitudinal faulting divided the Kekekabic Lake area into three distinct segments. Concurrent with or subsequent to longitudinal faulting, transverse faulting locally offset rock contacts. Sedimentary and volcanic rocks of the Kekekabic Lake area are representative of the middle portion of a calc-alkaline basalt-andesite-rhyolite volcanic pile accumulation which presumably developed within an island arc or continental orogenic system.
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    Autogenic signals in an experimental source-to-sink system
    (2015-12) Gazzetti, Edward
    Interpretations of the sedimentary rock record typically focus on allogenic forcing like fluctuations in relative sea-level and autogenic processes like fluvial avulsions and delta-lobe switching within the depositional system. I investigated the potential for drainage-basin-derived autogenic variability in sediment discharge to be preserved in the sedimentary rock record. I constructed a source-to-sink experimental apparatus to study the development of autogenic variability ‘signals’ in a net-erosional drainage basin and to trace these autogenic signals to a connected net-depositional basin (the ‘sink’), where they are preserved in a prograding fluvo-deltaic system. By maintaining constant tectonic uplift rate, climate (precipitation rate), and rock strength, I attempted to isolate and measure how allogenic forcing generates autogenic signals in the source terrane. Experimental results suggest that the interaction of landslides with channel processes in the drainage basin generates sediment-discharge variability. The scale of experimental landsliding is set by ridge relief, and landscapes with high rock strength, high uplift rate, and low precipitation rate have the potential to generate high-relief ridges. Thus, these systems can generate relatively large autogenic variability (+/- 10% from the mean) in sediment discharge. These experiments suggest that this autogenic variability in sediment supply propagates through the net-depositional fluvial system with minor time lags and can be preserved in the deltaic strata.
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    The Bedrock Geology of a Portion of the Cramer 15' Quadrangle, Lake County, Minnesota
    (1980-01) Lehman, George Albert
    The area studied consists of sections 20 - 29 and 32 - 36 of T60N, R6W of the Cramer, Minnesota 15' quadrangle. Units exposed include the anorthositic "series," troctolitic "series," and felsic "series" of the Duluth Complex, volcanic rocks of the North Shore Volcanic Group, melagabbroic-gabbroic intrusive rocks, diabasic rocks, and a hypabysal intrusive. Bedrock units are locally covered by a variety of glacial deposits related to the Rainy Glacial Lobe of the Wisconsin Ice Age. Troctolites and gabbros of the troctolitic series of the Duluth Complex display cummulate textures and regular cryptic (chemical) variation in the anorthite content of plagioclase (An78 to An58), the forsterite content of olivine (Fo70 to Fo50), and in the FeO/FeO+MgO ratio in augite (22 - 40). Orientations of igneous laminations as well as the areal distribution of rock types and cryptic variations strongly suggest the troctolitic series is a sill-like intrusion which differentiated in place as the result of crystal settling.
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    Calibration and Application of a New Paleotemperature Tool in Lacustrine Systems: TEX86 for Continental Paleoclimate Reconstruction
    (2005-11) Powers, Lindsay
    The calibration of the TEX86 (TetraEther indeX of tetraethers with 86 carbon atoms) paleotemperature proxy in lacustrine systems provides a new hydrologically independent paleothermometer, enabling high-resolution lake surface temperature reconstructions from large lakes. TEX86 is based on the relative abundance of cyclopentane containing membrane lipids (glycerol dialkyl glycerol tetraethers or GDGTs) of aquatic Crenarchaeota, a non-thermophilic Archaea. I have developed a calibration for the TEX86 paleotemperature proxy from a climatically diverse suite of globally distributed lacustrine systems (N=15). The results of this calibration show a strong linear relationship between TEX86 values and published mean annual and mean winter lake surface temperature. The TEX86 index appears to work best in large lakes, which are typically the best integrators of regional climate variability. Methanogenic/methanotrophic and hydrothermal Archaea are capable of producing some of the same isoprenoid tetraethers, and in certain cases can confuse the TEX86 signal. I have applied TEXs6 to lacustrine sediments from Lake Malawi, East Africa, to develop high-resolution paleotemperature records from the Last Glacial Maximum (LGM) to the present. I find a ~4 °C overall warming since the LGM, with temperature reversals of more than 2 °C during the Younger Dryas (12.5 ka BP) and in the early Holocene (Fig.1), possibly associated with the 8.2 ka climate event. The onset of warming in the Lake Malawi basin coincides with the BYRD oxygen isotope record of warming in Antarctica. While the range of temperatures observed in this record is not surprising, the timing of post-glacial warming, the thermal response to the YD, and the Holocene history of warming and cooling trends are providing important new insights into tropical climate dynamics on centennial to millennial scales. Additionally I have produced a temperature record from Lake Malawi spanning the past 700 years at ~50 year sampling resolution. This record shows an anti-phase relationship with solar forcing and primary productivity records ii through much of the record. In the past 100 years there is a strong coherence with solar irradiance and atmospheric CO2 concentrations with the temperature record indicating a possible shift in tropical climate response to external forcing.
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    Changes in channel geometry through the Holocene in the Le Sueur River, south-central Minnesota, USA
    (2017-03) Targos, Courtney
    Paleochannels preserved on terraces via meander cutoffs during an incisional period record the channel geometry and thus discharge at distinct points in time throughout a river’s history. We measured paleochannel geometry on terraces throughout the Le Sueur River in south-central Minnesota, to track how channel geometry has changed over the last 13,400 years. A rapid drop in base level 13,400 yr B.P. triggered knickpoint migration and valley incision that is ongoing today. Since the 1800’s, the area has developed rapidly with an increase in agriculture and associated drainage, directly impacting river discharge by increasing water input to the river. Five paleochannels were identified on terraces along the Le Sueur River from 1m-resolution lidar data. Ground Penetrating Radar (GPR) was used to obtain a subsurface image across paleomeanders to estimate the geometry of paleochannels. Paleochannel geometry and estimated discharge were then compared to modern conditions to assess how much change has occurred. Three lines were run across each paleochannel perpendicular to the historic water flow. Each of the 15 lines were processed using the EKKO Project 2 software supplied by Sensors and Software to sharpen the images, making it easier to identify the paleochannel geometry. Paleodischarge was determined using the Law of the Wall and Manning's Equation, using modern slope and roughness conditions. OSL samples were collected from overbank deposits on terraces to determine the time of channel abandonment, and supplemented with terrace ages obtained from a numerical model of valley incision. Paleodischarge coupled with depositional ages provide a history of flow conditions on the Le Sueur River. Results show an increase in channel widths from the time paleochannels were occupied to modern channel dimensions from an average of 20 meters to 35 meters. The change was not constant through time, as all paleochannels analyzed on terraces had similar-sized channels. The best way to determine paleogeometry was using the 'best interpretation' of GPR data couple with coring data; and paleodischarge was best estimated using Manning's equation with an n value of 0.035. Results show an increase in discharge compared to paleochannels of a factor of two. Uncertainty estimates in GPR-based paleogeometry can change paleodischarge calculations by 50 %. Incremental flood frequency analyses, based on data obtained from the Red Jacket stream gage at the outlet of the Le Sueur, suggest a 1.5- and 2-year flood of 102 m3/s and 154 m3/s, respectively, which is comparable to estimations of bankfull based on current channel geometry at the Red Jacket gage, validating the methodology. Problems associated with paleogeometry estimations are primarily due to meander bend preservation in the subsurface, challenging GPR interpretation. The increase in channel geometry and discharge implies that the increase in flow associated with drainage and climate change since the area’s development has greatly impacted the Le Sueur River. This resulted in a change in channel morphometry through increased erosion along the bluffs and banks, widening channels. This increase in erosion has directly impacted the amount of sediment delivered to the rivers from banks and bluffs, increasing the fine sediment load in this turbidity-impaired river system.
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    Characterization of precious metal mineral occurrences in the NorthMet deposit of the Partridge River Intrusion, Duluth complex, Minnesota, USA.
    (2011-08) Cervin, Daniel O.
    The NorthMet deposit is a Cu-Ni-PGE magmatic sulfide ore body located along the northwestern margin of the Partridge River Intrusion (PRI), which is part of the 1.1 Ga Duluth Complex. PolyMet Mining Company is currently seeking a permit to develop an open pit mine at the site, which is about 7 miles south the town of Babbitt, MN. During pilot-plant test runs by PolyMet, approximately 75% of the total mass of precious metals (75% is the average recovery of Pd, Pt, and Au) known to exist from assay data were recovered; total sulfide recovery was 90%. In a sulfide flotation beneficiation process, it is assumed that precious metals are contained within sulfide minerals as small (micron-sized) platinum group minerals (PGM), as Au-Ag minerals, or in solid solution. The 75% recovery implies that some precious metal mineral (PMM) phases may not be hosted by sulfide minerals. This study seeks to characterize the mineralogical and textural occurrences of PMM in the NorthMet ore feed and concentrates. This information is not only of importance to the beneficiation of NorthMet ores, but also to the understanding of the metallogenesis of PGE-Au in magmatic sulfide deposits. The energy dispersive spectrometer-equipped scanning electron microscope at University Minnesota Duluth was used in backscatter electron composition mode (BEC) to conduct detailed compositional scanning of polished thin sections to locate PMM. As the 75% precious metal recovery would predict, NorthMet PMM primarily occur in association with sulfide minerals. Of the 346 PMM investigated in this study, 267 (77%) were hosted by sulfide minerals (mostly chalcopyrite and pentlandite), either as inclusions or at sulfide grain boundaries. The remaining 23% (79) of PMM were found in a variety of primary silicates, secondary silicates, and apatite. Forty-eight percent of sulfide-hosted PGM are located at sulfide grain boundaries, 52% occur as inclusions in sulfide. 1) The lower recovery rate of precious metals relative to base metals in NorthMet ores is largely due to the textural and mineralogical occurrence of Au-Ag minerals, of which 55% are hosted by silicates and apatite. Furthermore, most Au-Ag minerals do not appear to be strongly attached to and intergrown with sulfide host minerals either as inclusions or at grain boundaries and are likely lost to tailings prior to introduction to sulfide flotation systems. 2) Platinum group minerals have a strong sulfide association: at least 90% are hosted in sulfide minerals. PGM occur in secondary silicates (7%) and in association with apatite (3%) in contact with, or close to sulfides. PGM primarily occur at sulfide grain boundaries in sulfide halo textures, usually in plagioclase. PGM do not occur as inclusions in primary silicate minerals. Sulfide boundary PGM are often intimately intergrown with adjacent silicate minerals. 3) An orthomagmatic model is invoked to explain the genesis of NorthMet ores. The strong sulfide association of PGM, the indirect sulfide association of Au-Ag, the general paucity of hydrous, secondary minerals in PGM-bearing sulfide halo textures, and the mostly well-preserved primary igneous textures indicate that magmatic processes formed the NorthMet ore body.
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    Chemostra Tigraphy and Climatostra Tigraphy of the Paleoproterozoic Snowy Pass Supergroup, Wyoming and Its Application for Correlation with Other Sequences in North America
    (1998-02) Bekker, Andrey
    The early Paleoproterozoic ocean and atmosphere experienced significant changes in climate and chemical composition. A global glaciation was followed by climatic amelioration. Chemical composition of the ocean, namely, carbon isotope values, changed dramatically during this time. Collected data support a glacial origin for the Headquarters and Vagner and possibly for the Campbell Lake Formations. Stable isotope values of limestones of the Vagner and Espanola Formations are similar, thereby strengthening correlation of the underlying glacial units. The Nash Fork Formation, based on carbon isotope values, was deposited at the end of the carbon isotope excursion. Study of carbonates of the Chocolay and Cobalt Groups showed similar carbon isotope values of the Gordon Lake Formation and the Kona Dolomite, supporting their correlation. Other carbonate units of the Chocolay Group that were considered correlative with the Kona Dolomite appear to have different carbon isotope systematics and are interpreted to be older.
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    The Colvin Creek Body, a Metavolcanic and Metasedimentary Mafic Inclusion in the Keweenawan Duluth Complex, Northeastern Minnesota
    (1996-02) Patelke, Richard Lee
    The Northern Colvin Creek body (CCB) within the 1100 Ma Duluth Complex (Complex), northeastern Minnesota, is a very large, rotated inclusion of Keweenawan basalt and sedimentary rock metamorphosed to pyroxene hornfels facies by immersion in the Complex. The inclusion is about 2500 m in strike length with a stratigraphic thickness of 800 m. Volcanic and sedimentary features indicate a stratigraphic top to the northwest; strike is about N60°E and dips are 70° to 90° to the northwest. Previously the CCB has been interpreted as an oxidized, metamorphosed basalt of the North Shore Volcanic Group (Tyson 1976) and by Severson and Hauck (1990) as an intrusive unit of the Partridge River intrusion (PRI). The body consists of two metavolcanic units and an overlying metasedimentary unit. One of the metavolcanic units is cut by a sill. The stratigraphic package is bounded to the north by a weakly recrystallized olivine gabbro and to the south and east (?) by a poorly exposed, moderately metamorphosed, oxide-rich, fine-grained augite troctolite that shows local assimilation of the margins of the inclusion; both of these igneous units are parts of the Partridge River Gabbro Complex of the PRI. In the two volcanic units mineralogy consists of plagioclase-augite-olivine-orthopyroxene-magnetite-ilmenite. Concentrations of augite replace amygdules that are round, sheeted, and pipe-like; recrystallized piagioclase phenocrysts are locally present. Grain sizes in these units range from very fine- to locally medium-grained, averaging fine-grained. Thin, discontinuous, irregular augite veins are common. Metasedimentary rocks are anorthositic gabbro to gabbroic anorthosite in mineralogical and chemical composition and are of relatively constant proportions of plagioclase-diopside-orthopyroxene-magnetite-ilmenite, with lesser hematite, hercynite, geikielite and apatite. Sedimentary features include millimeter to centimeter scale density-graded modal layering and cross-beds. Texture is fine-grained with very uniform grain size throughout the unit. The contact between the volcanic and overlying sedimentary rocks is a thin (0-2 m) interval of ferrosalite pyroxene- and plagioclase-rich rock with locally abundant cordierite, garnet, biotite, and hercynite. The inclusion is associated with a magnetic high similar to many others in the Partridge River Gabbro Complex. It is uncertain if the rocks of the Colvin Creek body are the cause of this magnetic high, or simply overlie a buried anomaly. Geochemical work has confirmed the unit subdivisions established in the field. It has indicated essentially isochemical metamorphism and has given evidence that the metavolcanic units are probably equivalent to intermediate olivine tholeiites of the North Shore Volcanic Group. The metasedimentary rocks are more problematic; they are not analogous to any of the typical interflow sandstones of the North Shore Volcanic Group as described by Jirsa (1980, 1984). At about 350 m they are as thick as the total measured section of North Shore Volcanic Group interflow sedimentary rocks, show no rock fragments, no quartz, no conglomeratic horizons, and no intercalated volcanic rocks. These metasedimentary rocks, however, appear to match a Keweenawan sandstone exposed near Phantom Lake, north of Two Harbors. The similarities include: both rocks are strongly magnetic, bedded and cross-bedded; plagioclase-rich and quartz-poor; and of uniform fine grain-size. Neither of these units can be strictly correlated with any other in the Keweenawan system.
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    A Comparison of Two Archean Ultramafic Pyroclastic Rock Units from the Superior Province, Northwestern, Ontario
    (1989-12) Schaefer, Stephen Jon
    Two Archean komatiitic pyroclastic rock units occur on opposite sides of the Quetico Fault in northwestern Ontario. The eastern unit, the Dismal Ashrock is located 3 km north of Atikokan, Ontario on the northern side of the Quetico fault within the Wabigoon Subprovince of the Superior Province. It is part of a supracrustal sequence (the Steep Rock Group) that overlies an Archean unconformity. The Grassy Portage Bay Ultramafic pyroclastic rock unit (GUP) is located 100 km to the west on the south side of the Quetico fault, and is part of an overturned succession comprising mafic metavolcanic rocks, GUP and metasedimentary rocks. The Quetico Fault is a dextral fault with a history of transpressive tectonics. The Dismal Ashrock is steeply inclined, little deformed and has undergone greenschist facies metamorphism, and it is divided into komatiitic lapilli tuff, komatiitic volcanic breccia, komatiitic volcaniclastic rocks and a mafic pillowed flow. The GUP outcrops form an arcuate fold interference pattern. The GUP is strongly deformed and has undergone amphibolite facies metamorphism. It is divided into komatiitic lapilli tuff and komatiitic volcanic breccia. The Dismal Ashrock and the GUP contain cored and composite lapilli - unequivocal evidence for explosive volcanism. Locally some of the lapilli fragments are highly vesicular (up to 30% by volume) - greater than reported for any other komatiites. Other fragments show no vesicularity. The low vesicularity of some of the pyroclasts and association with pillowed lava flows in the case of the Dismal Ashrock indicate phreatomagmatic volcanic activity. Explosive water-magma interaction was probably initiated by modified eruption characteristics produced from exsolving volatiles. The Dismal Ashrock and GUP are similar in chemical composition and plot on the border between peridotitic and basaltic komatiites on a Jensen AFM diagram. They are high in MgO, Cr and Ni; however, they are unusually enriched in Fe, Ti, Zr, Mn, P, Ba, Nb, Rb and Sr compared to other komatiites. Several lines of evidence indicate that this unusual composition could not have been caused by alteration or assimilation, and an enriched mantle source region is the likely cause. Many of the characteristics that Dismal Ashrock and GUP share are rare or unique on a global scale, indicating that the Dismal Ashrock and GUP are correlative in some manner.
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    Contact Metamorphism Adjacent to the Laramie Anorthosite Complex, Albany County, Wyoming
    (1996-05) Xirouchakis, Dimitrios
    The 1440 Ma old Laramie Anorthosite Complex, in SE Wyoming, intrudes Archean granitic gneisses and supracrustal rocks. In the central part of the complex, gneisses of pelitic and granitic composition are intruded and metamorphosed by the central anorthositic dome and the southwestern-most parts of the Maloin Ranch Pluton. The pelitic rocks exhibit field and microtextural features that suggest partial melting. Disruption of the foliation, subhedral to euhedral cordierite, orthopyroxene and oikociystic feldspars are commonly observed. Textural relations between phases suggest reactions between a mixture of crystals and silicate melt during cooling. The migmatites lack any evidence of prograde metamorphism. The granitic gneiss lacks any evidence of melting and contains garnet near the Anorthosite, and the Maloin Ranch Pluton. Pressure conditions of 3.25 (±0.5) kb were calculated from the displacement of the reaction Orthopyroxene + Sillimanite = Hercynitic Spinel + Cordierite, in the pelites. Garnet-biotite geothermometiy, in pelitic assemblages, gives temperatures that range from 620° to 800° C. The garnet-cordierite geothermometer, from pelitic assemblages, yields temperatures that range from 630° to 750° C. Garnet-biotite compositions from the granitic gneiss are within or close to the limits of the experimental calibration. Calculations yielded a peak metamorphic temperature of 850° C and lower retrograde conditions of 760° C. South of the southern anorthositic dome, mafic pyroxene hornfelses and problematic quartzrich metasediments(?) are encountered. In the enigmatic metasediments the textures indicate recrystallization during cooling. This unit does not retain any evidence of prograde metamorphism. In contrast, the mafic pyroxene hornfelses appear to reflect peak metamorphic conditions. The displacement of the reaction Oinopyroxene + Plagioclase = Gamet + Quartz in the metasediments, gives pressure conditions of 3.25 (±1.9) kb. Pyroxene and Fe-Ti oxide geothermometry, from both units, yields temperatures that range from 730° to 840° C. The 1400 Ma Sherman Granite intrudes the Anorthosite Complex and its aureole. The retrograde assemblages observed in the metamorphic rocks, and their areal distribution suggest that the granitic intrusion occurred while the aureole was cooling at 0.5-3 kb and about 600° C.
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    Contact Metamorphism of the Virginia Formation in the Minnamax Deposit St. Louis County, Minnesota
    (1979-10) Kirstein, Mark H
    The Middle Precambrian Virginia Formation, cut by diabase dikes, was intruded and contact metamorphosed by the Late Precambrian Duluth Complex near Babbitt, Minnesota. Sulfide mineralization of magmatic origin, with minor amounts formed by hydrothermal replacement, is concentrated at the irregular contact zone between the Virginia Formation and the Duluth Complex. Five miles south of Babbitt this mineralization constitutes the Minnamax Copper-Nickel Deposit, which is being investigated and evaluated underground by AMAX Exploration, Inc. The Virginia Formation consists of pelitic hornfels, calc-silicate pods, and "reaction" rims around the pods. The pelitic hornfels is dark gray, fine-grained, massive, and composed of plagioclase, hypersthene, and cordierite with local occurrences of orthoclase, biotite, and graphite. The calc-silicate pods are light gray, fine- to coarse grained, are spherical to ellipsoidal and range from 4 inches to 8 feet across. There are three types of pods; homogenous types with no mineral zones developed, layered types with mineral layers developed, and concentric types with mineral zones developed. The primary minerals are diopside, grossular garnet, plagioclase, sphene, wollastonite, and possibly some calcite, and quartz. From strikes and dips of relict bedding in pelitic horn.fels and from the broken, fra.ctured, and jumclad nature of calc-silicate pods deformation of the Virginia Formation appears intense. The "reaction" rims are dark gray, fine-grained, and up to 3 inches wide. They are composed of plagioclase, hypersthene and poikiloblastic clinopyroxene giving a composition intermediate between the pelitic hornfels and calc-silicate pods. The protolith of the pelitic hornfels appears to be a calcareous argillite and the calc-silicates a siliceous dolomitic limestone. The pods are believed to have originally been calcareous concretions in argillite with some being pieces brought up from the calcareous zone at the top of the Biwabik Iron Formation. The "reaction" rims developed after deformation took place, as they surround broken and fractured pods, and formed from diffusion of calcium from the pods into the pelitic hornfels. The metadiaba.se dikes are dark gray, fine-grained, and massive. They are composed of lathy plagioclase, augite, and hypersthene. A relict ophitic texture is evident and relict plagioclase phenocrysts have been resorbed. Sulfides consist of pyrrhotite, exsolved pentlandite, and chalcopyrite in pelitic hornfels and chalcopyrite with exsolved cubanite in calc-silicate pods. Minor ilmenite and magnetite is present in the sulfides. Alteration consists of uralitization of pyroxenes and sericitic and kaolinitic alteration of plagioclase. Quartz, calcite, apophyllite, anhydrite, fluorite, heulandite, laumontite, and prehnite are gangue minerals. This emplacement occurred after the main metamorphic event and formed by hydrothermal replacement. Based on the primary mineral assemblages present, the rocks fall in the pyroxene hornfels facies. The presence of plagioclase and wollastonite in the calc-silicate pods give a minimum temperature of 600 degrees Celsius at 2 kilobars pressure, and a mole fraction of CO2 in the vapor phase less than 0.25. An increase of albite in plagioclase can lower the temperature of the reaction forming plagioclase and wollastonite, and could cause the plagioclase and wollastonite to disappear with quartz and calcite stableo From the presence of laumontite, an upper limit of 350 degrees Celsius at 2 kilobars pressure can be given for the sulfides e:mplaced hydrothermally. A bottom temperature ranging from 250 to 300 degrees Celsius can be given by the presence of exsolved cubanite in chalcopyrite.
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    Deformation and Metamorphism of Tectonites Exposed in the New York and Clark Mountains, eastern California: A case for Proterozoic mid-crustal shortening in the Mojave Province
    (2005-08) Rieser, Michael Edwards
    During ~1.76-1.64 Ga crustal growth in southwest Laurentia, an oblique shear zone with components of left-lateral strike-slip and thrust motions juxtaposed two blocks of deep-seated Proterozoic crust presently exposed in the New York and Clark mountains of the Mojave tectonic province, eastern California. Two localities, Mineral Hill and Willow Wash, were subjected to peak metamorphic conditions of ~720°C, 6.5 kbar and ~780°C, 3.5 kbar, respectively, as determined by GASP barometry and Grt-Bt exchange thermometry. Ductile L-S tectonite fabrics consisting of a north-northwest striking, west-dipping tectonic and compositional foliation and a northwest-trending, shallow-plunging mineral stretching lineation characterize the penetrative deformation of both areas. High-temperature quartz c-axis fabrics confirm that peak metamorphic conditions accompanied deformation. Additionally, quartz petrofabric analysis reveals a strong lattice-preferred orientation (LPO) that is geometrically related to the stretching lineation and foliation. Asymmetric S-C foliations, folds, and feldspar "fish" measured in the field and in thin section yield reproducible top-to-the-SE shear sense indicators. Although quartz LPO is well preserved, flat-field extinction in quartz grains is interpreted as evidence of annealing related to post-kinematic regional heating. Synchronous granulitefacies metamorphism, medium metamorphic pressure, and oblique top-to-the-SE, sinistral shear suggest that the deep crust was simultaneously translated and contracted, placing 3.5 kbar crust structurally above 6.5 kbar crust. The kinematic fabrics and contrasting barometry of these two related tectonic blocks may offer a direct example of large-scale Paleoproterozoic strike-slip motions proposed by earlier workers (Bennett and DePaolo, 1987) on the basis of isotopic mapping. The apparent contraction may be related to the 1.705 "Ivanpah Orogeny", which juxtaposed the Yavapai and Mojave tectonic provinces (Wooden and Miller, 1990).
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    Deformation in the Archean Knife Lake Group, Vermilion District, Northeastern Minnesota
    (1989-01) MacArthur, James
    Finite strain analysis and detailed mapping of structures in Archean volcanic and sedimentary rocks in the eastern Vermilion District of northern Minnesota reveal three deformational events, the first of which appears to be responsible for the measured strain. D1 produced regional isoclinal folds with approximately E-W trending, gently plunging axes, and approximately vertical axial planes. A strong penetrative foliation occurs parallel to the axial planes of these folds and clasts in conglomerates and volcanic rocks have been strongly flattened in the plane of the foliation. D2 was a dextral simple shear event with the shear plane oriented approximately E-W which produced sigmoidal tension gashes and rotational microstructures. Kink bands indicative of EW shortening may also have been produced in an EW compressive component of this event. D3 was another simple shear event with the shear plane oriented E-W, dipping 60S with a sinistral sense of movement reflected on east-facing vertical planes or a north-side-up movement in plan view. Rotational microstructures and a local SC foliation were produced in the D3 event. Finite strain analysis reveals flattening strains consistent with D1 kinematics. Variations in measured strain are interpreted to be due to competence contrasts between strain markers and matrix. Analysis of the effects of competence contrast on apparent strain recorded by various lithologies reveals significant variations. Strain analysis using conglomerate clasts of several lithologies as well as lithic lapilli as markers thus gives an approximation of finite strain but is not sufficiently sensitive to reflect D2 and D3 strains in the study area.
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    Design and application of a proxy system model for the quantitative reconstruction of hydroclimate variabiility recorded by oxygen isotopes in lacustrine carbonate sediment
    (2021-01) Fernandez, Alejandro
    Oxygen isotope analyses of lacustrine sediment, which are widely used as proxies of past climatic variability, have become increasingly reliant on computational modeling approaches that allow for quantitative interpretations of past hydroclimate, constraining of water resources’ sensitivities to changes in climate, and direct comparisons of proxy data with climate models. In this study, we present the development, structure and application of a Proxy System Model (PSM) designed for Castor Lake (Washington, U.S.A): a well-understood, highly monitored small lake system. The principal goal is to improve upon the understanding of the relationships between climate and the stable oxygen isotope (18O) proxy system in the context of lake sediments, by addressing the impacts that a variety of climate variables, as well as non-climate relate factors such as basin morphology, vegetation, hydrologic setting and lake mixing, have on the isotopic signatures of resulting sediments in the lake, as well as to provide a quantitative basis from which well-informed reconstructions of past climate can be made. Following a calibration process based on over a century of compiled daily weather data as well as approximately 14 years of in-situ continuous measurements of lake level, temperature and water oxygen isotope samples, the PSM was shown to accurately reproduce seasonal, interannual and century-scale trends of sediment oxygen isotope values and water balance, with varying degrees of accuracy for different timescales. Model-based reconstructions of hydroclimate variables for an early Holocene (~10000 years B.P.) δ18O maximum in the Castor Lake sediment record show that cold-season (i.e. winter) precipitation and relative humidity must have been lower by 21% ± 5% and 14% ± 7%,respectively, in order for the observed sediment δ18O signature to be produced and recorded. Furthermore, air temperature and warm-season precipitations seem to be negligible controls on sediment δ18O signatures, opposite to what was expected following the temperature dependence of carbonate sediment formation and isotopic fractionation. These results showcase the advantages of the application of PSMs to the analysis of paleoclimate proxy records as a way to make well-informed quantitative interpretations of past climate change through the constraining of physical, chemical and biological processes that impact the formation of the sedimentary archive.
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    Development of a Copper-Nickel Industry in Northeastern Minnesota
    (1973-06) Saremba, Scott P
    Many 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.