Soil development on upland landscapes in east-central Iowa Peoria Loess deposits has been occurring for approximately the last 12,500 years. Weathering zone and pedogenic processes depend on environmental factors such as climate, precipitation, time, parent material, biota, and topography, among others. Analyzing the weathering zones of modern and paleosol profiles provides insight into current and paleo-environmental processes. This study employs several bulk geochemical analytic techniques (XRF, pXRF, LIBS, ICP-MS) to examine the weathering profiles formed in modern Peoria Loess deposits and underlying weathering profiles formed during the Farmdale Interstadial and the Sangamon Interglacial. Results indicate advanced weathering occurred in the paleosol sequences of the Farmdale and Sangamon compared to the modern weathering zone, based on depletion and enrichment of elemental concentrations. The interstadial/last interglacial paleosol weathering profiles exhibit increased depletion in CaO, MgO, Na2O, and K2O compared to the Holocene weathering profile formed in Peoria Loess. Enrichment of CaO and MgO in non-pedogenically altered Peoria Loess deposits is a possible indication of rapid loess accumulation, representing insufficient weathering of deposited material synchronous with deposition. Post-depositional weathering and hydrogeological mechanisms may also account for this mid-profile enrichment, providing for some complexity for interpretation. Regional comparison between three sediment cores - an agricultural field, a restored prairie and a pioneer cemetery - exhibit minor land-use influence on geochemical evolution with the agricultural field core exhibiting greater relative depletion in most oxides in the upper one meter, compared to the other sediment cores. However, slight regional heterogeneity in parent material, vegetation cover, and slope position may also account for geochemical variations. Therefore, it is difficult to conclude how the last 150 years of extensive land-use from human activity has impacted weathering and pedogenesis in this region. Additionally, this study validates using pXRF technology on Quaternary weathering profiles, and documents its technological shortcomings which provides essential information for drawing interpretations from these data.

Exposed weathering profiles of a series of Pololu lava flows in Kohala, Hawaii are ideal for investigating the sequence of reactions/reaction pathways of weathered basalt. Weathering reactions for saprolites show mineral sequences that include feldspar → halloysite ± gibbsite + solutes; clinopyroxene → hematite + minor halloysite + solutes; olivine → hematite + solutes; magnetite → hematite or other Fe-oxides/hydroxides. However, the presence of smectite in four samples suggests that smectite-group clays may form as short lived intermediates at the base of the weathering profile. Regionally, on Kohala, soils and saprolites are dominated by halloysite with small quantities of other clays such as kaolinite, gibbsite, and smectite. However, one horizon in the weathering profile at the study site in Kohala is dominated by gibbsite. Smectite is found at the base of the profile above impermeable areas where mass leaching has left increased alkaline and alkaline earth elemental (Mg, Ca, Na, and K) abundances relative to the parent rock. The amount of elemental gain varies from -5% to +75% for samples with smectite. Different climates generate different weathering profile depths. MASW (multi-channel analysis of surface waves) shows that the depth of the weathering profile is 15 meters. Seismic profiles correlate the depth of the weathering profile inland (~15 meters), with cliff face (~13 meters). Other than the gibbsite horizon, most mineral zones are too thin to be resolved through second-order velocity variations. P-wave reflection surveys are unsuitable for imaging the base of the weathering front because the transition to fresh rock may be gradational. However, within the saprolite section, boundaries between relict lava flow textures produce reflections that mimic expected stratigraphic patterns. Perpendicular to the shoreline, reflectors dip gently seaward, whereas parallel to the shoreline, lenticular packages of relict lava flows are observed.

Thesis (doctor of philosophy)--Göteborg University, 2006. / Includes bibliographical references.

Les cryptokarsts de Beez (Namur, Belgique) se sont développés au dépens de calcaires dolomitiques viséens, à la faveur de drains constitués par les filons sulfurés Fe-Pb-Zn, sous une couverture composée de pélites gréseuses viséo-namuriennes et de sables oligocènes. À Khamouda (Kasserine, Tunisie), les poches karstiques se sont développées suivant la stratification sub-horizontale des calcaires sénoniens de la Formation Douleb à partir d'une faille normale les mettant au contact de la couverture sableuse miocène (Formation Béglia). Dans les deux sites, des paragenèses riches et complexes s'installent aux interfaces entre encaissant carbonaté et remplissages karstiques. Des argilites blanches, principalement composées de phases silico-alumineuses et alumineuses, ainsi que des croûtes ferrugineuses sont toujours présentes. À Beez, l'argilite est constituée d'halloysite et de gibbsite. À Khamouda, elle s'enrichit de phases zincifères plus rares, telles que la sauconite, ainsi que d'un phyllosilicate à 7 Å et d'un hydroxyde de zinc amorphe. Des sulfates sont également néoformés, notamment du gypse, dissout par la suite mais dont les croûtes ferrugineuses comportent encore des indices, ainsi que de la jarosite à Beez. D'un point de vue fondamental, les systèmes cryptokarstiques, qui opposent une barrière carbonatée à la migration de fluides acides, sont des structures privilégiées pour l'étude et la compréhension de la migration et la fixation des éléments chimiques dans le domaine supergène. Dans les deux cas, les fluides météoriques acquièrent leur acidité (pH ~2 à Beez et pH~4 à Khamouda) par lessivage de la couverture sédimentaire sus-jacente et notamment par oxydation des sulfures qu'elle contient (pyrite à Beez, pyrite et sphalérite à Khamouda). Les principaux éléments mobilisés à Beez sont Si et Al et dans une moindre mesure Fe, Mn et les Terres Rares ; tandis qu'à Khamouda, les principaux éléments mobilisés sont Si, Al et Zn, et dans une moindre mesure Fe, Pb et les Terre Rares. La neutralisation des fluides au contact du mur carbonaté conduit dans un premier temps à la formation de sulfates (gypse, jarosite) et d'oxy-hydroxydes de fer, puis d'halloysite et d'hydroxydes d'aluminium à partir de pH 4,8-5,4. À Khamouda, les phases zincifères ne se forment que plus tardivement (pH < ~9,5). Dans les deux cas étudiés, nous avons mis en évidence l’évolution de phases minérales depuis des gels silico-alumineux jusqu’à des minéraux bien cristallisés, tels que l’halloysite, ou moins bien organisés, tels que certains oxydes de manganèse à Beez. Dans les deux gîtes, le microfaciès tubulaire de l'halloysite, correspondant à une croissance fissurale, prédomine par rapport au faciès sphéroïdal se développant habituellement au sein des masses de gel ; ce qui suggère une fracturation répétée des masses de gels précurseurs. Nous avons également établi que ces gels continuent à incorporer des cations des solutions percolantes, notamment du manganèse à Beez. La difficulté majeure de l'étude des altérations cryptokarstiques réside dans la détermination des âges des phénomènes. L'âge des couvertures sédimentaires impliquées dans les poches karstiques donne une première approximation. Ainsi, la phase majeure d'altération à Beez est post-oligocène suivie d'une réactivation quaternaire ; tandis que l'altération est post-miocène à Khamouda. Le site de Beez propose un éventail de minéralisations pouvant faire l'objet de datations radiométriques. Ces datations "absolues" doivent constituer une priorité forte à l'avenir. __________________________________________________________________________________________________ Résumé en anglais : The cryptokarsts from Beez (Namur, Belgium) were settled in dolomitic Visean limestones, in which vertical Fe-Pb-Zn sulphides veins play an important role as karstic drains. The sedimentary cover is made up of Viseo-Namurian siliceous shales and Oligocene sands. The cryptokarsts from Khamouda (Kasserine, Tunisia) were found in Senonian limestones (Douleb Formation). They expand from a down fault, which has brought limestones into contact with Miocene sands (Béglia Formation), following the sub-horizontal stratification. In both sites, complex paragenesis settled at the limestone/karst-filling interface. White clays, principaly composed of Si-Al and Al phases, and ferruginous crusts are the main paragenesis. In Beez, the white clays are made up of halloysite and gibbsite, while in Khamouda, they are enriched with uncommon zinciferous phases as sauconite (Zn-smectite), a 7Å-phyllosilicate and an amorphous Zn­hydroxide. Sulphates have also been found, as imprints of gypsum crystals in both sites, and as jarosite in Beez. Acid fluids percolated in the overlying sedimentary cover (pH~2 in Beez and pH~4 in Khamouda). The acidity is due to the oxidation of some sulphides (pyrite in Beez; pyrite and sphalerite in Khamouda). Cryptokarsts basically play an important role in chemical elements mobilization and trapping processes. In Beez, Si and Al have mainly been mobilized. Fe, Mn and the Rare Earth Elements (REE) have been mobilized too. In Khamouda, the main mobilized elements are Si, Al and Zn. Fe, Pb and REE have been mobilized too. The acid fluids are neutralized at the limestone karst-wall. It leads first to the neogenesis of sulphates (as gypsum and jarosite) and iron oxi-hydroxides (pH < 4,8). Then, halloysite and Al-oxi-hydroxides are formed (from pH~4,8-5,4 upward). In Khamouda, zinciferous phases developed lately (from pH~9,5 upward). In both studied systems, we clearly show the development of mineral phases from a Si-Al gel to well-crystallized minerals, as halloysite, or badly organized minerals, as some Mn-oxides from Beez. In both deposits, tubular halloysite, which usually develops in cracks, is prominent in comparison to spheroidal halloysite, which usually growths in gel masses. It suggests an extreme fracturing of the gel masses. We established that these gel masses mix cations from the percolating solutions. The main difficulty in cryptokarstic environments is to determine ages of weathering processes, nevertheless the age of overlying deposits give an idea. Thus, the major weathering stage in Beez is post-Oligocene (followed by a Quaternary reactivation), while weathering in Khamouda is post-Miocene. The cryptokarsts from Beez contain several mineral phases, which could be dated with radiometric methods. This "absolute" dating has to be the next step.

A forested first-order catchment in western Amazonia was monitored for 2 years to determine the chemical fingerprints of precipitation, throughfall, overland flow, pipe flow, soil water, groundwater, and streamflow. We used five tracers (hydrogen, calcium, magnesium, potassium, and silica) to distinguish “fast” flow paths mainly influenced by the biological subsystem from “slow” flow paths in the geochemical subsystem. The former comprise throughfall, overland flow, and pipe flow and are characterized by a high potassium/silica ratio; the latter are represented by soil water and groundwater, which have a low potassium/silica ratio. Soil water and groundwater differ with respect to calcium and magnesium. The groundwater-controlled streamflow chemistry is strongly modified by contributions from fast flow paths during precipitation events. The high potassium/silica ratio of these flow paths suggests that the storm flow response at La Cuenca is dominated by event water.

Provenance in the lower Belt-Purcell Supergroup is constrained based on geochemical systematics and chemical monazite ages of argillites and sandstones. Rare earth element (REE), Cr-Ni, and Th/Sc-Sc systematics is equivalent for both facies and consistent with a dominantly post-Archean source area. Detrital monazite chemical ages restrict major provenance for the Appekunny and Grinnell sandstones and argillites to Paleoproterozoic terranes at ~1800-1600 Ma, minor contributions at ~1600-1500 Ma, and marginal contributions from Archean terranes at ~2600, likely in Laurentia. Similar detrital age spectra for monazites of argillites and sandstones of the Appekunny Formation are consistent with a common provenance for the two facies.</p> <p>The Belt-Purcell sequence records three major diagenetic stages displayed in argillites and sandstones: (1) K-addition and rare earth element post-Archean upper continental crust (PA-UCC)-like pattern; (2) a stage characterized by heavy REE enrichment relative to light REE and HFSE fractionation, and U and Ce mobility; and (3) local dolomitization with REE and high field strenght elements (HFSE) mobility. REE and HFSE mobility are interpreted as the result of oxidized alkaline brines developed by dissolution of evaporites. Monazites from the Appekunny and Grinnell formations differ compositionally and texturally in two groups. Rounded or inclusions with ages >~1400 Ma, interpreted as detrital, have higher Th2O, Y2O3 and lower LREE/HREE contents than euhedral individual monazite grains with chemical ages <~1400 Ma that posses opposed compositional characteristics, and viewed as diagenetic. Monazites that span <~1400 to 300 Ma could be the result of basinal brine activity during stages (2) and (3). </p> <p>Chemical index of alteration (CIA) for argillites and sandstones, corrected for a diagenetic K-addition average 73 and 66 respectively. These results, coupled with correlation of CIA with Eu/Eu*, low K/Cs ratios, and low Sr, Ca, and Na relative to PA-UCC, could be interpreted as the result of an moderate weathered provenance in a hot, wet climate being drained by a large-scale river system. Presence of minor pristine feldspars lowers the CIA values, and may signify minor contributions from proximal source with short-river transport under the arid to semi-arid climate in the depositional setting. Moderate to intense weathering of the larger provenance may be associated with elevated levels of atmospheric CO2 degassed from a mantle plume implicated in the rifting of the supercontinent Columbia at ~1500 Ma.

Weathering steel is a high-strength, low-alloy steel which has been proven to provide a significantly higher corrosion resistance than regular carbon steel. This corrosion resistance is a product of the small amounts of alloying elements added to the steel, which enable it to form a protective oxide layer when exposed to the environment. The main advantage of its use in bridges is that, under normal conditions, it may be left unpainted, leading to significantly reduced maintenance and environmental costs. Weathering steel has been a material of choice for highway structures for almost half a century, and a very large number of structures have been constructed with it. Although its use has for the most part been successful, it has also become evident that, in circumstances where there is the presence of salt and sulphur oxides, its performance is deficient. In these situations the corrosion penetration rate is much higher than expected, and the oxide layer forms in thick layers. This presents an added risk, since these layers flake off and fall onto the roadway. The degree of corrosion on structures can be very different, even if the structural type, location, and climate are similar. Therefore the focus of the thesis is on the lifespan of weathering steel highway structures. Primarily this research is concerned with the effect of corrosion on the integrity of these structures, as well as ways of quantifying corrosion loss and protecting the structure from further corrosion. In order to determine the lifespan of weathering steel highway structures subject to different rates of corrosion, a probabilistic structural analysis program has been developed to assess the time-dependent reliability of the structure. This program used iterative Monte Carlo simulation and a series of statistical variables relating to the material, loading, and corrosion properties of the structure. A corrosion penetration equation is used to estimate thickness loss at a selected interval, and the structural properties of the bridge are modified accordingly. The ultimate limit states of shear, moment, and bearing, and the fatigue limit state of web breathing, are taken into account. Three types of structures are examined: simply-supported box and I-girder composite bridges, and a two-span box girder bridge. Based on the structural analysis of the corroding bridge structures presented herein, it can be seen that corrosion to the weathering steel girders can cause reduced service lives of the structures. I-girder bridges are shown to be more susceptible to corrosion than box girder bridges, with continuous box girder bridges showing the best performance. The amount of truck traffic does not affect the reliability of the bridge. The short-span and high strength steel bridges are more susceptible to corrosion loss, primarily because their girders have thinner sections. A two-lane bridge also has better performance than the wider bridges because the weight of the barriers and sidewalks is carried by fewer girders, so these girders are stockier. The web breathing limit state is less significant than the combined ultimate limit states. Lastly, and most importantly, inspection data from a highway bridge is used to demonstrate the benefit that can be derived from using field data to update the time-dependent reliability. The ultrasonic thickness gauge (UTG) is a common tool for thickness measurement of steel sections. When used to measure weathering steel, this instrument provides accurate data about the depth of corrosion pits, but not their lateral dimensions. The measurement does not include the corrosion layer on the opposite side of the plate from the one being measured; however, if the corrosion layer is on the measured face, a disproportionate increase in the measured thickness can be seen. In order to prevent or minimize corrosion loss, the steel is currently painted, a process with several environmental and financial disadvantages. Therefore, three novel protection methods have been assessed in a cyclic corrosion test: a zinc metallizing, an aluminum-zinc-indium alloy metallizing, and a zinc tape with a PVC topcoat. All these coatings are designed to act not just as barriers, but also as sacrificial anodes. The test was run for 212 24-hr cycles, over the course of which the all the coatings were proven effective at protecting the steel substrate, regardless of steel type and surface roughness and pretreatment. In conclusion, the threat to all types of weathering steel highway structures by contaminant-induced corrosion is significant, but inspection data permits a more accurate prediction of time-dependent reliability for a structure, and protective coatings are a promising method of slowing the advance of corrosion.

Weathering steel is a high-strength, low-alloy steel which has been proven to provide a significantly higher corrosion resistance than regular carbon steel. This corrosion resistance is a product of the small amounts of alloying elements added to the steel, which enable it to form a protective oxide layer when exposed to the environment. The main advantage of its use in bridges is that, under normal conditions, it may be left unpainted, leading to significantly reduced maintenance and environmental costs. Weathering steel has been a material of choice for highway structures for almost half a century, and a very large number of structures have been constructed with it. Although its use has for the most part been successful, it has also become evident that, in circumstances where there is the presence of salt and sulphur oxides, its performance is deficient. In these situations the corrosion penetration rate is much higher than expected, and the oxide layer forms in thick layers. This presents an added risk, since these layers flake off and fall onto the roadway. The degree of corrosion on structures can be very different, even if the structural type, location, and climate are similar. Therefore the focus of the thesis is on the lifespan of weathering steel highway structures. Primarily this research is concerned with the effect of corrosion on the integrity of these structures, as well as ways of quantifying corrosion loss and protecting the structure from further corrosion. In order to determine the lifespan of weathering steel highway structures subject to different rates of corrosion, a probabilistic structural analysis program has been developed to assess the time-dependent reliability of the structure. This program used iterative Monte Carlo simulation and a series of statistical variables relating to the material, loading, and corrosion properties of the structure. A corrosion penetration equation is used to estimate thickness loss at a selected interval, and the structural properties of the bridge are modified accordingly. The ultimate limit states of shear, moment, and bearing, and the fatigue limit state of web breathing, are taken into account. Three types of structures are examined: simply-supported box and I-girder composite bridges, and a two-span box girder bridge. Based on the structural analysis of the corroding bridge structures presented herein, it can be seen that corrosion to the weathering steel girders can cause reduced service lives of the structures. I-girder bridges are shown to be more susceptible to corrosion than box girder bridges, with continuous box girder bridges showing the best performance. The amount of truck traffic does not affect the reliability of the bridge. The short-span and high strength steel bridges are more susceptible to corrosion loss, primarily because their girders have thinner sections. A two-lane bridge also has better performance than the wider bridges because the weight of the barriers and sidewalks is carried by fewer girders, so these girders are stockier. The web breathing limit state is less significant than the combined ultimate limit states. Lastly, and most importantly, inspection data from a highway bridge is used to demonstrate the benefit that can be derived from using field data to update the time-dependent reliability. The ultrasonic thickness gauge (UTG) is a common tool for thickness measurement of steel sections. When used to measure weathering steel, this instrument provides accurate data about the depth of corrosion pits, but not their lateral dimensions. The measurement does not include the corrosion layer on the opposite side of the plate from the one being measured; however, if the corrosion layer is on the measured face, a disproportionate increase in the measured thickness can be seen. In order to prevent or minimize corrosion loss, the steel is currently painted, a process with several environmental and financial disadvantages. Therefore, three novel protection methods have been assessed in a cyclic corrosion test: a zinc metallizing, an aluminum-zinc-indium alloy metallizing, and a zinc tape with a PVC topcoat. All these coatings are designed to act not just as barriers, but also as sacrificial anodes. The test was run for 212 24-hr cycles, over the course of which the all the coatings were proven effective at protecting the steel substrate, regardless of steel type and surface roughness and pretreatment. In conclusion, the threat to all types of weathering steel highway structures by contaminant-induced corrosion is significant, but inspection data permits a more accurate prediction of time-dependent reliability for a structure, and protective coatings are a promising method of slowing the advance of corrosion.

Everything falls apart, but some materials do it with a specific panache, and once design leaves paper to be built, no project is complete until it falls. As creatures subject to time, we identify with things in which we see ourselves, we identify with our mortal buildings. Alchemy used material transformation as an active metaphor for human betterment. This thesis will search for ways that the inevitable indexing of time on the built environment can be used to catalyze a broader understanding of time and our place in it. Sympathetic engagement with our environments can form rich internal narratives while also fostering collective memory. Four materials form the basis of these investigations: Cedar, Copper, Iron and Marble. For each material, chemical properties, history and mythology are invoked to describe their particular temporal nature, an understanding of how they come together and fall apart. The four material chapters of this thesis mean to return a sense of cognitive depth to our relationship with materials without resorting to symbolism.

Provenance in the lower Belt-Purcell Supergroup is constrained based on geochemical systematics and chemical monazite ages of argillites and sandstones. Rare earth element (REE), Cr-Ni, and Th/Sc-Sc systematics is equivalent for both facies and consistent with a dominantly post-Archean source area. Detrital monazite chemical ages restrict major provenance for the Appekunny and Grinnell sandstones and argillites to Paleoproterozoic terranes at ~1800-1600 Ma, minor contributions at ~1600-1500 Ma, and marginal contributions from Archean terranes at ~2600, likely in Laurentia. Similar detrital age spectra for monazites of argillites and sandstones of the Appekunny Formation are consistent with a common provenance for the two facies.</p> <p>The Belt-Purcell sequence records three major diagenetic stages displayed in argillites and sandstones: (1) K-addition and rare earth element post-Archean upper continental crust (PA-UCC)-like pattern; (2) a stage characterized by heavy REE enrichment relative to light REE and HFSE fractionation, and U and Ce mobility; and (3) local dolomitization with REE and high field strenght elements (HFSE) mobility. REE and HFSE mobility are interpreted as the result of oxidized alkaline brines developed by dissolution of evaporites. Monazites from the Appekunny and Grinnell formations differ compositionally and texturally in two groups. Rounded or inclusions with ages >~1400 Ma, interpreted as detrital, have higher Th2O, Y2O3 and lower LREE/HREE contents than euhedral individual monazite grains with chemical ages <~1400 Ma that posses opposed compositional characteristics, and viewed as diagenetic. Monazites that span <~1400 to 300 Ma could be the result of basinal brine activity during stages (2) and (3). </p> <p>Chemical index of alteration (CIA) for argillites and sandstones, corrected for a diagenetic K-addition average 73 and 66 respectively. These results, coupled with correlation of CIA with Eu/Eu*, low K/Cs ratios, and low Sr, Ca, and Na relative to PA-UCC, could be interpreted as the result of an moderate weathered provenance in a hot, wet climate being drained by a large-scale river system. Presence of minor pristine feldspars lowers the CIA values, and may signify minor contributions from proximal source with short-river transport under the arid to semi-arid climate in the depositional setting. Moderate to intense weathering of the larger provenance may be associated with elevated levels of atmospheric CO2 degassed from a mantle plume implicated in the rifting of the supercontinent Columbia at ~1500 Ma.