Thesis (Ph. D.)--Boston University, 1991. / Interest in deep sea microbiota was stimulated by recent discoveries of productive redox communities associated with hydrothermal vents and brine seeps, and based on bacterial chemolithotrophy. This study investigates microbial destruction of mussel shells from a redox community at the base of the Florida Escarpment (3360 m), in comparison with microbial boring in shells of typical, low productivity areas of the ocean floor. An assemblage of eukaryotic and prokaryotic periostracum borers and their boring traces were discovered in shells of Bathymodiolus mussels from the base of the Florida Escarpment, and characterized. Microbial destruction of this protective layer results in colonization of secondary microbial inhabitants inside boreholes, and exposes the underlying mineralized shell to colonization and destruction by microbial endoliths. Microbial consumption of periostracum often proceeds in successive waves. These organisms show different "foraging" behaviors and leave accordingly varied boring patterns. These activities create a labyrinth of pits, holes and tunnels which, in tum, provide sheltered microenvironments for secondary microbial settlers, including primary producers, which all constitute an abundant food source for numerous ciliates and gastropods observed on the shells. This concerted attack on the periostracum eventually leads to the exposure of the mineralized shell. Such exposed areas are characterized by [TRUNCATED]

<p> The beach deposits at the head of the Lion's Head Peninsula are described and categorized according to the type, size and morphology of the rocks making up the deposit and their origins. This categorization emerges as a pattern of four zones along the l ength of the beach. </p> <p> The points at each end of the beach, which used to be in a much more defined bay, have been glacially eroded by re-entrants and undercut by postglacial lakes. Shales and dolomite from the escarpment make up this zone's deposits. </p> <p> Zone two is a dolomite cobble beach supplied by the escarpment's erosion from a blockaded late-glacial ice margin and the undercutting of postglacial lakes. </p> <p> Zone three is a mixture of the dolomite from the escarpment, lacustrine sand deposits, and glacial erratics. </p> <p> Zone four is made up of a distinct band of erratics deposited by the ice of the Georgian Bay lobe of the Late Wisconsin Glaciation. The Lion's Head promontory stood resistant to the flow of ice and caused it to deposit these large erratics which are still visible today. </p> / Thesis / Bachelor of Arts (BA)

<p> The Paleozoic bedrock surface of southern Ontario is dissected by an interconnected system of buried bedrock valleys that are infilled with thick successions of glacial, interglacial and fluvial sediments. These valleys can be several kilometers wide, reach depths of up to 250m and the coarse-grained units are known to host significant local and regional groundwater aquifers.</p> <p> Two buried bedrock valleys located near the Niagara Escarpment in the Region of Halton were under investigation in the fall of 1999 for their potential to host additional municipal groundwater aquifers to supply drinking water to the towns of Milton and Georgetown. Detailed logging of sediment recovered from eleven continuously-cored boreholes, drilled within the Georgetown and Milton bedrock valleys, forms the basis for this study. Four distinct facies types were identified within the borehole cores including sand, gravel, fine-grained sediment and diamict (sand-rich, mud-rich and clast-rich). These four facies types were used to subdivide the cores into six stratigraphic units based on textural characteristics and stratigraphic position. These six units form a stacked succession of aquifers and aquitards within the valley infill with two stratigraphic units being identified as potential municipal aquifers.</p> <p> The Georgetown buried bedrock valley contains narrow bedrock channel interpreted to have been fluvially incised, lying within a broader flat-bottom valley likely formed by glacial scouring of the bedrock. It is feasible that regional bedrock jointing created a zone of weakness that was later exploited by a drainage network. The valley infill sediments record the approach of the Laurentide Ice Sheet into southern Ontario during the Early to Mid-Wisconsin, and the subsequent overriding of the area during the Late Wisconsin period.</p> / Thesis / Master of Science (MSc)

The past few decades have seen rapid improvement in technologies related to remote sensing, specifically in digital photogrammetry and the use of unmanned aerial vehicles (UAVs). This has presented new opportunities to collect imagery at both a high temporal and spatial resolution to create detailed digital elevation models (DEMs) and investigate small-scale geomorphological features and their development over time. The high-resolution capacity of this methodology is well-suited to the study of a variety of terrains in which many critical geomorphological features are low relief and difficult or impossible to delineate using traditional remote sensing datasets. This study utilizes UAV-based imagery collection and data analysis, in conjunction with sedimentological analysis, of two study sites in Iceland and southern Ontario. The primary objective of this work is to explore the utility of integrating high-resolution spatial surveys with more traditional field techniques to identify geomorphological features, interpret their depositional origin, and quantify temporal changes in their form. The first study was completed on the forefields of Öldufellsjökull and western Sléttjökull, two surge-type outlet glaciers of the Mýrdalsjökull Ice Cap in southeast Iceland. Glacial deposits are important sources of paleoclimatic information but not all deposits are formed by processes that reflect the overall climatic conditions of a region; surge-type (fast-flowing) glaciers undergo periodic episodes of rapid ice movement, often unrelated to ambient climatic conditions. Remotely sensed data and field investigations were combined to complete a landsystem analysis of the forefields at each of Öldufellsjökull and western Sléttjökull, and an unmanned aerial vehicle (UAV) was used to collect high-resolution imagery of areas of particular interest. The forefields of Öldufellsjökull and western Sléttjökull, lack many of the characteristics typical of surge-type landsystems and instead are more similar to the active temperate landsystem common in Iceland. The identification of landforms considered to be diagnostic of surge-type glacier behaviour was only possible through a targeted high-resolution UAV survey suggesting that small-scale diagnostic landforms may be overlooked in many investigations. The second study area focused on the Niagara Escarpment in Hamilton, Ontario, a major landform resulting from extensive glacial and fluvial erosion of Paleozoic sedimentary rocks during the late Quaternary. In Hamilton, the Niagara Escarpment is a steep faced cuesta composed of Ordovician and Silurian sedimentary rocks. Recent rockfalls onto roads crossing the escarpment have raised serious concerns about its stability. To address these concerns, and to provide more information on erosional processes active along the escarpment in Hamilton, a comprehensive study of the Niagara Escarpment was completed including the collection of multi-temporal photogrammetric surveys of select rock faces, and detailed sedimentological and fracture analysis. A comprehensive lithological investigation was completed of all accessible rock outcrops in Hamilton to identify areas most likely to experience erosion based on site characteristics. A second component of this investigation was to evaluate the utility of using high-resolution imagery combined with Structure from Motion (SfM) software to detect temporal changes on the escarpment face. A staged erosion study was conducted in which lithological blocks of a known size were removed from the escarpment face at a selected site, to determine the lower limits of detection of erosion using this methodology. The study found that the location of block removal (erosion) was consistently identified, but the calculated volume of blocks removed was less accurately determined, differing by an average of 175% from the known volume of the block. A further study using this same methodology tested its ability to identify areas of natural loss (erosion) from the escarpment face. Based on multiple surveys taken 14 months apart at a selected study site, approximately one third of the area of interest experienced either loss (erosion) or gain (deposition) of material. There appear to be clear connections between lithology, density of fracturing, and the location of material loss (erosion); areas of the outcrop characterised by interbedded shales, and those areas exposing densely fractured sandstone or dolostone, were most likely to erode. The lithological characteristics of the Niagara Escarpment, including the strength of individual stratigraphic units, their vertical arrangement, and their density of fracturing, as well as climatic and hydrological factors (e.g., groundwater flow, location of surficial water features, mean annual temperature, mean annual precipitation etc.), all contribute to the amount and types of erosion active on the exposed rock face. The studies reported in this thesis have integrated high-resolution, close-range imagery with traditional field techniques to explore the characteristics and development of geomorphological forms in different terrain types. In each of the studies, the importance of collecting high-resolution imagery (<10 cm) to map geomorphological features of various scales is highlighted. / Dissertation / Doctor of Science (PhD)

Long, linear, high-relief escarpments mark many of the world's passive margins. These Great Escarpments have been interpreted to be the result of isostatic flexure, parallel slope retreat, and divide migration which accompanies rifting. It is unclear whether all these escarpments share this origin. Also uncertain is whether these features are formed via stable, steady-state processes or by climatic shifts or tectonic rejuvenation. The Blue Ridge Escarpment, eastern North America's great escarpment, is no different. A number of hypotheses attempt to explain the Blue Ridge Escarpment. These include lithologic variation between Blue Ridge and Piedmont rocks, the distance to ultimate base level, as well as, escarpment retreat resulting from post/syn-rift warping or faulting. We approach this problem from two directions. The first involves topographic comparisons and geologic observations to recognize and track divide migration. The second approach uses U-Th/He thermochronometry along two scarp-normal transects. Topographic analysis used data extracted from DEMs to compare three zones - the Upland, the Piedmont and the scarp zone itself. Parameters such as relief, drainage density, hypsometry, and slope are often used as proxies for relative erosion rates and the degree of maturity of a landscape. Results from these analyses indicate that the Upland and Piedmont zones are distinct landscapes, sharing very few topographic similarities, yet neither appears significantly more erodible than the other. Examination of parameters in the proximity of the escarpment point toward more rapid erosion here. Field evidence of this rapid scarp erosion (and thus divide migration) lies in the presence of beheaded stream channels, cobble roundness, and clast provenance. U-Th/He thermochronometry is a low temperature technique that allows us to calculate when rock cooled below 60-70C. Temperature is used as a proxy for depth, from which we can extract an exhumation rate. This method allows us to further test scarp genesis hypotheses. Preliminary results show older ages (~160) from the Upland surface than on the Piedmont lowland (~100 Ma). This confirms that the Piedmont surface is distinct from the Upland and demonstrates that it has experienced greater erosion. There is also some indication that ages "jump" across the Bowens Creek/Brevard fault system. Lastly, the ages appear to become younger approaching the escarpment which is indicative of scarp migration. As these results are preliminary, more data is required to prove or disprove these conclusions. / Master of Science

A previsão de áreas suscetíveis a escorregamentos translacionais rasos tem como fundamental etapa a investigação dos fatores condicionantes e dos mecanismos de ruptura. Algumas destas propriedades, como os parâmetros físicos e hidrológicos dos solos, são determinantes para a instabilização de encostas que estão sujeitas a eventos pluviométricos intensos. Uma destas propriedades é a condutividade hidráulica saturada, cujo comportamento pode influenciar no desenvolvimento de poro-pressão positiva ou levar à perda de sucção dos solos, ocasionando rupturas. Desta forma, o objetivo principal desta pesquisa foi analisar a distribuição lateral e vertical da condutividade hidráulica saturada (Ksat) dos solos e sua influência nos escorregamentos translacionais rasos na Serra do Mar (SP). Para tanto, foi selecionada uma bacia representativa da Serra do Mar e nela foram escolhidas três cicatrizes acessíveis e com limites bem preservados para a realização dos ensaios in situ. As profundidades onde foram realizados os ensaios foram definidas a partir da caracterização morfológica dos mantos de alteração nas trincheiras abertas no topo, no centro e na lateral das cicatrizes (0.25, 0.50, 1.00, 1.50, 2.00 e 2.50 m). Finamente, foram realizados os ensaios in situ utilizando-se o Permeâmetro de Guelph, utilizando-se duas cargas hidráulicas H para a que fosse possível calcular a Ksat empregando-se as equações de Richards, Laplace e a análise de Elricket al. (1989), embora tenha sido utilizada esta última para a análise da variação dos valores. A partir dos valores de Ksat, das propriedades físicas dos materiais (distribuição granulométrica, micro e macroporosidade, porosidade total. Além disso, foi analisada a tendência de variação entre 10-4 e 10-7 m/s, predominando da Ksat com a profundidade. Foram obtidos 41 valores de Ksat, os quais variaram entre as ordens de grandeza 10-5 e 10-6 m/s (82,5% dos valores), que mostraram a pequena variabilidade da Ksat nos perfis de alteração investigados, se comparada às diferenças observadas nas propriedades dos solos e corroboram com os trabalhos desenvolvidos na Serra do Mar. Quando confrontado com as propriedades físicas dos materiais (por exemplo, granulometria e porosidade total), observou-se, principalmente, a correlação positiva com a fração areia. De forma geral, foi possível identificar uma tendência de aumento da Ksat com a profundidade, assim como a existência de algumas descontinuidades hidráulicas significativas, tanto de redução quanto de aumento brusco da Ksat em uma pequena profundidade. / The prediction of landslides-prone areas has as fundamental step researching controlling factors and failure mechanisms. Some of these properties, such as the physical and hydrological soil properties are crucial to the instability of slopes subject to intense rainfall events. One of these properties is the saturated hydraulic conductivity, whose behavior can influence and lead to the development of positive pore-pressure or the loss of soil suction, causing failures. The main objective of this research was to analyze the lateral and vertical hydraulic conductivity (Ksat) of soils and their influence on shallow landslides in the Serra do Mar (SP). Therefore, we selected a representative basin in the Serra do Mar and there three accessible scars, well preserved, were chosen for in situ measurements. Was also performed the topographical characterization of the scars (slope angle, curvature and orientation and contributing area). The depths where the measurements were performed were defined from the morphological characterization of soil profiles in opened trenches at the top, at the lateral and inside the scars (0.25, 0.50, 1.00, 1.50, 2.00 and 2.50 m). At last, were performed the in situ measurements using the Guelph Permeameter, using two heads H for calculating Ksat using Richards equations, Laplace equations and Elrick et al. (1989) analysis, although the latter has been used to analyze the range of values. From the Ksat values and physical soil properties (e. g. grain size distribution, micro and macroporosity, total porosity) we discussed the role played by them in Ksat values. Moreover was analyzed the trend of Ksat variation with depth. We obtained 41 Ksat values, which varied between 10-4 e 10-7 m/s, mostly among the orders of magnitude 10-5 e 10-6 m/s (82.5% values), that showed the small variability of Ksat in the soil profiles if compared to the observed differences in soil properties, and corroborate with studies developed in the Serra do Mar. When confronted with the physical properties of materials (eg, grain size and total porosity), we observed mainly the positive correlation with the sand content. In general, we observed a tendency of increase of Ksat with depth, as well as the existence of some significant hydraulic discontinuities, both the sudden decrease as the increase in Ksat in a small depth.

Full-depth profile data reveal semidiurnal internal waves radiating from Mendocino Escarpment. Energy- and momentum-fluxes are lost between stations bracketing the first surface reflection to the north. A plausible interpretation is that wave energy is dissipated as a consequence of superposition of incident and reflected waves. Because there are no profiler data in the superposition region, a theoretical approach is used to bridge the gap. Assuming zonal independence, constant stratification and linear decay in the dissipation region, the forcing on the mean equations is evaluated with parameters consistent with Mendocino Escarpment data. Both superposition and dissipation cause momentum-flux divergence forcing. An Ekman-like balance is anticipated with predicted mean zonal flows u~O(1-2 cm/s), comparable to surface wind-forced Ekman currents.

A previsão de áreas suscetíveis a escorregamentos translacionais rasos tem como fundamental etapa a investigação dos fatores condicionantes e dos mecanismos de ruptura. Algumas destas propriedades, como os parâmetros físicos e hidrológicos dos solos, são determinantes para a instabilização de encostas que estão sujeitas a eventos pluviométricos intensos. Uma destas propriedades é a condutividade hidráulica saturada, cujo comportamento pode influenciar no desenvolvimento de poro-pressão positiva ou levar à perda de sucção dos solos, ocasionando rupturas. Desta forma, o objetivo principal desta pesquisa foi analisar a distribuição lateral e vertical da condutividade hidráulica saturada (Ksat) dos solos e sua influência nos escorregamentos translacionais rasos na Serra do Mar (SP). Para tanto, foi selecionada uma bacia representativa da Serra do Mar e nela foram escolhidas três cicatrizes acessíveis e com limites bem preservados para a realização dos ensaios in situ. As profundidades onde foram realizados os ensaios foram definidas a partir da caracterização morfológica dos mantos de alteração nas trincheiras abertas no topo, no centro e na lateral das cicatrizes (0.25, 0.50, 1.00, 1.50, 2.00 e 2.50 m). Finamente, foram realizados os ensaios in situ utilizando-se o Permeâmetro de Guelph, utilizando-se duas cargas hidráulicas H para a que fosse possível calcular a Ksat empregando-se as equações de Richards, Laplace e a análise de Elricket al. (1989), embora tenha sido utilizada esta última para a análise da variação dos valores. A partir dos valores de Ksat, das propriedades físicas dos materiais (distribuição granulométrica, micro e macroporosidade, porosidade total. Além disso, foi analisada a tendência de variação entre 10-4 e 10-7 m/s, predominando da Ksat com a profundidade. Foram obtidos 41 valores de Ksat, os quais variaram entre as ordens de grandeza 10-5 e 10-6 m/s (82,5% dos valores), que mostraram a pequena variabilidade da Ksat nos perfis de alteração investigados, se comparada às diferenças observadas nas propriedades dos solos e corroboram com os trabalhos desenvolvidos na Serra do Mar. Quando confrontado com as propriedades físicas dos materiais (por exemplo, granulometria e porosidade total), observou-se, principalmente, a correlação positiva com a fração areia. De forma geral, foi possível identificar uma tendência de aumento da Ksat com a profundidade, assim como a existência de algumas descontinuidades hidráulicas significativas, tanto de redução quanto de aumento brusco da Ksat em uma pequena profundidade. / The prediction of landslides-prone areas has as fundamental step researching controlling factors and failure mechanisms. Some of these properties, such as the physical and hydrological soil properties are crucial to the instability of slopes subject to intense rainfall events. One of these properties is the saturated hydraulic conductivity, whose behavior can influence and lead to the development of positive pore-pressure or the loss of soil suction, causing failures. The main objective of this research was to analyze the lateral and vertical hydraulic conductivity (Ksat) of soils and their influence on shallow landslides in the Serra do Mar (SP). Therefore, we selected a representative basin in the Serra do Mar and there three accessible scars, well preserved, were chosen for in situ measurements. Was also performed the topographical characterization of the scars (slope angle, curvature and orientation and contributing area). The depths where the measurements were performed were defined from the morphological characterization of soil profiles in opened trenches at the top, at the lateral and inside the scars (0.25, 0.50, 1.00, 1.50, 2.00 and 2.50 m). At last, were performed the in situ measurements using the Guelph Permeameter, using two heads H for calculating Ksat using Richards equations, Laplace equations and Elrick et al. (1989) analysis, although the latter has been used to analyze the range of values. From the Ksat values and physical soil properties (e. g. grain size distribution, micro and macroporosity, total porosity) we discussed the role played by them in Ksat values. Moreover was analyzed the trend of Ksat variation with depth. We obtained 41 Ksat values, which varied between 10-4 e 10-7 m/s, mostly among the orders of magnitude 10-5 e 10-6 m/s (82.5% values), that showed the small variability of Ksat in the soil profiles if compared to the observed differences in soil properties, and corroborate with studies developed in the Serra do Mar. When confronted with the physical properties of materials (eg, grain size and total porosity), we observed mainly the positive correlation with the sand content. In general, we observed a tendency of increase of Ksat with depth, as well as the existence of some significant hydraulic discontinuities, both the sudden decrease as the increase in Ksat in a small depth.

Groundwater chemistry on the Niagara Peninsula has been identified as highly mineralized in comparison to groundwaters collected from the same bedrock formations elsewhere in southern Ontario. Three geochemical zones were discerned using hierarchical cluster analysis and other geochemical and isotopic methods. The Escarpment Zone, located along the Niagara and Onondaga Escarpments, is characterized by unconfined aquifer conditions, parameters reflective of surficial contaminants, including road salt, and elevated HCO3, DOC, NO3-, coliform bacteria and tritium. In contrast, in the Salina Zone thick, low-permeability sediments and gypsiferous bedrock results in highly mineralized groundwaters with Ca-SO4 geochemical facies and elevated S2-, Ca2+, Mg2+, K+, Na+, SO42-, Cl-, Br-, Sr2+, NH4+ and CH4. The Guelph Zone contains the lowest electrical conductivity of the three zones and elevated F-. Outliers exist with groundwater geochemistry that differs from the local geochemical zone and the host aquifer. These sites have elevated SO42- (>1000 to 5200 mg/L) with depleted δ34SSO4 (-2.2 to 14.3‰ VCDT) signatures that differs starkly from Devonian and Silurian evaporites (~20 to 32 ‰) in the host formations. This exogenic SO4 was identified in a cross-formational northeast – southwest linear trend crossing three major groundwater flow systems. The lack of down-stream impact in these systems and tritium groundwater ages that are typically only decades old indicate a young, non-geological origin and implicate anthropogenic activities. Additionally, nine samples were identified with elevated methane concentrations and δ13CCH4 signatures within the thermogenic range. As thermogenic methane is not produced within shallow aquifers and would be short-lived in the presence of the ubiquitous sulfate, these samples imply recent upward migration of methane from depth through vertical conduits. Taken together, the evidence supports large-scale upward movement of fluids in the centre of the Niagara geochemical anomaly and more sporadic upward transport of gases over a wider area of the peninsula. The most likely vector is through corroded and leaking casings or boreholes of abandoned (century) gas wells that are common across the peninsula. / Thesis / Master of Science (MSc)

Hydrogeologic investigations were conducted on the drainage systems of an area of the Pennyroyal sinkhole plain of south central Kentucky. The degree of karstification of five area streams was studied to develop an understanding of the evolution of drainage as the landscape changes from a sandstone caprock plateau to a limestone sinkhole plain. The Chester Upland, capped by the Big Clifty Sandstone, possesses predominantly surface drainage and the Pennyroyal Plain, formed on Mississippian limestones, possesses considerable subsurface drainage. As the Chester Upland Escarpment retreats and surface streams are onto the limestones, the streams evolve to become subsurface streams. The five streams observed in the study (all flowing on limestones) demonstrated less karst development close to the Chester Escarpment and more karst development with increasing distance from the escarpment. Sediments derived from the escarpment and plateau blanket the stream beds thus perching the streams and preventing chemically aggressive water from forming karst solution features in the limestones. The streams farther away from the escarpment are removed from the sediment source and are therefore able to downcut into the limestone and invade the subsurface to become cave streams. Lithologic investigation of limestones exposed in stream beds revealed that minor resistant units can act to diminish downcutting and maintain short sections of surface flow. The stream investigated was not flowing on a perching layer, but instead was held on the surface by a stratigraphic control (spillover layer) that prevented subterranean stream invasion. Dye traces conducted on groundwater flow in the sinkhole plain revealed that the area drainage pattern is changing as surface streams invade the subsurface and that integration between drainage basins is taking place. Stream piracy and stream diversion are occurring in the subsurface causing alteration of the existing topographic drainage divides that developed before the surface streams invaded the subsurface. A general model is presented which shows the evolution of surface drainage to subsurface drainage, as the Chester Escarpment continues its northwestward retreat.