Dissertations / Theses on the topic 'Environmental geology'

The role of insolation as an instigator for crack initiation in rock is still a continuously perplexing topic. An immense amount of data has been collected on the influence of insolation on cracking—however, ongoing questions arise regarding the role this process plays in physical weathering. A study conducted by Dr. Martha Cary Eppes (2016) focused on the role of insolation in the initiation of cracking on a granite boulder in a temperate climate (North Carolina, USA), where 11 months of continuously recorded acoustic emissions (AE) data were used as a proxy for cracking. When these data were compared with simultaneously collected climate and rock surface data, it was found that insolation is a preliminary and contributing factor of crack initiation. However, this comprehensive data set was only representative of one climate zone—therefore, it was necessary to evaluate this relationship in other climates to support these conclusions. The following is a comparative study involving a similar granite boulder placed for an unprecedented three-year period in a semi-arid climate (New Mexico, USA). Utilizing the instrumentation of the Eppes 2016 study, acoustic emission sensors, strain gages, thermocouples, moisture sensors, and a site-located scientific weather station were deployed and monitored. During the 3-year study, 303,912 AE events (avg. 101,304 per year) occurred over a total 14,853 individual minutes over 713 days. A total 212,856 events occurred between 12:58 p.m. and 9:04 p.m. accounting for 70% of the overall deployment period. Comparable to the results of the Eppes 2016 study, high-event days (≥ 50 events) accounted for 98% of total events. Both boulders experienced the majority of events in the northern hemisphere and eastern position of the rock and no trends were indicated concerning the timing of events with precipitation. The results of this study 1) support the hypotheses that diurnal insolation contributes to the initiation and continuation of physical rock weathering and cracking whether alone or combined with temperature variations, and 2) suggest that this is characteristic of variable global locations, climates, and rock types.

Magnetic susceptibility is a property that can be used to effectively determine the compositional changes of mineral materials in soil. The objective of this study is to detect the presence of magnetic particles related to the migration of fly ash from a nearby coal-burning power plant over parts of Pointe Coupee Parish, LA. This is based on the idea that the fly ash that is released into the atmosphere during the coal burning process contains heavy metals and magnetic particles in the form of ferrospheres, which can be used to trace back to the source. Maps of the top and sub soil were generated to differentiate the magnetic susceptibility values of the heavy metals potentially attributed to the migration and settling of fly ash onto the surface from any pre-existing or naturally occurring heavy metals in the sub soil. A 60 km² area in Pointe Coupee Parish was investigated in approximately 0.5 km² subsets.

At each site, a minimum of 20 magnetic susceptibility measurements were obtained using a field probe along with discrete surface and subsurface samples collected for subsequent laboratory analysis. Samples of fly ash obtained directly from the source were also analyzed to verify the field and laboratory analysis. Contour maps representing the spatial distribution of the fly ash along with histograms of magnetic susceptibility values, reflective light microscope, and chemical analysis indicate a correlation between the proximity to the power plant and the predominant wind direction. Acquisition curves of the isothermal remanent magnetization demonstrate the presence of predominantly low coercivity minerals (magnetite) with a small amount of a high-coercivity phase. The microstructure of the magnetic fractions of the fly ash along with select top and sub soil samples were observed using a reflective light microscope for identifying and confirming the presence of ferrospheres associated with fly ash.

This study examines the natural background concentrations of arsenic in the soils of southwest Oregon, using new samples in addition to data collected from previous theses (Khandoker, 1997 and Douglas, 1999). The original 213 samples were run by ICP-AES with a reporting limit of 20 ppm, and only three samples had detected values. The original samples were tested again (2013) at a lower reporting limit of 0.2 ppm by ICP-MS, as were 42 new samples (2013), to better ascertain the natural levels of arsenic in undisturbed soils. The aim is to add to the existing DEQ data set, which has been used to establish new regulatory levels based on natural levels in the environment that are both safer and more economically viable than the former risk-based remediation levels (DEQ, 2013).

The maximum and mean concentrations, respectively, for each province (with high formation map unit) are 85.4 and 21.99 ppm for South Willamette Valley (Tfee), 45.4 and 5.42 ppm for the Klamath Mountains (Jub), 11.9 and 2.76 ppm for the Cascade Range (Tbaa), 10.6 and 5.15 ppm for the Coast Range (Ty), 2.32 and 1.29 ppm for the Basin and Range (Qba) and 1.5 and 1.20 ppm for the High Lava Plains (Tmv).

In addition, the distribution and variance of arsenic in the A and B soil horizons is assessed in this study by comparing deviation at a single site, and also by comparing A and B horizons of 119 PSU sites. One of 18 new sites sampled for this study (distinguished with the HH prefix), site HH11, was randomly chosen to evaluate differences at a single location. Site HH11 is an Inceptisol soil above volcanic rock (KJdv map unit) located at 275 meters elevation in Douglas County within the Klamath province. Five samples were taken from the A and from the B horizons at site HH11. The means and standard deviations were 3.74 ± 0.44 for the A horizon and 4.53 ± 0.39 for the B horizon. The consistency and low deviation within each horizon indicate that a single sample within a horizon is a good representative of that horizon and supports the field methodology used in this study of taking only one sample in the A horizon and one sample in the B horizon.

Wilcoxon Rank-Sum test determined that A and B horizons for the 119 sites that had data for both the A and B horizons were not statistically different (p-value 0.76). Arsenic concentration is not associated with a particular horizon for these sites. However, differentiation between soil horizons increases with age (Birkeland, 1999), as does accumulation of the iron oxides and sulfide minerals on clay surfaces (McLaren et al., 2006) which concentrate in the B horizon. These associations warrant further study to see how they relate to arsenic level, soil development and age in Oregon soils.

Lastly, this study statistically examines six potentially important environmental predictors of naturally occurring arsenic in southwestern Oregon: site elevation, geomorphic province, mapped rock type and age, and sample soil order and color (redness). A Classification and Regression Tree Model (CART) determined soil order, elevation and rock type to be of significant importance in determining arsenic concentrations in the natural environment. According to the regression tree, arsenic concentrations are greater within Alfisol and Ultisol/Alfisol and Vertisol soil orders, at lower elevations below 1,207 meters, and within soils from sedimentary, mixed volcanic/sedimentary and unconsolidated rock types.

The need for an expedient and economical field method for identifying the upper boundary of the capillary fringe (CF) led to an investigation of the clay-rich surficial units of two sites in New Iberia, Louisiana. Tension-sensing instruments capable of indirectly measuring water content were installed to monitor changing subsurface conditions throughout the vadose zone in response to water table fluctuation and rainfall. Tension measurements of 10 kPa and 33 kPa, correlated with the agricultural concept of field capacity by previous studies, functioned as indicators of two possible upper capillary fringe surfaces. Interpreted tension boundaries were plotted at depth to outline temporal changes in capillary fringe thicknesses, which ranged from approximately 1–5 ft depending on rainfall rates.

A comparison of gravimetric water content profiles with interpreted tension boundaries suggested that CF thickness was heavily influenced by the presence and composition of surficial fill, root systems, and the depth of the shallow water table. Collected tension and water content measurements were plotted as water retention points onto a series of estimated soil water retention curves (SWRCs). The hysteretic nature of soil-water retention relationships of the clay-rich media, evidenced by several examples of near equivalent water contents corresponding to vastly different tension measurements, and vice versa, illustrated the potential errors in basing capillary fringe thickness solely on tension measurements. While tension measurements did prove useful in recording variable conditions in the vadose zone, further research into accounting for hysteresis is required before tension boundaries can be employed in capillary fringe surface identification.

Changes in the concentration of atmospheric carbon dioxide (pCO2) affect global climate. Accurate determination of paleo-pCO2 can therefore provide information on the response of climate to changing pCO2. Such pCO2 proxies have been developed from a variety of terrestrial (e.g., plant stomata, paleosol carbonate, and liverworts) and marine (e.g., alkenones and boron) substrates. However, these proxies show a wide range of values and uncertainty throughout the Cenozoic and especially for the early Paleogene (53-63 mya). Here, I demonstrate the use of the carbon isotope composition of n-alkanes extracted from C3 plant waxes as an accurate recorder of changes in atmospheric chemistry. My results show that the uncertainty and range of pCO2 estimates determined using this new proxy are similar to other proxies. Because n-alkanes are abundant, chemically resistant, and not subject to degradation, this proxy represents an excellent opportunity to reconstruct pCO2 across the last 400 Myr of Earth history. By examining across 4 different chain lengths (n-27, n-29, n- 31, and n-33), I find that only n-29 and n-31 show clear changes in carbon isotope discrimination in response to changes pCO2, whereas chain-lengths n-27 and n-31 did not show any significant response. Using chain lengths n-29 and n-31, I calculate early Paleogene pCO2 = 566 ? 190 and 469 ? 165 ppmv (median ? 1?), respectively. These results demonstrate that n-alkanes can serve as a potential pCO2 proxy across geologic timescales.

Many methods have been employed to study coastline change. These methods range from historical map analysis to GPS surveys to modern airborne LiDAR and satellite imagery. These previously used methods can be time consuming, labor intensive, and expensive and have varying degrees of accuracy and temporal coverage. Additionally, it is often difficult to apply such techniques in direct response to an isolated event within an appropriate temporal framework. Here we utilize a new ground based Canopy Biomass LiDAR (CBL) system built at The University of Massachusetts Boston (in collaboration with the Rochester Institute of Technology) in order to identify and analyze coastal change on Lovells Island, Boston Harbor. Surveys of a bluff developing in an eroding drumlin and beach cusps on a high-energy cobble beach on Lovells Island were conducted in June, September and December of 2013. At each site for each survey, the CBL was set up and multiple scans of each feature were taken on a predetermined transect that was established parallel to the high-water mark at distances relative to the scale of the bluff and cusps. The scans from each feature were compiled, integrated and visualized using Meshlab. Results from our surveys indicate that the highly portable and easy to deploy CBL system produces images of exceptional clarity, with the capacity to resolve small-scale changes to coastal features and systems. The CBL, while still under development (and coastal surveying protocols with it are just being established), appears to be an ideal tool for analyzing coastal geological features and is anticipated to prove to be a useful tool for the observation and analysis of coastal change. Furthermore, there is significant potential for utilizing the low cost ultra-portable CBL in frequent deployments to develop small-scale erosion rate and sediment budget analyses.

The search for clean, fresh water is of the utmost importance, especially considering the highly industrialized age in which we live and the rising demand caused by increasing population. Many once-clean groundwater reservoirs have been tainted due to the inadequate storage and handling procedures for hazardous materials. One such site operated as a wood-preservation facility between 1937 and 1999 located in western Louisiana in the town of DeRidder. The contaminants that leached into the soils and groundwater supply at this site included creosote, a coal-tar distillate that is an amalgamate of several toxic constituents. The contamination was first detected in 1981, and within the year monitoring wells were installed to evaluate the extent of the pollution. For this study, 61 monitoring wells, 16 of which consistently record hazardous compounds within the subsurface, were analyzed in order to evaluate the temporal and spatial changes of contamination. The data were further correlated with rising and falling groundwater levels, precipitation data, and lithology in order to better understand the trends of the constituents and how they are affected by their environment. Additionally, an indication as to the efficiency of the current remediation practices put in place is examined by evaluating the diminishing contamination values over time compared to previous studies in the area. Hazardous levels within the soil are at their peak near the contamination sources, and spread outward while following the direction of local groundwater flow. This study shows that the total contamination quantities are slowly declining due to the current remediation practices, however, the total area covered by contamination fluctuates over time, and is currently in a state of expansion towards the southwest. A correlation between rainfall events and contamination spikes was noted in a previous study of the area, however, no such correlation was observed in the more recent data.

This project explored the potential fate and transport of seawater-based drilling fluid used in the Antarctic Drilling Program (ANDRILL) South McMurdo Sound project (SMS). The SMS drilling reported a loss of 5.6 × 10 ⁵ liters of drilling fluid to the surrounding formation throughout a borehole depth of 1139m. The introduction of these drilling fluids raise concerns of potential contamination to a pristine, isolated environment. The volume of fluid lost to the subsurface is unrecoverable and will only break down through natural attenuation processes, such as biodegradation. The objectives of this study are to estimate the extent of fluid migration laterally from the borehole and to determine when biodegradation of the water-based drilling fluid is effectively occurring. Variable density groundwater flow modeling (SEAWAT) was used to simulate the environment around the borehole. Applying stresses similar to the drilling events produced an estimate of how far fluid will be transported as drilling fluid is being circulated. Results show the fluid to migrate up to 7.5m into the subsurface. Additionally, laboratory microcosms were set up to incubate drilling fluid samples at various temperatures (5, 25, and 50°C) under aerobic and anaerobic conditions. Experimental data collected over 188 days was analyzed to evaluate the time frame when biodegradation of drilling fluids occurred. Carbon isotope fractionation ( ¹³C/¹²C) was used to determine the ability of the drilling fluids to be used as a food source. Biological data observed changes in microbial growth using DNA quantification, and changes in microbial communities using Biolog EcoPlates™. Results show a positive correlation between the increase of δ¹³C (‰) values and an increase in DNA (ng/µl) quantity. Data from geochemical and community changes indicate biodegradation of the drilling fluid occurred between time 40 and time 100. The methods employed to investigate fate and transport is a unique approach, and applied to these water-based drilling fluids for the first time in this study.

The Mauch Chunk Group has been interpreted as a product of multiple transgressions and regressions (Miller and Eriksson, 2000; Beuthin and Blake, 2004). An outcrop containing the upper Hinton Formation and Princeton Formation, the middle two formations of the Mauch Chunk Group, occurs along US-460 in Princeton, West Virginia, 2.6 kilometers east of the Interstate 77 Princeton exit. In order to understand the sedimentology and depositional history at those outcrops, sedimentologic logs were compiled, facies were identified and bundled into facies associations, photographic panoramas with line drawing overlays were constructed, and rock samples were taken. From the logged sections and facies architecture, a depositional history was interpreted. That history was supplemented with a provenance study where the samples were analyzed with a scanning electron microprobe to document oxide weight percentages. The upper Hinton Formation and the Princeton Formation were deposited through a combination of autocyclic and allocyclic processes. The mineralogy does not conclusively tie the sandstone deposits to the same source; however, mineral identifications did indicate the provenance to be an area with both igneous and metamorphic rocks. The presence of growth faulting indicates that the location of the cross-bedded sandstone that comprises the Princeton Formation at the US-460 outcrop may have been influenced by syn-depositional tectonism.

The Chico Aquifer System is a sole source aquifer located in the southwest region of Louisiana. A comprehensive study of the groundwater level of the Upper, Massive, and “200-foot” sands was undertaken to produce potentiometric surfaces for every five years from 1940 to 2015. The historical surfaces were produced for two different periods of the year; peak water-level months (non-irrigation season from January to March) and trough water-level months (irrigation season from May to July). ESRI ArcGIS extensions Arc Hydro Groundwater and Geostatistical Analyst were used to evaluate the spatial variability of the potentiometric surfaces, and ordinary kriging interpolation models were used to produce the surfaces. The cross-validation process indicated that the models were unbiased with satisfactory accuracy. From 1945 to 2015, Acadia Parish had the highest overall groundwater level decline (44.4 feet), followed by Evangeline Parish (32.6 feet), and Jefferson Davis Parish (29.63 feet). After high declines from 1945 to 1980 (33.2 feet), Calcasieu Parish showed signs of recovery since 1980 (+16.3 feet). The rate of change of the potentiometric surface for all parishes in the Chicot Aquifer System was higher from 1945 to 1980 than from 1980 to 2015. The grand average of the change in the potentiometric surface for the Chicot Aquifer System since 1945 was a decline of 23.3 feet. As society continues to improve water resource management, the results and methods presented here demonstrate an improvement in historical hindcasting that could create better plans for water management in the future.

Mountain Lake is one of only two natural lakes in the state of Virginia. The lake's origin has been attributed to either a natural solution-collapse basin, or to a landslide damming the valley of northwesterly flowing Pond Drain, or to a NW-SE trending fracture lineation. The lake is located within the breached northwest limb of a gently plunging anticline, a part of the larger Valley and Ridge physiographic province. In recent years, the lake drained almost completely, exposing the lake bottom and revealing the presence of four sinkhole-like depressions, containing piping holes at their sides and bottoms, at the northeastern and northwestern margins of the lake. This study focuses on the most likely origin of large sandstone blocks present at the northern end of the lake in an area locally referred to as "Rock City", including mapping of the block locations and analyzing the mode and extent of displacement that they have undergone. An additional objective is to investigate the piping potential of the lake-bottom sediment and its role in seepage out of the lake basin causing lake-level fluctuations.

Mapping of Rock City was conducted by taking GPS readings at the corners of the rock blocks and using ArcMap Software. Investigations of the displacement mode of the rock blocks was done by comparing the measured orientations of principal discontinuity sets, forming the rock-block boundaries, with discontinuity orientations of undisturbed outcrops within the headscarp, using stereonet analysis. Grain size analysis, Atterberg limits, and a compaction-mold permeameter test were used to evaluate lake sediment's susceptibility to piping.

Field observations and discontinuity data analysis indicate that Rock City is a landslide that dammed the valley of Pond Drain, consequently forming the lake. The primary mode of slope movement involves lateral spreading that is associated with extension occurring along discontinuities. The Tuscarora Sandstone rock blocks comprising Rock City were detached from the scarp face along a northwest-southeast trending joint set and were displaced laterally towards the west. A seismic event appears to be the most likely triggering mechanism for slope movement.

Laboratory testing reveals that lake-bottom sediment is susceptible to piping, which is the primary mechanism responsible for the formation of the lake-bed depressions and lake-levels fluctuations. Grain size analysis reveals that lake-bottom sediment consists predominantly of fine sand and silt, both of which are highly susceptible to piping. Results of the compaction-mold permeameter test show that the hydraulic gradient at which lake-bottom sediment starts to pipe, the critical hydraulic gradient, ranges between 1 and 10, depending on the density, grain size distribution and cohesive properties of the sediment.

The Mediterranean Outflow Expedition, which concluded in early 2012, provides an outstanding opportunity to address paleoceanographic questions about the evolution of the Mediterranean and North Atlantic climate system over the past six million years. The expedition recovered over 6 km of sediments. This provides an excellent archive for the study of paleoclimatic, paleoceanographic, and other paleoenvironmental changes and will also provide chronostratigraphic, plate tectonic, and geomagnetic constraints. Results are presented from the upper part of Site U1389 (36 25.515’N; 7 16.683’W), which is located approximately 90 km west of the Spanish city of Cadiz, in a water depth of 644 mbsl. This site is located in the “channels and ridges” sector of the larger Cádiz Contourite Depositional System (CDS). The sedimentary section extends for 990 m from the early Pliocene to Holocene and is represented by a thick, rapidly accumulated, and very uniform series of contouritic sediment. Paleomagnetic and rock magnetic measurements were carried out at 1-cm resolution on 36 m of U-channel samples from the composite stratigraphic section with the goal of extracting a high-resolution record of the magnetostratigraphy, the relative geomagnetic paleointensity, and the variability of the paleoenvironmental conditions. Step-wise demagnetization of the natural remanent magnetization yielded a well-defined interval over a portion of the Holocene with the deepest part of the section being younger than 60 ka. Sediment ages were determined by using an age model based on proprietary oxygen isotope data from Francisco J. Sierro. Interpolation of the age model shows sedimentation rates averaging near 70 cm/kyr. A relative paleointensity record was extracted by normalizing the NRM by ARM. These results along with the lack of power in the Milankovitch frequencies in the spectral analysis of the NRM/ARM and NRM/k signals support the interpretation that the RPI record is not influenced by environmental factors and accurately represents changes in global-scale paleomagnetic field intensity. Interpretation of the environmental records indicates cyclic warming and cooling, as that correlates well with sapropels, finer grains and warmer climate, and Heinrich Events, coarser grained IRD and cooling climate.

The comparison of IODP U1389 to proven records of GLOPIS reveals a high fidelity with few discrepancies and due to the locality of the site, proves the reliability of the RPI records. All usual criteria for paleointensity studies suggest that the upper portion of Site U1389 yielded a reliable high-resolution record of relative paleointensity, which provides a vital basis for global correlations of future studies.