Global 𝛿^18O indicates that the late Pliocene/early Pleistocene (LP/EP) was characterized by quasi-cyclic variations of continental ice volume with a period at ∼ 41- kyrs. However, it is well-known that high-latitude summer insolation intensity, the mechanism conventionally believed to control ice sheet growth/decay, is paced by cycles near 21-kyrs. This mismatch constitutes the "41-kyr World Problem." Isolating Northern Hemisphere ice volume change during the LP/EP is a promising approach for testing recent 41-kyr World hypotheses. A previous study of planktic 𝛿^18O at ODP Site 625, located in the northern Gulf of Mexico, documented negative isotopic excursions attributed to episodic discharge of ^16O-enriched meltwater to the study site via the Mississippi River. However, the lack of a benthic 𝛿^18O stratigraphy left the Site 625 time-scale highly uncertain. Here, we present a Site 625 benthic 𝛿^18O stratigraphy for the LP/EP, which improves the Site 625 time-scale through correlation to the global 𝛿^18O signal of the LRO4 Stack. The new Site 625 chronology suggests the previous age-model may have artificially enhanced the 1/_41-kyr frequency, while reducing natural temporal variability. Upon comparing the timing of twelve planktic 𝛿^18O anomalies at Site 625 to cycles of obliquity and June 21, 65°N insolation, no clear relationship is observed. However, comparison of Site 625 planktic 𝛿^18O to benthic records clearly indicates that northern Gulf of Mexico surface waters were at times severely impacted by locally and/or regionally manifested influences beyond the global norm, thus demonstrating the need for further inquiry of planktic 𝛿^18O anomalies.

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No description available.

Mineral-mineral partition coefficients (D) measured on mantle peridotites by ICP-MS can compliment what is known from experimental studies and put additional constraints on the temperature, pressure and compositional dependence of trace element partitioning in the mantle. Analyses of the data collected here shows that temperature and Na content of the clinopyroxene have the largest effect on trace element partitioning between ortho-and clinopyroxene in spinel peridotites. The Ca-Tschermak molecule in clinopyroxene, in turn, has a lesser control on partitioning in the natural sample than observed experimentally. Importantly chemical disequilibrium or transient metasomatic effects appear to control the orthopyroxene/clinopyroxene partitioning for the most incompatible elements, and that partitioning is a function of orthopyroxene concentration. The first 57Mössbauer determinations of Fe3+/ΣFe ratios in lherzolitic spinels and pyroxenitic garnet-clinopyroxene pairs from xenoliths of the sub-oceanic mantle beneath Hawai'i give a range in calculated oxygen fugacity (fO2) of 4 log units (-3 to +1 ΔlogfO2 (FMQ)). The Hawaiian peridotites are more oxidized than the oceanic upper mantle as recorded in MORB and abyssal peridotites, but less oxidized than arc peridotites. There are no correlations between fO2 and temperature or major element compositions. Instead, correlations between light REE DOpx/Cpx and fO2 in the peridotites suggests that metasomatism affects oxygen fugacity decoupled from the degree of melt depletion. The garnet pyroxenites are more reduced than the peridotites and estimates of the oceanic upper mantle. The fO2 of Hawaiian pyroxenites is the product of complex interaction between melts buffered with changing volatile species from predominantly H2O at reducing conditions to CO2-rich at the pressure, temperature and fO2 of the peridotites. A relationship between Mg# and Fe3+/ΣFe ratios in both clinopyroxene and garnet that is not evident in garnet peridotites points to evolution of the parent melt as controlling the bulk Fe2O3 of the pyroxenite cumulates. Koidu eclogites, with Nb/Ta ratios varying from sub- to superchondritic, have Nd and Hf isotopic compositions that are decoupled. The Nd-Hf isotopic compositions indicate an origin other than subducted oceanic crust. Unradiogenic Pb-isotope ratios indicate these eclogites have an ancient component (>2 Ga). Coincidental high Nb/Ta ratios, unradiogenic Sr and Pb isotopes require the involvement of a fluid to fractionate Rb/Sr, U/Pb and Nb/Ta. This process is consistent with dehydration during Archean subduction, however, Nd and Hf isotopic compositions are complicated by multiple fractionation events and open system behaviour that does not identify a common precursor. If the high Nb/Ta reservoir is composed of Koidu type eclogite, the extreme isotopic compositions measured here preclude them from participating in any meaningful way to present day basaltic volcanism (MORB-OIB array). / A Dissertation submitted to the Department of Earth, Ocean and Atmospheric Sciences in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Fall Semester, 2010. / October 25, 2010. / eclogite, Koidu, Sr isotopes, Nd isotopes, Pb isotopes, Hf isotopes, HI, garnet pyroxenite, xenolith, trace elements, LA-ICP-MS, Mossbauer, oxygen fugacity, spinel peridotite / Includes bibliographical references. / Vincent J. M. Salters, Professor Directing Dissertation; Michael Bizimis, Professor Co-Directing Dissertation; Albert E. Stiegman, University Representative; Munir Humayun, Committee Member; Leroy A. Odom, Committee Member.

In this study, a laboratory analog is used to simulate the conduit and matrix domains of a Karst aquifer. The conduit domain is located at the bottom of the transparent plexiglas laboratory analog and glass beads occupy the remaining space to represent the matrix domain. Water flows into and out of the two domains separately and each has its own supply and outflow reservoirs. Water and solute are exchanged through an interface between the two domains. Pressure transducers located within the matrix and conduit domains of the analog provide data that is processed and stored in digital format. Dye tracing experiments are recorded using time-lapse imaging. The data and images produced are analyzed by a spatial analysis program. The results present a plausible argument that laboratory analogs can characterize groundwater water flow, solute transport, and mass exchange between the conduit and matrix domains in a Karst aquifer. The analog affirms the predictions of a numerical model and demonstrates the need of laboratory analogs to provide verification of proposed theories and the calibration of mathematical models. Quantification of solute and water exchange between conduit and matrix domains is needed is for accurately modeling groundwater flow and transport processes and that information is provided by this experimental study. / A Thesis submitted to the Department of Geological Sciences in partial fulfillment of the requirements for the degree of Master of Science. / Fall Semester, 2008. / November 19, 2008. / Calibrate Numerical Model, Matrix Domain, Conduit Domain, Solute Transport, Groundwater Flow, Karst, Matrix, Conduit, Flow Cell, Laboratory Model, Bench Top Model, Hydrology, Laboratory Analog / Includes bibliographical references. / Bill Hu, Professor Directing Thesis; Stephen Kish, Committee Member; James Tull, Committee Member.

<p>The Grenville Province is a highly metamorphosed region of the Canadian shield which contains numerous lithotectonic domains of various ages and characteristics all affected by the c.a. 1.0 Ga Grenville Orogeny. The present study investigates, through reconnaissance neodymium isotope mapping, three under-mapped areas of the Province: the Weslemkoon study area of Ontario and the Saguenay and Baie Comeau study areas of central Quebec. These locations represent areas where previous studies have identified the presence of older crustal blocks which predate the Grenville Orogeny. But further detailed mapping is required to test and formulate interpretations regarding their evolutionary history.<br /> The Weslemkoon Study area is found within the Central Metasedimentary Belt (CMB) of Ontario. The CMB has been interpreted as a composite arc belt (on the basis of structural studies of shear zones) or alternatively, as a failed ensialic rift zone (on the basis of isotope evidence and geometrical relationships). The Grimsthorpe Domain found within the CMB is of major importance in investigating both of these interpretations. In the situation where the CMB is viewed as a composite arc belt, the Grimsthorpe Domain has been interpreted as an allochthon on the basis of its bounding shear zones. However, in current research which views the CMB as a juvenile rift zone, the Grimsthorpe Domain has been interpreted as a horst structure composed of remnant old crust that formed in situ. The latter situation considers evidence from isotope signatures as well as the en echelon geometry of marble domains which are predominant on either side of, but completely absent from the Grimsthorpe Domain. This raises the possibility that the Grimsthorpe Domain did indeed form in situ. The Weslemkoon Batholith largely lies within the Grimsthorpe Domain but extends past the eastern shear zone of the Grimsthorpe Domain. Thus it provides an ideal location to test whether the Grimsthorpe Domain is an allochthon or a horst. <br /> The present study finds that there are consistent Nd isotope signatures spanning the boundary of the Grimsthorpe Domain indicating that the shear zones are reflective of metamorphism, but not transportation of this block of crust. As well, the extent and geometry of old crust is defined and found to have isotope signatures relating this structure to the flanks of the rift zone and thus strengthening the argument that the Grimsthorpe Domain represents a horst structure. Further, the juvenile and old blocks have a ringed geometry in which inter-fingered lobes are identified.<br /> The Saguenay and Baie Comeau study areas of central Quebec are located within the Central Gneiss Terrain and Baie Comeau Segment found within the Allochthonous Polycyclic Belt. While anorthosite-mange ritecharnockite- granite suites have received much attention in the literature, the basement rocks have only recently been studied in any detail with identification of Quebecia. Quebecia, a broad juvenile 1.5 Ga arc terrane has been defined on the basis of relatively homogenous Nd isotope signatures indicating a common basement. Previous studies identified a few isolated areas of crust with signatures predating the Quebecia terrane and these are investigated in detail in this study.<br /> Through more detailed isotope analysis and mapping of the Saguenay and Baie Comeau regions, the extent and geometry of these old blocks of crust have been defined. These old crustal blocks are completely encompassed by the Quebecia arc terrane which the present study interprets as indicating that Quebecia represents a composite arc where fragments of old crust were incorporated into an area dominated by juvenile subduction-related magmatism. These fragments are possibly connected to form a 'panel' of old crust running through the younger Quebecia arc terrane. Hence their identification provides a critical piece of evidence in understanding the geological evolution of the central Grenville Province.</p> / Master of Science (MS)

<p>Additional files uploaded from CD</p> / <p>This study was conducted over two years (2005 and 2007) and consisted of data collected over one wet season and one dry season at two beaches, separated by a rocky headland, located along the Pacific coast of the Nicoya Peninsula, Costa Rica. Although the beaches are concurrent along a 7 km stretch of coastline, both are characterized by a unique combination of: beach slope, length and shape; sediment composition, size and mineralogy; and vegetation. These beaches have discrete land uses. Playa Guiones is a tourist beach that is experiencing rapid development and Playa Pelada is the only local beach that provides boat access for local fishermen. It was hypothesized that the active tectonism in the region combined with the distinct wet/dry seasons will result in dynamic beaches with distinct morphology. <br /> The first objective is to quantify and explain changes in sediment accretion or deposition between the two distinct seasons. The second objective is to quantify longer term temporal coastline changes through analysis of air photos and satellite imagery from 1940 to 2005 for the region. It was hypothesized that this time series will provide evidence of the influence of tectonics on coastline position. <br /> This analysis involves a comparison of Digital Elevation Models (DEMs) created from real-time kinematic GPS data collected in June 2005 and January/February 2007 with aerial photography and satellite imagery representing the period 1940-2005. Results show that from wet to dry season there is substantial net sediment accumulation for Playa Guiones and net sediment erosion for Playa Pelada. It should be noted that the seasons were particularly dry and particularly wet, thus, the results may indicate maximum levels of variation. The time series analyses of the digital imagery show little variation of coastline position during the period of record. The digital imagery was severely limited by the resolution and scale of the imagery. It appears that these beaches experience moderate to large amount of seasonal variation but are relatively stable over a longer time period.</p> / Master of Science (MS)

<p>PAH contamination is a significant threat to human and ecosystem health worldwide. The development of novel, efficient bioremediation systems can serve to reduce this threat by more effectively removing PAHs from contaminated environments. An improved understanding of the interactions between microbes and P AHs is essential to developing better methods to monitor P AH biodegradation, which should in turn lead to improvements in actual PAH biodegradation. This thesis developed novel process level and community-level understanding of the responses of microbes to PAH contamination, knowledge which could prove useful in the development of improved techniques for monitoring and enhancing PAH biodegradation. <br /> The first paper (Chapter 2) examined the response of microbial communities to P AH contamination, through PLF A analysis of specific microbial communities in Hamilton Harbour, Ontario, Canada. Increased PAH contamination was found to have caused reductions in microbial biomass, and while community composition was different between sites exposed to high and low levels of PAH contamination, none of the differences in community composition could be definitively identified as having been caused by the presence of PAH. The PAH profile at the less contaminated study site was found to have changed relative to a previous study, suggesting either a change in PAH source occurred, or resuspended PAH-contaminated sediment from elsewhere in the harbour was deposited at that site.<br /> In the second paper (Chapter 3), a novel approach using stab le carbon and radiocarbon PLF A analyses was used to establish bacterial preference for P AH as a carbon source and identify microbial carbon cycling pathways in P. frederiksbergensis bacteria. Stable and radiocarbon isotopic analyses of P. frederiksbergensis PLF A suggested P. frederiksbergensis metabolism was heterotrophic, but it was found to primarily utilize dissolved inorganic carbon (DIC) as a carbon source for PLF A biosynthesis. Isotopic data suggested metabolism of organic carbon was minimal, and as such, P. frederiksbergensis is most likely an unsuitable candidate organism for use in in situ PAH biodegradation projects. <br /> Increased knowledge of microbial carbon cycling pathways and microbial community responses to PAH contamination will lead to improvements in P AH remediation, in turnleading to improvements in ecosystem health and reduced exposure risks to humans.</p> / Master of Science (MS)

<p>In this study, the potential of using white-tailed deer archaeological bones as an additional climatic proxy to track droughts in the Maya area at a very local scale is assessed.</p> <p>The oxygen and carbon isotopic compositions (δ¹⁸O and δ¹³C) on chronological series of numerous white-tailed deer bones, excavated from three Maya archaeological sites (Piedras Negras and Motul de San Jose, Peten region, Guatemala, and Lamanai, Orange Walk district, Belize) have been measured.</p> <p>It is considered that the isotopic composition of deer bones reflects a multi-year average of relative humidity and local precipitation amounts (δ^l8O ) as well as environmental conditions such as the type of food ingested by the animal (δ¹³C). The aim of the present work was principally to delineate the conceptual background needed to replace the obtained isotopic values in their context and understand their signification.</p> <p>The results of geochemical analyses of deer bones are considered as reliable, in accordance with predicted values. However, the number of analyzed bones must be sufficient to accurately describe the variations of past climate variations. The major findings of this study are: (1) the use of Fourier Transform Infra Red spectroscopy is not a reliable way to detect diagenetically altered samples, (2) the climate during the apogee of the Classic Maya period was more variable than today, with more extremes pluri-annual wet and dry conditions, (3) no significantly dry climatic conditions occurred at the time the city of Piedras Negras started to decline and (4) dry conditions were probably responsible of the final abandonment of the site.</p> / Master of Science (MS)

<p>As cities continue to expand, the environmental impacts associated with increasing car usage remains an issue of concem. However, telework, an altemative form of working arrangement, has the potential to reduce the impacts associated with driving. In this study, we investigate how social interaction impacts the decision to telecommute. Data are obtained from the McMaster Telework Online Survey, which collects detailed information from McMaster University employees concerning their knowledge and experience with telework, feelings and opinions about home-based work and other lifestyle choices, and other information related to telecommunications. A unique characteristic of the survey is that it captures interactions among colleagues at work. The "colleague connection" measures the extent to which social interactions influence an individual's decision to adopt telework. The results of this research indicate that social interactions at work, as well as socio-demographic and work-related characteristics, do influence an individual's decision to adopt telework.</p> / Master of Arts (MA)