Department: Geological Sciences ![[clear]](close-x.png "Remove this limiter")
191 matches in the database.
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2.
Ahn, Soo Yeun.
Ediacaran-Cambrian Stratigraphy and Paleontology of Western Nevada and Eastern California.
Degree: PhD, Geological Sciences, 2010, Ohio State University
► The Ediacaran-Cambrian transition was an important time span from both geologic and…
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▼ The Ediacaran-Cambrian transition was an important time span from both geologic and biologic perspectives. It was a time of dramatic evolutionary changes such as the diversification of early metazoans, the development of resistant skeletons in many taxa, and the escalation of prey-predator systems. In North America, the transition is well recorded in terminal Neoproterozoic to Cambrian strata of Esmeralda County, Nevada, and adjacent Inyo County, California. Strata recording this transition are the Deep Spring Formation (Ediacaran-Cambrian), and the Campito, Poleta, and Harkless formations (Cambrian). For many years the Deep Spring, Poleta, and Harkless formations were informally divided into mappable members. New, formal names are proposed for the members of these formations. In ascending order the new members are the Dunfee, Montezuma, and Gold Point members of the Deep Spring Formation; the Lida, Indian Springs, and Clayton members of the Poleta Formation; and the Weepah and Alkali members of the Harkless Formation. Two formal members of the Campito Formation, the Andrews Mountain Quartzite and the Montenegro Member, have long been recognized. The Deep Spring Formation and succeeding formations have the transition from a microorganism-dominated record to the more diverse and complex record of the Phanerozoic. Stromatolites are common in the Dunfee Member of the Deep Spring Formation, and fossilized microbial mats (“wrinkle structures”) are present in siltstone layers of the Montezuma Member. Microbial mats or microbially stabilized substrates are inferred to be responsible for the fine preservation of Ediacaran trace fossils as well as sedimentary structures. In Cambrian strata, microbial related structures are mostly wrinkle structures and gas escape structures. Trace fossils have a trend toward increasing diversity, complexity, and abundance across the Ediacaran-Cambrian transition, although behavioral patterns are conserved. These changes parallel faunal changes across the same interval of strata. Trace fossils in the Ediacaran part of the Deep Spring Formation include Bergaueria, Palaeophycus, Planolites, and other simple resting, dwelling, and perhaps foraging traces. A new genus and species of trace fossil, Nevadichnos planum, is described from the Montezuma Member of the Deep Spring Formation. Cambrian trace fossils of the Nevada-California succession include Bergaueria, Monomorphichnus, Palaeophycus, Planolites, Rusophycus, and Treptichnus pedum. Although the morphologies of Cambrian tracemakers may have been different in the Cambrian than in the Ediacaran, the basic behavioral patterns of feeding and dwelling were already developed in the Ediacaran. Chalcopyrite and limonite commonly occur within burrows, especially in Planolites. Precipitation of these minerals is probably related to decay processes associated with biofilm development in burrows.
Advisors/Committee Members: Babcock, Loren E.
Subjects: Paleontology
Keywords: Ediacaran; Cambrian; trace fossils; Great Basin
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3.
Allen, Gerald R.
An Analysis of the Fate and Transport of Nutrients in the Upper and Lower Scioto Watersheds of Ohio.
Degree: PhD, Geological Sciences, 2011, Ohio State University
► Surface water quality data are available from many public and private agencies…
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▼ Surface water quality data are available from many public and private agencies across the United States. But, how can they be effectively utilized to help resolve the complex biogeochemical relationships of surface waters? The present study examined available stream and reservoir water quality, stream discharge, and meteorological time-series datasets for the Upper and Lower Scioto watersheds in central Ohio. The focus was on the fate and transport of nutrients, specifically nitrate and total phosphorus, in the streams and surface water reservoirs of these predominantly agricultural watersheds. The study area is composed of seven sub-watersheds, five of which contain major surface water reservoirs. Mean nitrate values for the more “riverine” J. Griggs and O’Shaughnessy reservoirs were more than double those for the more “lacustrine” Hoover and Alum Creek Lake reservoirs, and were at least partially due to the different reservoir morphometries and resultant residence times. Nitrate concentrations have gradually decreased over the periods of record in all four reservoirs. Phytoplankton populations in Hoover and Alum Creek Lake reservoirs are ecologically driven, while populations in O’Shaughnessy and J. Griggs reservoirs are weather and stream flow dependent. The Big Darby Creek contains no major reservoirs or stream impoundments. From 1973 to 2008, annual-mean discharge ranged from 6.8 m3s-1 to 26.8 m3s-1 with an average of 16.1 m3s-1. Fall months were periods of lowest discharge, with spring to mid-summer months typically having highest discharge values. Nitrate and total phosphorus concentrations exhibited a wide range with means closely similar to the values in O’Shaughnessy and J. Griggs reservoirs. Nitrate concentrations have slowly increased in the Big Darby Creek study area from 1973 to 2010. Quadratic model regression analysis showed nitrate concentration had a strong positive relationship with corresponding daily-mean discharge, but total phosphorus concentration was uncorrelated. Seasonal nitrate and daily-mean discharge trends were positive and similar except for fall, which could have been biased by a lack of concentration data for low flows. An analysis of stream flow dynamics suggests that chloride is primarily associated with ground water and is negatively related to stream discharge. Nitrate concentration is predominantly associated with precipitation generated surface runoff or tile-drained discharges from crop lands. The nitrate reservoir in the soil horizon of the Big Darby Creek watershed is gradually depleted from winter to fall. A conceptual model for the prediction of nitrate concentration at the USGS gaging station at Chillicothe, terminus of all study area surface water, is the sum of the calculated nitrate concentrations of all seven sub-watersheds. Main components of the model are the calculation of daily discharge and nitrate concentrations for the individual sub-watersheds. The model is specifically designed to capture the effect widespread precipitation events have on individual sub-watershed areas, and can be modified for the prediction of other watershed nutrient concentrations. This study has provided an important first step in the quantitative interpretation of the origin of complexity in the development of understanding of nutrient distribution in large watersheds.
Advisors/Committee Members: Schwartz, Franklin.
Subjects: Geochemistry; Geology; Hydrologic Sciences; Hydrology; Water Resource Management
Keywords: Upper and Lower Scioto; fate and transport; nutrients; phytoplankton; reservoirs; conceptual model
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5.
Asgharzadeh, Mohammad Forman.
Geodynamical analysis of the Iranian Plateau and surrounding regions.
Degree: PhD, Geological Sciences, 2007, Ohio State University
► The Middle East is a tectonically active region where the interaction between…
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▼ The Middle East is a tectonically active region where the interaction between crustal units produce devastating earthquakes and volcanic eruptions. The region holds within its boundaries the Tethyside Orogeny and is limited to the north by the Intermediate Orogeny. The Iranian Plateau sets within the Tethyside collage and has been affected by the closure of Paleo- and Neo-Tethys Oceans during the Mesozoic and Cenozoic. For instance, large oil and gas fields have formed along the sutures of these two former oceans in northeastern Iran, the Persian Gulf and the Zagros Mountains. This dissertation involves analyzing the geodynamical processes of the Iranian Plateau by studying surface, airborne and satellite gravity and magnetic data collected across the Plateau and its surrounding regions. To provide a basis for a more accurate analysis of the region's lithospheric stresses, a high-resolution crustal thickness model is developed using spectral correlation analysis and gravity inversion. The results of this modeling suggest a thickened crust beneath the Anatolian Plateau, Sistan and Zagros Mountains, plus the Caspian Sea. Next, a regional scale morpho-tectonic interpretation of Iran's aeromagnetic data is developed that characterizes the magnetic anomalies of the country. The results of this analysis suggest that the crust of Iran is divided into a number of small plates, with boundaries that are characterized by strong positive magnetic anomalies. Large magmatic assemblages in northern and western Iran are characterized by strong negative magnetic anomalies. In support of the objectives of the pending GOCE gravity and SWARM magnetic low-Earth orbiting satellite missions, the theory for numerically estimating the full gravity and magnetic scalar, vector and tensor fields of the spherical prism is summarized. As an application, the gravity and magnetic fields that the GOCE satellite and SWARM constellation of satellites may observe over the tectonically active region of the Middle East, roughly centered on Iran are estimated.
Advisors/Committee Members: von Frese, Ralph R.B.
Subjects: Geophysics
Keywords: Iran; gravity; gradient; magnetics; satellite
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6.
Barrett, Kelly A.
Identifying Building Sites in Summit County, Colorado: Geography, Geology, and GIS.
Degree: MS, Geological Sciences, 2009, Ohio State University
► A Geographic Information System (GIS) was developed to identify future home and…
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▼ A Geographic Information System (GIS) was developed to identify future home and business sites in Summit County, Colorado, one of the fastest growing regions in the country. The permanent population is projected to be 31,500 by 2010, an increase of 25 percent from 2000 (Colorado Department of Local Affairs Demography Section). Also, in the winter the population of the county may increase to 150,000 or more during peak ski weekends (Summit County Planning Department, 2003). The county will continue development to accommodate the growing population and tourists that flock to ski resorts and other vacation facilities in this very popular and accessible region. The GIS developed here includes data for: land ownership, topography (slope and aspect), bedrock and surficial geology, soil types, presence and orientation of bedrock lineaments, locations of water wells, culture (cities, roads, emergency facilities, etc.), and city and county zoning regulations. By incorporating and correlating features of all of these, it was possible to identify areas within Summit County that can accommodate increases in permanent population and the surges that characterize the tourist industry in Colorado. Because of its location in the high country of Colorado, about 80 percent of the county (496 sq mi of a total 620 sq mi) is administered by the U.S. Forest Service and the U.S. Bureau of Land Management. However, the GIS developed here identified almost 13 percent of the county that is suitable for development – a number that could change subject to the ruling of the county or town planning commission. Twelve areas that range in size from 1.6 to 3.5 sq mi (4 to 9 sq km) were highlighted initially, and three of these were selected for follow-up evaluation: two near the town of Breckenridge (3.3 and 3.5 sq mi), and one near the town of Frisco (3.1 sq mi). The techniques developed in the GIS are directly applicable to the remaining nine of the twelve areas, and anywhere in the world where data and requirements are similar.
Advisors/Committee Members: Pride, Douglas.
Subjects: Geology
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7.
Bartkowiak, Brandon Michael.
Ground-water flow modeling of the impact of quarry dewatering on water levels in the fractured carbonate aquifer, Kelleys Island, Ohio.
Degree: MS, Geological Sciences, 2009, Ohio State University
► To aid in determining the impact of quarry dewatering on Kelleys Island,…
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▼ To aid in determining the impact of quarry dewatering on Kelleys Island, Ohio, three steady-state, numerical models were constructed using MODFLOW. Paleozoic aged carbonate rocks under thin glacial till deposits form the bedrock aquifer. A 200-acre quarry in the western part of the island began active dewatering in June 2005.A Case 1 model was constructed assuming a homogeneous carbonate aquifer and was calibrated against measured water levels and quarry discharge rates. Two additional models were created—one assuming an anisotropic aquifer, the other assuming a layered heterogeneous aquifer. All models were compared to measured hydraulic head values to assess a statistical goodness of fit. The results of this study are not conclusive because none of the three models had an acceptable goodness of fit. This may be due to overly simplistic assumptions regarding the influence of fractures and bedding planes on the ground-water flow system.
Advisors/Committee Members: Bair, Dr. E. Scott.
Subjects: Geology
Keywords: Kelleys Island; quarry; dewatering; MODFLOW
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8.
Bates, Jeffrey Kenneth.
An evaluation of digital elevation models and geotechnical properties of the glacial deposits in Franklin County, Ohio, using a geographic information system.
Degree: PhD, Geological Sciences, 2007, Ohio State University
► The importance of unconsolidated deposits is reflected in the extensive use of…
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▼ The importance of unconsolidated deposits is reflected in the extensive use of these materials in Franklin County, Ohio. This study organizes geologic and geotechnical data in a geographic information system (GIS) to better understand the nature of the unconsolidated materials in this area. These data are then utilized to update the bedrock topography maps, evaluate the relationship between the geotechnical data and the diamictons, and to refine the interpretation of the surficial geology of the study area. It was found that discrepancies are common between the surface elevation of geologic borings and the current surface elevation, represented by a digital elevation model (DEM) constructed in this study. It was also shown that there are considerable differences in the surface representation between the DEMs constructed here and DEMs obtained from the USGS. Elevation differences between the DEMs and the surface elevations of geologic borings were confirmed by performing GPS surveys at several boring locations. This study concludes that the USGS DEMs do not always accurately represent the current surface in this area, primarily because of land surface modifications by humans. Accurate DEMs are important to surficial mapping, as these efforts often rely on this surface representation for the correct vertical placement of subsurface data. The utilization of DEMs for other purposes is also explored here, showing that the outcome of a particular application can be affected by the DEM utilized. The updated bedrock topography maps are used to compare the bedrock drainage patterns, slopes, and aspect to some of the unconsolidated sediments. An evaluation of the geotechnical data is made to assess whether geotechnical properties of the diamictons show consistent variations with depth, and to determine if differences exist between diamictons found on carbonate and clastic bedrock. Standard penetration test values, Atterberg limits, and texture are found to differ somewhat for the diamictons above the different bedrock types, possibly attributed to different source materials for the tills. The diamicton properties in this area suggest they should be re-interpreted as deformation till. Geotechnical data from certain borings also imply that lacustrine deposits are present in several locations in northern Franklin County.
Advisors/Committee Members: Krissek, Lawrence A.
Keywords: geology; glacial geology; geotechnical; digital elevation model; geographic information systems
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10.
Beem, Lucas H.
Ice Stream Shear Margin Basal Melting, West Antarctica.
Degree: MS, Geological Sciences, 2008, Ohio State University
► Basal water lubricates and enables the anomalous flow feature of ice streams…
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▼ Basal water lubricates and enables the anomalous flow feature of ice streams in the West Antarctic Ice Sheet. As surface melt is insufficient to supply the base with the volume of water known to be there, basal melting must be the source of this water. How basal melt patterns vary spatial can be an insight into the dynamics of ice streams, which remain incompletely described by glaciological theory. Through a heuristic model extended from the work of Whillans and Van der Veen (2001) and Van der Veen et al. (2007) a spatial pattern of basal melt for the Whillans Ice Stream emerged that offer hypotheses for the onset of streaming flow, shear crevasse development and observed morphological changes of a slowing and widening ice stream.The limitations and the uncertainties of this model make the determination of exact basal melt rates difficult, but the patterns of melt rate distribution are robust. This allows for a perspective to better understand current dynamics and how basal melt may play a role in the ice stream's future development.
Advisors/Committee Members: Jezek, Kenneth.
Subjects: Geology; Geophysics
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12.
Bhattacharya, Indrajit.
ANALYSIS OF SURFACE MELTING AND SNOW ACCUMULATION OVER THE GREENLAND ICE SHEET FROM SPACEBORNE MICROWAVE SENSORS.
Degree: PhD, Geological Sciences, 2010, Ohio State University
► Continuous monitoring of changes in the Greenland ice sheet from both space…
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▼ Continuous monitoring of changes in the Greenland ice sheet from both space and air borne sensors has been conducted since the early 1970’s. Since the mid-1990’s dramatic changes occurring on the Greenland ice sheet have been observed both from space borne sensors and field work. These changes, primarily mass loss from the ice sheet, are related to the observed trend of earth’s warmer climate in recent decades both in peer reviewed journals and in popular media. This dissertation addresses two parameters that contribute to Greenland ice sheet mass balance estimates. The first factor is characterization of surface melting of the Greenland ice sheet from satellite-based passive and active microwave sensors. We use a wavelet based edge detection technique to delineate surface melt from brightness temperature measured by passive microwave sensors. Along with brightness temperature data, we also use normalized backscatter data from the Quick Scatterometer (QuikSCAT) as an independent sensor for comparison with the radiometer derived results. We use a semi-empirical threshold based method for surface melt detection from QuikSCAT. Our results show a step-like, consistent increase in melt area of the Greenland ice sheet since 1995. This step-like increase is also observed in the mean summer air temperature along portions of the Greenland coast. The 1995 step-like increase of melt area (and melt index, a measure of melt intensity) is correlated with a distinct change of the North Atlantic Oscillation (NAO) index (from positive to negative) after 1995. The second factor is mass accumulation in the upper reaches of the ice-sheet. We use an empirical model that correlates mean annual brightness temperature to annual accumulation rate. We apply a microwave emission model for the dry snow region of Greenland to show that 37 GHz vertically polarized brightness temperature data are better suited to capture the inter-annual variability of snow accumulation. Using our model we estimate a snow accumulation time series from brightness temperature for 150 km x 150 km area around Summit Camp in central Greenland. Using measured surface velocities and ice thickness we calculate the surface mass balance for our study area. We find a positive mass balance of 3.18 ± 6.0 cm/yr. Our mass balance derived elevation change is in agreement with satellite altimeter data and published results of other researchers.
Advisors/Committee Members: Jezek, Kenneth.
Subjects: Geophysics
Keywords: Cryosphere, Passive Microwave , Scatterometer, Greenland, Melting , Snow Accumulation, Radiative Transfer
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13.
Birkos, Elizabeth.
Controls on Stable Oxygen Isotope Concentrations in Coropuna and Quelccaya Peruvian Ice Cores Over the Last 200 Years.
Degree: MS, Geological Sciences, 2009, Ohio State University
► Oxygen isotopes are useful proxy records in ice cores because of the…
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▼ Oxygen isotopes are useful proxy records in ice cores because of the selective fractionation process that occurs during evaporation and condensation of water molecules, yet the controls on these fractionation processes are under debate for tropical ice core records. Two ice cores from the eastern and western range of the Peruvian Andes (Quelccaya Summit Dome and Coropuna Caldera Core) are annually resolved for the last 200 years and provide an excellent means for comparison to localized instrumental meteorological records as well as regional measures of past climate. The oxygen isotope histories from these cores show no significant correlation with temperature or precipitation from two nearby meteorological stations or an automated weather station on the summit of Quelccaya. Yet significant correlation is found on a regional scale with Lake Titicaca water levels as well as equatorial Pacific sea surface temperatures over recent time. However, overall trends for the last century offer conflicting evidence to this end. On centennial and millennial time scales, temperature has been shown to be positively correlated with oxygen isotopes in tropical ice cores, yet the mechanisms for this control need further research.
Advisors/Committee Members: Thompson, Lonnie.
Subjects: Geology
Keywords: paleoclimatology; Quelccaya ice cap; Coropuna; oxygen isotopes; tropical glaciers; Peru; Andes
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20.
Brown, Abel K.
A global GPS data reprocessing strategy: Implications for the reference frame, orbital solutions, and trends in zenith delay parameters and total column water vapor (1994 - 2011).
Degree: PhD, Geological Sciences, 2011, Ohio State University
► The primary focus of this work is to derive a long-term global…
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▼ The primary focus of this work is to derive a long-term global trends in precipitable water vapor using atmospheric path delays as observed by continuously operating GPS stations from 1994 to present. Atmospheric water vapor plays a key role in global climate change but the exact mechanics of this process is poorly under- stood. Measuring the atmospheric path delay between the GPS satellite and ground station, it is possible to estimate the total water vapor content as a derived quantity independent of hardware configuration or environmental factors at continuous GPS locations. Globally distributed continuous GPS stations have existed with sufficient density for climate studies since around 1994 making GPS derived atmospheric path delay an excellent tool for global water vapor studies. A global GPS data set of more than 1000 stations has been reprocessed from 1994 to present to ensure maximum homogeneity of satellite orbits, ground station coordinates, and thus atmospheric delay estimates. The observed mean trend in precipitable water vapor based on zenith total delay measurements at GPS station locations is small at 0.094 ± 0.030 mm per decade while regional trends are often quite large w.r.t this mean trend, at times by an order of magnitude. Furthermore these large regional trends are polarized where positive trend regions are cancelled out by other negative trend regions. Precipitable water vapor estimates from the meteorological model ERA-Interim yield a mean trend over all land of 0.113 ± 0.007 mm per decade and a mean trend of 0.078 ± 0.017 mm per decade when restricted to GPS station locations only.
Advisors/Committee Members: Michael, Bevis.
Subjects: Atmospheric Sciences; Earth; Geophysical; Geophysics
Keywords: GPS, precipitable water vapor, zenith delay, global trend, reprocessing
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22.
Buffen, Aron Maurice.
Abrupt Holocene climate change: Evidence from a new suite of ice cores from Nevado Coropuna, southwestern Peru and recently exposed vegetation from the Quelccaya Ice Cap, southeastern Peru.
Degree: MS, Geological Sciences, 2008, Ohio State University
► Three ice cores drilled to bedrock atop Nevado Coropuna, southwestern Peru reflect…
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▼ Three ice cores drilled to bedrock atop Nevado Coropuna, southwestern Peru reflect Holocene and late glacial stage climate variability. Two cores measure <34 m in length yet provide seemingly continuous >16 kyr histories, and thus represent the shortest known ice cores to extend from the present into the last glacial. High major ion concentrations and dust particle diameter ratios identify a succession of abrupt and severe Holocene droughts on the Altiplano centered at 3.4, 4.2, 5.6, 7.5, 8.2 and 10.1 kyr B.P. Modern precipitation availability in the region is dominated by ENSO variability on interannual timescales and these events may thus reflect extended periods of El Niño-like conditions in the tropical Pacific. The Deglaciation Climate Reversal, the tropical counterpart to the Northern Hemisphere Younger Dryas stadial, is marked by large, abrupt stable isotopic depletion, with δ18O ~9-10 per mil lower at this time relative to the early Holocene. This δ18O shift is remarkable as it is ~4-5 per mil greater than that observed in any previously drilled central Andean ice core record. In concert with marked, synchronous deuterium-excess increases, these shifts may be explained by a coeval southward migration of the ITCZ. Decreased major ion and dust concentrations and low dust particle diameter ratios likely reflect increased central Andean precipitation at this time, in agreement with other regional paleoclimate records.A complete history could not be produced for the third core due to conflicting dating results. Annual resolution over the past 244 years allows for a detailed assessment of recent regional climate change and its relation to possible forcings. Decadal δ18O variability is strongly correlated with tropical Pacific sea surface temperatures and lends support to precipitation, via the amount effect, controlling δ18O on these timescales. On longer timescales, temperature plays an increasingly important role in governing this parameter and it is suggested that 20th century δ18O enrichment is influenced by recent tropospheric warming resulting from anthropogenic greenhouse gas emissions. Radiocarbon dating of well preserved, in-place vegetation exposed by the retreating Quelccaya Ice Cap, southeastern Peru constrains the last time the ice cap's extent was smaller than at present. Seventeen plant samples from two sites along the central western margin collectively date to 4.7 and 5.1 kyr B.P. and strongly indicate that current ice cap retreat is unprecedented over the past ~5 millennia. Seventeen vegetation samples interbedded in a nearby clastic sedimentary sequence suggest ice-free conditions at this site from ~5.2 to at least ~7 kyr B.P., and place minimum constraint on early- to mid-Holocene ice cap extent. A growing body of globally distributed, independently dated paleoclimate records collectively identifies a series of contemporaneous abrupt climate change events during the Holocene that are generally coeval with reductions in solar output. A mechanistic hypothesis for these events, involving the tropical Pacific shifting to an El Niño-like mean state via a non-linear response of the coupled ocean-atmosphere system to reduced radiative heating, is discussed. Support for this explanation utilizing the abrupt drought events captured in the CRC1 record is equivocal.
Advisors/Committee Members: Thompson, Dr. Lonnie.
Subjects: Geology
Keywords: ice core; climate change; paleoclimatology; tropical glaciers; Holocene; Nevado Coropuna; Quelccaya Ice Cap; Peru; Andes; South America
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24.
Carroll, Kelly Patrick.
Permeability of Lake Ice in the Taylor Valley, Antarctica: From Permeameter Design to Permeability Upscaling.
Degree: MS, Geological Sciences, 2008, Ohio State University
► Research on lake ice permeability in the McMurdo Dry Valleys, Antarctica required…
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▼ Research on lake ice permeability in the McMurdo Dry Valleys, Antarctica required the design and construction of a novel multi-support, field based, gas permeameter. The permeameters simple design allows rapid, precise, and non-destructive permeability measurements in a harsh polar environment. The research goals using the multi-support gas permeameter (MSGP) are to (1) determine lake ice physical hydrology through the investigation of primary permeability, (2) how permeability affects the mechanics and physics of fluid and gas transport through lake ice, (3) describe any variable nature of lake ice permeability, (4) scale up permeability to different sections of the lakes, and (5) document the change in permeability during the austral spring. The multi-support gas permeameter is of original design, however, a tip seal system utilizing the developments of a laboratory-based permeameter by Tidwell and Wilson (1997) was incorporated. The tip seal design has five interchangeable components, with inner seal radii of 0.15cm, 0.31cm, 0.63cm, 1.27cm, and 2.54cm, and outer radii twice the inner, which allows multiple gas diffusion depths, thus permitting permeability measurements over a wide variety of ice thickness and formation. The system delivers a positive pressure of 0 to 100kPa of compressed laboratory grade nitrogen (N2) gas into the tip seal interface that is in direct contact with the ice being tested. The volumetric flow rate, absolute injection pressure, barometric pressure, and temperature of the N2 gas penetrating the ice are recorded manually from a digital readout. The permeability is then calculated using a modified version of Darcys Law. Spot primary permeability measurements were used to scale permeability readings up to the entire lakes surface areas. The two lakes are influenced by different environmental conditions including source of wind (continental or marine influence), amount of sunlight (ablation rate), and ice conditions (annual and perennial ice lasting approximately 7 to 10 years). Measurements were made on a small scale (nine sample points per 81cm2 area) and were repeated weekly over a four-week period from early to late austral spring. By understanding the heterogeneity in smallest of scales at the different sampling sites (and through any temporal changes), the lakes’ permeability heterogeneity could be factored out and scaled up to reflect the primary permeability of the entire lake as a single, homogenous system. Data analysis revealed little difference in surficial primary permeability over a large spatial area, regardless of ice type sampled or the environmental conditions encountered. Although slight trends of permeability variability were noticed, the ice is intrinsically semi-permeable on the primary level. Average primary permeability of void spaces between ice crystals was at approximately 10-13 to 10-14 m2 for all in situ measurements. Observation revealed that although there was little difference in primary permeability of lake ice in general, it is very permeable due to secondary structures (fractures, bubbles, and lenses) contained within the ice column. This study dealt exclusively with the primary permeability and could not quantitatively constrain the secondary, and therefore, the overall permeability of the lakes.
Advisors/Committee Members: Carey, Anne.
Subjects: Hydrology
Keywords: permeability; dry valleys ice; permeameter; lake ice; lake hoare; lake fryxell
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27.
Codispoti, Julie E.
Speleothem Genesis in Ohio Caverns: How Erosion of Overlying Strata Resulted in Different Speleothem Characteristics.
Degree: MS, Geological Sciences, 2011, Ohio State University
► Ohio Caverns in southern Logan and northern Champaign counties, Ohio, is highly…
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▼ Ohio Caverns in southern Logan and northern Champaign counties, Ohio, is highly decorated in calcitic speleothems ranging in color from rusty red to white. The cave formed in the Devonian Columbus Limestone and is believed to be more than two million years old, forming before Pleistocene ice advances. Carbon dating of sediment samples in the cave was used to determine if the sediments were deposited in the cave by glacial processes, thus bounding a minimum age of the cave. Some areas of the cave contain a red, rusty colored flowstone that covers the cave walls with a wavy water “sheeting” appearance and does not form the traditional speleothems associated with caves. Other parts of the cave contain white flowstones that have the familiar appearance of speleothems and, in places grow directly from and on the rust colored speleothems indicating a change in mineralization. This change likely occurred from chemical alterations in the overlying strata consisting of the Ohio Shale, the Columbus Limestone, and in the thickness and character of soils prior to and after glaciation. A cave entrance currently being built exposes a cross section of glacial material, Ohio Shale, and Columbus Limestone. Float and in-situ rocks as well as soil material from a fracture and two ceiling rock cores drilled in the Historical Tour path, were collected for XRD analysis to characterize the mineralogy. The results show the samples are predominantly dolomite and only a few of the minerals are iron or manganese bearing. Well log data and visual observation provide clues that the Ohio Shale is still present over top of the cave. Sediment collected from Overlook Hole contained very little carbon and pollen for dating and paleoclimate information. It was the goal of this work to determine if changes in overlying strata caused the color change of speleothems in Ohio Caverns.
Advisors/Committee Members: Bair, Scott.
Subjects: Geological; Geology
Keywords: Ohio Caverns
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29.
Cosler, Douglas Jay.
Numerical investigation of field-scale convective mixing processes in heterogeneous, variable-density flow systems using high-resolution adaptive mesh refinement methods.
Degree: PhD, Geological Sciences, 2006, Ohio State University
► Three-dimensional, field-scale (~ 100 m) convective mixing processes in heterogeneous porous media…
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▼ Three-dimensional, field-scale (~ 100 m) convective mixing processes in heterogeneous porous media are examined. The focus is on fluid mixing rates and density-dependent macrodispersion, and the influence of small-scale (~ centimeters) instability development on large-scale variable-density flow and solute transport behavior. Dynamic adaptive mesh refinement methods (AMR) and a higher-order (solute advection term), mass-conservative Eulerian-Lagrangian discretization scheme for the solute transport equation are used to construct a new numerical code (DensTransAMR) that automatically adjusts to multiple scales of convective mixing processes by translating and adding/removing telescoping levels of progressively finer subgrids during a simulation. Because the flow and transport solutions for each subgrid are computed independently, field-scale simulations are broken into multiple smaller problems that can be modeled more efficiently and with finer detail. Two types of numerical experiments are performed: freshwater injection in a saltwater aquifer and dense fluid injection in a freshwater aquifer. Convective mixing rates are related to the geostatistical properties of the aquifer (variance and mean of the log permeability distribution, horizontal and vertical correlation scales), the fluid density difference, the magnitude of local small-scale dispersion, the effects of different permeability field realizations, the injection well size and orientation, hydraulic parameters such as injection rate and regional hydraulic gradient, and the spatial resolution. Convective mixing in heterogeneous porous media is shown to be more amenable to prediction than previously concluded. Computed three-dimensional fluid mixing rates are related to mathematical expressions for density-dependent macrodispersivity that are based on stochastic flow and solute transport theory and are a function of log permeability variance, the correlation scale, and a time-dependent parameter. Different instability patterns are generated when a different permeability field realization is used, the source location changes, or the mesh spacing is varied. However, long-term fluid mixing rates (i.e., after the mixing zone becomes large compared with the correlation scale) do not change if the fluid and macroscopic porous media properties (mean permeability, variance, and correlation lengths) remain constant. Porous media variability on scales smaller than the correlation lengths has an effect on the fluid mixing zone volume but does not affect long-term mixing rates.
Advisors/Committee Members: Ibaraki, Motomu.
Keywords: three-dimensional variable-density flow; solute transport; numerical model; adaptive mesh refinement; convective fluid mixing; heterogeneous porous media; stochastic transport theory; aquifer storage and recovery; subsurface remediation
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30.
Cramer, Bradley D.
Application of Integrated High-Resolution Biochemostratigraphy to Paleozoic Chronostratigraphic Correlation: Recalibrating the Silurian System.
Degree: PhD, Geological Sciences, 2009, Ohio State University
► The stratigraphic record preserves a library of global climate change that allows…
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▼ The stratigraphic record preserves a library of global climate change that allows us to use the past as the key to the present by studying prior examples of the multiple climate states of our planet’s history. The cause and affect relationships within the global climate system as well as the triggers and eventual consequences of prior examples of global environmental change are all preserved in the rock record. This global library is well-utilized for records from the recent past but there is diminishing attendance as one moves to the parts of the library containing older and older global environmental records. This is largely due to the difficulty in obtaining, reading, interpreting, and correlating global environmental records from the distant past. The work presented here is from the Silurian Period, including an interval from roughly 440 to 423Ma (Millions of years ago), and demonstrates that it is possible to produce a timescale for an interval hundreds of millions of years ago that nearly matches the resolution of more recent time periods. By producing a Phanerozoic timescale of equal resolution and fidelity throughout, over 500 million years of global environmental history can be brought to bear on our understanding of the modern climate system. Such a goal is decades away however, but this dissertation has begun to show that, at least for some portions of the Silurian, global chronostratigraphic correlation on the order of thousands of years (kyr) is achievable. The integration of high-resolution (often cm-scale) carbonate carbon isotope chemostratigraphy with high-resolution biostratigraphy of conodonts and graptolites as a chronostratigraphic tool, ‘biochemostratigraphy’, is documented in detail throughout this work which is presented in three parts. The document is divided into sections dealing with the chronostratigraphic potential, the practical application, and the chronostratigraphic consequences of integrated high-resolution biochemostratigraphy. Biochemostratigraphic data from Ohio, Indiana, Kentucky, Tennessee, New York, Nevada, Sweden, the United Kingdom, Estonia, and Latvia are presented including an interval from the Aeronian Stage of the Llandovery Series to the Homerian Stage of the Wenlock Series. New chronostratigraphic charts for the Silurian are provided including the first portion of an orbitally-tuned Silurian timescale as well as potential revisions to Silurian lithostratigraphic terms in use in the American Midcontinent.
Advisors/Committee Members: Saltzman, Matthew.
Subjects: Earth; Geology; Oceanography; Paleontology
Keywords: Silurian, carbon isotope, conodont, graptolite, chronostratigraphy, correlation, Baltic, North America
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