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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Holocene paleohydrology from Lake of the Woods and Shoal Lake cores using ostracodes, thecamoebians and sediment properties

Mellors, Trevor 07 September 2010 (has links)
Ten sediment cores (2.0-8.5 m long) from various locations in Lake of the Woods (LOTWs) and Shoal Lake (SL) were recovered in August 2006, using a Kullenberg piston corer. From the study of the macrofossils (primarily ostracodes and thecamoebians) and the sediments in six processed cores, variations in paleoconditions were observed both spatially and temporally, and the timing of these changes were identified in over 10,000 years of postglacial history. Ostracodes disappeared from the LOTWs record from about 9000 to 7600 calendar years before present (BP) (about 5800 in SL), after LOTWs became isolated from glacial Lake Agassiz. Thecamoebians appeared in many cores around 2000 calendar years BP, with the earliest appearance at 9200. Buried paleosols in three cores indicate portions of the lake dried on several occasions during the Hypsithermal, perhaps indicating the region’s future climate response. One core contained a pink clay bed indicative of the Marquette readvance about 11,300 years (BP), and the subsequent input of water from the Superior basin.
22

Mapping the Spatial-Temporal Variation in Ras Ghanada Seagrass Meadows and Sand Shoals between 1996, 2006 & 2012

Brookbank, Ryan 27 April 2017 (has links)
Seagrass meadows offshore Ras Ghanada, as elsewhere, are an important component to the ecosystem providing numerous benefits to both aquatic and human life. This work focused on mapping the spatial and temporal distribution of seagrass meadows offshore Ras Ghanada using aerial photography acquired in 1996 and high-resolution satellite images captured in 2006 and 2012. The movements of sand shoals were also tracked, so as to further explain the dynamics of this ecosystem, as it is the area between the shoal crests that hosts the best developed seagrass meadows. The natural limiting factor for seagrass on the Ras Ghanada coastal shelf seems to be the fact that they cannot inhabit the (mobile) crests of the sand shoals, but rather, are restricted to the (more stable) sands of the shoal troughs. In the considered time period, both sand shoals and seagrass meadows migrated predominantly in a southeastern direction. The changes of seagrass that occurred in this study occurred on a fairly rapid timescale, in such that they were able to come back when there was disturbance as long as they had available habitat to move into. Furthermore, although seagrass cover declined by 3.4% from 1996 – 2012, there was a greater increase than decline in the areal coverage of seagrass post-Khalifa port construction in 2010. If sediments offshore Ras Ghanada can remain stable and the waters are not polluted by further construction, seagrasses should continue to thrive in the future.
23

INTERPRETATION OF THE DEPOSITIONAL ENVIRONMENTS AND SOFT-SEDIMENT DEFORMATION IN THE UPPER TANGLEWOOD MEMBER (UPPER ORDOVICIAN) OF THE LEXINGTON LIMESTONE, CENTRAL KENTUCKY, U.S.A.

Koirala, Dibya R. 01 January 2017 (has links)
The upper Tanglewood Member is the final member of the Lexington Limestone and is well-known for its soft-sediment deformation. This study has confirmed the carbonate-shoal-complex origin of the unit, and detailed study shows that its development took place during five small-scale, sequence-like, fining-upward cycles related to eustasy and tectonics. Four lithofacies are represented in the unit. Facies analysis of each cycle shows that the thickest and coarsest part of each cycle corresponds to previously uplifted basement-fault blocks; the occurrence of thick, coarse facies on the same fault blocks suggests that the blocks continued to experience uplift due to Taconian far-field forces generated on the eastern margin of Laurentia. The upper Tanglewood Member includes six deformed horizons that can be traced into equivalent parts of the Clays Ferry and Point Pleasant formations. Concurrence of four lines of evidence, suggested by Ettensohn et al. (2002d) for interpretation of seismites, indicates that the widespread horizons of deformation are seismogenic in origin. Reactivation of basement structures due to Taconian far-field forces probably induced seismicity on the intra-platform carbonate complex so as to produce soft-sediment deformation. Petrographic investigation indicates that most of the cements in the upper Tanglewood limestones appear to be late diagenetic, fresh-water phreatic cements. Comparing the petrography of deformed and undeformed portions of the same horizon showed no significant differences in terms of cementation, indicating that cementation occurred primarily after deformation. The primary impact of deformation on the microstructure of the unit was the randomization of grain fabric and the increased presence of broken intraclasts.
24

Micropalaeontology, palaeoenvironments and sequence stratigraphy of the Sulaiy Formation of eastern Saudi Arabia

Alenezi, Saleh January 2016 (has links)
The Sulaiy Formation, which is the oldest unit in the Lower Cretaceous succession, is conformably overlain by the Yamama Formation and it is a challenge to identify the precise age of the two formations using foraminifera and other microfossil assemblages. In the eastern side of Saudi Arabia, the Sulaiy Formation and the base of Yamama Formation are poorly studied. The main objectives of this study is to enhance the understanding of the Sulaiy Formation sequence stratigraphical correlation, regional lateral variations and palaeoenvironmental investigation. Lithological and semi-quantitative micropalaeontological analysis of 1277 thin sections taken from core samples from nine cored wells providing a geographically representative distribution from the Saudi Arabian Gulf. These cores intersected the base of the Yamama Formation and the Sulaiy Formation in the total thickness of cored wells of 843.23 meters (2766.5 feet). On the evidence provided by the foraminifera, the Sulaiy Formation is considered to represent the Berriasian to the lowermost Valanginian. The investigation of the micropalaeontology has provided considerable insights into the biocomponents of Sulaiy and the base of Yamama formations in order to identify their biofacies. These microfossils include rotalid foraminifera, miliolid foraminifera, agglutinated foraminifera, calcareous algae, calcispheres, stromatoporoids, sponge spicules, problematica (e.g. Lithocodium aggregatum), molluscs, corals, echinoderms and ostracods. Systematics of planktic and benthic foraminifera is accomplished using the foraminiferal classification by Loeblich and Tappan (1988) as the main source. The assemblage contains foraminifera that recorded for the first time in the Sulaiy Formation. Other microfossils were identified and recorded to help in the identification of the sedimentary environments. The investigation of the micropalaeontology and the lithofacies analysis have provided evidence the identification of the various lithofacies. About twenty four microfacies were identified on the basis of their bio−component and non-skeletal grains. The lithofacies and the bio−component results have provided the evidence of the sedimentary palaeoenvironmental model namely the Arabian Rimmed Carbonate Platform. This palaeoenvironmental depositional model is characterised by two different platform regimes. They are the Platform Interior and the Platform Exterior each of which have unique sedimentary lithofacies zones that produce different types of lithofacies. Each lithofacies is characterised by special depositional conditions and palaeobathymetry that interact with sea level changes and the accommodation space. The important palaeoenvironments are intertidal, restricted lagoon (subtidal), open marine, deeper open marine, inner shoal, shoal and platform margin. Generating, and testing, a depositional model as a part of formulating a sequence stratigraphical interpretation of a region is a key to understanding its geological development and – ultimately – reservoir potential. The micropalaeontology and sedimentology of the Sulaiy Formation in the subsurface have indicated a succession of clearly defined shallowing−upwards depositional cycles. These typically commence with a deep marine biofacies with wackestones and packstones, capped with a mudstone-wackestone maximum flooding zone and an upper unit of packstone to grainstones containing shallow marine biofacies. The upper part of the Sulaiy Formation is highstand-dominated with common grainstones that host the Lower Ratawi reservoir which is capped by karst that defines the sequence boundary. This karst is identified by its abundant moldic porosity that enhanced the the reservoir quality by increasing its porosities into greater values. Integration of the sedimentology and micropalaeontology has yielded a succession of shoaling−upwards depositional cycles, considered to be 4th order sequences, that are superimposed on a large scale 3rd order system tract shallowing−upwards, highstand-associated sequence of the Sulaiy Formation. The Lower Ratawi Reservoir is located within the latest high-stand portion of a third-order Sulaiy Formation sequence. The reservoir consists of a succession of several sequences, each of which is sub-divided into a lower transgressive systems tract separated from the upper highstand systems tract by a maximum flooding surface (MFS/Z). The last of these depositional cycles terminates in beds of porous and permeable ooid, or ooidal-peloidal, grainstone. The reservoir is sealed by the finer-grained sediments of the Yamama Formation.
25

The Spratly Islands dispute : decision units and domestic politics

Chung, Christopher, Humanities & Social Science, Australian Defence Force Academy, UNSW January 2004 (has links)
This thesis presents a cross-national, cross-regime examination of foreign policy decision-making in the Spratly Islands dispute, focusing on China, Malaysia and the Philippines. It argues that how and why these countries have acted in particular ways towards the dispute relates to the relationship among foreign policy decision-making, government behaviour and domestic politics. The theoretical foundation of the study is foreign policy analysis. It applies the decision units approach advanced by Margaret and Charles Hermann and Joe Hagan to investigate who made foreign policy decisions on the Spratly Islands dispute in the three countries during the period 1991-2002, and how this influenced government behaviour. In addition, the contextual influence of domestic politics is considered. Four case studies inform the empirical analysis: the approaches taken by Malaysia and the Philippines to bolster their respective sovereignty claim, China???s establishment of a comprehensive maritime jurisdictional regime covering the Spratly Islands among other areas, China-Philippines contestation over Mischief Reef and the development of a regional instrument to regulate conduct in the South China Sea. Three conclusions are drawn. First, the decision units approach identifies the pivotal foreign policy decision-makers in each of the countries examined and the process involved. Second, it explains the relationship between decision unit characteristics -- self-contained or externally influenceable -- and each government???s behaviour towards the dispute. Injecting domestic politics into the analysis highlights motivations of and constraints faced by decision-makers, conditioning the form and content of government action. Third, it demonstrates a low predictive capability: the ???fit??? between hypothesised and actual government behaviour is poor. While it is not a comprehensive analytical tool, the combined decision units-domestic politics approach offers deeper insight into government decisions and behaviour on the Spratly Islands dispute than hitherto reported in the literature.
26

The Spratly Islands dispute : decision units and domestic politics

Chung, Christopher, Humanities & Social Science, Australian Defence Force Academy, UNSW January 2004 (has links)
This thesis presents a cross-national, cross-regime examination of foreign policy decision-making in the Spratly Islands dispute, focusing on China, Malaysia and the Philippines. It argues that how and why these countries have acted in particular ways towards the dispute relates to the relationship among foreign policy decision-making, government behaviour and domestic politics. The theoretical foundation of the study is foreign policy analysis. It applies the decision units approach advanced by Margaret and Charles Hermann and Joe Hagan to investigate who made foreign policy decisions on the Spratly Islands dispute in the three countries during the period 1991-2002, and how this influenced government behaviour. In addition, the contextual influence of domestic politics is considered. Four case studies inform the empirical analysis: the approaches taken by Malaysia and the Philippines to bolster their respective sovereignty claim, China???s establishment of a comprehensive maritime jurisdictional regime covering the Spratly Islands among other areas, China-Philippines contestation over Mischief Reef and the development of a regional instrument to regulate conduct in the South China Sea. Three conclusions are drawn. First, the decision units approach identifies the pivotal foreign policy decision-makers in each of the countries examined and the process involved. Second, it explains the relationship between decision unit characteristics -- self-contained or externally influenceable -- and each government???s behaviour towards the dispute. Injecting domestic politics into the analysis highlights motivations of and constraints faced by decision-makers, conditioning the form and content of government action. Third, it demonstrates a low predictive capability: the ???fit??? between hypothesised and actual government behaviour is poor. While it is not a comprehensive analytical tool, the combined decision units-domestic politics approach offers deeper insight into government decisions and behaviour on the Spratly Islands dispute than hitherto reported in the literature.

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