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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.
11

The Investigation on Fibrous Veins and Their Host from Mt. Ida, Ouachita Mountains, Arkansas

Chung, Jae Won 30 September 2004 (has links)
I have studied syntectonic veins from shales and coarse calcareous sands of the Ordovician Womble Shale, Benton uplift, Arkansas. All veins are composed of calcite with minor quartz and trace feldspar and dolomite or high-Mg calcite in the coarser veins. All host lithologies have a pressure-solution cleavage, more closely spaced in the fine-grained shale beds. The vein internal fabrics are coarsely to finely fibered, with a strong host-rock grain size control on fiber width. The finest fibers are in veins with shale host and the coarsest in the coarse-grained calcareous sandstone. Fiber aspect ratio is inversely proportional to host grain size; more equant vein grains are found in the veins hosted in the coarse host fraction. Within one outcrop, the δ13C and δ18O compositions of the host lithologies range from 1.5 to -3.0 per mil and 7.5 to -14.0 per mil (VPDB), respectively. By contrast, the δ18O composition of the veins is remarkably constant (-13.5 per mil) among veins of starkly different fabrics. This composition is identical to that of the coarse calcareous sandstone lithology in the outcrop. No cathodoluminescence or stable isotope zoning was observed in the veins. In addition, there were no gradients in Ca or Si in the vicinity of the veins, suggesting either that the host did not contribute these elements or that diffusion was not the rate-limiting step to vein formation. In any case, the wide variety of veins was probably formed from meter-scale migration of fluid derived from local calcite-rich layers in calcareous sandstone.
12

Sedimentary response to the tectonic uplift of the Kyrenia Range, northern Cyprus, in its Eastern Mediterranean tectonic setting

Palamakumbura, Romesh Niranjan January 2016 (has links)
The Kyrenia Range forms part of an approximately east-west lineament extending from northern Cyprus to southern Turkey. During Plio-Pleistocene the northern Cyprus segment of the lineament uplifted to ca. 1000 m above modern sea level. Plio- Pleistocene sediments document the uplift of the Kyrenia Range. A combination of sedimentology and a range of dating techniques including uranium series, optical stimulated luminescence (OSL), strontium isotopes and magnetostratigraphy are used to help understand the geological processes controlling uplift. Shallowing from a deepmarine basin to a shallow-marine, cool-water carbonate ramp represents the earliest uplift of the Kyrenia Range. The base of the carbonate ramp is made up of thick-bedded, benthic foraminiferal-rich grainstones, which are discontinuously overlain by calcareous red algal-rich rudstones. Erosively overlying this sequence is a coral- and molluscrich conglomerate, representing a short-lived relative sea-level fall. The upper part of the carbonate ramp sequence is composed of cross-bedded grainstone representing a shoreface environment. Interbedded with the upper grainstone facies are occasional fluvial conglomerates. The shallowing-upward marine environment represents the earliest emergence of the Kyrenia Range. After a major break in deposition, six marine and non-marine terraces (K0 to K5) reflect the sedimentary response to the main phase of tectonic uplift of the Kyrenia Range. The K0 terrace, the oldest and highest terrace, is composed of megabreccia and is interpreted as representing a major phase of rapid tectonic uplift. The K2-K5 terraces form a series marine to non-marine terraces on the northern flank of the range and also non-marine terraces on the southern flank of the range. The terraces on the northern flank each begin with a major marine transgression followed by a regressive sedimentary sequence. Marine environments range from nearshore open-marine below the storm-wave base, to shoreface, foreshore (beachrock), and backshore lagoonal environments. The non-marine environments range from aeolian dune to fluvial drainage systems. The fluvial systems are characterised by channelised debris-flow deposits interbedded with mudstones and palaeosols. The non-marine deposits on the southern flank of the range comprise a series of fluvial drainage systems. The fluvial systems on the southern flank of the range comprise a mixture of planar-bedded and channelised conglomerates, mudstones and aeolianites. Portable luminescence data are used to correlate quantitatively the K4 and K5 terraces on both the northern and southern flanks of the range. Each of the K4 and K5 terraces produce a unique luminescence signal, which is used as the basis for correlating the lower terraces. The unique luminescence signals of the K4 and K5 terraces are likely to be caused by varying sedimentary histories of the quartz and feldspar grains within the two terraces. The shallow-marine environments surrounding the Kyrenia Range prior to major uplift were dated using strontium isotopes and palaeomagnetism. The results of this dating suggest that marine environments persisted throughout the Early Pleistocene. U-series and OSL dating were used to date the K4 and K5 terraces on the northern flank of the range. The U-series results indicate that the marine deposits of the K4 terrace formed during several Middle Pleistocene interglacial stages. The OSL dating shows that the aeolian dunes of the K5 terrace formed during a Late Pleistocene glacial stage. The formation of the K2-K5 terraces was controlled by the interaction between tectonic uplift, climatic change and global eustatic sea-level change. The basal marine deposit of each terrace formed during an interglacial stage. Major fluvial deposition also occurs during the interglacial period as a result of a wetter climate. The inter-glacialglacial transition resulted in major fluvial erosion as a result of falling global sea-level. Aeolian carbonate deposition was dominant during the glacial stage, which represent arid climatic conditions. The only exception to this is the K4 terrace, which represents three glacial stages. The K1-K3 terraces can be correlated with the global sea-level curve suggesting approximate ages for each terrace, and ca. 600 ka for the entire K1- K5 terrace sequence. The Kyrenia Range underwent rapid uplift during the late Early Pleistocene at >1.2 mm/yr, followed by continuous but slower uplift during the Middle to Late Pleistocene. These results indicate that the uplift occurred in tandem with the Troodos Massif in southern Cyprus. The driving mechanism of the uplift of the Kyrenia Range is likely to be related to the collision of the Eratosthenes Seamount with the Cyprus trench to the south of the island. The seamount-trench collision resulted in compressional tectonics around Cyprus within the large-scale tectonic setting resulting from the early stages of convergence of the African and Eurasian plates.
13

Les organisations communautaires de femmes afro-américaines à Chicago : enjeux et stratégies de l’éducation et de l’ascension sociale / African American women’s community voluntary organizations in Chicago : issues and strategies of education and upward social mobility

Powell, Carrie 11 December 2017 (has links)
En puisant d’une part dans une tradition propre à la communauté africaine-américaine d’entretenir et d’étendre les liens familiaux et communautaires et d’autre part dans la tradition de l’ « activist mothering », les femmes africaines américaines se sont organisées au sein de leur communauté pour faire face aux problèmes qu’elles rencontrent en société. S’étant fédérées autour des deux combats abolitionniste et suffragiste au cours du 19e siècle et dans les réseaux préexistants des églises afro-américaines, cette solidarité donnera naissance au tournant du XXème siècle à un réseau de clubs de femmes noires activistes. En effet, le mouvement de clubs de femmes noires reposa sur une tradition de self-help, issue de l’idéologie de l’ « uplift ». Cette étude traverse donc le vingtième siècle, jusqu’à nos jours, et décrit les stratégies des réformatrices noires contemporaines, tout particulièrement au sein du West Side Chapter du National Council of Negro Women à Chicago, qui, tout en s’adaptant aux besoins évolutifs de la communauté, illustre des éléments d’héritage et une survivance de leur activisme. Les femmes afro-américaines organisent leur communauté à travers un processus d’empowerment et se placent dans un double mouvement de changement de conscience des individus et de transformation sociale des institutions. C’est donc un activisme empreint de pragmatisme mais dont la visée est politique. Il doit se comprendre dans la situation d’oppression constante dont sont historiquement victimes les Afro-Américains au sein de la Nation américaine. C’est donc des stratégies de résistance qui sont décrites dans ce travail, qui soulignent la résilience et les ressources des femmes noires en milieu défavorisé.L’importance de la famille dans les démarches de cette association va illustrer une continuité avec les préoccupations premières des clubs du début du XXème siècle. La forme de famille encouragée par l’association Sankofa Safe Child Initiative met en effet en lumière une circulation facilitée des enfants au sein des familles afro-américaines à l’étude et ce depuis plusieurs générations. Cette « tradition » qui se perpétue sera mise en lien avec les phénomènes de fosterage, courant en Afrique et de par le monde, bien qu’ici en seront spécifiés le mode ainsi que la fonction c’est-à-dire un usage stratégique de la famille au sein de cette communauté pour faire face aux défis qui se posent à elle, particulièrement en milieu hostile. / Spawning from a tradition of maintaining and extending kinship and community ties, and secondly from a tradition of activist mothering, African American women have organized within their community to solve the predicaments they face in society. From their organizing experience in the abolitionist movement as well as the early women’s movement of the 19th century and relying on the networks they established through their church work, an African American club movement formed at the turn of the 20th century. Indeed, the Black women’s club movement built upon a tradition of self-help, defined by the uplift ideology. As this thesis spans the twentieth century till today, this essay describes the strategies employed by contemporary African American women reformers, specifically the West Side chapter of the National Council of Negro Women in Chicago, who constantly adapt to the evolving needs of their community but still inherited from this legacy.Through an empowerment process, African American women seek to change the people’s consciousness and transform social institutions. It is an activism with a pragmatic edge but a political goal. Acknowledging the oppression weighing on the African American community, the strategies described in this study are strategies of resistance, with a particular interest in the resilience and the resources of Black women in the underserved communities.The focus on family issues in these associations’ approach shows a continuity with the primary preoccupations of the clubs at the turn of the century. The form of the family promoted by the association Sankofa Safe Child Initiative sheds light on a facilitated circulation of children among the African American families under study, through several generations. This “tradition” will be linked to the fosterage phenomenon, current in Africa and other parts of the world, of which the mode as well as the function will be specified, notably a strategic use of the family within the underserved African American community to face challenges in a hostile environment.
14

Seismic activity and end- or post-glacial faults in northern Fennoscandia, focusing on Sweden

Oyama, Kie January 2016 (has links)
During the late or post Weichselian glacial periods, about 9500 years ago, several faulting associated with large scale earthquakes were triggered in northern Fennoscandia. The end- or post-glacial scarps have a range of the lengths c. 3 to 155 km and the heights 0 to 30 m while most of them are reverse faults trending NE-SW with SE dips. In this literature study, I try to compile the estimated history and cause of seismicity in northern Sweden, and predict the future activity. The result indicates that although the timing of these faulting might not be in the same phase of deglaciation, the upheaval induced by glacial retreating is considered as the major factor of these paleoseismicity. Since the strain from glaciers has been mostly released, the main cause of recent earthquakes in this region is tectonic stress accumulation. Accompanied by the progress of observing techniques such as drilling and grand penetrating radar detection especially in this decade, the geometry of these glacially induced faults and recent micro-seismicity in the vicinity of these scarps have been detected better and better. According to the results, the recorded epicenters form clusters in the east side of the faults’ zone. It implies the correlation between recent seismicity and end- or post-glacial faults. However, there is still insufficient data of the faults’ structure and previous seismicity in order to clarify the faults’ geometry, the age of main movements and estimate their future activity. More investigations are expected to take place in this region.
15

HOW DO THE STRUCTURES OF THE LATE PALEOZOIC OUACHITA THRUST BELT RELATE TO THE STRUCTURES OF THE SOUTHERN OKLAHOMA AULACOGEN

Jusczuk, Steven John 01 January 2002 (has links)
The thin-skinned structures of the late Paleozoic Ouachita thrust belt intersect the basement structures of the Southern Oklahoma aulacogen beneath the Mesozoic strata of the Gulf Coastal Plain in southeastern Oklahoma. The Ouachita thrust belt forms a large northwest-directed salient which extends primarily in the subsurface from central Mississippi northwestward to Arkansas and eastern Oklahoma, and from there, southwestward toward central Texas. Kinematics are complicated in the center of the Ouachita salient, where the average southwesterly strike of thrust faults is nearly perpendicular to average trend of compressional basement structures in the Southern Oklahoma aulacogen (Arbuckle uplift) and Muenster arch. Furthermore, the frontal fault of the Ouachita thrust belt curves sharply eastward around the southeastern end of the Arbuckle uplift, and bends sharply to the west between the Arbuckle uplift and the Muenster arch farther south in Texas. Nine new interpreted structural cross sections show the structural complexity of the area where the Ouachita thrust belt intersects the Arbuckle uplift and Muenster arch. Detailed study of the structural geology of the Ouachita Mountains and Arkoma basin indicates that along-strike changes in structural style evidently are related to along-strike changes in mechanical stratigraphy (relative thicknesses of weak units, in contrast to stiff units). The middle part of the Stanley Group (Formation) evidently serves as a wavelength transition and/or volume compensation zone. Along-strike change in stratigraphic level of detachments and abrupt eastward thickening of the Atoka Formation along the Ouachita thrust front strongly affected the structural style of the Ouachita thrust belt. Regional stratigraphy, palinspastic restorations of the footwall cutoff of the Ti Valley fault, and an abrupt change in character of seismic reflectors indicate an abrupt facies transition in the Middle Ordovician-Mississippian succession along the southeastern flank of the Arbuckle uplift and southwestward toward the deep southeastern part of the Ardmore basin. Out-of-syncline structures in the Bryan smallscale salient, distinct sub-thrust angular unconformities imaged on seismic profiles, and sediment dispersal patterns in the early Atokan-Desmoinesian strata of the northern Fort Worth basin (south of the Muenster arch) all indicate that the Tishomingo-Belton and Muenster structures were pre-thrust structural highs.
16

Unroofing History of the Northwestern Ethiopian Plateau: Insights from Low-Temperature Apatite Thermochronology

Bowden, Shelby 01 October 2018 (has links)
The geology of Ethiopia is dominated by the Ethiopian Plateau that is similar in elevation to, but aerially larger than, the Colorado Plateau. Several rivers have incised through the plateau, creating gorges that reach up to 1.5 km in depth. The plateau uplifted to its current elevation and was subsequently incised sometime after the Oligocene flood basalt event that signaled the arrival of the African Superplume below Kenya and Ethiopia. Due to its size and extent, published climate modeling has indicated that Late Cenozoic plateau formation could have been a driving force in the East African Cenozoic climate changes. Although uplift timing has potentially far-reaching impacts to several scientific disciplines, uplift is not well constrained, and several published studies present contradictory data. This study aims to elucidate the uplift timing of the Ethiopian Plateau through the use of river incision timing as a proxy for uplift. Methods employed to accomplish incision timing include low temperature apatite fission track and (U-Th)/He thermochronology, thermal modeling, and scanning electron microscopy backscatter electron detection (SEM-BSE). Basement samples for thermochronologic dating were collected from the Didessa River Canyon near Nekemte. (U-Th)/He dating was conducted at the Arizona State University Group 18 Laboratory where 17 apatite grains were dated, while GeoSeps Services LLC performed the apatite fission track analysis. Results indicate that after crystallization between 797-630 Ma during the East African Orogen, the rocks experienced rapid exhumation to within 1400-3000 m of the surface in the Jurassic. The Cenozoic flood basalt event at 31-29 Ma caused a massive outpouring of basalts that forced the lowest sample into the partial retention zone where it remained for an extended period of time while accumulating radiation damage. Rapid cooling from 8 Ma to present represents a recent exhumation history of the Ethiopian Plateau, suggesting that the plateau’s high elevation gain was achieved within the last 10 Ma. This integrated apatite (U-Th)/He and fission track study is the first of its kind addressing East African Cenozoic tectonics.
17

Pre-Cretaceous erosional surface of the Llano Uplift region, Central Texas

Sobehrad, Susan Je 24 February 2012 (has links)
Historical research reveals a repeating pattern of uplift, erosion, and deposition in the region of the Llano Uplift, central Texas. This report examines the topography of the pre-Cretaceous landscape. The data consist of points, in three dimensions, that are located on the erosional surface, as determined by three methods. Category I data lie upon the contact between Cretaceous strata and underlying Paleozoic sediments or Precambrian basement; Category II data are defined in the subsurface from well logs; and Category III data are topographic high points where the Cretaceous has eroded away, but the underlying unit has not eroded (an exhumed surface). Digital mapping procedures were used to create triangulated irregular networks, three dimensional scenery, and topographic profiles. The digitally reconstructed surface is compound, consisting of higher, older erosional surfaces, incised into by rejuvenated stream activity to create lower, younger surfaces. This valley/divide topography, which is regional in extent, could not have been visualized without modern GIS technology. / text
18

Late Eocene Uplift of the Al Hajar Mountains, Oman, Supported by Stratigraphy and Low-Temperature Thermochronology

Hansman, Reuben J., Ring, Uwe, Thomson, Stuart N., den Brok, Bas, Stübner, Konstanze 12 1900 (has links)
Uplift of the Al Hajar Mountains in Oman has been related to either Late Cretaceous ophiolite obduction or the Neogene Zagros collision. To test these hypotheses, the cooling of the central Al Hajar Mountains is constrained by 10 apatite (U-Th)/He (AHe), 15 fission track (AFT), and four zircon (U-Th)/He (ZHe) sample ages. These data show differential cooling between the two major structural culminations of the mountains. In the 3km high Jabal Akhdar culmination AHe single-grain ages range between 392 Ma and 101 Ma (2 sigma errors), AFT ages range from 518 Ma to 324 Ma, and ZHe single-grain ages range from 62 +/- 3Ma to 39 +/- 2 Ma. In the 2 km high Saih Hatat culmination AHe ages range from 26 +/- 4 to 12 +/- 4 Ma, AFT ages from 73 +/- 19Ma to 57 +/- 8 Ma, and ZHe single-grain ages from 81 +/- 4 Ma to 58 +/- 3 Ma. Thermal modeling demonstrates that cooling associated with uplift and erosion initiated at 40 Ma, indicating that uplift occurred 30 Myr after ophiolite obduction and at least 10 Myr before the Zagros collision. Therefore, this uplift cannot be related to either event. We propose that crustal thickening supporting the topography of the Al Hajar Mountains was caused by a slowdown of Makran subduction and that north Oman took up the residual fraction of N-S convergence between Arabia and Eurasia.
19

Modeling Temporal Bias of Uplift Events in Recommender Systems

Altaf, Basmah 08 May 2013 (has links)
Today, commercial industry spends huge amount of resources in advertisement campaigns, new marketing strategies, and promotional deals to introduce their product to public and attract a large number of customers. These massive investments by a company are worthwhile because marketing tactics greatly influence the consumer behavior. Alternatively, these advertising campaigns have a discernible impact on recommendation systems which tend to promote popular items by ranking them at the top, resulting in biased and unfair decision making and loss of customers’ trust. The biasing impact of popularity of items on recommendations, however, is not fixed, and varies with time. Therefore, it is important to build a bias-aware recommendation system that can rank or predict items based on their true merit at given time frame. This thesis proposes a framework that can model the temporal bias of individual items defined by their characteristic contents, and provides a simple process for bias correction. Bias correction is done either by cleaning the bias from historical training data that is used for building predictive model, or by ignoring the estimated bias from the predictions of a standard predictor. Evaluated on two real world datasets, NetFlix and MovieLens, our framework is shown to be able to estimate and remove the bias as a result of adopted marketing techniques from the predicted popularity of items at a given time.
20

Geologic Mapping of the Vernal NW Quadrangle, Uintah County, UT, and Stratigraphic Relationships of the Duchesne River Formation and Bishop Conglomerate

Webb, Casey Andrew 01 August 2017 (has links)
Detailed mapping (1:24,000), measured sections, and clast counts in conglomerates of the Duchesne River Formation and Bishop Conglomerate in the Vernal NW quadrangle in northeastern Utah reveal the middle Cenozoic stratigraphic geometry, the uplift and unroofing history of the eastern Uinta Mountains, and give evidence for the pulsed termination of Laramide uplift. The Unita Mountains are an EW-trending reverse fault bounded and basement-cored, Laramide uplift. The oldest unit of the Duchesne River Formation, the Eocene Brennan Basin Member, contains 80-90% Paleozoic clasts and <20% Precambrian clasts. Proximal to the Uinta uplift the conglomerates of this member are dominated by Paleozoic Madison Limestone clasts (70-90% of all clasts). Farther out into the basin, Paleozoic clasts still dominate in Brennan Basin Member conglomerates, but chert clasts are more abundant (up to 43%) showing the efficiency of erosion of the carbonate clasts over a short distance (~5 km). Conglomerates in the progressively younger Dry Gulch Creek, Lapoint, and Starr Flat members show a significant upward increase in Precambrian clasts with 34-73% Uinta Mountain Group and 8-63% Madison Limestone. Duchesne River Formation has a significant increase in coarse-grained deposits from the southern parts of the quadrangle (20-50% coarse) to the northern parts (75% coarse) nearer the Uinta uplift. The lower part of the Duchesne River Formation exhibits a fining upward sequence representing a tectonic lull. Clast count patterns show that pebbly channel deposits in the south maintain similar compositions to their alluvial fan counterparts. To the north, the fine-grained Lapoint and Dry Gulch Creek members of the Duchesne River Formation appear to pinch out completely. This can be explained by erosion of these fine-grained deposits or by lateral facies shifts before deposition of the next unit. Starr Flat Member conglomerates were deposited above Lapoint Member siltstones and represent southward progradation of alluvial fans away from the uplifting mountain front. Similarities in composition and sedimentary structures have caused confusion surrounding the contact between the Starr Flat Member and the overlying Bishop Conglomerate. Within the Vernal NW quadrangle, we interpret this contact as an angular unconformity (the Gilbert Peak Erosion Surface) developed on the uppermost tilted red siltstone of the Starr Flat Member sometime after 37.9 Ma. Stratigraphic and structural relationships reveal important details about the development of a Laramide mountain range: 1) sequential unroofing sequences in the Duchesne River Formation, 2) progradation of alluvial fans to form the Starr Flat Member, 3) and the unconformable nature of the Gilbert Peak Erosion Surface lead to the conclusion that there were at least 3 distinct episodes of uplift during the deposition of these formations. The last uplift episode upwarped the Starr Flat Member constraining the termination of Laramide uplift in the Uinta Mountains to be after deposition of the Starr Flat Member and prior to deposition of the horizontal Bishop Conglomerate starting at about 34 Ma. This, combined with 40Ar/39Ar ages of 39.4 Ma from the Dry Gulch Creek and Lapoint member, show that slab rollback related volcanism was occurring to the west while the Uinta Mountains were being uplifted on Laramide faults. These new 40Ar/39Ar ages constrain the timing of deposition and clarify stratigraphic relationships within the Duchesne River Formation; they suggest a significant unconformity of as much as 4 m.y. between the Duchesne River Formation and the overlying Bishop Conglomerate, which is 34-30 Ma in age, and show that Laramide uplift continued after 40 Ma in this region.

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