Le climat primitif martien fascine la recherche martienne. Identifier avec le plus de précision possible les conditions primitives martiennes permettrait de contraindre les différents états de l’eau au cours de l’histoire martienne. Aujourd’hui deux hypothèses font débat, la première est celle d’un climat chaud et humide régnant à la surface de Mars à la fin du Noachien/début Héspérien. La deuxième, à l’inverse, semble indiquer que le climat aurait été froid et englacé sur les plus hautes altitudes martiennes. Néanmoins, cette deuxième hypothèse est souvent contestée, car contrairement à la présence de marqueur d’eau liquide à la surface de Mars, aucune morphologie de surface attestant d’un climat froid n’avait été identifiée. Au cours de cette thèse, nous avons étudié de manière morphométrique les structures et morphologies à la surface de Terra Sabaea, qui constitue 1% de la superficie totale de la planète. Ces structures constituent des héritages morphologiques des activités climatiques passées. Afin de caractériser au mieux l’origine érosive de ces structures, nous avons créé une nouvelle méthode d’analyse morphométrique à partir de différentes méthodes terrestres et martiennes. Cette nouvelle méthode permet d’extraire plus de 20 données exploitables par vallée. Il a donc été question de mesurer un maximum de vallée afin d’établir une base de données que nous avons comparée avec des bases de données de morphologies terrestres et martiennes. Grâce à cette analyse, il a été possible de mettre en évidence, la présence d’un paysage glaciaire dans la région de Terra Sabaea. Ce paysage est composé de (1) vallées glaciaires liées avec (2) des cirques glaciaires. La source de cette glace semble être (3) des calottes de plateaux locales à des altitudes > 3500 m. Nous avons donc démontré pour la première fois la présence de morphologies glaciaires attestant d’un climat froid il y a 3.6 Ga. Néanmoins, la présence de telles morphologies n’indique pas que l’ensemble de Terra Sabaea était englacé. L’analyse morphométrique a démontré la présence de morphologie fluviatile géographiquement proche des morphologies glaciaires et souvent à la même altitude, entre 1500 et 3500 m. Cette observation nous a permis de mettre en évidence (4) que la pente était un facteur qui influençait sur l’état de l’eau. En effet, pour une même altitude, les morphologies fluviatiles sont situées sur les pentes douces (< 3°) alors que les morphologies glaciaires sont situées sur les remparts internes des cratères d’impacts présentant une forte pente (> 10°). Cependant (5) l’altitude semble également être un facteur déterminant puisque l’on ne retrouve pas de morphologie glaciaire à des altitudes < 1500 m. L’analyse des terrains de Terra Sabaea a également mis en évidence (6) qu’il existait un lien génétique entre les morphologies glaciaires de hautes altitudes et les vallées fluviatiles plus bas. En effet, il est possible de suivre une vallée qui prend sa source sur les hauts plateaux englacés en amont, jusqu’en aval où elle rejoint des morphologies témoignant d’une activité fluviatile. Cette continuité dans les morphologies glaciaires et fluviatiles permet (7) de mieux définir l’origine des vallées ramifiées, et notamment l’origine de Naktong vallis, et il semblerait que la fonte des glaces a joué un rôle dans leurs formations. De plus, cette continuité morphologique permet de supposer qu’il existait (8) un cycle de l’eau similaire à la Terre dans la région de Terra Sabaea il y a 3.6 Ga. / The primitive Martian climate fascinates Martian research. Identifying Martian primitive conditions as accurately as possible would make it possible to constrain the different states of water during Martian history. Today two hypotheses are debated, the first is that of a hot and humid climate prevailing on the surface of Mars at the end of the Noachian / early Hesperian. The second, on the contrary, seems to indicate that the climate was cold and glacial on the highest Martian altitudes. Nevertheless, this second hypothesis is often disputed, because unlike the presence of liquid water marker on the surface of Mars, no surface morphology attesting to a cold climate had been identified. In this thesis, we studied morphometrically structures and morphologies on the surface of Terra Sabaea, which constitutes 1% of the total surface of the planet. These structures constitute morphological legacies of past climatic activities. In order to better characterize the erosive origin of these structures, we have created a new method of morphometric analysis from different terrestrial and Martian methods. This new method makes it possible to extract more than 20 exploitable data per valley. It was therefore a question of measuring a valley maximum in order to establish a database that we compared with databases of terrestrial and Martian morphologies. Thanks to this analysis, it has been possible to highlight the presence of an ice landscape in the Terra Sabaea region. This landscape is composed of (1) glacial valleys linked or not with (2) glacial cirques. The source of this ice appears to be (3) local plateau caps at altitudes> 3500 m. We thus demonstrated for the first time the presence of glacial morphologies attesting to a cold climate there are 3.6 Ga. Nevertheless, the presence of such morphologies does not indicate that the whole of Terra Sabaea was glaciated. Morphometric analysis has demonstrated the presence of fluvial morphology geographically close to glacial morphologies and often at the same altitude, between 1500 and 3500 m. This observation allowed us to highlight (4) that the slope was a factor influencing the state of the water. Indeed, for the same altitude, fluvial morphologies are located on gentle slopes (<3 °) while glacial morphologies are located on the inner walls of impact craters with a steep slope (> 10 °). However (5) altitude also seems to be a determining factor since we do not find glacial morphology at altitudes <1500 m. Terra Sabaea land analysis also revealed (6) that there is a genetic link between high altitude glacial morphologies and lower river valleys. Indeed, it is possible to follow a valley that has its source on the highlands glaciers upstream, downstream where it joins morphologies testifying to a fluviatile activity. This continuity in glacial and fluvial morphologies makes it possible (7) to better define the origin of branched valleys, and in particular the origin of Naktong vallis, and it seems that melting ice has played a role in their formations. Moreover, this morphological continuity makes it possible to suppose that there existed (8) a cycle of water similar to the Earth in the region of Terra Sabaea there is 3.6 Ga.

In 1899, Robert T. Hill led the first scientific exploration of the remote segment of the Rio Grande known as the Big Bend. Hill’s observations from this expedition were published in an article titled “Running the Cañons of the Rio Grande.” At the time of Hill’s expedition, the stream flow of the Rio Grande was largely depleted by water development in the upstream portions of the basin. The continued overallocation of the Rio Grande has led to the degradation of aquatic ecosystems in the Big Bend, one of North America’s largest transboundary protected areas, such that management of natural resources in this region is a high priority. Many of the native species in this region are listed as threatened or endangered due to habitat loss, which is driven by channel narrowing. Thus, excess fine sediment, along with invasive riparian species, has been identified as negatively impacting ecological resources in the Big Bend and studies recommend increased stream flow as the most effective tool for managing excess fine sediment. Aside from historical accounts, there was previously no estimate of the Rio Grande’s natural flow regime nor an adequate understanding of how the role of characteristic floods in the Big Bend shaped the pre-disturbance channel. In the following two studies, we fill in these crucial knowledge gaps by estimating the pre-disturbance flow regime of the Rio Grande, describing how channel narrowing is not spatially uniform in the Big Bend, and analyzing past floods to determine the role of past flood regimes in shaping alluvial deposits that contribute to channel narrowing.

No description available.

Three paleo-environments were studied. The first project concerned the Manson Impact and the effect of the Black Hills on the resulting fall-out from this asteroid strike. Samples of the Crow Creek Member were taken east of the Black Hills in Nebraska and South Dakota and samples from the Red Bird Member were taken from the west, in Wyoming. These samples were examined for chemical weathering, soot, shocked quartz, and fossils. The Crow Creek samples had shocked quartz (indicative of an impact), severe chemical weathering, soot, and evidence of tsunamis. There were few calcareous fossils. The Red Bird showed no signs of chemical weathering, a distinct absence of soot and shocked quartz and an abundance of fossils. These results indicate that the Black Hills were large enough to pose an atmospheric and oceanic barrier to the effects of the Manson Impact. The second project dealt with dinosaur eggs which were found in Montana. The eggs were examined and subjected to Computed Tomography Scans. The egg-shell, matrix, and volcanic ash were studied. The egg-shell was found to be from an undescribed oolithic species, and revealed that a transgressive event transpired after the eggs had fossilized. The matrix revealed that the eggs were laid in a flood-plain. The ash revealed a high amount of tungsten and yielded a high percentage of potassium for future dating. The eggs themselves revealed that intact embryos were within. This project has provided information on dinosaur nesting behavior. In the third project corals were examined to determine the usefulness of sampling different architectural structures for evaluating environmental proxies. Coral was collected at the Verde Reef. The different architectural structures were sampled using SIMS, and LA-ICP-MS to selectively sample the small architectural structures. Oxygen isotope ratios and elemental: calcium ratios were compared among the different structures. It was found that dissepiments intake isotopic oxygen and elements at different rates than other structures. This has an impact in sampling corals for environmental proxies, but, because of the very small amount of mass contained in the dissepiments that bulk analyses would not be significantly affected.

No description available.

No description available.

Detection of large-magnitude coastal events, especially in wave-dominated retrograding barrier settings, has traditionally relied upon lithological evidence, such as distinct overwash sand layers within the muddy backbarrier sequences. In tide-dominated environments, unconformities in marsh stratigraphy have been interpreted as rapid drowning or erosion events caused by large storms. In transitional mixed-energy backbarrier environments, however, clearly identifiable event horizons are rare, due to unfavorable conditions for peat formation or to a lack of overwash. To address these challenges, the present study utilized X-ray fluorescence (XRF), magnetic susceptibility (MS), and X-ray diffraction (XRD) techniques to identify anomalies within 4-to-7-m-thick sequences recovered from Sewell Point, Cape May, New Jersey. In these cores, at least five peaks were identified that exhibit up to three-to-four-fold increase in Fe (up to 6.2%) and Ti (up to 0.5%) concentrations and a substantial increase in MS values (> 200 μSI). The sand fraction at these intervals exceeds 40% and is represented by moderately well-sorted, negatively-skewed, fine-grained sand (2.7 φ). Fe, Ti, and MS are positively cross correlated due to the relatively high content of sand-sized heavy minerals such as magnetite, rutile, ilmenite and biotite, as well as phlogopite and muscovite mica. These minerals were also identified using a Rigaku Dmax/B X-ray diffraction device. Seven radiocarbon-dated in situ samples of intertidal gastropods and the few available rhizomes indicate that the Sewell Point sequence accumulated over the past 900-1,000 years, at an average sedimentation rate greater than 4.5 mm/yr, which is consistent with its proximity to a historically active tidal inlet. Lithological anomalies at Sewell Point are interpreted as the signatures of episodic large-magnitude sediment fluxes into the paleo-lagoon. The calibrated ages of organic remains (mollusks and rhizomes) constrain chronology and allow interpretation of these stratigraphic layers as event horizons with historical storms of 1594, 1743 and 1821, along with pre-historic storms in the 11th-13th centuries. This research indicates that geochemically diagnostic intervals offer an effective tool for detection of event horizons and their regional correlation in mixed-sediment backbarrier settings. / Geology

Historical records suggest that the coastlines of the British Virgin Islands (BVI) and the Sultanate of Oman have been subjected to catastrophic storm and tsunami events throughout recorded history. In 1945, a 7.8 magnitude earthquake -100 km south of Karachi, Pakistan generated a tsunami that impacted the coast of Oman and resulted in over 4000 deaths. Although the 1945 tsunami deposit has been documented, no other paleo-tsunami deposits have been identified despite the fact that historical and paleo-seismic records suggest the contrary. Similarly, the north-eastern islands of the Caribbean, particularly Anegada, BVI, have been subjected to intense hurricane strikes over the past 300 years. Due to its position relative to the Atlantic Ocean and the Puerto Rico Trench, Anegada is a potential recorder of local (e.g. 1690, 1867) and trans-oceanic tsunami events (e.g. 1755 Lisbon) as well. Potential tsunami overwash events at both locations are expected to be intermingled with marine incursions resulting from major storms and Holocene sea level change. Discerning between storm and tsunami overwash is problematic and usually favours a storm interpretation due to their frequency in the geologic record. This bias and lack of properly constrained geologic evidence has hindered the accuracy of tsunami prediction models, and subsequently, the assessment of seismic and tsunami hazards at both locations. Several studies employ the use of foraminifera to distinguish between storm and tsunami deposition; however, they are traditionally conducted in contrasting settings where differences between the terrestrial and marine realms are easily detected. Marine influenced settings lack the same degree of contrast; therefore, microfossil analysis alone is not effective. This dissertation investigates the use of foraminiferal taphonomy as an overwash indicator in two types of coastal settings: 1. a silisiclastic arid system lagoon (Sur, Sultanate of Oman), and 2. semi-tropical carbonate marine ponds (Anegada, British Virgin Islands). Although traditional microfossil taphonomic characteristics have been reported in some overwash studies, no multi-variate investigation into their usefulness as tsunami or storm indicators has previously been conducted. This dissertation shows that the surface condition (e.g. angularity, color, size, fragmentation, etc.) of foraminifera provides important information regarding the origin of overwash deposits and is useful in detecting older deposits at both locations when combined with other proxies. Several important contributions have resulted from this research: 1. Taphofacies analysis helped to constrain sediment provenance and modern nearshore hydrodynamics in an arid system lagoon that could not be achieved with traditional foraminiferal analysis alone. 2. The combined use of foraminiferal provenance and taphonomy was effective in identifying the 1945 Makran Trench tsunami at Sur Lagoon and will be a good indicator of older events at this location; a point which is particularly significant since no geologic evidence of previous tsunami events has ever been recorded. High abundances of predominantly marine taxa coupled with high abundances of large test sizes, fragments and fossil specimens were found to be indicators of tsunami deposition in contrast to lagoon deposition which was characterized by smaller test sizes and less robust lagoon taxa. 3. The preservation of the reefal dwelling Homotrema rubrum, a common encrusting foraminifer in Caribbean reef settings, provided the direction of origin of an overwash event deposited in marine ponds at Anegada and constrained the list of potential overwash candidates. Large and highly preserved Homotrema fragments that are typical of modem reef and storm wrack sediment were found in high abundances within Sand and Shell Sheet in three marine ponds at Anegada. A decrease in the abundance of highly preserved specimens from north to south throughout the ponds, coupled with mollusc taphonomic data strengthens a tsunami interpretation for the deposit. This dissertation shows that taphofacies analysis has broad application to event stratigraphy in a variety of coastal systems. Although the application of taphonomic analysis between the two contrasting environments was widely different, in both cases, taphonomic data provided indicative information regarding the origin of deposition of overwash units at Anegada, BVI and Sur, Sultanate of Oman. / Thesis / Doctor of Philosophy (PhD)

In the context of expanding public concern about the healthfulness of food, this thesis examines how health is understood and taken up in individuals’ everyday activities of eating. Sociological frameworks emphasize the complex relations shaping health practices in context; however, a greater focus on the structured nature of practice has weakened appreciation of the agent. Food scholars investigating choice and constructions of healthy food and eating categories, highlight processes involving meaning, experience, action, and identity, at work in contexts of healthy eating. To better locate the agent of health practices, and to connect a health practices approach to healthy eating scholarship, this study draws on theory and methods from the symbolic interactionist tradition in an analysis of lived experiences of healthy eating. Using ethnographic data, including qualitative interviews with 18 adopters of the Paleo Diet, and analysis techniques from grounded theory, this study aims to add nuance to current sociological understandings of health practices. Findings reveal that subjective understandings of the relationship between food and health evolve through interpretive processes involving meaning. By connecting cultural understandings of health to personal, embodied experiences, adopters achieve multilayered understandings of healthy eating that legitimate and catalyze their commitment to their diet. Facing challenges to achieving a Paleo diet, adopters, as agents, engage in material and symbolic work to create “doable” and “livable” versions of Paleo better aligned with resources, preferences, and understandings. Adopters also construct and work to maintain valued identities surrounding their practice; however, Paleo identities are spoiled identities, as adopters sought to manage conflicting expectations of what constitutes healthy eating, and impressions of who eats a Paleo diet. This thesis demonstrates how an interactionist perspective that appreciates the processual, subjective, and interactional elements of agents’ situated and contextual practices, can be usefully brought in to investigate and inform understandings of activities affecting health. / Thesis / Doctor of Philosophy (PhD)

The purpose of this study was to explore what exactly bound post-Second World War American conservatives together. Since modern conservatism's recent birth in the United States in the last half century or more, many historians have claimed that both anti-communism and capitalism kept conservatives working in cooperation. My contention was that the intellectual founder of postwar conservatism, Russell Kirk, made imagination, and not anti-communism or capitalism, the thrust behind that movement in his seminal work The Conservative Mind. In The Conservative Mind, published in 1953, Russell Kirk created a conservative genealogy that began with English parliamentarian Edmund Burke. Using Burke and his dislike for the modern revolutionary spirit, Kirk uncovered a supposedly conservative seed that began in late eighteenth-century England, and traced it through various interlocutors into the United States that culminated in the writings of American expatriate poet T.S. Eliot. What Kirk really did was to create a counter-narrative to the American liberal tradition that usually began with the French Revolution and revolutionary figures such as English-American revolutionary Thomas Paine. One of my goals was to demystify the fusionist thesis, which states that conservatism is a monolithic entity of shared qualities. I demonstrated that major differences existed from conservatism's postwar origins in 1953. I do this by using the concept of textual communities. A textual community is a group of people led by a privileged interpreter—someone such as Russell Kirk—who translates a text, for example Burke's Reflections on the Revolution in France, for followers. What happens in a textual community is that the privileged interpreter explains to followers how to read a text and then forms boundaries around a particular rendering of a book. I argue that conservatism was full of these textual communities and privileged interpreters. Therefore, in consecutive chapters, I look at the careers of Russell Kirk, John Lukacs, Christopher Lasch, and Paul Gottfried to demonstrate how this concept fleshed out from 1953 and well into the first decade of the new millennium. / Ph. D.