No description available.

No description available.

Large δ13C excursions present at the Permian-Triassic boundary are thought to indicate a considerable release of isotopically light carbon into the atmosphere (Retallack and Jahren, 2008). The largest of these excursions (-22.2 ‰) was measured in organic matter from Antarctica (Retallack and Jahren, 2008). Antarctic coals are known to be heavily intruded by Jurassic dikes and sills, and the δ13C values of the organic matter may have been influenced by later thermal alteration. In order to evaluate the influence of rank and maceral content on isotopic composition, a total of 335 samples described as Permian-age "coal" were obtained primarily from the United States Polar Rock Repository. Most of the organic matter from Permian coal seams in Antarctica has been extensively altered after burial by localized high heat flow and, in some cases, contact metamorphism associated with dikes and sills; this thermal alteration has likely changed the δ13C values of the organic matter. The rank of the samples prior to intrusion is estimated to be medium to high volatile bituminous. The majority of the samples analyzed (96%) have been altered to above low volatile bituminous rank based on vitrinite reflectance, most (83%) are semi- to meta-anthracites, and a few have been altered to anisotropic cokes. The samples do not follow the typical burial maturation geochemical track, as they are higher in volatile matter (%, daf) and O (%, dmmf), and lower in H (%, dmmf) than coals of the same rank that have undergone normal burial maturation. Carbon stable isotopic data indicate a weak correlation with coal rank as well as with the amount of pyrolitic carbon. Although the isotopically lightest samples measured in this study are located within what is interpreted to be the Permian-Triassic boundary, the effects of thermal alteration of organic matter on δ13C values must be considered in any interpretation of Permian-Triassic atmospheric conditions.

Magister Scientiae - MSc / Antarctica provides some of the most extreme environments on earth. Low temperatures, low water availability and nutrient deficiency are contributing factors to the limited colonisation of Antarctic biotopes, particularly in the continental Dry Valleys. The survival of microorganisms in this harsh continent provides the basis for the significance of this study. This study aimed to explore microbial phylotypic diversity across a 500 m altitudinal transect in the Miers Dry Valley, Ross Desert, East Antarctica. The study also attempted to infer from phylogenetic data, the possible presence of indicative phenotypes which might contribute to a functional microbial community. / South Africa

Subglacial water plays an important role in the regulation of an ice sheet's mass balance. It may be the dominant control on the velocities of ice streams and outlet glaciers on scales of months to millennia. Recent satellite observations of ice surface elevation changes have given researchers new insights into how subglacial water is stored and transported. Localized uplift and settling of the ice surface implies that lakes exist beneath the ice sheet that are being filled and drained on relatively short time scales. %At the base of an ice sheet water can be transported through a variety of drainage networks or stored in subglacial lakes. Here, a numerical investigation of the mechanisms of transport and storage of subglacial water and the associated time scales is presented. Experiments are carried out using a finite element model of coupled ice and water flow. The first experiment seeks to understand the relationship between the depth of a basal depression and the area over which the feature affects basal water flow. It is found that as the perturbation to a topographic depression's depth is increased, water is rerouted in response to the perturbation. Additionally it is found that the relationship between perturbation depth and the extent upstream to which its effects reach is nonlinear. The second experiment examines how the aspect ratio of bed features (prolate, oblate, or equidimensional) influences basal water flow. It is found that the systems that develop and their interactions are mediated by both the topography and the feedbacks taken into account by the coupling of the systems in the model. Features oriented parallel to ice and water flow are associated with distributed fan systems that develop branches which migrate laterally across the domain and interact with one another on monthly and yearly timescales. Laterally oriented features develop laterally extensive ponds. As the ratio of longitudinal to lateral dimension of the topography is increased, a combination of these two water distributions is seen.

Thesis (Ph.D.)--University of Melbourne, School of Earth Sciences, 2007. / Typescript. Includes bibliographical references (leaves 197-215).

The Friis Hills is an isolated plateau standing as much as 600 m above surrounding topography in the McMurdo Dry Valleys region or Antarctica.Preserved on the plateau surface is a sequence of early to middle Miocene-aged dritis. At the eastern edge of the plateau, these drifts fill a shallow paleovalley to a depth of at least 35 m. The drills are exposed in a natural cross-section where modern topography crosscuts the paleovalley. Establishing an age and an environmental interpretation for these deposits is important because Antarctic paleoclimate records are lacking from the Mid-Miocene Climate Optimum. Two drifts fill the ancient paleovalley in the eastern Friis Hills. The upper drift is here named Cavendish drift: the lower is here named Friis drift. Cavendish can be subdivided into three units, whereas Friis drift can be subdivided into two units. Each of these units is a horizontal bed that laps on paleovalley sidewalls. The lowest, Friis II, is a compact diamicton that is overlain by a nearly in-situ bedded volvanic ash. Based on [20]Ar/[39]Ar dating, the ash is 19.76 [plus/minus] 0.07 Ma old. A second diamicton, Friis I, conformably blankets Friis II and was discovered to hold fossileferous interbeds. Both Friis I and II contain erratic clasts and both are lodgemont tills deposited from small, locally derived, alpine glaciers. Bedrock striations show ice flow to the northeast at azimuths between 025? to 032?, parallel to the trend of the paleovalley axis. Above these, Cavendish I. II. and III were deposited when thick ice covered the Friis Hills. Where the Cavendish drift laps onto paleovalley sidewalls, bedrock striations show ice flow from 077? to 150?. Cavendish drift was deposited sometime alter 19.8 Ma but before 14 Ma. when the Dry Valleys glacial records show that regional glaciers became cold-based. Downcutting eventually isolated the Friis Hills plateau, resulting in the preservation of the drift sequence. This event was most likely associated with growth or the East Antarctic Ice Sheet 14 Ma ago. This age constraint means that the tills preserved in the Friis Hills date from a time just before the East Antarctic Ice Sheet expanded and became a permanent feature. Based on the age-dated stratigraphy presented in this thesis, future work focusing on fossiliferious interbeds could provide unique and important constraints on Miocene climate change. / North Dakota State University. Department of Geosciences

Investigating openwork block accumulation has the potential to further our understanding of rock weathering, the control of geological structure on landforms, the production of substrates for biological colonisation and the impacts of climate change on landform development and dynamics. Various models for the development of these landforms have been proposed. This includes in situ weathering, frost heave and wedging. Furthermore, it has been suggested that cold-based ice has the potential to preserve these features rather than to obliterate them. Blocky deposits are also frequently used as proxy evidence for interpreting palaeoclimates. The morphology and processes acting on a blockfield located on the Northern Buttress of the Vesleskarvet Nunataks, Dronning Maud Land, Antarctica (2°W, 71°S) were investigated and characterised. Given block dimensions and orientations that closely resembled the parent material and only small differences in aspect related characteristics observed, the blockfield was found to be autochthonous with in situ block production and of a young (Holocene) age. Small differences in rock hardness measurements suggest some form of aspect control on rock weathering. South-facing sides of clasts were found to be the least weathered. In comparison, consistently low rock hardness rebound values for the north-facing aspects suggest that these are the most weathered sides. Additional indicators of weathering, such as flaking and pitting, support analyses conducted for rock hardness rebound values. Solar radiation received, slope gradients and snow cover were found to influence weathering of clasts across the study site. Furthermore, ambient temperatures and wind speed significantly influenced near-surface ground temperatures dynamics. However, the lack of a matrix and paucity of fine material in textural analyses suggest a limited weathering environment. It is suggested that the retreat of the Antarctic ice sheet during the last LGM led to unloading of the surface, causing dilatation and subsequent fracturing of the bedrock along pre-existing joints, leading to in situ clast supply. Subsequent weathering and erosion along other points or lines of weakness then yielded fines and slight edge rounding of clasts.

Indiana University-Purdue University Indianapolis (IUPUI) / Petrography of the sand fraction, particle size analysis, and detrital zircon U/Pb isotope data, and pebble count data were collected from Byrd Glacier moraines and central/western Ross Sea till in order to study the glacially-driven sedimentological dynamics of the Byrd Glacier and to trace material transported from the Byrd Glacier into the Ross embayment. Most of the petrographic data show evidence of local derivation with the exception of the sites from the Lonewolf Nunataks as indicated by exotic rock types within the sand and pebble fractions. This, in conjunction with particle-size data of the samples from the Lonewolf Nunataks indicate that material from underneath the East Antarctic Ice Sheet (EAIS) is being transported to the surface and deposited in this area. The U/Pb ages of zircons from the Byrd Glacier show dominant populations of Ross to Pan-African ages (~533 - 610 Ma) with varying populations of older (Grenville to Archean) zircons. Late Precambrian (~588 – 610 Ma) aged detrital zircons in samples from the head of the Byrd Glacier are older than other dated grains found in the vicinity and may be evidence of early development of the Ross belt or represent evidence of sub-glacial extension of the Mozambique structure found in Dronning Maud Land. The west central Ross Sea till samples have a variety of mineral and lithic fragments that include a dominant population of polymict at certain depth intervals. Detrital zircon data suggests the potential provenance of two of these intervals may be derived from Marie Byrd Land and possibly the Byrd Glacier. Using sand petrography and U/Pb detrital zircon age dating, positive correlation was found between specific samples from the head of the Byrd Glacier and the western Ross Sea. The ice-sheet flow models of Stuiver et al. (1981), Licht and Fastook (1998), and Licht et al. (2005) each show potential support from aspects of this study. It is possible that dynamic ice-flow regime changes of the West and East Antarctic Ice Sheets into the Ross Sea may have occurred some time during the LGM as suggested by geochemical and petrographical evidence found within intervals of central and western Ross Sea cores.

Esta pesquisa teve o objetivo de resgatar, através da memória do trabalhador, seu cotidiano de trabalho na Companhia Antarctica Paulista de Ribeirão Preto/SP. Nesse sentido, foi investigado como o trabalhador foi contratado pela cervejaria e as funções que exerceu; a organização do trabalho e a divisão de tarefas; a rotina do trabalhador e o relacionamento com outros funcionários e com os chefes; o papel do sindicato e as possíveis reivindicações; a importância do trabalho executado e o significado de trabalhar para esta cervejaria e, por fim, o que significou o fechamento da fábrica para aqueles trabalhadores que dedicaram sua vida ao trabalho nesta indústria. Para tanto, foi utilizada a metodologia da História Oral, a partir da realização de entrevistas com ex-funcionários da Companhia Antarctica Paulista, de Ribeirão Preto/SP, escolhidos aleatoriamente, por indicação sucessiva. Após realizadas as entrevistas, foram apresentadas fotografias da fábrica, de produtos e algumas mais atuais do interior de outras fábricas da Antarctica, já que a de Ribeirão Preto já havia encerrado suas atividades para auxiliar o resgate da memória dos entrevistados. Os dados obtidos, a partir da realização das entrevistas, foram analisadas de forma qualitativa, pela qual se buscou aproximações e divergências, tanto de opiniões quanto da realidade apresentada. / This research aimed to rescue, through the memory of the workers, their daily lives working in Antarctica Paulista Company in Ribeirão Preto/SP. In this sense, it was investigated how the workers were hired by the brewery and their functions; the work organisation and the labour Division; the routine of the employees and the relationship among the staff and the chiefs; the role of the Union and the possible workers claims; the importance of the work performed by the workers and the meaning of work for this brewery and, finally, what the ending of the activities of the factory meant to the those workers who have dedicated their lives to the company. To achive this purpose, we used the methodology of Oral history, conducting interviews with former employees of Companhia Antarctica Paulista in Ribeirão Preto/SP, chosen at random, by successive indication. To assist the recovery of memory of the interviewed ones, after the interviews, photographs were presented from the factory, the products and some nowadays photographs from the inner part of other Antarctica factories since the Ribeirão Pretos plant had already closed its activities. The data obtained from carrying out the interviews, were analyzed qualitatively, by which sought both differences and approaches of opinions about the reality presented.