Regional and local changes in the climate have been driving rapid glacial retreat in many glaciers since the Little Ice Age. This retreat provides a unique opportunity to study succession across the chronosequences of glacier forelands. Patterns of plant colonization and succession on terrain exposed by retreating glaciers give insight into factors influencing alpine ecosystem change and recovery. Understanding these patterns and processes is important for conserving alpine landscapes and flora as glaciers disappear. This study sought to investigate how various biotic and abiotic factors influence plant successional patterns in the dynamic alpine environment of Sperry Glacier, a Little Ice Age, mid-latitude cirque glacier in Glacier National Park, Montana. Through field data collection, additional Geographic Information System (GIS) derived variables, and subsequent geostatistical analysis, I specifically assessed: (1.) vegetative trends (percent cover, species richness, Shannon's diversity, species evenness, composition, and species turnover) over a 170-year chronosequence, and (2.) vegetative trends over field and GIS-derived site conditions (e.g., surface fragmentation, concavity, flow accumulation, and solar irradiance). Sixty-one plots (each 8 square meters) were placed throughout the glacier foreland using a random sample stratified by terrain date. Percent cover, species richness, Shannon's diversity, and species evenness were calculated for each plot. All sampled vegetation was identified with taxonomic resolution down to species whenever possible. I assessed vegetative trends across terrain age ranges using Kruskal-Wallis and Dunn's tests. I used two models, generalized linear models (GLMs) and Classification and Regression Trees (CARTs), to assess field and GIS-derived biophysical correlates (e.g., surface fragmentation, concavity, terrain variables, and solar irradiance with vegetative trends), followed by Kruskal-Wallis tests, Dunn's tests, and scatterplots. Species richness and vegetation cover were greater on older terrain. Plant composition changed over terrain age, with Penstemon ellipticus favoring older terrain and Boechera lemmonii favoring moderately aged terrain. Moderate drainage and concave plots, which were important in the GLMs, explained increased species richness and Shannon's diversity across different site conditions. The CARTs were able to predict species richness, vegetation cover, Shannon's diversity, and species evenness with surface fragment sized from gravel to cobble, topographic position index, and flow accumulation. These findings show that both temporal and biophysical site conditions influence successional trends across the foreland, though different vegetation measures are most influenced differently. / Master of Science / Regional and local changes in the climate have been driving rapid glacial retreat in many glaciers since the Little Ice Age. This retreat provides a unique opportunity to study succession across glacier foreland terrain that has been uncovered for different lengths of time. Patterns of plant colonization and succession on terrain exposed by retreating glaciers give insight into factors influencing alpine ecosystem change and recovery. Understanding these patterns and processes is important for conserving alpine landscapes and flora as glaciers disappear. This study sought to investigate how various biotic and abiotic factors influence plant successional patterns in the dynamic alpine environment of Sperry Glacier, a Little Ice Age, mid-latitude glacier in Glacier National Park, Montana. Through field data collection, additional Geographic Information System (GIS) derived variables, and subsequent geostatistical analysis, I specifically assessed: (1.) vegetative trends (percent cover, species richness, Shannon's diversity, species evenness, composition, and species turnover) over terrain uncovered between zero and 170-year, and (2.) vegetative trends over field and GIS-derived site conditions (e.g., surface fragmentation, concavity, flow accumulation, and solar irradiance). Sixty-one plots (each 8 square meters) were randomly placed within each terrain age range throughout the glacier foreland. Percent cover, species richness, Shannon's diversity, and species evenness were calculated for each plot. Shannon's diversity is a measurement of a community's diversity and uses both species richness and evenness to calculate diversity. All sampled vegetation was identified with taxonomic resolution down to species whenever possible. I assessed vegetative trends across terrain age using several statistical comparison tests. I used two types of statistical models to assess field and GIS-derived biophysical correlates (e.g., surface fragmentation, concavity, terrain variables, and solar irradiance with vegetative trends), followed by comparison tests and scatterplots. Species richness and vegetation cover were greater on older terrain. Plant composition changed over terrain age, with the species Penstemon ellipticus (rocky ledge penstemon) favoring older terrain and Boechera lemmonii (Lemmon's rockcress) favoring moderately aged terrain. Moderate drainage and concave plots explained increased species richness and Shannon's diversity across different site conditions. Species richness, vegetation cover, Shannon's diversity, and species evenness could be predicted with surface fragments sized from gravel to cobble, topographic position index, and flow accumulation. These findings show that both temporal and biophysical site conditions influence successional trends across the foreland, though different vegetation measures are most influenced differently.

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This thesis develops a better knowledge of the extent and timing of glaciations in southern Argentina throughout the Quaternary. It provides a detailed understanding of successive major glacial outlet lobes in the Lago Pueyrredón valley. The glacial and glaciofluvial deposits in the valley, as elsewhere in the region, are extremely well-preserved and reflect punctuated glacial advances between ~ 1.1 Ma and ~ 17 ka. Several intermediate glaciations are undated, constrained by the limited time frame of radiocarbon age dating, the limited potential volcanic sites for K-Ar or 40Ar/39Ar age dating, and erosion and exhumation problems associated with cosmogenic-nuclide surface exposure ages on moraines. This thesis provides a new chronology for the mid-Quaternary glaciations based on methodological advances in cosmogenic-nuclide surface exposure age dating. This is done by deriving ages from glacial outwash terrace sediment and demonstrating their reliability. The work shows that for younger (i.e., last glacial) moraines, well-constrained ages can be derived from the common-practice of dating large boulders on the moraine surface. However, on older moraines, the ages so-derived become considerably scattered. This is interpreted to be caused primarily by boulder exhumation as a consequence of moraine erosion, resulting in shorter residence of some boulders at the surface relative to the moraine formation date. By contrast, glacial outwash surfaces in this area, if carefully chosen, can be shown to have undergone little aggradation or erosion, and thus have had long and consistent surface exposure since formation. Provided these surfaces can be stratigraphically linked with the glacial limits, they can provide good surface exposure ages. This has been convincingly confirmed in one location by a sequence of ages obtained from a 10Be concentration depth-profile which demonstrate the surface stability and lack of inherited nuclides. Using these methods, cosmogenic 10Be and 26Al surface exposure ages indicate successive major advances occurred at ~ 1.2 Ma, ~ 600 ka, ~ 260 ka and ~27 – 17.5 ka. These are correlated with global marine and ice core records.

O Subgrupo Itararé apresenta o registro sedimentar mais expressivo da glaciação que assolou a Bacia do Paraná durante o Neopaleozóico. Próximo à borda leste da bacia, em especial na área do estudo, entre os municípios de Sorocaba e Itapetininga, este registro é caracterizado basicamente por depósitos glaciomarinhos, representativos de períodos de mar relativamente mais baixo intercalados com registros de mar relativamente alto. Através da definição e análise de fácies foi possível identificar, na área do estudo, 15 (quinze) unidades faciológicas: Diamictito maciço compactado, Diamictito maciço não compactado, Diamictito maciço compactado deformado, Diamictito tabular, Diamictito lenticular, Arenito maciço tabular, Arenito maciço lenticular, Arenito com estratificação gradacional, Arenito com estratificação cruzada e granodecrescência ascendente, Arenito com estratificação cruzada de baixo ângulo e truncamentos, Siltito maciço, Siltito maciço com clastos dispersos, Folhelho ou argilito maciço, Folhelho ou argilito maciço, com clastos dispersos e Interlaminado. A análise dessas fácies, bem como seu agrupamento em associações diagnósticas (AF1, AF2, AF3 e AF4), permitiu o reconhecimento de tratos de sistemas deposicionais, TSMB, TST, TSMA e TSRGi, os quais, por sua vez, levaram à identificação de 9 (nove) seqüências de 3ª ordem, que permitiram o estabelecimento um arcabouço cronoestratigráfico para os sedimentos do Subgrupo Itararé, ao longo do perfil selecionado na área do estudo. Para se realizar a correlação pretendida entre os sedimentos do Subgrupo Itararé na área do estudo e os aflorantes na região localizada ao sul do Arco de Ponta Grossa no Paraná e Santa Catarina, foram identificados planos ou horizontes que podem ser utilizados, segundo suas características, como datum litoestratigráfico e datum bioestratigráfico. Os resultados das análises palinológicas, bem como os próprios dados físicos de superfície, demonstraram confiabilidade e viabilidade de correlação. A análise petrográfica efetuada em quatro amostras de arenitos revelou porosidades da ordem de 8 a 13%, o que permitiu caracterizar esses sedimentos como potencialmente bons para reservatórios relativamente a hidrocarbonetos ou aqüíferos. / The Itararé Subgroup (Carboniferous-Permian) of the Paraná Basin of southeastern Brazil contains the thickest, most extensive and one of the longest records of late Paleozoic glaciation in all of the Gondwana supercontinent. In the studied area, situated between the cities of Sorocaba and Itapetininga, São Paulo State, this record is characterized by glaciomarine sediments depicting intercalation of periods of high and low relative sea-level. Facies analysis of the glacigenic sediments allowed the identification of 15 lithofacie units: compact massive diamictite, massive non compact diamictite, massive non compact deformed diamictite, tabular diamictite, lenticular diamictite, massive tabular sandstone, massive lenticular sandstone, sandstone with gradational bedding, sandstone with cross bedding and normal grading, sandstone with low angle cross bedding and truncations, massive siltstone, massive siltstone with clasts, massive shale or mudstone, massive shale or mudstone with dispersed clasts and laminites. The analysis of facies and their clustering into the associations AF1, AF2, AF3 and AF4 enabled the identification of the systems tracts TSMB, TST, TSMA and TSRGi and 9 sequences of 3rd order. These provided the base to set up a local chronostratigraphic framework for the Itararé Subgroup in the studied area. In view of the possibility of correlation between the sediments of the studied area and those outcropping in the south of the Ponta Grossa arch, in the States of Paraná and Santa Catarina, some datum planes were determined. The results of the palinological analysis as well as the surface data surveyed pointed out that this correlation is feasible. Petrographic analysis of 4 samples of sandstones indicated porosities between 8 and 13 % which characterize them as potentially reservoirs for water and hydrocarbon.