Dissertations / Theses on the topic 'Fossil Paleobotany Paleobotany'

Thesis (Ph. D.)--West Virginia University, 2009.
Title from document title page. Document formatted into pages; contains xi, 240 p. : ill. (some col.), maps (some col.). Vita. Includes abstract. Includes bibliographical references.

Previous studies in Yellowstone National Park (YNP) suggest intensification of the summer-dry and summer-wet patterns in Yellowstone during the early Holocene when increased summer insolation caused atmospheric circulation patterns to strengthen. To examine this hypothesis further, pollen and high-resolution charcoal records were analyzed from Blacktail Pond to reconstruct fire and vegetation histories near the present transition between summer-wet and summer-dry conditions. The site currently lies in Pseudotsuga parkland with Artemisia steppe at lower elevations around the pond. The site supported sparse tundra prior to 12,000 cal yr B.P. and fires were uncommon. Between 12,000 and 11,000 cal yr B.P, fire activity increased and Picea-Pinus parkland was established. These changes are consistent with increasing temperature and moisture. Between 11,000 and 7600 cal yr B.P., pollen evidence of a Pinus-Picea-Abies forest is consistent with increased winter moisture, while high fire activity at this time indicates that summers had lower effective moisture than at present. Between 7600 and 4000 cal yr B.P., vegetation around the site shifted to parkland dominated by Pinus, Picea, Pseudotsuga, and Artemisia indicating that effective winter moisture decreased. Fire activity continued to be high during this time suggesting summers maintained low effective moisture. The development of Artemisia steppe around the site over the last 4000 years indicates that effective winter moisture decreased, while decreased fire activity indicates that effective summer moisture increased during this time. Winter conditions during the early Holocene that resemble a summer-wet site along with summer conditions at the same time resembling a summer-dry site could be a result of the geographical setting of Blacktail Pond near the boundary between these two precipitation regimes. Poaceae/Artemisia pollen ratios were used to infer wet/dry climate oscillations during the late Holocene. The fluctuations correspond well with other paleoclimate data from northern Yellowstone National Park (Gennett and Baker, 1986; Hadly, 1996; Meyer et al., 1995), and suggest that conditions were drier from 3775-3125, 2475-2225, 1700- 675, and 425-75 cal yr B.P.

Fossil plants in the Upper Triassic Chinle Formation are preserved in fluvial channel, overbank, and lacustrine deposits. Plant-bearing units in these deposits are classified into seven types based on these depositional environments or subenvironments. Taphonomic characteristics of these assemblages, and of individual plant fossils within them, indicate that most plant fossils have either not been transported far from their growth sites or are preserved in situ. One particular deposit in the central part of Petrified Forest National Park preserves fossil plants in three associations: (1) allochthonous logs in basal lags in a channel-fill/lateral accretion deposits; (2) autochthonous horsetail trunks and parautochthonous horsetail leaves in a crevasse-splay deposits; and (3) parautochthonous and autochthonous cycadaceous, fern and other types of leaves, and erect and prostrate trunks in a paludal/distal splay deposits. Exposures of contemporaneous high-sinuosity channel and overbank deposits in this area enabled the reconstruction of the local paleogeography, paleohydrology, and paleoecology at a high resolution. Fossil plant assemblages of the Upper Triassic Chinle Formation are concentrated in the lower members of the formation. The lower part of the Chinle Formation was deposited in an incised valley system. Depositional, hydrological, and near-surface geochemical conditions in the incised valley system were conducive to preservation of terrestrial organic material, even though regional conditions were characterized by seasonal/monsoonal precipitation and groundwater conditions. Fossil plant assemblages preserved in these types of fully terrestrial incised valley-fills are taphonomically biased towards riparian wetland environments.

Thesis (Ph. D.)--University of Oregon, 2000.
Typescript. Includes vita and abstract. Includes bibliographical references (leaves 237-250). Also available for download via the World Wide Web; free to University of Oregon users.

South-western Australia is a globally significant hotspot of plant species diversity, with high endemism and many rare plant species. Proteaceae is a major component of the south-western flora, though little is known about how its diversity developed. This prompted the present study to investigate changes in the abundance and diversity of Proteaceae, in south-western Australia, by concurrently studying three sediment sequences of different ages over the Cainozoic and a modern pollen rain study. Modern pollen-vegetation relationships in the two Proteaceae species rich nodes of the northern and southern sandplains were quantified. It was found that Proteaceous genera can contribute up to 50% of the total pollen rain. Banksia/Dryandra pollen was the most abundant with Isopogon, Petrophile and Lambertia also commonly noted. The vegetation and environmental setting during three pivotal periods of the Cainozoic: Holocene, Pliocene and Eocene, were investigated. Eocene sediment from Lake Lefroy confirmed the presence of a Nothofagus dominated rainforest in the Middle to Late Eocene. At this time Proteaceae species were at least as diverse as today, if not more so, contributing up to a maximum of 42% of the total pollen rain. Taxa recorded included: Banksieaeidites arcuatus, Propylipollis biporus, Proteacidites confragosus, Proteacidites crassus, Proteacidites nasus and Proteacidites pachypolus. Several taxa remain undescribed and unnamed. This study also identified that Proteaceae pollen representation varies across small lateral distances. Thus as samples varied spatially and temporally, single core samples are not sufficient to identify spatial patterns in Proteaceae or other low pollen producing taxa. Some 7.91 cm of laminated Pliocene sediment from Yallalie, south-western Australia, was also examined. It covers 84 years of record and confirmed other regional reports that south-western Australia was covered by a rich vegetation mosaic consisting of heathy and wet rainforest elements. Although Proteaceae species were a consistent component of the pollen counts, diversity and abundance (maximum of 5%) was low throughout the studied section. Banksia/Dryandra types were most commonly noted. A 2 m core was retrieved from Two Mile Lake, near the Stirling Ranges and provided an early Holocene vegetation history. Geochemical and palynological evidence recorded little change, suggesting the environment of deposition was relatively uniform. Proteaceae species were noted throughout the core, though in low numbers, at a maximum of 3.5 % of the total pollen rain. Banksia/Dryandra was the most abundant while Isopogon, Lambertia, Petrophile and Franklandia were also noted. A regression model was developed through the modern pollen rain study to predict the number of Proteaceae in the vegetation. This was also applied to the fossil pollen records. The estimated number of Proteaceae species in the Eocene suggests a maximum of 20 and a minimum of 10 taxa. For the Pliocene record, an estimated 7 - 9 species was found and for the Holocene pollen, between 7 - 8 were present. Thus the Eocene was similar in Proteaceae diversity to today. The results from the Pliocene and Holocene suggest that Proteaceae diversity was lower than today. Findings of this research indicate that Proteaceae species are an important and consistent component of vegetation in south-western Australia over the Cainozoic. It is likely that both changing pollination mechanisms and changes in associated vegetation are important in the determining the dispersal of Proteaceaous pollen. By understanding how the vegetation has changed and developed in south-western Australia, present vegetation can be managed to include intra-specific variation and ensure the majority of species are conserved for present and future generations to enjoy.

Está demonstrado em plantas atuais que níveis atmosféricos de CO2 e frequência estomática estão inversamente correlacionados. A utilização de dados estomáticos na calibração das curvas de CO2 paleoatmosférico do Fanerozoico tem sido eficiente não apenas para o Cenozoico, mas também apresenta excelente correspondência desde o Eodevoniano. Cutículas de glossopterídeas provenientes das jazidas de carvão de Faxinal (RS) e Figueira (PR), incluídas em níveis estratigráficos distintos da Formação Rio Bonito (Sakmariano e Artinskiano respectivamente), viabilizaram análises para floras desenvolvidas sob a vigência de megaciclo icehouse. Cabe ressaltar que o uso de glossopterídeas, classificadas dentro do grupo extinto das Pteridospermophyta, esbarra na impossibilidade de se estabelecer um equivalente ecológico atual, dada a ausência de relações taxonômicas, estruturais e ecológicas com grupos viventes. Portanto, optou-se por uma abordagem proposta por outros autores como alternativa para diferentes grupos de pteridospermas, que consistiu em comparar entre si resultados de análises estomáticas na morfo-espécie Glossopteris communis Feistmantel procedente de distintos níveis associados a carvões na Bacia do Paraná. O objetivo geral do presente estudo foi estabelecer possíveis relações entre os padrões estomáticos calculados e flutuações nos teores de CO2 paleoatmosférico. A metodologia consistiu em resgatar mecanica e quimicamente as cutículas da rocha matriz, clareá-las em solução de Schulze e montá-las em lâminas de gelatina glicerinada para observação em microscopia de luz transmitida. A observação deu-se com auxílio de filtro de contraste por interferência diferencial e as contagens foram feitas com o auxílio de programa para análise de imagens. As técnicas de estudo compreenderam cálculos de densidade estomática (DE- número de estômatos por unidade de área da folha) e índice estomático (IE- percentual de estômatos sobre o total de células epidérmicas). Os resultados obtidos foram de DE média= 234,73 e IE médio= 15,7 para a jazida de Faxinal (Sakmariano) e de DE média= 284,14 e IE= 18,9 para a jazida de Figueira (Artinskiano). Esses valores enquadram-se dentro da curva global de CO2 atmosférico para o Fanerozoico (modelo GEOCARB). As frequências estomáticas mais baixas das folhas do Faxinal com relação àquelas de Figueira foram relacionadas a processo de reversão temporária da tendência global de baixos teores de CO2 atmosférico para a base do Permiano. Essa reversão é atribuída à provável influência de fatores paleoecológicos locais relativos à grande extensão das turfeiras na parte sul da bacia, responsável pela emissão em larga escala de gases-estufa. Além disso, a flora de Faxinal está preservada em uma camada de tonstein, registro de atividade vulcânica que poderia ter afetado os níveis de CO2. Por outro lado, as turfeiras de registro muito esparso ocorrentes no nordeste da bacia, em intervalo mais jovem, por sua pequena extensão e ausência de indícios de vulcanismo, não alteraram o padrão paleoatmosférico. Estudos focados no final do Paleozoico têm especial relevância porque, nesse intervalo vigoravam, nas diferentes paleolatitudes, condições ambientais análogas àquelas ocorrentes na atualidade, como a existência de calotas de gelo nos pólos e períodos de aquecimento global.
In extant plants stomatal frequency and the concentration of the atmospheric CO2 have been shown to correlate inversely. The use of stomatal data to calibrate phanerozoic paleoatmospheric CO2 curves has been considered a reliable technique not only for the Cenozoic estimates but also for results obtained since the Early Devonian. Glossopterid cuticles from Faxinal and Figueira coalfields (respectively in Rio Grande do Sul and Paraná States) from distinct stratigraphic levels in the Rio Bonito Formation allowed stomatal counting for floras developed under icehouse megacycle. However, it is important to highlight that the efficiency of Glossopteris, classified in the extinct group of Pteridospermophyta, is restricted as paleo-CO2 proxy for the Paleozoic due to the difficulty of establishing a nearest living equivalent for it, given the lack of taxonomic, structural and ecological relationships with extant groups. Thus it was here adopted an alternative approach proposed by different authors analyzing other groups of pteridosperms, which consists in comparing results obtained from the morphospecies Glossopteris communis Feistmantel between two different coal levels in the Paraná Basin. The general aim of this study was to establish possible relations between the calculated stomatal patterns and the fluctuation in the paleoatmospheric CO2 levels. The methodology consisted in mechanically and chemically isolating the cuticles from the matrix rock, bleaching them with Schulze solution and then mounting glycerin jelly slides for observation in transmitted light microscopy. The microscopic observation was made using a differential interference contrast filter and the counting was carried out with the help of software for image analysis. The study techniques included the calculation of stomatal densities (SD- number of stomata per foliar area unit) and of stomatal indices (SI- a ratio of the number of the stomata to the total number of epidermal cells). The results were mean SD= 234.73 and mean SI= 15.7 in Faxinal coalfield (Sakmarian) and mean SD= 284.14 and SI= 18.9 in Figueira coalfield (Artinskian). These values agree with the curve of global atmospheric CO2 for the Phanerozoic (GEOCARB model). The lower stomatal frequencies detected at the climax of the coal interval (Faxinal coalfield, Sakmarian) when compared to the higher ones obtained in leaves from a younger interval (Figueira coalfield, Artinskian) could be attributed to temporarily high levels of atmospheric CO2. Therefore, the occurrence of an extensive peat generating event at the southern part of the basin and the consequent greenhouse gases emissions from this environment may have been enough to reverse regionally and temporarily the reduction trend in atmospheric CO2. Additionally, the Faxinal flora is preserved in a tonstein layer, which is a record of a volcanic activity that could also imply a rise in atmospheric CO2. During the Artinskian, the scarce generation of peat mires, as revealed by the occurrence of thin and discontinuous coal layers, and the lack of volcanism evidences would be insufficient to affect the general low CO2 trend. Studies focused in the Late Paleozoic are especially relevant because of the presently shared icehouse climate with glacial-interglacial cyclicity which includes times of global warming.

The pollen, plant macrofossil and aquatic fossil stratigraphies from a transect of sites in the Sierra Nevada, California, were examined to deduce paleoenvironmental change since the late-Wisconsinan. Fossil pollen samples were compared to modern pollen samples from both sides of the Sierra Nevada crest. Modern samples corresponded largely to modern vegetation units, validating the use of pollen for this purpose in mountainous environments. Vegetation change during the Holocene was largely contemporaneous on both sides of the crest at elevations where lake cores and meadow sections were analysed. Deglaciation occurred by ca. 12,500 yr BP at a site on the east side, and by ca. 11,000 yr BP at a west side site. Prior to ca. 10,000 yr BP, few trees were found around the higher elevation sites. An open forest with trees characteristic of the modern Sierra Montane and Upper Montane forest grew around the mid- to high elevation sites by the early Holocene. Montane chaparral species, such as bush chinquapin, mountain mahogany and probably huckleberry oak, with sagebrush, were most abundant then. Along with lowered lake levels or absence of perennially standing water, and greater affinities to modern pollen samples from the more arid east side, these observations suggest drier conditions than today. However, by ca. 6500-5500 yr BP, effective precipitation increased, as shown by increases in subalpine conifers (mountain hemlock and red fir) and higher lake levels, and less affinities to modern samples from the east side. Modern vegetation developed at most sites within the last 2-3 millenia. Specific changes in the vegetation at this time included a reduction in upper elevational limits of mountain hemlock and red fir, with possible downslope retreat of whitebark pine, indicating greater cooling and/or wetter conditions. This is consistent with the record of wet meadow genesis as well as tree-ring and Neoglacial chronologies.

The Early Cretaceous (Berriasian) Hope Bay flora is one of the most diverse assemblages from the Mesozoic of Antarctica. Collected in 1902 by the Swedish Antarctic Expedition of 1901-1903 from Hope Bay at the northern tip of the Antarctic Peninsula, and described in 1913 by T. G. Halle, it has served as a classic reference collection for Jurassic and Cretaceous southern hemisphere paleobotanical studies. Because the systematics of the flora were outdated by the enormous advances in our understanding of fossil plants during the last 70 years, it was in serious need of revision. This revision has reduced the number of taxa from 61 to 42 species. Newly erected species are Otozamites rowleyi, Kachchhia schopfii, Ticoa jeffersonii, and Araucaria antarctica. New combinations are Todites grahamii and Thinnfeldia salicifolia. The genera Kachchhia, Ticoa, and Weltrichia are new occurrences at Hope Bay. Represented in the flora are members of the Hepatophyta, Arthrophyta, Pteridophyta, Pteridospermophyta, Cycadophyta, Cycadeoidophyta, and Coniferophyta. Not surprisingly, when compared with other Gondwana floras, the Hope Bay flora shows the greatest similarity with other Antarctic floras. There is also a close affinity with the floras of South America and New Zealand. Taxonomic similarity between these floras is best explained by paleogeographic proximity.
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Ce projet porte sur la reconstitution paléo-écologique d'un environnement forestier fossile retrouvé sur un plateau au sud-ouest de l'île Bylot. Il a comme objectifs 1) de préciser la chrono-stratigraphie du site; 2) d’établir une liste et une succession des différents taxons polliniques retrouvés dans les différentes unités stratigraphiques du site; 3) d’estimer leur âge et 4) d’en inférer des conditions climatiques (température et précipitations). Plusieurs coupes stratigraphiques ont été excavées puis échantillonnées afin de réaliser des analyses stratigraphiques, paléomagnétiques et polliniques. Un GPS différentiel fut également utilisé afin de caractériser à petite et grande échelle les unités stratigraphiques associées aux unités organiques fossiles. Les résultats des analyses granulométriques indiquent la séquence de dépôt suivante au sein d’une dépression dans la roche en place (schiste tertiaire) : 1) un diamicton glaciaire local ; 2) un sédiment limoneux d’origine glacio-lacustre ; 3) une unité organique tourbeuse; 4) une unité de type alluvial ; 5) un sédiment fluvio-glaciaire et 6) un diamicton glaciaire d’origine allochtone. Les analyses polliniques suggèrent une végétation similaire à celle présente près de la limite des arbres actuelle, environ 2000 km plus au sud. Les conditions climatiques plus humides et plus chaudes permettaient notamment la croissance du pin (Pinus type strobus et banksiana), de l’épinette (Picea cf. mariana), de l’aulne (type crispa et incana) et du mélèze (Larix, indifférencié). Enfin, les études paléomagnétiques et la présence d’espèces éteintes suggèrent un âge pour les dépôts organiques fossiles situé entre 2,14 et 2,15 Ma ou entre 2,581 et 3,040 Ma.
The project focuses on the paleo-ecological reconstitution of a fossil forest environment found on a plateau on the southwest part of Bylot Island, in the Canadian Arctic. The objectives were 1) to describe the chrono-stratigraphy of the site; 2) to establish a list and the succession of different pollen taxa found in organic and inorganic fossil units of the site; 3) to estimate their age and 4) to infer the past climatic conditions of the site. Several stratigraphic cuts were excavated and sampled for stratigraphic, paleomagnetic and pollen analyses. Also, a differential GPS was used to characterise the stratigraphic units associated with the organic fossil units at a small and large scale. Results of the granulometric analysis suggest the following deposition sequence starting from a depression in the bedrock (tertiary shale): 1) a glacial diamicton with local clasts; 2) a silty sediment of glacio-lacustrine origin; 3) an organic peat unit; 4) an alluvial type unit; 5) a fluvio-glacial sediment and 6) a glacial diamicton of allochtone origin. The pollen analyses suggest vegetation similar to that of the current tree-line limit, situated about 2000 km south of the site. The climatic conditions were warmer and more humid, allowing the local growth of pines (Pinus type strobus and banksiana), spruce (Picea cf. mariana), alder (Alnus type crispa and incana) and larch (Larix, undifferentiated). Paleomagnetic analyses and the presence of extinct species finally suggest an age for the organic fossil deposits of between 2,14 and 2,15 My or most likely between 2,581 and 3,040 My.

To assist in developing a more precise understanding of past climatic changes in southern Africa, further pollen analytical research is required. In the past, pollen sites in the subregion have been restricted to swampy areas such as permanent springs and peat deposits. While such sites are often rare as a consequence of the aridity of the country, rich polliniferous deposits can be found in the peatlands surrounding coastal lakes in the Maputaland Coastal Plain. The Mfabeni peatland, situated on the eastern shores of St. Lucia, contains relatively old sediments dating back to >45000 years bp at a depth of 7.80m. A multi-proxy approach, comprising radiocarbon, stable carbon isotope (513C) and palynological analysis, was applied in the investigation of Late Quaternary climatic conditions and vegetation changes along the Maputaland Coastal Plain. A single 10 m sediment core, dating back to >45000 years bp, was extracted from the Mfabeni Peatland. A detailed fossil pollen analysis of Mfabeni sediments indicated the existence of extensive Podocarpus-abundant coastal forests before ca. 44500 years bp. The onset of wetter local conditions after this time is inferred from forest retreat and the development of swampy conditions, which prevailed until ca. 25000 Cal years BP. Conditions during the Last Glacial Maximum (LGM; 18000 years BP) are inferred to have been generally colder and drier, as evidenced by forest retreat and replacement of swampy reed/sedge communities by dry grassland. A significant depletion in 813C values at ca. 18200 Cal years BP indicates the dominance of C3 vegetation during the LGM, reflecting considerably colder conditions. This is in agreement with palaeoenvironmental indications from elsewhere in the Transvaalian Ecozone, although conditions at Mfabeni were more moderated in their manifestation, which can be attributed to the proximity of this site to the ocean. Cool, relatively moist conditions are inferred for the Holocene Altithermal (ca. 8000-6000 years BP), as evidenced by forest growth and expansion during this time. Warm, dry conditions are inferred for the Late Holocene, with the establishment of grassland/savanna type vegetation in the area after ca. 2000 Cal years BP.
Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2005.