Concentrations of rare earth (REE), U, Th, and other trace elements (TE) were measured using LA-ICP-MS along transects across five Late Eocene brontothere bones from the terrestrial Late Eocene Chadron Formation of Nebraska and four Miocene marine mammals from the Atlantic Coastal Plain. Samples were analyzed to determine REE diffusion periods, and to determine if histological factors affect post mortem uptake of REE/TE. In terrestrial fossil bones, concentrations of REE are highest at the bone surface and decrease with depth into the trabecular bone, consistent with diffusion-limited models. Histology may affect REE incorporation. An outer circumferential layer (OCL) is preserved along the outer 1 mm of the brontothere rib (F08-10) and femur (F08-09). REE concentrations in the OCL are much lower than in the underlying bone, indicating either lower incorporation or post fossilization leaching. REE concentrations are sometimes elevated in trabecular bone and Haversian systems, which may act as secondary diffusion pathways. REE concentration gradients are generally steeper in marine fossils than in terrestrial fossil bones, indicating longer periods of REE uptake in terrestrial fossils. Calculated periods of diffusion in terrestrial environments are 2.2 +/- 0.5 to 54.8 +/- 1.5 ka (based on a wetness factor of 0.5 +/- 0.1). Periods of diffusion for marine environments range from ca. 0.9 +/- 0.2 to 2.8 +/- 0.6 ka. However, within some terrestrial samples U is introduced into the bone over a much longer time span, possibly as a function of fluctuating redox conditions. If these values are representative, diffusion-fossilization periods are shorter in marine/lacustrine/spring/channel environments due to constant water saturation. Saturation of a bone during diffusion may also affect the morphology of REE signatures within the bone. In terrestrial bones, REE are strongly fractionated with depth, producing signatures varying from light-REE enriched at the surface to middle-REE depleted at depth. However, depth fractionation of REE is much less pronounced in marine bones, which may result from the introduction of fluid unreactive. These differences in REE fractionation are consistent with a greater influence of multiple secondary REE/TE diffusion paths in marine samples. Periods of diffusion for terrestrial samples differed within a single bonebed accumulation (2.2 +/- 0.5 to 54.8 +/- 1.5 ka). However, REE signatures are internally consistent with one another within the bonebed indicating that groundwater chemistry did vary during fossilization. If groundwater chemistry changes during diffusion, bone could be recording different signals, which has implications for using post-mortem REE/TE/Isotopes for paleoenvironmental reconstruction. Previous studies of soft tissue preservation in fossilized bone have inferred shorter periods of diffusion and suggested that the rate of diffusion must outpace the rate of decay. Diffusion periods in bone from well drained terrestrial settings are too long to preserve soft tissue. However, periods of diffusion in marine fossil bones are much shorter, suggesting the possibility for bio-molecule preservation. / Geology

Includes Publication list by the author as appendix A. "July 2003." Includes bibliographical references (leaves 308-324) A stratigraphically detailed taxonomic study of fossil bryozoans within the Late Eocene sediments of the St Vincent Basin, South Australia. These taxa are compared with existing knowledge of fossil and recent faunas in Australia and other regions to enhance understanding of bryozoan evolution and dispersal. Bryozoan taxa and growth forms are used to interpret the palaeoenvironments of the Eocene Vincent Basin.

Includes Publication list by the author as appendix A. / "July 2003." / Includes bibliographical references (leaves 308-324) / xi, 324, [36] leaves, 61 leaves of plates : ill (some col.), maps ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / A stratigraphically detailed taxonomic study of fossil bryozoans within the Late Eocene sediments of the St Vincent Basin, South Australia. These taxa are compared with existing knowledge of fossil and recent faunas in Australia and other regions to enhance understanding of bryozoan evolution and dispersal. Bryozoan taxa and growth forms are used to interpret the palaeoenvironments of the Eocene Vincent Basin. / Thesis (Ph.D.)--University of Adelaide, School of Earth and Environmental Sciences, Discipline of Geology and Geophysics, 2003?

No description available.

Durante o Eoceno e o Oligoceno (55 a 23 Ma) a Terra esteve sujeita a período de grandes mudanças climáticas. Registros geológicos, reforçados por modelos climáticos, indicam que o clima global durante esse período passou de estágio praticamente livre de calotas polares para situacao climática próxima a que hoje podemos encontrar na Antártica. Grande parte desses registros são indiretos, retirados de sedimentos de fundo marinho ou de material fóssil. Evidência terrestre clara da variação climática (greenhouse-icehouse) para o Eoceno-Oligoceno pode ser encontrada em Wesele Cove, ilha Rei Jorge, Antártica Ocidental. Tais evidências correspondem a uma sucessão de cerca de 60m com pelo menos 13 derrames de lava basáltica, de alguns metros de espessura cada, sobreposta, em contato erosivo, por diamictito e arenito. A sucessão basáltica é correlacionada com a Formação Mazurek Point/Hennequin, datada radiometricamente como do Eoceno, e o diamictito e arenito correspondem ao Membro Krakowiak Glacier da Formação Polonez Cove, datada, paleontológica e radiométricamente como pertencente ao Oligoceno inferior. Cada camada de basalto toleítico exibe uma zona inferior, mais espessa (1 a poucos metros), de rocha fresca, que é seguida transicionalmente por uma zona de alteração, variando de alguns decímetros a 1-1,5 m de espessura. O pacote de basalto está inclinado 25º para leste, provavelmente por tectonismo. A sucessão foi recentemente exposta devido ao rápido recuo da atual geleira Wyspianski. A evidência inicial de campo sugere que a sucessão representa um registro geológico de variação paleoclimática de condições mais amenas para condições glaciais, que pode ser correlacionada com a mudança do ótimo climático do final do Eoceno (greenhouse) para as condições de icehouse do Oligoceno, registradas na curva de paleotemperatura cenozóica estabelecida pela determinação de 18O em carapaças de foraminíferos. Este estudo teve como foco central a análise estratigráfica e geoquímica da ocorrência, a fim de interpretar a sucessão de eventos paleoclimáticos documentados no afloramento e analisá-los, no contexto da história paleoclimática da Antártica. Os dados obtidos mostraram que a transição de zonas não alteradas para alteradas observada em cada derrame de basalto pode de fato ser atribuídas à ação moderada de processos intempéricos no topo de cada derrame. Eles também demonstram uma origem glacial, em parte subglacial com contribuição marinha, dos diamictitos sobrepostos, que apresentam feições, tais como, clastos de litologias e tamanhos variados, facetados e estriados, clastos tipo bullet shaped, clastos partidos por congelamento, estrias intraformacionais e fósseis marinhos encontrados na matriz do diamictito. As condições climáticas amenas responsáveis pelo intemperismo do basalto durou até o surgimento do último horizonte de lava, seguida por movimentação tectônica que inclinou o pacote. Esses eventos indicam condições paleoclimáticas menos rigorosas relativamente longas durante o Eoceno, precedendo o estabelecimento do manto de gelo oligocênico nesta parte da Antártica. / During the Eocene and Oligocene (55 23 Ma) the Earth was undergoing a period of great climatic changes. Geological records, reinforced by climate models indicate that global climate during this period went from a stage in which the Earth was virtually free of polar ice caps to a stage close to what we find today in Antarctica. Most of these records are indirect, taken from the deep-sea cores or fossil material. Clear terrestrial evidence of climate change (greenhouse-icehouse) for the Eocene-Oligocene transition is found in Wesele Cove, King George Island, West Antarctica. This evidence includes a succession of at least thirteen, few meters thick, basaltic lava flows overlain disconformably by diamictite and sandstone. The basaltic section is correlated with the Mazurek Point/Hennequin Formation, radiometric dated as Eocene, and the diamictite and sandstone correspond to the Krakowiak Glacier Member of the Polonez Cove Formation, dated as Early Oligocene, on paleontological and radiometric basis. Each tholeiitic basalt layer exhibits a lower, thicker (1 to few meters) fresh zone, transitionally followed up by a zone of saprolith, varying from decimeters to 1-1.5 m in thickness. The entire basalt package of around 60 m, is tilted 25º to the east. The succession has been recently exposed due to fast retreat of the present Wyspianski Glacier. The initial field evidence suggests that the succession represents the geological record of paleoclimatic variation from mild to glacial conditions, that could correlate with the change from the late Eocene optimum climatic (greenhouse) to icehouse conditions in the Oligocene, as recorded on the Cenozoic paleotemperature curve established by 18O determinations on calcareous foram tests. This study had focus on the stratigraphy and geochemistry analysis of the occurrence, in order to interpret the succession of palaeoclimatic events documented in outcrop and analyze them in the context of paleoclimatic history of Antarctica. Data obtained consistently showed that the supposed transition from unaltered to altered zones observed in each basalt layer may in fact be assigned to the moderated action of weathering processes on top of each flow. They also demonstrate a glacial, in partly subglacial with marine contribution, origin for the overlying diamictites, which has features such clasts of diverse lithologies and sizes, faceted and striated clasts, bullet shaped clasts, clasts broken by freezing and thaw, intraformational striae and marine fossils found in the matrix of the diamictite. The mild paleoclimatic conditions responsible for weathering of the basalt lasted until the emplacement of the highest lava horizon, followed by tectonic movement that tilted the package. These events indicate a relatively long paleoclimatic mild conditions during the Eocene, preceding the establishment and displacement of the Oligocene ice-sheet in this part of Antarctica.

The climatic history of the planet Earth is characterized by long- and short-term climatic variations. Oxygen isotopic data clearly shows how during the Cenozoic (from 65 Ma to the present) our planet shifted over time, from greenhouse to icehouse climate states up to the present. Along this progressive cooling, the record is dotted by rapid warming and cooling transient events, from which the causes are not yet fully understood. One problem with paleoceanographic reconstructions is that the older the event, the harder it is to find a sedimentary record in which the paleoclimatic proxies are preserved enough to be used with confidence. This work has the goal of illustrating the possibility to develop a new paleoenvironmental indicator based on the magnetic properties of magnetite crystals synthetized by magnetotactic bacteria. The sensibility of such crystals to small changes in dissolved oxygen content in the pore water and water column is well known, and can be exploited to reconstruct such changes from the sedimentary record. Qualitative information regarding this topic are defined in scientific literature, but, so far, no quantitative study has been performed. This is the first attempt to quantify the preservation of biogenic magnetite as a function of oxygenation state of waters, and is based on recent sediment extracted from cores collected in the coastal region of Rio de Janeiro (Saco do Mamanguá, Paraty). From these, where it was possible to obtain magnetic data relative to magnetite crystals together as well with as direct measurements of pore water chemistry. The results of this first attempt were used to analyze climatic and oceanographic conditions in two other sites, representative of key past environmental events during the Paleocene. The first case study was performed in a newly descripted sedimentary outcrop in central Turkey, of middle Eocene age, representative of a period of rapid warming (Middle Eocene Climatic Optimum, MECO). The second case study was done using material from a marine sediment core collected in the Ross Sea (Antarctica) that covers from the late Eocene to the Middle Miocene, a period that saw the onset of the modern, permanent ice sheet cover in the Antarctic continent. / A historia climática da Terra é caracterizada por variações climáticas de curto e longo prazo, com variações de condições, as vezes extremas. Dados de isótopos de oxigênio mostram claramente que durante o Cenozoico (desde 65 Ma até o presente) o nosso planeta passou de uma fase quente caracterizada por marcado efeito estufa (durante o Paleoceno) para um período progressivamente mais frio em direção ao presente. Ambos esses estados são caracterizados pela alternância de eventos transientes quentes e frios de relativa curta duração, sendo que destes a maioria ainda não é plenamente compreendida. Um dos principais problemas das reconstruções paleoceangráficas é que quanto mais antigo o evento mais difícil encontrar sequências sedimentares cujo registro de proxies paleoambientais seja preservado e confiável. Este trabalho visa explicitar a possibilidade de desenvolver um novo indicador paleoambiental, baseado em propriedades magnéticas de cristais de magnetita biosintetizados por bactérias magnetotáticas. Tais cristais biogênicos são notavelmente sensíveis a pequenas variações de oxigênio dissolvido na coluna de água e na agua intersticial entre os poros dos sedimentos marinhos, e essa sensibilidade pode ser explorada para reconstruir variações climáticas no registro sedimentar do passado. Informações qualitativas estão disponíveis na literatura cientifica mas, até agora, não existem estudos que quantifiquem essa relação. Esta primeira tentativa de quantificar a preservação de magnetita biogênica em função do estado de oxigenação de águas se baseia em testemunhos coletados na costa do estado do Rio de Janeiro (Saco do Mamanguá, Paraty), onde foi possível coletar dados magnéticos relativos aos cristais de magnetita biogênica concomitantemente a medidas diretas de química da água intersticial. Os resultados desse primeiro estudo foram aplicados para reconstruções de variações climáticas e oceanográficas em duas seções que registram importantes mudanças climáticas durante o Paleogeno. No primeiro caso, um afloramento localizado na Turquia central de idade Eocenica e representativo de um período de rápido aquecimento (Ótimo Climático do Eoceno Médio, Middle Eocene climatic Optimum, MECO). No segundo caso, um testemunho coletado no Mar de Ross (Antártica) que abrange o período entre o Eoceno superior e o Mioceno médio, durante o qual houve a formação da primeira cobertura de gelo permanente no continente antártico.

The age of the Bridgerian/Uintan boundary has been regarded as one of the most important outstanding problems in North American Land Mammal “Age” (NALMA) biochronology. The Bridger Basin in southwestern Wyoming preserves one of the best stratigraphic records of the faunal boundary as well as the preceding Bridgerian NALMA. In this dissertation, I first developed a chronological framework for the Eocene Bridger Formation including the age of the boundary, based on a combination of magnetostratigraphy and U-Pb ID-TIMS geochronology. Within the temporal framework, I attempted at making a regional correlation of the boundary-bearing strata within the western U.S., and also assessed the body size evolution of three representative taxa from the Bridger Basin within the context of Early Eocene Climatic Optimum. Integrating radioisotopic, magnetostratigraphic and astronomical data from the early to middle Eocene, I reviewed various calibration models for the Geological Time Scale and intercalibration of 40Ar/39Ar data among laboratories and against U-Pb data, toward the community goal of achieving a high precision and well integrated Geological Time Scale. In Chapter 2, I present a magnetostratigraphy and U-Pb zircon geochronology of the Bridger Formation from the Bridger Basin in southwestern Wyoming. The ~560 meter composite section spans from the lower Bridger B to the Bridger E, including the Bridgerian/Uintan NALMA boundary in the uppermost part of the section. Analysis of samples from 90 sites indicates two paleomagnetic reversals that are correlated to an interval spanning Chrons C22n, C21r, and C21n by comparison to the Geomagnetic Polarity Time Scale (GPTS). This correlation places the Bridgerian/Uintan faunal boundary within Chron C21n, during the initial cooling phase following the peak of the Early Eocene Climatic Optimum. Based on the bio- and magnetostratigraphic correlation, I provide correlation of other Bridgerian/Uintan boundary-bearing sections to the GPTS, demonstrating that in the western North America, the Bridgerian/Uintan boundary occurs everywhere in Chron C21n. In addition, U-Pb zircon geochronological analyses were performed on three ash beds from the Bridger Formation. High-precision U-Pb dates were combined with the paleomagnetic polarity data of the same ash beds as well as the integrative chronostratigraphy of the basin to assess prior calibration models for the Eocene part of the GPTS. The data from the Bridger Formation indicate that the Option 3 age model of Westerhold et al. (2008) best reconciles the geochronological data from all of the ash beds except for one. Thus I favor this Option 3 model, which indicates the ages of 56.33 Ma and 66.08 Ma for the Paleocene-Eocene Thermal Maximum and Cretaceous/Paleogene boundary, respectively. In Chapter 3, the body size evolution of three mammalian taxa from the Bridgerian NALMA was analyzed within the context of Bergmann’s Rule, which poses a correlation between the size of endotherms and climate (latitude). The Bridgerian NALMA is from a time of global cooling following the peak of the Early Eocene Climatic Optimum, thus according to Bergmann’s Rule, the Bridgerian mammals are expected to increase in size. This hypothesis is tested among Notharctus, Hyopsodus, and Orohippus, using the size of molar dentition as a proxy for their body size. These taxa represent three different ecomorphs, and I investigated if these taxa showed a pattern of body size change consistent with the prediction made by Bergmann’s Rule, and how their ecological adaptation may have affected their response to the climate change. Prior to analyzing the body size evolution, specimens of Notharctus and Hyopsodus were identified to species based on dental characters. This practice differs from previous studies in which species identification relied on relative size of the individuals and stratigraphic levels of origin. Within the new framework of morphologically determined species identification, five species of Notharctus were recognized, among which, N. pugnax, N. robustior and N. sp. indet. exhibited statistically significant body size increase in the time span of interest. Based on morphological analyses of Hyopsodus dentition, I recognized five species. Dentition-based body size analysis showed that H. lepidus and H. despiciens exhibited a statistically significant change towards larger size within the sampled interval. When analyzed at the generic level, a statistically significant increase was observed for both Notharctus and Hyopsodus. Finally, a genus-level analysis of Orohippus showed a lack of statistically significant size increase over the study interval. Thus, among the three taxa from the Bridgerian, Bergmann’s Rule is supported by Notharctus and Hyopsodus, at least at the genus level, but not by Orohippus, although the patterns are more variable at the intraspecific level. In Chapter 4, 40Ar/39Ar dates were obtained from sanidines from the middle Eocene Henrys Fork tuff and Upper Carboniferous Fire Clay tonstein, with the goal of making highly precise measurements of these two samples, keyed to the Fish Canyon monitor standard. Analytically, both samples were well characterized, as had been shown previously. The irradiation disk was arranged such that there would have been control from the Fish Canyon surrounding each of the unknown pits. However, due to several complications in the lab during the course of the experiment, only the analyses from one run disk (Disk 677) were of the quality needed for the goals of the study. As a result, the Fish Canyon sanidine standards that were irradiated near the center of the irradiation disk had to be discarded, and thus, the neutron fluence could not be mapped out precisely across the entire disk. The 40Ar/39Ar age relative to Fish Canyon sanidines is 47.828 ± 0.205 Ma and 311.937 ± 1.282 Ma for the Henrys Fork tuff and Fire Clay tonstein, respectively (1σ, including error on the age of the monitor). Because the ages were both offset about the same amount, I explored the option of using the U-Pb ID-TIMS ages of the Henrys Fork tuff and Fire Clay tonstein to test the agreement in the chronometers. The Henrys Fork tuff was dated at 48.260 ± 0.107 Ma (1σ, including error on the age of the monitor) using the Fire Clay sanidines and assuming its age is the U-Pb zircon age. The Fire Clay tonstein was dated at 314.593 ± 0.699 Ma (1σ, including error on the age of the monitor), using the Henrys Fork sanidines and assuming its age is the U/Pb zircon age. Although the complications encountered render these data unpublishable, they show great promise as the ages of each sanidine sample, tied to the other ash using the other ash’s U-Pb age, give results that are in close agreement between the two chronometers on the same sample (e.g., 314.593 ± 0.699 Ma vs. 314.554 ± 0.020 Ma at 1σ for sanidine and zircon respectively from the Fire Clay tonstein, and 48.260 ± 0.107 Ma vs. 48.265 ± 0.008 Ma 1σ for sanidine and zircon respectively from the Henrys Fork tuff).

Les plus anciens anthropoïdes fossiles sont issus de plusieurs formations géologiques asiatiques de l'Eocène moyen à tardif (47 à 34 millions d'années), parmi lesquelles la formation de Pondaung (Birmanie) a délivré la faune la plus diverse. L'objectif de cette thèse est de reconstituer la paléogéographie, l'environnement et le climat de l'Eocène birman afin de mieux comprendre leur histoire évolutive. Dans un premier temps, l'évolution de la provenance du sédiment de Birmanie centrale a été étudiée par une approche alliant pétrographie, lithostratigraphie et géochimie isotopique. L'étude montre que la Birmanie centrale est restée à l'écart de tout apport sédimentaire himalayen et tibétain et formait, à l'Eocène, une bande côtière connectant l'avant-pays indien avec la région de la Sonde. Les paléoenvironnements de la formation de Pondaung ont ensuite été reconstitués par une approche combinant sédimentologie fluviale, pédologie et paléobotanique. Ces approches révèlent un paysage de marécages saisonniers, de forêts ripariennes et d'espaces ouverts, développés sous un climat tropical à forte saisonnalité. Les bois fossiles identifiés représentent différents écotones forestiers similaires à ceux des forêts de mousson actuelles. L'étude en isotope stable de gastéropodes fossiles et de dents de mammifères confirme un régime de précipitation semblable à la mousson moderne. Les paléoenvironnements de Pondaung contrastent avec l'idée d'épaisses forêts primaires comme habitat préférentiel des premiers anthropoïdes et lient leur biodiversité aux zones tropicales saisonnières, où les plus grosses espèces, comme les amphipithécidés, étaient particulièrement compétitives. / The fossil record of the first anthropoids is currently fed by several Middle to Late Eocene Asian strata (47 to 34 millions years ago), of which the Pondaung Formation in Myanmar has yielded the most diverse and prolific fauna. The aim of this PhD is to reconstruct the paleogeography, paleoenvironments, and paleoclimate of the Eocene Burmese successions in order to better constrain the early evolutionary history of the anthropoids. The sediment provenance of central Myanmar was first studied using a multi-proxy approach, combining petrography, sedimentology and isotope geochemistry. Results show that central Myanmar was isolated from any Himalayan or Tibetan input and additionally formed a narrow coastal band linking the Indian foreland with the Sunda area during the Eocene. Alluvial palaeoenvironments of the Pondaung Formation were then reconstructed through a combined sedimentological, pedological and paleobotanical approach. Results revealed a mosaic landscape with seasonal swamps, riparian forests, and open areas, expanding under a tropical climate with significant seasonality. Fossil woods form different ecotones similar to those of modern days monsoonal forests. Paleoclimate reconstruction through stable isotope geochemistry on mammalian fossil teeth and fossil gastropods confirms a monsoonal, modern-like rainfall regime in the Eocene. Pondaung paleoenvironments contrast with the idea of Eocene evergreen rainforests as a preferential living environment for the first anthropoids and link the Eocene biodiversity of anthropoid fauna to the tropical seasonal areas, where the biggest species, such as the amphipithecids, were particularly competitive.

Os depósitos cenozoicos da Antártica Ocidental, especialmente aqueles da transição Eoceno-Oligoceno, fornecem importantes dados geológicos sobre as mudanças climáticas ocorridas ao longo da Era Cenozoica e de seu impacto na biosfera austral. Assembleias fósseis, incluindo de foraminíferos, foram relatadas para unidades de todas as épocas cenozoicas, em afloramentos dos arquipélagos James Ross e Shetlands do Sul. Todavia, os diamictitos das Formações Hobbs Glacier (Mioceno) e Weddell Sea (Plio-Pleistoceno), que afloram nas ilhas James Ross e Seymour, ainda não haviam sido alvo de análises micropaleontólogicas visando a obtenção de microfósseis com paredes inorgânicas. Foram analisadas amostras de 12 seções estratigráficas da Ilha Seymour, incluindo estratos do topo da Formação La Meseta (Eoceno) e de diversos níveis das formações Hobbs Glacier e Weddell Sea. Pela primeira vez foram encontradas assembleias de microfósseis com paredes inorgânicas, constituídas principalmente por foraminíferos, na porção superior da Formação La Meseta e em estratos das formações Hobbs Glacier e Weddell Sea. Na Formação La Meseta foram encontrados restos autóctones ou parautóctones de foraminíferos Textularia sp., primeira ocorrência do gênero para a unidade. Na Formação Hobbs Glacier, a assembleia autóctone ou parautóctone melhor preservada é composta pelo foraminífero lagenído Oolina stellula e pelo radiolário Larcopyle polyacantha. O foraminífero rotaliído Bolivina sp. é raro e representa um resto alóctone na unidade. Para a Formação Weddell Sea, a assembleia autóctone ou parautóctone melhor preservada é constituída pelo foraminífero lagenído Favulina hexagona e pelo planctônico Globigerinita uvula, além do rotaliído Globocassidulina subglobosa e do radiolário L. polyacantha nos mesmos e em outros níveis. Nos depósitos miocênicos e plio-pleistocênicos ocorrem também foraminíferos aglutinados grandes de táxons típicos de mar profundo, cujas feições tafonômicas indicam sua reelaboração a partir de depósitos mais antigos, possivelmente do Paleoceno, tendo em vista sua associação tafonômica e estratigráfica com o foraminífero Reticulophragmium garcilassoi, um fóssil-índice dessa época. Além de R. garcilassoi, ocorrem outros táxons típicos de assembleias de mar profundo na Formação Hobbs Glacier, como Alveolophragmium orbiculatum, Ammodiscus sp. nov., Ammodiscus pennyi, Ammomarginulina cf. aubertae, Bathysiphon sp. 1, Bathysiphon sp. 2, Cyclammina placenta e Nothia robusta. Na Formação Weddell Sea, as grandes formas aglutinadas são representadas por Ammodiscus sp. nov., Bathysiphon sp. 1, Budashevaella cf. laevigata, Cyclammina cancellata, Glomospira charoides, Saccammina grzybowski, Sculptobaculites barri e Verneulinoides cf. neocomiensis. Alguns táxons da Ilha Seymour podem ser associados àqueles dos depósitos paleocênicos da Nova Zelândia e Nova Guiné, sugerindo alguma correlação cronológica. Embora o registro fossilífero das formações La Meseta, Hobbs Glacier e Weddell Sea seja rarefeito, foi possível identificar restos autóctones ou parautóctones que indicaram a composição parcial das comunidades infaunais e planctônicas que habitavam a região durante a deposição das unidades. Os poucos fósseis-índice encontrados corroboram as idades já propostas paras as formações. Para a Formação Weddell Sea, as assembleias autóctones ou parautóctones e as formas planctônicas permitiram redefinir o contexto deposicional da unidade como glacio-marino, e não plenamente glacial, como anteriormente proposto. / Western Antarctic deposits, especially those from the Eocene-Oligocene transition, provide important geological data on Cenozoic global climate changes and their impact on the southern biota. Fossil assemblages, including foraminifers, are known from geological units from all Cenozoic epochs, in outcrops of the James Ross and South Shetlands archipelagos. However, the diamictites of Hobbs Glacier (Miocene) and Weddell Sea (Plio-Pleistocene) formations, exposed in James Ross and Seymour islands, were never subjects of micropaleontologic analysis targeting inorganic-walled microfossils. Twelve stratigraphic sections on Seymour Island were analyzed, including the top of the La Meseta Formation (Eocene) and several strata of Hobbs Glacier and Weddell Sea formations. Assemblages of inorganic-walled microfossils, composed mainly of foraminifers, were found for the first time in the La Meseta Formation and in strata from the Hobbs Glacier and Weddell Sea formations. Autochthonous or parautochthonous remains of the foraminifer Textularia sp. were found in the La Meseta Formation, being the first occurrence of the genus in this unit. The best preserved autochthonous or parautochthonous assemblage from Hobbs Glacier Formation is composed of the Lagenid foraminifer Oolina stellula and radiolarian Larcopyle polyacantha. The Rotaliid foraminifer Bolivina sp. is rare and represents an allochthonous elements in this formation. In the Weddell Sea Formation, the best preserved autochthonous or parautochthonous assemblage is composed of the Lagenid foraminifer Favulina hexagona and the planktonic Globigerinita uvula, as well as the Rotaliid foraminifer Globocassidulina subglobosa and the radiolarian L. polyacantha in the same and in other strata. In these Miocene and Plio-Pleistocene deposits also occur large agglutinated foraminifers typical of the deep sea, whose taphonomic features indicate their reelaboration from older deposits, possibly from the Paleocene, given their taphonomic and stratigraphic association with the foraminifer Reticulophragmium garcilassoi, a Paleocene index-fossil. Besides R. garcilassoi, other typical deep-sea taxa occur in the Hobbs Glacier Formation, such as Alveolophragmium orbiculatum, Ammodiscus sp. nov., Ammodiscus pennyi, Ammomarginulina cf. aubertae, Bathysiphon sp. 1, Bathysiphon sp. 2, Cyclammina placenta and Nothia robusta. In the Weddell Sea Formation the agglutinated specimens are represented by Ammodiscus sp. nov., Bathysiphon sp. 1, Budashevaella cf. laevigata, Cyclammina cancellata, Glomospira charoides, Saccammina grzybowski, Sculptobaculites barri and Verneulinoides cf. neocomiensis. Some taxa from Seymour Island also occur in the Paleocene deposits of New Zealand and New Guinea, suggesting some chronological correlation. Although the fossil record of the La Meseta, Hobbs Glacier and Weddell Sea formations is sparse, it was possible to identify autochthonous or parautochthonous remains that indicate the partial composition of the infaunal communities and plankton that thrived in the area during the deposition of the units. The few index-fossils found corroborate the ages already indicated for the deposits. For the Weddell Sea Formation, the autochthonous or parautochthonous assemblages and the planktonic specimens allowed the redefinition of its depositional setting as glacial-marine, and not fully glacial, as previously proposed.

A study of a 250 ft. (76.2 m) stratigraphic interval that includes the Eocene-age Felix coal of the Wasatch Formation was undertaken in the Powder River Basin of Wyoming to establish a depositional model based on the interrelations of coal-seam geometry, coal maceral composition, and spatial distribution of adjoining rocks. Regional cross sections and maps of major rock bodies were prepared from 147 measured stratigraphic sections and 56 geophysical logs. Trends in maceral and chemical properties within the Felix coal were identified from petrographic and geochemical analyses of 72 coal channel samples. The combined data sets indicate that the thickest portions of the coal are underlain by widespread, interconnected, sandstone-dominated fining-upward sequences (< 50 ft. or 15 m thick over a 300 sq. mi. or 777 sq. km area) whereas areas of thin or split coal are underlain by stacked predominantly fine grained, coarsening-upward sequences (< 50 ft. or 15 m thick). Above the coal, fining-upward sequences are concentrated over thin coal areas and widespread (> 20 mi., 32 km wide) coarsening-upward sequences overlie thick coal areas. Megascopic and petrographic description of the coal indicates that the brightest coal contains the greatest amount of huminite. This type coal occurs in the lowest portion of the seam and directly above clay partings in thick coal areas and in split benches · on the margin of the deposit. The central and upper portion of the seam is predominantly dull, and inertinite percentages increase towards the top of the seam. The deposits below the Felix resulted from north-northwest flowing meandering rivers. Thick peat represented by thick portions of the Felix coal accumulated upon this sandstone-dominated, poorly compactible platform that was free of sediment influx. Areas of thin and split Felix coal, underlain by fine-grained, more-compactible sediments, attracted water-borne elastics that interrupted peat accumulation. The base and split portions of the seam are the remains of predominantly coniferous trees that grew within a nutrient-rich environment, and the duller central and upper portions of the seam indicate oxidation associated with a raised peat deposit. Ash falls and fires during late stages of peat accumulation may have contributed to the demise of the swamp. After vegetation died large lakes formed and were subsequently filled by crevasse deposits from streams. The final phase of compaction of the fine-grained lake sediments and the thick underlying peat attracted anastomosed alluvial channels.