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Williams, David J. "The provenance of middle Eocene to late Eocene sands, Willunga Embayment, South Australia /." Title page, table of contents and abstract only, 1989. http://web4.library.adelaide.edu.au/theses/09S.B/09s.bw722.pdf.
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Rivero, Cuesta Lucía. "Response of Phytoplankton to Climatic Changes during the Eocene-Oligocene Transition at the North Atlantic ODP Site 612." Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-256769.
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The development of modern glacial climates occurred during the Eocene-Oligocene transition (34 to 35.5 Ma) when a decrease of atmospheric CO2 led to a global temperature fall. The ocean was deeply affected, both in the surface and the deep-sea, suffering a strong reorganization including currents and phytoplankton distribution. Spanning that time, 35 samples from the North Atlantic Ocean Drilling Program Site 612 have been analyzed by counting coccoliths abundance in different size groups (< 4 µm, 4 to 8 µm and > 8 µm) and silica fragments abundance. Absolute coccoliths abundance were estimated with two different methods, the “drop” technique and microbeads calibration. In addition, a fragmentation index was calculated to assess the preservational state of the samples. The results obtained fit in the global picture of a decrease in phytoplankton abundance across theEocene-Oligocene boundary, although coccolith and silica fragments abundances show slight different patterns. Absolute abundances estimates showed a large difference between the “drop” and the microbeads methods. The temperature at which samples are dried seems to affect microbeads distribution, leading to an underestimation at temperatures higher than 60º C. In future work the current dataset will be updated with additional calibration and replicate counts to confirm that the “drop” estimates are the more valid results. As the fragmentation index was fairly constant in all samples, no major differences in nannofossil preservation were inferred. Coccoliths abundance drops are thought to be triggered by global temperature fall, general decrease of atmospheric CO2, changes in oceanic circulation, pulses of nutrients or a combination of those.<br>Under tidsspannet som täcker övergången mellan eocen och oligocen, för ungefär 35.5 till 34 miljoner år sedan, genomgick jordens klimat en stor förändring. Under eocen hade vår planet ett varmare klimat och var i ett så kallat ”greenhouse state”. Mot slutet av denna period och i början av oligocen skiftade emellertid klimatet till en kallare regim, ett så kallat ”icehouse state”. Under detta tillstånd minskade andelen koldioxid i atmosfären vilket medförde att den globala temperaturen minskade. Vidare påverkades också havet och speciellt de fytoplankton som levde där, då de påverkas av temperatur och inflödet av näringsämnen. Fytoplankton står för en betydande del av jordens pågående fotosyntes samt är basen av den organiska matkedjan. Syftet med denna undersökning är att studera förekomsten av coccoliter, små kalcitplattor som produceras av en typ av nannoplankton som kallas coccolitoforider. Coccoliter från en djuphavskärna härstammande från norra Atlanten har därför samlats in och för-ändringen av mängden fytoplankton över nämnda tidsspann mätts. Vidare har också bitar av kisel från andra växtplankton räknats. Resultatet av denna studie var att båda grupperna var rikligare under den sista delen av eocen men mängden sjönk snabbt i början av oligocen. Det finns inte tillräckligt med information för att reda ut orsakerna av detta, men det är troligt att minskningen i temperatur och CO2-tillgängligheten för fotosyntesen är viktiga faktorer.
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Kordesch, Wendy E. C. "Middle Eocene greenhouse climate instability." Thesis, University of Southampton, 2016. https://eprints.soton.ac.uk/402327/.
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Understanding warm climate states is increasingly important as projections of anthropogenic climate change indicate atmospheric carbon dioxide concentrations in the coming century not previously seen on Earth for tens of millions of years. The Eocene (~56-34 Ma) is a critical period in the long-term Cenozoic climate evolution, encompassing the transition from widespread greenhouse warmth and high atmospheric carbon dioxide levels pervasive during the early Eocene to an icehouse world with major Antarctic ice sheets and cooler temperatures. Increasingly, it has become apparent that global climate during this transition was not gradual; the middle Eocene is characterized by significant short-term climate variability with recent findings including both transient warming and cooling events. However, the timing, and nature of many of the climate fluctuations during this interval are poorly constrained. To this end, this thesis aims to better characterize the long-term background trends and investigate the nature of short-term transient perturbations during the greenhouse climate of the middle Eocene. In Chapter 2, new nine million year long benthic foraminiferal stable isotope records (~46 to 38 Ma) generated from recently drilled equatorial Pacific sediments with excellent age control are presented. These are the first records to document that the seven enigmatic equatorial Pacific Carbon Accumulation Events (CAEs) are not associated with transient global cooling and/or glaciation events, as previously hypothesized. Further, new carbonate accumulation records in Chapter 3 provide the first robust evidence for the presence of CAEs 3 and 4 in the Atlantic basin. Together, these findings constrain the feasibility of potential CAE forcing mechanisms and imply that there are only two viable mechanisms; (1) solute flux from continental weathering, and (2) increased organic carbon burial from marine assemblage changes. A new compilation (including new and published records) of carbonate accumulation records from a paleodepth transect (2-4 km) in the Atlantic and Pacific basins provides the first multi-basin look at deep-sea carbonate burial at high temporal resolution across the Middle Eocene Climatic Optimum global warming event (~40 Ma). New CCD and lysocline interpretations reveal for the first time that multiple rapid fluctuations (< 100 kyrs) and extreme lysocline shoaling (reaching > 2 km water depth) are superimposed on long-term trends. This finding implies multiple pulses of carbon input to the ocean–atmosphere system during the MECO and provides critical time constraints to potential forcing mechanisms, which have so far remained elusive. In the final Chapter 4, new lithological and geochemical data from the Atlantic and Pacific Basins are presented which reveal the global nature of the transient ‘C19r event’ (~41.5 Ma) and confirm that the event meets the criteria to be defined as a ‘hyperthermal’. Further, analyses of the stable isotope datasets suggests that the C19r event was not exceptional and is one (albeit the most extreme) of a large number of transient ‘warming’ events throughout the middle Eocene, adding to the growing body of data implying that hyperthermal occurrence is pervasive outside of the very warm late Paleocene and early Eocene.
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Murray, Alison M. "The Eocene cichlids (Perciformes:Labroidei) of Mahenge, Tanzania /." Thesis, McGill University, 2000. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=37794.
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A new genus and five new species of fossil cichlid fishes (Perciformes: Labroidei) are described from Mahenge, Tanzania. These cichlids represent the oldest confirmed fossils of the family, dating from the middle of the Eocene. The specimens share many lepidological characters, and, from comparison with other members of the family, are identified as being a monophyletic group. Therefore, they are described as belonging to a single genus, Mahengechromis gen. nov., named for the type locality. Detailed anatomical study of the well-preserved specimens allows five species to be identified, M. plethos, M. rotundus, M. brachycranium , M. ellipticus, and M. curvifrons spp. nov. These species are distinguished on the basis of osteological characters, including the shape of the frontal bones, hyomandibulae and opercular bones. The species are believed to be endemic to the type locality, which, along with monophyly of the species, indicates that these fishes formed a species flock. This suggests that the capacity for cichlids to form species flocks arose early in the family's history.<br>Previously published phylogenetic analyses of the family Cichlidae have included few characters that can be used to incorporate fossil material. Osteological features that may be useful for determining relationships are identified and used in a phylogenetic analysis of the family. The results of this analysis are compared with the results of previous analyses to determine the usefulness of the characters. This comparison indicates that most osteological characters are homoplastic among cichlids, although some of the characters may prove to be phylogenetically useful. Although phylogenetic analysis of osteologic characters does not result in a well-resolved phylogeny, the most parsimonious placement of the fossil cichlids from Mahenge is in a relatively basal position among the African lineages, as the sister group to the hemichromine cichlids from West Africa.<br>The biogeographic relationships of members of the Cichlidae are examined based on information from the fossil record and the interrelationships of the lineages within the family. Two suggestions have been made for the age of the family; either the cichlids originated in the Early Cretaceous or they evolved near the end of the Mesozoic. The later time of origin would have required a trans-Atlantic dispersal. Based on the distribution of Recent and fossil cichlids, the latter hypothesis is accepted. A reconstruction of the dispersal patterns and possible means of dispersal are evaluated.
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Adams, D. P. M. "Cretaceous and Eocene geology of South Westland." Thesis, University of Canterbury. Geology, 1987. http://hdl.handle.net/10092/7117.
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The Cretaceous and Eocene sequence of South Westland crops out within a 6km wide coastal area from Ship Creek to the Mahitahi River.
The oldest unit, the Otumotu Formation (Motuan-Arowhanan), lies with angular unconformity on the Paleozoic Greenland Group. It is divided into two members, an older Tauweritiki Member (new) overlain by the Topsy Member. Both are entirely clastic but the lower unit is significantly coarser ranging from boulder conglomerate to mudstone, while granule conglomerate, sandstone analysis of sedimentary features to pebble breccia and the upper member comprises and mudstone. Detailed suggests that the lower member represents alluvial fan and plain sedimentation in a tectonically active setting changing to a more stable semi-arid fluvial and lacustrine depositional regime in the younger deposits.
The Butler Formation (new) (Piripauan), which lies unconformably on the Otumotu Formation, consists of conglomerate, sandstone and mudstone, with high and medium volatile bituminous coal seams. The sediments represent an environment of rivers and coal forming swamps and lakes which produced thick (up to 3m) coal seams.
The Tauperikaka Formation (new), previously the Tauperikaka Coal Measures, (Haumurian) overlies the Butler Formation, with a disconformity marked by a low relief scour surface, and is divided into the Moeraki (lower), Paringa (middle) and Rasselas (upper) Members. The Moeraki Member consists of pebble conglomerate, cross-bedded and horizontally bedded pebbly and granular sandstone and carbonaceous massive
silty mudstone. The sequence is thought to represent a coastal fluvial environment. The Paringa Member includes large scale planar tabular cross-bedding with mud drapes
(“tidal bundles”), bi-directional flaser bedded, trough and planar cross-bedded sandstone, siltstone and mudstone. The depositional environment is interpreted as a tide dominated coastline. The Rasselas Member, which consists of interbedded burrowed and structureless glauconitic sandstone in which both the density and diversity of burrows and the sediment grain size decrease upwards, was probably deposited in a large open marine bay.
The sediments of the Otumotu, Butler and Tauperikaka Formations are derived from a Greenland Group and Tuhua Group source which probably lay to the west of the basin. The change in depositional environment within the Tauperikaka Formation, from a marginal marine to an off shore marine environment is responsible constituents in the sediment composition, and the rock fragment component has been greatly depleted.
The eruption of the Arnott Basalt towards the end of the Haumurian is possibly related to extension which led to thinning of the crust.
The Eocene Law Coal Measures (new) (Kaiatan) are composed of clast supported very well rounded cobble to pebble conglomerate, well sorted medium sandstones, carbonaceous siltstone and mudstone and thick (up to 4m) high volatile bituminous coal seams. The sequence is interpreted as marginal marine, with coal forming reed swamps developing between fluvial clastic fans. A marine transgression from the east resulted in the end of coal measure sedimentation. The Tititira Formation (Miocene) lies unconformably on the Law Coal Measures.
Differences in coal type and coal geochemistry distinguish the coal in the Butler Formation from coal in the Law Coal Measures. The pH of the Law Coal Measure swamps was elevated by a marine influence which has produced a distinctive coal type characterised by a low Tissue Preservation Index. The coal also contains very little
inertinite compared with coal from the Butler Formation. The Coal in the Law Coal Measures can be distinguished using the relatively high Na₂O content which is totally organically associated and is present in a constant amount within different seams. The Butler Formation coal contains a high proportion of clay compared to the coal in the Law Coal Measures and has negligible Na₂O.
A thrust system involving both Paleozoic basement and cretaceous and Tertiary cover rocks has developed in post, Miocene time and accounts for a substantial amount of shorting (in the range of 40km and possibly more). The Mistake fault, a splay off the Alpine Fault, is the sole thrust of the Mistake Thrust Sheet which is part of a duplex thrust system which has subsequently been buckled into an antiformal stack. The anti formal stack includes at least two other thrust sheets, one below and one above the Mistake Thrust Sheet. The thrust complex appears to extend south to Milford Sound and up to 100km north of the area mapped and it is likely similar thrust systems are developed along the entire length of the Alpine Fault.
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Coxall, Helen Katherine. "Hantkeninid planktonic foraminifera and Eocene palaeoceanographic change." Thesis, University of Bristol, 2000. http://hdl.handle.net/1983/8efa1d22-0ff8-45a3-9a5c-bd5ea90e266f.
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The morphological and ecologicalevolution of middle-upper Eocene planktonic foraminiferal family Hantkeninidae is investigated in the context of the dramatic palaeoceanographic and climatic changes that marked the transition from Paleogene "greenhouse" to Neogene "icehouse" climatic conditions. Morphometric analysis proves that evolution in family Hantkeninidae was gradual but complex in detail with periods of relative stasis. Multiple lines of evidence demonstrate that Hantkenina evolved from planispiral clavate genus Clavigerinella and not, as was previously believed, from Pseudohastigerina micra. The ancestor of Clavigerinella was probably a low trochospiral form Paragloborotalia sp., which has been recognized for the first time in this study at a number of sites. Trends in chamber inflation, tubulospine angle and the position of the tubulospine on each chamber show the most dramatic evolutionary changes, indicating that these are the most useful characters for taxonomy. These morphological changes correlate well with known palaeoceanographic changes as well as the shift in hantkeninid ecology from a deep to a surface water habitat. Hantkeninids underwent pronounced adaptive evolution in depth habitats during the initial phase of the climatic transition. Lower middle Eocene forms lived in a cool deep-water environment within or below the oceanic thermocline and shifted to warmer surface waters in the late middle Eocene. They evolved in the low latitudes and were primarily. a tropical-subtropical group. The occurrence of Hantkenma australis at relatively high northerly and southerly latitudes during the middle Eocene may record a temporary expansion of warmer water conditions into these regions, possibly representing a hitherto unknown "hyperthermal" event. Clavigerinella is rare in middle Eocene open-ocean sequences but occasionally occurs in relative abundance in other localities (such as on continental margins and oceanic seamounts), suggesting that it was specialized for living in upwelling regions. A revised taxonomy of family Hantkeninidae is presented that reflects new understanding ofhantkeninid evolution. The reconstructed phylogeny demonstrates that the tubulospine-bearing genera Hantkenina and Cribrohantkenina represent a monophyletic clade. Multivariate analysis suggests that more than one morphological population existed at several times and that these may represent biological species. The results demonstrate that the hantkeninids are not merely passive recorders of ocean conditions but have instead evolved morphology and changed habitat in response to climate change.
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Baky, Alaaeldin Mohamed Abdel. "Maastrichtian to early Eocene calcareous nannofossils from Egypt." Thesis, University College London (University of London), 1988. http://discovery.ucl.ac.uk/1317747/.
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A study of calcareous nannofossils from the Maastrichtian-Early Eocene from Egypt has resulted in the recognition of four Maastrichtian and seven Early Tertiary biostratigraphic zones. These nannoplankton zones are based upon local ranges and compared with the zones proposed by Martini (1971), Sissingh (1977), Verbeek (1977) and Romein (1979). A new zone, the Fasciculithus ragaae Zone is described and the E1lipsolithus macellus Zone and the Fasciculithus tympaniformis Zone are emended. Study of the vertical ranges of the species provided many markers (including the zonal markers) with distinctive first and/or last occurrence levels. The uppermost Maastrichtian and Lower Danian are missing in the study sections. There is no change in the lithology at the Cretaceous-Tertiary boundary as observed in the Esh Mellaha area, but biostratigraphic evidence shows that there is a time gap and the boundary missing. This boundary is, however, marked by a conglomerate band at Gebel Urn El Ghanayem, a thin bed of black non-calcareous shale at Gebel Duwi and a change in the lithology from chalky limestone (upper part of Sudr Chalk Formation) of Maastrichtian age to shale (lower part of Esna Shale Formation) of Early Palaeocene age at Wadi Tarfa. No continuous Cretaceous-Tertiary boundary sequence was analysed. The palaeoenvironment during the Maastrichtian-Early Eocene according to the nannofossil assemblages, was a warm open marine inner to outer shelf, although the absence of late Maastrichtian and early Danian age sediments limits observation and comment. One hundred and sixty five species have been identified. Descriptions, remarks and figures as well as schematic drawings of many species are presented. A new family RHOMBOASTERACEAE, a new genus Diadochiastozygus, five new species Fasciculithus ragaae, F. gelelii, Discoaster atefii, D. duwiensis and D. amrii are described. New combinations for Bomolithus megastypus, B. cantabriae, Diadochiastozygus imbriei, D. saepes, D. eosaepes, Tranolithus tarboulensis, Vekshinella dorfii and V. compacta are proposed. The evolution of some Cretaceous and Early Tertiary nannofloral groups is discussed and a link between the Bomolithus and Discoaster groups proposed.
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Sexton, Philip. "Foraminiferal taphonomy, palaeoecology and palaeoceanography of the Eocene." Thesis, University of Southampton, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.416473.
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Sahy, Claudia Diana. "Geochronology and chronostratigraphy of the Eocene-Oligocene transition." Thesis, University of Leicester, 2014. http://hdl.handle.net/2381/28952.
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This thesis integrates high-precision (<0.2%, 2σ) [superscript 206]Pb/[superscript 238]U dating of zircons from volcanic tuffs intercalated in key Late Eocene-Oligocene marine and terrestrial sedimentary successions, with high-resolution biostratigraphic and magnetostratigraphic data sets in order to critically examine the accuracy and precision of the numerical age calibration of the Eocene – Oligocene transition (EOT). Weighted mean [superscript 206]Pb/[superscript 238]U ages from the Italian Umbria-Marche and North American White River Group (WRG) sedimentary successions are 0.4-1.0 Myr younger than legacy [superscript 40]Ar/[superscript 39]Ar biotite and sanidine data from the same tuffs (calibrated relative to Fish Canyon sanidine at 28.201 Ma). [superscript 206]Pb/[superscript 238]U calibrated age-depth models were used to constrain the age of magnetic reversals between 26.5-36 Ma (C8r-C16n.2n). Interpolated magnetic reversal ages are consistent with relatively constant seafloor spreading rates, and provide a fully integrated and robust chronostratigraphic framework for the EOT, as shown by mutual consistency of chron boundary ages from the Umbria-Marche basin and the WRG between 31-36 Ma. These data effectively eliminate the discrepancies between astronomically tuned and radio-isotopically calibrated time scales of the EOT. An evaluation of the fidelity of planktonic foraminifer bioevent based chronostratigraphy across the EOT indicates that the last occurrence of hantkeninids and the last common occurrence of Chiloguembelina cubensis which mark the Eocene-Oligocene (34.090 ± 0.074 Ma) and Rupelian – Chattian (28.126 ± 0.175 Ma) boundaries are not timetransgressive across oceanic basins. However, other Oligocene planktonic foraminifer bioevents occur 0.4-0.8 Myr later in the western Tethys than in tropical and subtropical open ocean settings. In the WRG sedimentary succession, the first and last appearance datums of key Late Eocene mammal taxa show diachroneity of ca. 1 Myr over a distance of 400 km. Long-term aridification recorded by the WRG appears to be time-transgressive, and progressed gradually from west to east, while abrupt Early Oligocene cooling reported from WRG outcrops in NE Nebraska was synchronous with Early Oligocene glaciation of Antarctica.
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Cameron, Adele Jane. "Ocean circulation during Eocene extreme "greenhouse" climatic warmth." Thesis, Open University, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.699820.
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The Early Eocene (47-56 Ma) 'greenhouse' climate represented the warmest climatic conditions witnessed in the last 90 million years, with peak Eocene warmth (the Early Eocene Climatic optimum, EECO) occurring around 50-52 Ma (Sexton et al. 2006; Bijl et al. 2009; Zachos et al. 2008; Littler et al. 2014) with subsequent global cooling thereafter (Sexton et al. 2006; Zachos et al. 2008). Ocean circulation plays a critical role in redistributing thermal energy across the planet and providing ventilation to the deepest parts of the ocean. Understanding how it may have operated in a globally warm world with little equator-to-pole gradients is paramount to understanding how it may respond to increasing temperatures today. The prevailing view of the early Eocene ocean was that deep-water formation was confined to the Southern Ocean, with little or no deep-water formation in the North Atlantic, unlike today. This study explores whether there is evidence for deep-water formation in the high latitude North Atlantic during the extreme climatic warmth of the early Eocene and its stability across transient climatic excursions. It also explores the strength and vigour of ocean circulation and whether this was influenced by the global decline in temperature following early Eocene peak-warmth. It utilises the neodymium isotopic signature of fossilised fish teeth (εNd) that is widely utilised to trace the movements of deep-water masses and can be used to reconstruct paleooceanic circulation along with detrital εNd that is an indicator of sediment provenance. It combines these with fish tooth rare earth element concentrations and sediment core XRF. Four key locations are utilised. Two on the Newfoundland margin in the West North Atlantic, and one from the high North Atlantic in the Labrador Sea, both idea1 locations to identify the potential outputs of North Atlantic deep-water formation. The fourth site is Demerara Rise in the Equatorial Atlantic, chosen to monitor changes in the dominant source of deep-water sources from the North or the South.
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Gregory, Kathryn Mary. "Late Eocene paleoaltitude, paleoclimate, and paleogeography of the Front Range region, Colorado." Diss., The University of Arizona, 1992. http://hdl.handle.net/10150/185985.
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Erosion beveled the Laramide Front Range uplift in Colorado to a surface of low relief by the end of the Eocene. This study uses paleobotanic climate analysis techniques to determine the paleoelevation of this regional surface by examining the overlying 34.9 Ma Florissant flora. Multiple regression models explaining 93.4% of the variance in mean annual temperature (MAT), 86.1% of the variance in growing season precipitation (GSP) and 65.7% of the variance in rainfall distribution were derived from J. A. Wolfe's dataset of 31 leaf physiognomic character states from 86 modern vegetation sites. When applied to a new collection of 29 species from the Florissant flora, estimates of MAT = 10.7 ± 1.5°C, and GSP = 55.6 ± 12.5 cm, with precipitation occurring mostly during the growing season, are derived. This paleoclimate estimate is corroborated by data from late Eocene Sequoia affinis from Florissant. Higher mean ring width of the fossil trees as compared to modern counterparts can be explained by a climate with summer mean monthly temperatures ≥ 14°C and summer mean monthly rainfall >1.5 cm. The estimated MAT, when combined with coeval sea level MAT and terrestrial lapse rate, implies an elevation of 2.3-3.3 km for Florissant, which is indistinguishable from the modern elevation of 2.5 km. The elevation of Florissant is tied to that of the Great Plains by the Wall Mountain Tuff, so the Great Plains were also high. The elevation was created either by underplating and/or mass transfer in the Laramide, or by mantle uplift of crust thickened by pre-Laramide tectonics. This elevation estimate implies that: (1) Pliocene uplift is not required to explain the present elevation. Thus, late Tertiary plateau uplift in the western US was not a contributing factor to the marked global cooling since 15 Ma; and (2) in the late Eocene, regional surfaces of planation could be formed at elevations significantly above sea level but below tree line. The surface was possibly formed from a lack of storminess; a preponderance of small storm events will diffusively smooth topography.
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Julian, Meaghan Elizabeth. "Benthic foraminiferal faunal changes during the Eocene/Oligocene climate transition at Ocean Drilling Program (ODP) sites 1209A and 1211A from the Shatsky Rise, central Pacific Ocean." Thesis, [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-1519.
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Meunier, Mathias. "Biodiversity, biostratigraphy, disparity and macroecology of middle Eocene radiolarians (Rhizaria) : insights to their biotic response to the Middle Eocene Climatic Optimum (MECO)." Electronic Thesis or Diss., Université de Lille (2022-....), 2023. http://www.theses.fr/2023ULILR078.
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L'Optimum Climatique de l'Éocène Moyen (MECO) est un évènement de réchauffement climatique qui s'est produit il y a 40 Ma, interrompant temporairement la tendance générale au refroidissement observée durant l'Éocène. Bien que le MECO soit l'une des perturbations climatiques les plus importantes du Paléogène, son impact sur la biosphère demeure encore mal connu. Via un large éventail de méthodes quantitatives, cette thèse vise à étudier la dynamique de la paléodiversité et la disparité morphologique des radiolaires au cours du MECO, afin de mieux comprendre les bouleversements biotiques qui lui sont associés. La première étape de ce travail a consisté à dresser la liste taxinomique exhaustive des espèces de radiolaires éocènes rencontrés dans deux domaine géographiques distincts : l'Atlantique équatorial (ODP Site 1260) et l'Atlantique septentrional (ODP Site 1051). Au total, 276 taxons ont été identifiés, dont 37 nouvelles espèces. S'appuyant sur le cadre cyclostratigraphique développé au Site 1260, la biozonation des radiolaires tropicaux a également été affinée. Les âges absolus de 71 bioévènements ont été calibrés et, par comparaison avec l'enregistrement fossilifère du Pacifique équatorial, nous avons démontré la synchronicité des bioévènements qui définissent les limites des biozones de l'Éocène moyen. Une fois les cadres taxonomiques et biostratigraphiques clarifiés, l'objectif de cette thèse était d'évaluer l'impact du réchauffement climatique sur les radiolaires. Pour ce faire, deux grandes catégories de mesures ont été utilisées. D'une part, nous avons effectué une analyse quantitative de l'assemblage fossile du site 1051. Cette étude détaillée n'a révélé aucun changement de faune important au cours du MECO. Seule une légère augmentation de la richesse taxinomique a été documentée, due à la migration de certaines espèces tropicales vers les hautes latitudes durant la phase de réchauffement. D'autre part, des méthodes de géométrie morphométrique ont été employée pour quantifier la disparité morphologique du squelette des radiolaires. Cette étude s'est concentrée sur une espèce de nassellaire (Podocyrtis papalis) du Site 1260. Nous avons montré que les fluctuations de la disparité morphologique du contour du squelette coïncidaient avec le pic de température du MECO. Ce signal est interprété comme un indicateur de stress biologique induit par le réchauffement climatique<br>The Middle Eocene Climatic Optimum (MECO) is a global warming event that occurred ca. 40 Ma and temporarily interrupted the long-term Eocene cooling trend. Although the MECO represents one of the larger climatic disruptions of the Paleogene, its impact on the biosphere is still poorly understood. Based on a wide range of quantitative methods, this thesis aims to study the radiolarian paleodiversity dynamics and morphological disparity through the MECO, in order to gain a deeper understanding of the biotic perturbations associated with this climatic event. The taxonomic understanding of middle Eocene radiolarian species was first clarified, by documenting at the species level two well-preserved radiolarian faunas recovered from two distinct geographic regions: the equatorial Atlantic (ODP site 1260) and the North Atlantic (ODP site 1051). A total of 276 species were identified, including 37 new to science. Taking advantage of the cyclostratigraphic framework developed at Site 1260, we refined the global tropical radiolarian biozonation. The absolute ages of 71 radiolarian bioevents were calibrated and, by comparison with the equatorial Pacific record, the synchroneity of primary bioevents was demonstrated. Once the taxonomic and biostratigraphic frameworks were clarified, the main aim of this thesis was to assess the radiolarian biotic sensitivity to climate change. Two categories of metrics were used to achieve this objective. On the one hand, we performed a whole assemblage quantitative analysis at ODP Site 1051. This detailed investigation of the radiolarian fauna did not reveal any prominent turnover during the MECO, but only a slight increase in radiolarian taxic richness due to the poleward migration of several tropical radiolarian species. On the other hand, we applied geometric morphometric approaches to quantify the morphological disparity of radiolarian shell through the MECO interval. This study was focused on a single species (Podocyrtis papalis) from Site 1260, and showed that fluctuations in morphological disparity coincide with the warmest interval of the MECO. This signal is interpreted as an indicator of biological stress induced by the warming event
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Dubin, Andrea Rose. "A magmatic trigger for the Paleocene-Eocene thermal maximum?" Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/98670.
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Thesis: Ph. D., Joint Program in Chemical Oceanography (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2015.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references.<br>Fifty-six million years ago Earth experienced rapid global warming (~6°C) that was caused by the release of large amounts of carbon into the ocean-atmosphere system. This Paleocene-Eocene Thermal Maximum (PETM) is often cited as an analogue of anthropogenic climate change. Many trigger mechanisms for the carbon release at the PETM have been proposed. Common to all scenarios is rapid release of isotopically light carbon (<¹³C/¹²C values) from methane hydrates, terrestrial or marine organic matter, as indicated by a pronounced excursion to light carbon isotope values across the PETM. I test the hypothesis that the PETM warming and isotope excursion were caused by the intrusion of a magmatic sill complex into organic-rich sediments in the North Atlantic. The intrusion of magma into sedimentary rocks will cause heating and metamorphic reactions in a thermal aureole around the intrusion. If these sediments are rich in organic matter, large volumes of isotopically light carbon are rapidly released. I examine geochemical evidence from lead, osmium, and organic carbon to place constraints on the extent the carbon isotope excursion during the PETM may have been caused by contact metamorphism of organic-rich sediments. Potential terrestrial and submarine analogs are examined to determine the behavior of these elements during thermal alteration. Furthermore, geochemical evidence from sediment cores at the PETM provides additional information about what might have caused the carbon isotope excursion. I find that lead is not a suitable proxy for carbon mobilization to the overlying seawater during contact metamorphism. Osmium, however, is mobilized together with carbon. Making reasonable assumptions for the ¹⁸⁷Os/¹⁸⁸Os of the sediments from the North Atlantic Magmatic Province (NAMP), constrained by the ¹⁸⁷Re/¹⁸⁸Os of organic-rich sediments and the depositional age of the sediment, the entire marine osmium isotope anomaly at the PETM could be explained without the need to invoke enhanced continental weathering. Based on estimates of the extent of mobilization of organic carbon relative to osmium, approximately 47% to 60% of the carbon released at the PETM may have been derived from thermal alteration of organic-rich sediments in the NAMP.<br>by Andrea Rose Dubin.<br>Ph. D.
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Edgar, Kirsty M. "Palaeoclimatology, stratigraphy and biotic responses in the middle Eocene." Thesis, University of Southampton, 2008. https://eprints.soton.ac.uk/65670/.
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The Middle Eocene (37 to 49 million years ago, Ma) was characterised by warmer global temperatures and higher atmospheric carbon dioxide (pCO2) levels than today with only small/non-existant icesheets. Because predicted pCO2 levels for the coming century have not been seen on Earth since at least ~40 Ma thus, the primary objective of this thesis is to improve our understanding of the nature, timing and consequences of carbon perturbations in the Middle Eocene between 39 and 43 Ma. In Chapter 3, a new (instrument specific) methodology for measuring Mg/Ca in foraminiferal calcite is developed to enable the simultaneous measurement of additional trace elements indicative of foraminiferal test contamination. This new methodology enables Mg/Ca data to be screened more efficiently for contamination and increases confidence in palaeoceanographic reconstructions based on the Mg/Ca palaeotemperature proxy. In Chapter 4, new foraminiferal stable isotope records (~5 kyr resolution) from Demerara Rise in the equatorial Atlantic are generated to test the hypothesis that the onset of continental ice sheets in the Northern Hemisphere occurred at ~41.6 Ma in the Middle Eocene, 30 million years earlier than previously thought. The new data herein, indicate that if continental ice sheets were present, they were small and easily accommodated on Antarctica with no need to invoke storage of ice in the Northern Hemisphere. The dearth of appropriate Middle Eocene sedimentary sections on which to work means that a well calibrated timescale for this interval remains to be produced. In Chapters 5 and 6, this problem is addressed using Middle Eocene sediments recovered from the Blake Nose plateau in the western North Atlantic. A new high resolution magnetic stratigraphy and new quantitative foraminiferal biostratigraphic counts were developed between 39.5 and 42.0 Ma, which allows re-assessment and refinement of previous magnetostratigraphic and biostratigraphic interpretations. This provides excellent age control for these sediments and new calibrations to the Geomagnetic Polarity Time Scale (GPTS). In Chapter 7, the first high-resolution quantitative planktic foraminiferal assemblage counts were developed for the global warming event the Middle Eocene Climatic Optimum (MECO) between ~39.5 and 41.5 Ma. New biotic records show that the MECO was accompanied by significant biotic shifts that suggest a shift from warm, oligotrophic surface waters to warmer, more productive surface waters during the MECO.
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Clifton, Abigail Joy. "The Eocene flora of Svalbard and its climatic significance." Thesis, University of Leeds, 2012. http://etheses.whiterose.ac.uk/21133/.
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Fossil plant remains are preserved within the deposits of the Eocene Aspelintoppen Formation on Svalbard. These sediments form the youngest continental deposits of early Paleogene age. The Aspelintoppen Formation sediments represent crevasse splay, backswamp and ephemeral lake deposits that represent a broad lowland floodplain that was subject to frequent flooding. The forests grew at a palaeolatitude of 75°N. New collections (1032 specimens) ofthe Aspelintoppen Formation flora are dominated by angiosperms including the Fagaceae? (Ushia olafsenii), Betulaceae (Corylites and Craspedodromophyllum), Hamamelidaceae (Platimelis pterospermoides), Platanaceae (Platimeliphyllum and Platanus), Ulmaceae (Ulmites ulmifolius), Trochodendraceae (Zizyphoides flabella), Cercidiphyllaceae Trochodendroides), Juglandaceae (Juglans laurifolia) and Hippocastinaceae (Aesculus longipedunculus). In addition, conifer fossils include Metasequoia shoots and cones, as well as Thuja shoots. Fern fronds of Osmunda and Coniopteris are present, along with the horsetail Equisetum. The Aspelintoppen Formation vegetation grew locally on the floodplain with angiosperms dominating the riparian environment and a mixed angiosperm Metasequoia-dominated flora in the backswamp environment, with Equisetum and ferns occupying the margins of ephemeral lakes and post-disturbance environments. The Aspelintoppen Formation flora is similar in composition and ecology to other early Paleogene Arctic floras from the Canadian Arctic, Greenland, Alaska and north-east Russia, showing that Polar Broadleaved Deciduous Forests were a dominant part of the Arctic environment. Palaeoclimate estimates were derived from the 22 angiosperm morphotypes using both physiognomic and nearest living relative methods. CLAMP results are considered to be the most reliable and indicate that the Eocene climate of Svalbard was temperate with a mean annual temperature of 11.6°C, a warm month mean of 18.rC and a cold month mean of 4.5°C. Precipitation estimates indicate high levels of precipitation with growing season precipitation estimates from 320 to 1531mm, and a strong wet or dry seasonal signal with 356 to 656mm precipitation for the three wettest months and 112 to 247mm for the three driest months. These estimates support sedimentary evidence that Eocene Arctic environments were seasonally warm and wet.
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Guest, Rachel L. "Description and phylogenetic analysis of a new alligatoroid from the Eocene of Laredo, Texas." Thesis, University of Iowa, 2014. https://ir.uiowa.edu/etd/4636.
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Wallett, Lane A. "Eocene selachian fauna from nearshore marine deposits, Ampazony, Northwestern Madagascar /." Connect to online version, 2006. http://ada.mtholyoke.edu/setr/websrc/pdfs/www/2006/147.pdf.
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Scrivan, Leonie Jane. "Diversity of the mid-Eocene Maslin Bay flora, South Australia /." Title page, contents and abstract only, 1993. http://web4.library.adelaide.edu.au/theses/09PH/09phs434.pdf.
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Bains, Santo. "Climate change and biological feedbacks at the Palaeocene-Eocene boundary." Thesis, University of Oxford, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.403931.
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Hathway, B. "The Eocene to Miocene geology of southwest Viti Levu, Fiji." Thesis, Oxford Brookes University, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233454.
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Broadbent, Tom. "Low latitude pacific palaeoceanographic change across the Eocene/Oligocene boundary." Thesis, Bangor University, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.529758.
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Dagher, Marcelle Bou. "Lower Eocene shelf smaller foraminifera a comparative inter-regional study." Thesis, University College London (University of London), 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260930.
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Sulaiman, Nursufiah Binti. "Late Eocene palaeoenvironment and palaeoclimate of the US Gulf Coast." Thesis, University of Birmingham, 2017. http://etheses.bham.ac.uk//id/eprint/7752/.
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This thesis presents new micro palaeontological and geochemical palaenvironmental proxy data through the late Eocene into the earliest Oligocene from a clay-rich succession from the US Gulf Coast. It is based on samples from the Yazoo Clay Formation, recovered in the Mossy Grove Core near Jackson, Mississippi. This represents an apparently continuous section of relatively uniform lithology, clay-rich deposits that host very well preserved assemblages of calcareous nannofossils, foraminifera and organic biomarkers. This thesis makes use of these to generate a detailed calcareous nannofossil taxonomy, high-resolution calcareous nannofossil assemblage data and coccolith-fraction bulk isotope data, as well as pilot planktonic foraminifera abundance and isotope records. It also develops pilot data for organic biomarkers that demonstrate the presence and utility of biomarker proxies for ancient sea surface temperatures within the Yazoo Clay. The results of this project characterize the late Eocene US Gulf Coast as a sub-tropical shelf sea environment that experiences several stages of sea surface cooling and increasing nutrient contents - potentially linked to sea level fall - in the late Eocene and earliest Oligocene. The most important finding of this project is evidence for cooling and major perturbations to the climate-carbon cycle significantly before the onset of the major phases of Antarctic glaciation.
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Pedley, Antony. "Eocene foreland basin carbonatae facies, the external Sierras, Spanish Pyrenees." Thesis, Royal Holloway, University of London, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.261690.
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This thesis explores the controls on carbonate platform formation in foreland basins through a study of the facies, and depositional architecture, of the Middle Eocene Guara Limestone Formation, from the External Sierras, Northern Spain. The Guara Limestone Formation formed in a ramp environment on the Iberian foreland margin of the South Pyrenean Foreland Basin. The facies are foraminifera and algal limestones, with minor shallow marine siliciclastics. A facies model has been erected indicating 19 facies, grouped into 6 facies associations. Using these facies and associations, the evolution of the platform has been studied. A progradational lime-mud and clastic rich lowstand systems tract marks the initiation of deposition, the lowstand systems tract being deposited during a period of low relative sea level rise. This is overlain by an aggradational and retrogradational, carbonate grain rich, transgressive systems tract. This was deposited as the rate of relative sea level rise increased. Parasequences have been redefined herein to allow successions of a similar stratigraphic hierarchy to be encompassed in the same name. The aggradational section of the platform containing both shallowing and deepening upward parasequences. The deepening upwards parasequences were created by base level rise driven by tectonic subsidence and eustatic sea level rise. The aggradational platform margin indicates that inner-ramp production, even with the absence of coral reefs, was able to keep pace with relative sea level rise. Relative sea level rise was sufficiently rapid to preclude the development of peritidal facies and evaporites, despite suitable arid climatic conditions. Platform retrogradation, in the late transgressive systems tract, and eventual drowning, was caused by a further increase in the rate of relative sea level rise. This was created by an increase in the rate of foreland subsidence due to the formation of antiformal stacks in the Pyrenean Axial Zone to the north. Following drowning, a progradational, clastic and lime-mud rich highstand systems tract developed. Initially the rate of relative sea level rise was rapid during the highstand systems tract, this rate probably decreasing as the sequence boundary is approached. The observed increase through time of the rate of tectonic subsidence is typical of foreland basins, and is in contrast to the exponential decay of subsidence seen in passive margins. A number of other controls can be seen to have affected the Guara Limestone Formation ramp. These may affect any carbonate system; though some may be favoured specifically in foreland basin settings. Tidal action formed a series of grainstones shoals at the shelf margin, tidal effects may be favoured in narrow foreland basins due to tidal amplification, and also the limitation of wave and storm effects due to a restricted fetch. The basin was well circulated, with effective exchange between basin and platform, and salinity was normal to possibly slightly lower than normal. The biota displays a chlorozoan assemblage, but is depleted in corals due to their global decline at this time. Sediment and nutrient input onto the platform was low, leading to a resource limited environment favouring the development of large benthic foraminifera. Localised tectonics, in the form of small scale folding, produced a series of marked effects on the platform, these include: the generation of angular local unconformities, and a variation and narrowing of biofacies belts. In summary, foreland basins may display a complicated interaction between eustatic sea level variation and tectonic subsidence. In contrast to other basin types, this tectonic subsidence increases through time until eventual uplift. This provides a dominant control on the stratal architectures observed. This thesis illustrates, therefore, the potential of the use of such detailed facies and platform models to elucidate both the local, and the regional scale, controls on platform development and basin evolution.
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Moss, Jamie. "Tectonic controls on Eocene deltaic architecture, Jaca Basin, Spanish Pyrenees." Thesis, Durham University, 2005. http://etheses.dur.ac.uk/3730/.
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The Jaca Basin lies to the south of the Pyrenean mountain chain, in Spain, and was formed by the Late Cretaceous and Tertiary convergence between the Iberian and European tectonic plates. During the Bartonian (Middle Eocene), sediment flux from the uplifting Pyrenees was deposited in this basin as the Belsué-Atarés Fm. deltaic system. At the same time, southward propagation of deformation from the orogen created a number of emergent thrusts and thrust-related anticlines along the margins of the basin and within the basin itself. The effect that the growth of these kilometre-scale structures had on the coeval marine depositional systems is the focus of this work. Although the effects that uplifting intrabasinal structures have on fluvial systems and the effects that basin margin structures have on marine systems are well covered in the literature, the influence of intrabasinal compressive structures on coeval marine sedimentation has been largely neglected. By undertaking detailed fades, palaeocurrent and compositional analysis of the Belsué-Atarés Fm. deltaics across the Jaca Basin, it has been found that local tectonics had the strongest control on the marine sedimentation. The structurally defined basin margins largely acted as barriers to external depositional systems, causing large parts of the basin to be dominated by marl deposition. However, a total of four structurally controlled low points through the northern and southern basin margins allowed the entry of large volumes of Pyrenean axial zone sediments, beginning at 41.5 Ma. These were composed of silts, sands and pebbles, and formed the axial deltaic system. Once in the basin, a total of ten, kilometre-scale, growing thrust-related anticlines acted as barriers to the progradation of the axial system, causing facies associations to vertically aggrade behind each structure. At 37.5 Ma, after 4 Myr of vertical aggradation, a basin-wide fall in relative sea-level allowed the facies associations to rapidly prograde, breaching the crests of each of the barrier anticlines. The principal controls on the distribution of facies associations through time (sequence development) in the Jaca Basin were therefore local tectonic ones, with relative sea-level being secondary. This finding calls into question the work of the few existing studies into marine intrabasinal growth structures, which tended to use passive margin sequence stratigraphic concepts i.e. assume that relative sea-level was the primary control on sequences. The development of new techniques, such as numerical modelling, is needed before these types of complex geological situations can be fully understood. The results of this work will be of great relevance to basin dynamics and fold kinematics studies, and for hydrocarbon exploration in thrust-top basin settings.
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Lelono, Eko Budi. "Palynological study of the Eocene Nanggulan Formation, Central Java, Indonesia." Thesis, Royal Holloway, University of London, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.743090.
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Vinyoles, i. Busquets Andreu. "Sediment routing systems of the Eocene Tremp-Jaca basin: Stratigraphic analysis and numerical models." Doctoral thesis, Universitat de Barcelona, 2021. http://hdl.handle.net/10803/672479.
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The Eocene South-Pyrenean foreland basin provides a continuum of outcrops representing a Source to Sink sediment routing system from subaerial canyons to deep marine environments. On this context, the specific objective of this study is: (a) to contribute to the knowledge of the chronostratigraphy and the basin infill of the study area; (b) to analyze the evolution of the sedimentation rates on the Tremp-Jaca basin; and (c) to generate numerical models to (i) assess the sediment routing and sediment balance and, (ii) to evaluate the basin response to the propagation of climatic and tectonic signals.
Two new magnetostratigraphic sections are built on the Tremp-Jaca basin; the Olsón (Ainsa basin) and the Yebra de Basa sections (Jaca basin). The Olsón section provides a late Lutetian to early Priabonian age for the Escanilla formation in the Ainsa basin, and the same age range is provided on the Yebra de Basa section for the strata encompassed between the Sabiñánigo sandstone and the Santa Orosia formation.
The age constrains provided by these new sections and the data sorted from a systematic review of the literature have been used for an analysis of the sedimentation rates in the Tremp-Jaca basin. The studied sections were decompacted by backstripping to correct the differential burial compactions between the sections. This study shows that sedimentation rates may not show the expected variations related to depozone distribution. This lack of correlation between the depozones and the sedimentation rates are consequence of the lagged response to deformation front shifts and the complexity in the structure of the wedge-top. This complexity result in a widespread subsidence related to the emplacement of basement units in the hinterland. Also underfilled forelands may develop high sedimentation rates in the initial stages of wedge-top as basin gradients are a continuation to those developed in the previous foredeep phase. Sedimentation rates in overfilled areas are controlled by accommodation. In underfilled areas, the main control is clastic supply. During graded shelf regressive stages, maximum sedimentation rates are in foreset areas. In the transgressive stages, maximum sedimentation rates are at the topset. In out-of-grade periods, high sedimentation rates are in deep marine areas.
The results obtained above have been used to feed forward stratigraphic models, using Dionisos software, to test and understand the different parameters affecting the sedimentary infill of the basin. A first model on the sediment routing systems of the Tremp-Jaca basin, based on the data from the sedimentation rates analysis, succeeds on reproducing the sedimentary routes that can be deduced from the paleocurrent patterns on the Tremp-Jaca basin, validating the inputted data. A second forward stratigraphic model, based on architectural and cyclostratigraphic analysis from previous works, determines that the high-frequency Milankovitch cyclicity of the Belsué-Atarés delta (Sierras Exteriores) is primarily forced from the sediment supply and secondary from the eustasy.<br>A les conques Eocenes Sudpirenaiques d’avantpaís hi ha un continu d’afloraments representatius de les rutes sedimentàries del sistema Source to Sink, des de canons subaeris fins a ambients marins profunds. En aquest context, aquest estudi té com a objectiu (a) contribuir al coneixement de la cronoestratigrafia i el reompliment de les conques de l'àrea d'estudi; (b) analitzar l’evolució de les taxes de sedimentació a la conca de Tremp-Jaca; i (c) generar models numèrics per (i) avaluar les rutes sedimentàries i el balanç sedimentari i (ii) avaluar la resposta de la conca a la propagació de senyals climàtics i tectònics.
S’han construït dues noves seccions magnetostratigràfiques a la conca de Tremp-Jaca; les seccions d’Olsón (conca d’Aïnsa) i de Yebra de Basa (conca de Jaca). La secció d’Olsón proporciona una edat Luteciana superior fins a Priaboniana inferior per a la part superior de la formació Escanilla a la conca d’Aïnsa. A la secció de Yebra de Basa s’obté la mateixa franja d’edat pels estrats entre el gres de Sabiñánigo i la formació de Santa Orosia .
Les edats proporcionades per aquestes noves seccions i les dades obtingudes a partir d'una revisió sistemàtica de les dades publicades, s'han utilitzat per a una anàlisi de les taxes de sedimentació de la conca de Tremp-Jaca. Les seccions estudiades han estat descompactades per backstripping per corregir l’enterrament diferencial que resulta en estadis de compactació diferents entre les seccions estudiades. Aquest estudi mostra que les taxes sedimentaries poden no mostrar les variacions esperades en relació a la distribució de les depozones. Aquesta manca de correlació entre les depozones i les taxes de sedimentació són conseqüència del retard en la resposta als canvis en la posició del front de deformació al wedge-top. Aquesta complexitat resulta en l’expansió de la subsidència relacionada amb l’emplaçament d’unitats basals al hinterland. Aquesta complexitat resulta en una major subsidència relacionada amb l’apilament d’unitats basalts al hinterland. També les conques d'avantpaís underfilled poden desenvolupar altes taxes de sedimentació en els estadis inicials del wedge-top, ja que els gradients sedimentaris són la continuació dels desenvolupats a la fase de foredeep anterior. Les taxes de sedimentació a les àrees overfilled estan controlades per l’acomodació. A les àrees underfilled, el control principal és l’aport de sediments. Durant els episodis regressius de les plataformes gradades, les taxes de sedimentació màximes es donen al topset. En els períodes no-gradats, les taxes de sedimentació més elevades es troben a les àrees marines profundes.
Els resultats obtinguts s’han utilitzat per alimentar dos forward stratigraphic models, utilitzant el software Dionisos, per provar i entendre els diferents paràmetres que defineixen el reompliment de la conca. Un primer model en els sistemes de rutes sedimentàries de la conca de Tremp-Jaca, basat en les dades provinents de l’anàlisi de les taxes de sedimentació, té èxit en reproduir les rutes sedimentàries que es poden deduir dels paleocorrents de la conca de Tremp-Jaca, validant les dades introduïdes. Un segon model, a partir de dades arquitecturals i cicloestratigràfiques de treballs previs, determina que les ciclicitats de Milankovitch d’alta freqüència del delta de Belsué-Atarés (Sierras Exteriores) són primàriament forçats per l’aport sedimentari i secundàriament per l’eustàcia.
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Díaz, Poveda Leonardo. "Evolución sedimentaria y estructural del Eoceno superior, Cordillera oriental de Colombia, Sur América." Doctoral thesis, Universitat de Barcelona, 2016. http://hdl.handle.net/10803/396371.
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Colombia se encuentra situada en la esquina NW de Sur América, este sector de gran complejidad tectónica es un margen destructivo por convergencia de placas. Convergen las placas de Suramérica, de afinidad continental, y las placas Pacifica y Caribe, de afinidad oceánica. La complejidad está en que la placa Pacifica subduce a la placa de Suramérica en el sector sur de Colombia y en la parte media colisiona oblicuamente. La placa Caribe colisiona también oblicuamente, generando un régimen transpresivo y en la parte norte colisiona con la placa Suramericana a lo largo de una zona de fallas transformantes dextrales.
Las unidades del Eoceno superior en Colombia son el producto de la interacción de las placas tectónicas, las cuales controlaron las condiciones de formación y depositación en las subcuencas. Primero, con base en el levantamiento de columnas estratigráficas de esta secesión, se establecieron secciones de control de las unidades litoestratigráficas, definidas inicialmente por Porta (1974). Se realizó también una división en secuencias deposicionales de tipo Trangresivo –Regresivo T-R que se aplicó al registro sedimentario del Jurásico superior – Holoceno con el fin de poder tener una idea del armazón general de la cuenca. Se determinaron seis secuencias de tercer orden para el mesozoico y cinco de segundo orden para el terciario.
La sucesión de interés, Eoceno superior, corresponde a una secuencia deposicional que fosilizaba la superficie de primer orden constituida por la discordancia del Eoceno inferior. Esta secuencia se depositó en tres subcuencas alargadas con dirección del eje NE, a partir de la topografía generada por la inversión de la cuenca mesozoica, lo cual dio lugar a una geometría de subcuencas tipo valles de incisión paralelos entre sí. Los resultados de los estudios de paleocorrientes soportan este resultado y el de un basculamiento hacia el NE con una paleopendiente promedio de 0,006° característica de este tipo de cuencas.
Los movimientos verticales datados con huellas de fisión significan el inicio de la etapa contractiva en el Masstrichtiense seguido del clímax de deformación contractiva en el Eoceno inferior, generando los umbrales que separaron las tres subcuencas del Eoceno superior.
Las nueve curvas de subsidencia total corregida con la paleobatimetría y la erosión, nos muestran muy bien la evolución de la acomodación sedimentaria durante la etapa Jurásico superior-actual, así mismo reflejan el efecto de carga por apilamiento estructural y flexión en las cuencas de antepaís de los llanos y Valle del Magdalena lo cual se inició alrededor de los 40 Ma (Eoceno superior).
La evolución de la cuenca se realizó en cuatro etapas: 1). Extensión paleozoica (Paleozoico Superior), 2). Inversión triásica, 3). Extensión mesozoica. (Jurásico Superior – Cretácico), y 4) Inversión paleógena (Paleoceno superior – Holoceno). Durante esta etapa de inversión la cuenca Jurásico superior – Cretácica sufrió un acortamiento hasta del 55% que equivale a 250 km para llegar al estado deformado actual.
La nueva configuración paleogeográfíca generada por contracción compartimentalizó la cuenca cretácica generando las tres subcuencas terciarias. Estas subcuencas desarrollaron sistemas predominantemente fluviales de ríos anastomosados que corrían hacia el N. Los sistemas de abanicos aluviales quedaban junto a las fracturas activas y en la parte cercana a los umbrales más levantados que actuaron de potente área fuente. De las subcuencas del Valle Medio del Magdalena y de la Cordillera Oriental. En determinados momentos las partes septentrionales registran la entrada de facies transicionales de estuario, en los sectores más distales de los sistemas fluviales.
Los materiales del Eoceno superior estudiados constituyen el mejor reservorio de todos los sistemas petrolíferos de Colombia. Por esta razón, la caracterización de la roca almacén y su localización y predicción de distribución, es esencial para la exploración y producción de campos existentes y la predicción de nuevos prospectos. A partir del nuevo modelo obtenido para el Eoceno superior, se abren toda una serie de grandes posibilidades para desarrollar nuevos play concepts de estudios exploratorios de hidrocarburos.<br>Colombia is located in the northwest corner of South America, in an área tectonically highly complex as it corresponds to a destructive margin due to the convergence of several plates. There, the South American Plate of continental affinity, and the Pacific and Caribbean plates of oceanic affinity, all converge. The complexity is associated with subduction of the Pacific Plate underneath the South American Plate in the southern part of Colombia, where in the central part the two plates collide obliquely. The Caribbean plate also collides obliquely against the South American Plate, generating conditions characteristic of a transpressive regime; in the northernmost part this collision occurs along a zone of dextral transforming faults.
The stratigraphic units corresponding to the late Eocene in Colombia are the product of the interaction of tectonic plates, which controlled basin formation and their subsequent depositional conditions. Porta (1974) firstly defined the lithostratigraphic units based on a series of sections surveyed as part of the fieldwork carried out at the time. Later, a series of transgressive-regressive (T-R) depositional sequences were defined for the late Jurassic-Holocene section, which allowed establishing a general stratigraphic framework of the basin. Thus, a total of six third order sequences for the Mesozoic and five second order sequences for the Tertiary, were defined.
The upper Eocene section, as the interval of interest, corresponds to a depositional sequence that buries a first order Surface representing the early Eocene unconformity. This sequence was deposited in three NE trending elongated sub-basins, associated with the paleo topography resulting from the structural inversion process affecting the Mesozoic basin; the resulting relief formed corresponds to a geometry represented by parallel sub-basins representing incised valleys. Paleo current analyses confirm such orientation as well as a major northeast tilting of the area, which exhibits an average paleo-inclination of 0.006°, which characterizes this type of basins.
Vertical movements dated through fission track studies indicate that the contractional event started in the Maastrichtian with its climax occurring in early Eocene. This late event generated the highs which separated the three late Eocene sub-basins.
A total of nine (9) total subsidence curves were prepared and corrected using paleobathymetry as well as the amount of section removed by erosion. They illustrate very well the evolution of the accommodation space from late Jurassic to Present, and also reflect the load associated with structural piling as well as the flexure on the Llanos and Middle Magdalena basins, which commenced approximately 40 Ma in late Eocene.
The evolution of the basin involved four (4) main stages, as follows: 1) Paleozoic extension (Late Paleozoic), 2) Triassic inversion, 3) Mesozoic extension (Late Jurassic-Early Cretaceos), and 4) Paleogene inversion (Late Paleocene – Holocene). During this late stage of inversion, the late Jurassic-Cretaceous basin underwent shortening of 55%, which corresponds to approximately 250 km, before reaching the present-day configuration.
The new paleogeographic configuration generated under contractional conditions, compartmentalized the Cretaceous basin creating three tertiary sub-basins. A series of fluvial systems running northwards, including dominantly braided and anastomosed streams, dominated sedimentation in the sub-basins. On the other hand, alluvial fan systems were located along an active fracture system, located next to the structural highs, which were uplifted and acted as provenance areas for the Middle Magdalena Valley and Cordillera Oriental sub-basins. Nevertheless, at certain times the northern portions of the sub-basins witnessed estuarine transitional facies, particularly in the distal parts of the fluvial systems.
Upper Eocene sandstones form the best reservoir for all the Colombian petroleum systems Therefore, characterization, location and predicting distribution of reservoirs are fundamental in exploration and field production. The new model proposed for late Eocene reservoirs opens up tremendous potential for the generation of new play concepts, which should be part of any sound hydrocarbon exploration program to be performed in the future.
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Belazi, Hadi S. "Sedimentology of Middle-Upper Eocene formations, Nafoora-Augila field, Libya (SPLAJ)." Thesis, Imperial College London, 1986. http://hdl.handle.net/10044/1/8580.
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Poole, Imogen. "A palaeoecological study of the "twigs" from the Eocene London Clay." Thesis, Royal Holloway, University of London, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.734435.
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Moss, Graham. "The Port Willunga Formation : Eocene/Oligocene boundary stratigraphy and foraminiferal turnover /." Adelaide, 1989. http://web4.library.adelaide.edu.au/theses/09SB/09sbm913.pdf.
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Carozza, David. "Carbon cycle box modeling studies of the Paleocene-Eocene thermal maximum." Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=66818.
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Approximately 55 million years ago, an unprecedented amount of light carbon was abruptly released into the ocean and atmosphere. This event, known as the Paleocene-Eocene thermal maximum (PETM), is documented by large negative carbon isotope excursions in marine and soil carbonates and by global environmental changes. Models have been applied to constrain the amount of carbon released during the PETM. In this study, the Walker-Kasting carbon cycle box model is revisited and, after correcting its carbon isotope equations, it is used to resolve a discrepancy in previous emission estimates. In addition, the atmospheric methane box model of Schmidt-Shindell is coupled to the Walker-Kasting model to explore the role of methane during the PETM. This coupled model is then combined with results from other modeling studies to demonstrate that the PETM may have been caused by the rel ease of approximately 3500 Pg C of thermogenic methane into the Atlantic Ocean.<br>Il y a environ 55 millions d'années, une quantité sans précédent de carbone a été brusquement libérée dans l'océan et l'atmosphère. Cet événement, désigné de maximum thermique Paléocène-Eocène (PETM), est identifiable par de remarquables excursions négatives de del13C en carbonate marin et sol, et par des bouleversements environnementaux d'échelle globale. Plusieurs modèles ont été utilisés afin d'estimer la quantité de carbone émise durant le PETM. Cette étude reprend le modèle du cycle du carbone de Walker-Kasting, révise ses équations du del13C et l'utilise pour résoudre un désaccord entre des estimés antérieures de l'émission totale. Le modèle du méthane atmosphérique de Schmidt-Shindell est également couplé à celui de Walker-Kasting dans le but d'examiner l'importance du méthane durant le PETM. Finalement, ce modèle couplé, en combinaison avec les résultats d'autres modèles, est implémenté pour démontrer que le PETM aurait pu être engendré par l'émission de 3500 Pg C de méthane thermogénétique à l'océan Atlantique.
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Swei, Giuma Hedwi. "Sedimentology, diagenesis and reservoir characteristics of Eocene carbonates Sirt Basin, Libya." Thesis, Durham University, 2010. http://etheses.dur.ac.uk/491/.
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The reservoir quality of Middle Eocene carbonates in the intracratonic Sirt Basin (at the northern margin of the African continent) is strongly influenced by depositional facies and various diagenetic modifications. This thesis investigates the petrography, sedimentology, diagenetic evolution and hydrocarbon potential of the Middle Eocene Gialo Formation in the subsurface of the north-central Sirt Basin based on data from core samples and well logs from five boreholes in the Assumood and Sahl gas-fields. Reducing risk in exploration demands an understanding of reservoir facies development, which is governed by the type and distribution of depositional facies and their diagenetic history. Seven major carbonate facies (and 20 microfacies) have been identified in this study and are interpreted as predominantly deposited under shallow-marine conditions within the photic zone, as indicated from their richness in phototrophic fauna and flora. These include lagoon (back-bank), main bank, fore-bank and open-marine facies, all of which were deposited on a homoclinal ramp type of carbonate platform. The type and distribution of the Gialo depositional facies were influenced by basin-floor architecture and environmental controls. The basin floor was shaped through pre-Eocene structural development into a series of elevated platforms and deep troughs. Platform facies were deposited across three broad facies belts: (1) inner-ramp, dominated by dasycladacean molluscan wackestone/packstone, nummulitic-bryozoan packstone, bryozoan wackestone; (2) mid-ramp, dominated by nummulitic packstone and Discocyclina-nummulitic wackestone; and (3) outer-ramp, dominated by fragmented nummulitic packstone. Troughs were dominated by thick successions of lime mudstone containing rare fine skeletal fragments and nummulites, with deposition taking place in a deeper-marine environment, below the photic zone. Present-day reservoir characteristics of the Gialo Formation are the net result of modification to the original depositional characteristics caused by diagenesis. This diagenesis took place on the seafloor, under burial, and in the meteoric diagenetic environment. Early marine diagenetic processes affecting the Middle Eocene Gialo carbonates resulted in micritization of bioclasts. Later diagenesis in meteoric to burial environments resulted in dissolution of aragonitic bioclasts, cementation (syntaxial overgrowths on echinoid grains, and blocky to equant, non-ferroan cements), neomorphism, pressure dissolution, compaction and fracturing. δ18O and δ13C values in the Gialo Formation range between -1.06 and -4.16‰ PDB, and 0.76 and 1.89‰ PDB, respectively. These values are mostly marine values, although some alteration is likely. The more negative oxygen of the cements suggests precipitation within the shallow-burial environment under the influence of meteoric water and / or precipitation at higher temperatures during further burial. The carbon isotopic signatures are typical marine values. There is a strong relationship between porosity and the diagenetic processes that-affected the Gialo sediments. Generally the porosity in the Assumood and Sahl fields is either primary or secondary, enhanced by dissolution and fracturing of the sediments. Reduction in porosity in the investigated sediments is mainly due to cementation and compaction. The common pore-types in the Gialo Formation are intergranular, moldic, intragranular, vuggy and scattered fractures. Porosity ranges from poor to very good (<1% to ~37%) and permeability varies from low to high (<1mD to 100mD). These variations in porosity and permeability are strongly related to facies changes, which were influenced by depositional environment and diagenetic processes. Shallow-water packstones/rudstones containing both primary intergranular and secondary biomouldic porosity have the best reservoir quality. The Gialo Formation is an important gas producing reservoir in the Assumood, Sahl and other surrounding fields. The gas which is generated from the gas-prone Sirt Shale source rock of the northern Ajdabiya Trough possibly migrated onto the Assumood Ridge from the northeast through late Cretaceous, Paleocene and early Eocene carbonates, before being trapped beneath the Augila Shale (Upper Eocene) which is the principal regional seal in the area. This integrated study has helped to understand the reservoir heterogeneity and potential of the Gialo carbonates and based on this current wells are being completed appropriately, as, hopefully, will future wells too. The facies pattern is different from one well to another, which does suggest that there was a strong tectonic control, that is differential tectonic subsidence and/or fault control, or that deposition was controlled by autocyclic processes. The different vertical positions and numbers of transgressive-regressive cycles in each well make formation-wide correlation problematic. The lack of correlation in terms of cycle thickness, as well as facies, between wells, also suggests autocyclic processes. Third and fourth-order relative sea-level (RSL) changes do not appear to have been a major control on deposition during this Middle Eocene time.
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Dawber, C. F. "The middle Eocene climate transition : insights from foraminiferal and sedimentary records." Thesis, University of Cambridge, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.598412.
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New seawater oxygen isotope reconstructions support the presence of a dynamic cryosphere since the early Middle Eocene with significant ice storage in both hemispheres. The onset of early Cenozoic glaciation is hypothesised to be intimately linked with levels of atmospheric <i>p</i>CO<sub>2</sub>. The relationship between bottom water carbonate saturation and the trace metal composition of the benthic foraminifera <i>Oridorsalis umbonatus </i>is investigated using core top and Middle Eocene data sets. B/Ca, Li/Ca and Sr/Ca ratios are correlated with bottom water carbonate saturation, whilst Mg/Ca ratios primarily record bottom water temperature. Discrepancies in Middle Eocene estimates of bottom water carbonate saturation that are based on applying core top calibrations to down-core records of B/Ca, Li/Ca and Sr/Ca indicate that there are some gaps in our understanding of the proxy systematics. The Barton Clay Formation at Alum Bay on the Isle of Wight was studied to assess whether there is evidence for sea level variations during the Middle Eocene. An integrated magneto-bio-chemostratigraphic age model for the Barton Clay Formation is also presented. Third- and fourth-order sequence stratigraphic cycles are identified in records of grain size, sediment properties, faunal assemblage and foraminiferal diversity indices, and are consistent with 40-60 meter variations in water depth. These cycles can be correlated to other successions within the basin on the basis of litho- and biostratigraphic markers. Evidence of reworked clasts and calcareous nannofossils is consistent with episodic uplift within the basin during the Bartonian and at present, precludes the calculation of eustatic sea level variations. The amplitude and duration of water depth variations in the Barton Clay Formation are consistent with glacio-eustacy.
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Bordet, Esther-Jeanne. "Eocene volcanic response to the tectonic evolution of the Canadian Cordillera." Thesis, University of British Columbia, 2014. http://hdl.handle.net/2429/46271.
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The Ootsa Lake Group (OLG) represents a voluminous episode of Eocene volcanism across the Interior plateau of British Columbia (BC), in the Canadian Cordillera. Remarkable aspects of the rocks (lithology, texture, volume, extent, and geochemistry) suggest that even though they formed along an active continental margin, the tectonic setting was different from a classic arc. The OLG was defined by field mapping, U-Pb and ??????Ar/?????Ar geochronology, major and trace elements geochemistry, and three-dimensional modelling of the thickness and structure. A new tectonic model for the evolution of the Canadian Cordillera in the Paleogene is proposed using this comprehensive dataset.
The OLG stratigraphy comprises a thick sequence of rhyolite and dacite lava, locally capped by andesite. Onset, duration and termination of volcanism are equivalent across the Interior plateau, and are constrained between 54.7 and 46.6 Ma by new U-Pb and ??????Ar/?????Ar geochronology.
OLG lavas yield a ???volcanic arc??? signature (diagnostic high-K calc-alkaline trend, and trace and rare earth elements patterns), suggesting supra-subduction zone contributions from a hydrated mantle wedge. However, a similar signature may be inherited from partial melting of crustal reservoirs composed of older accreted volcanic arc crust. This is supported by Sr isotope data indicating variable crustal contributions to melts across BC. OLG intermediate rocks were likely derived from mantle melting, but dominantly silicic compositions support partial melting of the crust as a dominant magma producing mechanism.
Eocene volcanic rocks cover at least 65,000 km?? of BC, but their original extent may have been almost continuous from southwestern Yukon to Idaho. Coeval volcanism and extensional deformation contributed to the accumulation and preservation of volcanic products in extensional basins, up to 4000 m thick in some locations. With such dimensions, the OLG may have attained the status of a Silicic Large Igneous Province prior to erosion.
The cause of OLG volcanism and coeval extension is attributed to the sudden ingress of hot sublithospheric mantle within a previously metasomatized mantle region, following cessation of subduction and a slab break. The resulting thermal anomaly progressed across a ???slab gap??? beneath BC, leading to mantle and lower crustal melting, crustal anatexis and magmatism.
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McKervey, John Antony. "The petrogenesis of the Eocene Challis Volcanic Group, Idaho, western U.S.A." Thesis, Open University, 1998. http://oro.open.ac.uk/57877/.
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The rocks of the Challis Volcanic Group, Idaho are investigated and constraints on their petrogenesis used to evaluate the tectonic control on the formation of early, extensionassociated magmatism in the western U. S. A. New and published 40Ar-39Ar analyses indicate that the rocks of the Challis Volcanic Group erupted between - 50 and 45 Ma at extrusion rates estimated at 0.01 to 0.03 km3 yr 1. The rocks have high-K calcalkaline/ shoshonitic compositions and incompatible trace element analyses show them to be LILE and LREE enriched ((La/Yb) -7 to 20) but relatively depleted in Nb, Ta and Ti (e. g. Nb/La < 0.5 in the main). All rocks have high initial 87Sr/86Sr (0.70673 to 0.71135) and low 143Nd/144Nd (0.51151 to 0.51234) ratios in comparison to oceanic basalts. The rocks are interpreted to result from partial melting in both spinel and garnet facies of heterogeneousm, ajor elementd epleted,L REE enriched but Nb, Ta and Ti depletedp eridotite source regions in the lithospheric mantle. The origin of these LREE enriched source regions is most probably related to mantle metasomatism in a subduction zone tectonic setting, although the' age of these events are not constrained. The petrogenesis of the Challis Volcanic Group is broadly similar to early magmatism from areas of the Cordillera to the south (e. g. Colorado River Trough), but contrasts with areas to the north where crustal melting apparently dominates (e. g. northern Idaho: Omineca Belt). Thus it is suggested that the syn-compression thermal history of the Cordillera, immediately prior to extension and early magmatism, varies significantly between southern and northern Idaho. This variation correlates spatially with the northern limit of compression within the Laramide Foreland Province (. 75 to 45/30 Ma). Compressional deformation within the Laramide Foreland Province may be coincident with a period of sub-horizontal subduction and therefore partial melting of the mantle lithosphere may be related to the removal of this subducted slab from beneath the lithosphere, although this remains poorly constrained. A comparison is made between the Challis Volcanic Group and Archaean sanukitoids, to suggest that the Tertiary rocks may provide a tectonomagmatic analogue for these particular late Archaean rocks. The implications of this comparison for late Archaean tectonics and crustal growth are discussed.
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Cotton, Laura. "Paleogene larger benthic foraminifera of Tanzania and the Eocene-Oligocene Transition." Thesis, Cardiff University, 2012. http://orca.cf.ac.uk/42726/.
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Mass extinctions are important events for the evolution of life on Earth but often the mechanisms behind them are poorly understood. The Eocene - Oligocene Transition (EOT) had a profound and lasting influence on global climate and, though not one of the “big 5” mass extinction events, widespread extinctions in many fossil groups have been recognised. Larger benthic foraminifera (LBF), one of the most conspicuous and widespread fossil groups during the Eocene, are known to have experienced a rapid global overturning during the EOT, including the extinction of long-ranging families such as the Discocyclinidae, Orbitoclypeidae, Pellatispiridae and a number of species in the Nummulitidae. However, detailed records through the transition are rare, and few complete sections are known; the timing and causes of extinctions therefore remain uncertain. Extensive field samples from the southern Tanzanian coastal region along with Tanzania Drilling Project (TDP) samples are used to give an overview of Eocene to Miocene LBF and to produce high resolution stratigraphic records of LBF events across the EOT. Two further important EOT sites, Fuente Caldera, Spain and Melinau Gorge, Sarawak, both with unresolved questions relating to LBF at the EOT were studied for comparison. The field samples combined with the TDP data cover an area of approximately 200 km from Kilwa to the Mozambique border. Initial comparisons with Tethyan and Indo-Pacific faunas show perhaps an intermediate assemblage in the Eocene and some similarities with the Indo-Pacific in the Miocene. However in both epochs there are features distinctive of an East African or western Indo-Pacific fauna. Additionally, this work identifies many previously unreported localities and provides a solid basis for future work. Three of the TDP sites span the EOT and contain abundant LBF. Extensive calcareous micro-, nannofossil and stable isotope studies of these cores allow the LBF stratigraphy to be tied to global stratigraphy. These records show that the LBF extinction event occurs close to the Eocene/Oligocene boundary (EOB), as defined by the extinction of the planktonic foraminiferal Family Hantkeninidae, rather than at the prominent oxygen isotope excursion in the early Oligocene that signifies maximum ice growth and global sea-level fall. New bulk isotope data from the Melinau Limestone of Sarawak further support this conclusion. In Fuente Caldera, where the extinction level was previously reported to be within the Oligocene, extensive reworking means that an EOB extinction is also likely at this site. This correlation raises new questions about the cause of the extinctions and has important implications for global larger benthic foraminiferal stratigraphy.
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Charles, Adam J. "Palaeoceanographic change during the Palaeocene/Eocene thermal maximum in Arctic Spitsbergen." Thesis, University of Southampton, 2011. https://eprints.soton.ac.uk/336449/.
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The interaction of the ocean, atmosphere and ice in the Arctic region plays a critical role in modulating global climate. However, recent observations have illustrated the region is changing rapidly in response to anthropogenically-induced warming. Given the uncertainty in climate model predictions, one way to analyse the response of the Arctic to warming is to generate records through transient warm intervals from the geological past. However, the most pronounced warming event of the Cenozoic, known as the Palaeocene/Eocene thermal maximum (PETM), is poorly documented in the Arctic region. Therefore, in order to place further constraints on environmental conditions in the high Arctic during the PETM, this thesis documents results from two new PETM localities in the Spitsbergen Central Basin, the BH9/05 core and the Bergmanfjellet outcrop section. Results from sedimentological, palynofacies and dinoflagellate cyst (dinocyst) analyses have been compared to previous results from the Longyearbyen section (Spitsbergen) and Intergrated Ocean Drilling Project Site 302-4A in order to analyse spatial and temporal changes across the event in this high Arctic setting. Analysis of Fe and Mn XRF time-series from core BH9/05 has been used to construct a cyclostratigraphic age model to constrain temporal changes. Together with radio-isotopic dating of a bentonite layer within the PETM, the cyclostratigraphic age model implies that the onset of the event occurred on a falling limb of the 405 kyr eccentricity cycle (between 55.728 and 55.964 Ma). Given that other early Palaeogene transient warming events (hyperthermals) have consistently been documented at the peak of both 100 and 405 kyr eccentricity cycles, or on the rising limb of such cycles, this suggests the PETM may have been initiated by a different mechanism compared to other hyperthermals. Furthermore, comparison of dinocyst assemblages across the Spitsbergen Central Basin illustrates a pronounced influx of the low salinity tolerant taxon Senegalinium during the PETM, consistent with a regime of enhanced precipitation and runoff. Such conditions led to salinity stratification, which together with elevated productivity and the warming of Arctic waters led to sedimentary anoxia and enhanced burial of marine organic matter. As the mechanisms driving anoxia and elevated productivity seen in the Central Basin would be expected to occur across the Arctic region, it is probable that the enhanced burial of contemporary marine organic matter was a pan-Arctic phenomenon in marginal settings. Given the burial of this type of organic matter sequesters carbon directly from the exogenic system, this suggests that the Arctic would have been a significant carbon sink during the PETM.
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Al-Alaween, Mohammad. "An organic geochemical study of the Jordanian Eocene Marl oil-shales." Thesis, University of Newcastle upon Tyne, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.744759.
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Unconventional natural energy resources, such as oil shales, constitute significant petroleum exploration opportunities. One promising example, which was deposited in an extended shelf environment of the Campanian-Eocene southern Neo-Tethyan margin, is the organic-rich marlstone in Jordan. In this study, new high-resolution depth profiles of bulk and molecular geochemical proxies are presented, collected from three cores drilled in central Jordan. Despite pronounced fluctuations in total organic carbon (TOC) (min. 0.4, max. 36.8, av. 11.0 %) and total sulphur (TS) (min. 0.1, max. 8.7, av. 2.7 %), Hydrogen Index (HI) values between 500 and 900 (mg HC/g TOC), along with high abundances and variability of sulphur bearing organic compounds, indicate preservation of type IIS kerogen. Molecular maturity marker derived indices from both the saturate and aromatic fractions were interpreted' with the aid of multivariate statistics (PCA). The results suggest thermal maturity levels spanning from immature to the kerogen type IIS early oil window and good to excellent source rock potential, consistent with TOC/S relationships, Tmax, the amount and composition of bitumen, and petrographic observations. The hydrocarbon (HC) compound class (e.g. n-alkanes, isoprenoids, steranes, hopanes) distributions support a primary marine source of the organic matter (OM) with some minor but variable contributions from terrestrial OM precursors. Consistent with marine OM source, the petrographic observations suggest OM to have largely undergone intense bacterial reworking, resulting in amorphous OM (AOM) and rarely primary OM remnants. The presence of specific biomarkers for photic zone euxinia, bottom water anoxia, and water column stratification, including isorenieratane, lycopane, and gammacerane, confirm a strongly reducing and at times even euxinic depositional environment with intermittent more oxygenated periods. These overall extreme redox conditions, which developed within a shallow rather proximal shelf system, significantly enhanced the preservation potential of hydrogen-rich OM and, in the absence of a significant supply of reactive Fe, favoured the incorporation of sulphur into the OM.
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Canile, Fernanda Maciel. "Evidências geológicas de mudanças climáticas (greenhouse-icehouse) na Antártica Ocidental durante a passagem Eoceno-Oligoceno." Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/44/44141/tde-08012011-203025/.
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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.<br>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.
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Smith, Nicholas E. "Acquiring three-dimensional data from small mammalian teeth laser scanning Eocene marsupials /." Huntington, WV : [Marshall University Libraries], 2007. http://www.marshall.edu/etd/descript.asp?ref=779.
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Smyth, Helen. "Eocene to Miocene basin history and volcanic activity in East Java, Indonesia." Thesis, Royal Holloway, University of London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.417139.
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King, Christopher. "Stratigraphy of the London Clay Formation (Early Eocene) in the Hampshire Basin." Thesis, Kingston University, 1991. http://eprints.kingston.ac.uk/20552/.
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Stratigraphy of the London Clay Formation (Early Eocene) in the Hampshire Basin Lithological logging and micropalaeontological analysis of selected exposures and boreholes in the London Clay Formation of the Hampshire Basin has enabled detailed correlation and subdivision of the Formation. The sediments are classified into nine main lithofacies, deposited in marine shelf and marginal-marine environments. The recognition and correlation of numerous minor stratigraphic discontinuities within the Formation enables its subdivision into 22 depositional sequences. Within each sequence, an initial marine-flooding transgressive episode characterised by glauconitic sediments is followed by progradation of shallow marine and marginal marine facies from the basin margin. Cross-stratified sands with basal erosional contacts at the top of some sequences record rapid sea-level falls, with channelling of the shelf. The depositional sequences within the London Clay Formation are mainly fourth order parasequences, and are interpreted as induced by eustatic sealevel fluctuations. The detailed stratigraphic record is used to produce a coastal on1ap curve for the time-interval covered by the London Clay Formation. 85 species of benthonic foraminiferids and 79 species of ostracods are recorded from the London Clay Formation. Their taxonomy is summarised. Other microfossil groups including calcareous 'microproblematica', planktonic foraminiferids, diatoms, serpulids and bryozoa have also been studied. The biostratigraphic significance of all these groups is assessed, and selected biostratigraphic events are utilised for correlation within the Hampshire Basin. Correlation with other areas in North West Europe is discussed. The biostratigraphic and magnetostratigraphic data is summarised in order to attempt placement of the London Clay Formation within the standard geochronological scale. The palaeogeographical context of the Hampshire Basin during the Early Eocene is assessed.
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Heri, Alexandra Regina. "Geochemistry, geochronology and isotope geochemistry of eocene dykes intruding the Ladakh batholith." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2012. http://hub.hku.hk/bib/B50899624.
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Eocene dykes intruding the Ladakh batholith were sampled along the southern margin of the Trans-himalayan plutonic arc in Ladakh, NW-India. Approximately 30 dykes were encountered in the 40 km trail between Leh and Hemis Shugpachan. The dykes in the east of the field are trending E to NE and those in the west trending N to NW, exhibiting sub-parallel orientations within each area. Eighteen dykes were sampled (two of them multiple times) and subjected to petrographic, geochemical and isotopic analyses. They exhibit various degrees of differentiation from basaltic to rhyolitic compositions and are mainly composed of plagioclase, quartz, hornblende (s.l.) and/or biotite and magnetite. Furthermore, dykes in the eastern part of the field area contain quartz xenocrysts resulting from crustal assimilation, while no relict quartz was found in the west. The dykes exhibit alteration phases and features suggesting that they underwent autometamorphism, i.e. hydration reactions due to igneous cooling. Whereas the dykes in the east of the field area record low-T alteration, the mineral parageneses in the west are typical for alteration at elevated temperatures typical for greenschist metamorphic facies. Al-in-hornblende barometry performed on Magnesio-hornblende and Tschermakitic-hornblende phenocrysts of the least altered dyke indicates formation in upper-amphibolite metamorphic facies conditions and pressures of about 6 kbar corresponding to an intrusion depth of approximately 20 km.
Major and trace element analyses and Rb-Sr and Sm-Nd isotope analyses revealed a stunning variability in geochemistry and isotopic composition amongst the coeval dykes. All dykes exhibit LREE enrichment and HREE depletion as well as negative Tb and Nb anomalies characteristic for subduction-related intrusives and extrusives. Their REE patterns support a clear subdivision into chemically distinct groups. The group hypothesis was further tested and found valid using statistical tools designed to assess similarity/dissimilarity amongst individuals of a group with a common ancestor, such as hierarchical cluster analysis and multidimensional scaling. The dykes are cogenetic, but clearly not consanguineous, i.e. have not formed from one, progressively differentiating magma chamber.
The variability observed in Sr-Nd isotopes can be explained by the dykes having undergone differing degrees of crustal assimilation. In particular the dykes in the east containing quartz xenocrysts show negative iiNd) and positive N(Sr) values caused by crustal assimilation, whereas the dykes in the west with no quartz xenocrysts exhibit positive qqNd) and N(Sr) near zero. 39Ar-40Ar dating by incremental heating of several hornblende-bearing dykes revealed crystallization ages between 50 and 54 Ma, whereas two biotite-bearing dykes gave ages of 45 and 37 Ma, likely to be cooling or recrystallisation ages.
The combination of structural field evidence with petrographic, petrologic, geochemical, isotopic and geochronological analyses demonstrates that the dykes, although sharing a common origin, i.e. having formed in the same tectonic setting at roughly the same time, have undergone further geological processes leading to an unexpected diversification of the dykes. These findings provide ample scope for further in-depth and breadth investigations on “late-magmatic dykes” in the future.<br>published_or_final_version<br>Earth Sciences<br>Doctoral<br>Doctor of Philosophy
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Sayer, Zoë Rebecca. "The Nummulitique : carbonate deposition in a foreland basin setting, Eocene, French Alps." Thesis, Durham University, 1995. http://etheses.dur.ac.uk/6103/.
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The Eocene Nummulitique (Lutetian to Priabonian) has been studied in the external chains of the French Alps in Haute Savoie and Haute Provence. The Nummulitique unconformably overlies the Mesozoic passive margin succession and represents the onset of sedimentation in the Alpine Foreland Basin which formed due to lithospheric flexure caused by the advance of the Alpine orogeny. The base of the formation is marked by a regional erosional unconformity that developed during subaerial exposure of the Alpine foreland. The Nummulitique may be divided into two informal members: the lower Infranummulitique, a succession of terrigenous carbonates, and the overlying Nummulitic Limestone, a shallow marine carbonate ramp succession. The Infranummulitique is composed of terrigenous carbonates thought to have been derived from the uplifted and eroding foreland which were redeposited in local depocentres due to the topography on the erosion surface. The Infranummulitique can be divided into four facies associations: i) a lenticular conglomerate/nodular marl deposited from ephemeral streams, ii) a sheet conglomerate deposited in a marginal marine fan delta, iii) a Cerithium marl deposited in a brackish water coastal plain/lagoon and iv) a Microcodium wackestone deposited from coastal marine channels. The Nummulitic Limestone is marked by the appearance of the first fully marine foraminifera and a change from terrigenous to autochthonous carbonate sedimentation on a low-energy ramp dominated by larger benthonic foraminifera. The inner-ramp is represented by the deposition of bioclast shoals (packstones and grainstones) dominated by either calcareous red algae, Nummulites or peloids. The middle-ramp is dominated by mud-rich wackestones with a fauna of flat foraminifera, with local winnowed accumulations attributable to storm reworking. The outer ramp and basin are represented by mudstones and marls with a sparse benthos. The Nummulitique shows a marked cyclicity within an overall deepening upwards succession which is interpreted to be the combined effects of tectonic basin subsidence and high-frequency (4th order) eustatic sea-level variations. As the basin developed, the eustatic signature producing the small-scale cyclicity was successively overprinted by accelerating basin subsidence which controlled the stratigraphy of the underfilled foreland basin. Initially, the carbonate productivity is able to keep pace with the relative sea-level changes and the ramp prograded into the basin. The combination of accelerating subsidence rates and nutrient and detrital influx from the approaching orogenic wedge reduced the carbonate productivity and the ramp drowned, leading to pelagic marl deposition. The drowning surface and small-scale cyclicity have been used to correlate between measured sections within each field area, but problems occur in correlating between areas due to the migration of the foreland basin producing a diachronous sedimentary succession, which shows a similar development around the Alps, regardless of the age of the sediments. This diachroneity is evident in the two study areas with similar sediments, cycles and key surfaces developed at different stages of the basin development. The similarity in the successions demonstrates that the early sedimentation in the French Alpine Foreland Basin was controlled primarily by flexural subsidence.
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Scudder, Christopher A. "Structure and Emplacement of the Eocene Golden Horn Batholith, North Cascades, Washington." Thesis, San Jose State University, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10815329.
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<p> The 48 Ma Golden Horn batholith is a ~310 km<sup>2</sup>, shallow intrusion constructed of sub-horizontal sheets in the crystalline core of the North Cascades of Washington. It is the only large body of granite in an orogen dominated by 96–45 Ma tonalite, and probably intruded during ridge subduction. The oldest and structurally highest unit of the batholith is diorite, followed by alkaline granite, one feldspar-biotite granite, two feldspar-biotite granite, and finally granodiorite, the youngest and structurally lowest unit. The batholith displays a weak NE-striking foliation restricted to the center of the intrusion and a stronger NW-striking foliation formed throughout the batholith with an associated weak, NW-trending and shallowly plunging lineation. Foliation is coupled across the northwestern and parts of the southern contact, and likely records a NE-SW shortening component in an overall transtensional regime. Most Golden Horn dikes intruding host rock are felsic, but there are some mafic dikes. These steeply dipping dikes tend to form swarms and strike NE and E-W. The NE-striking dikes reflect regional NW-SE extension. Parts of the southern contact are marked by xenolith-rich zones, which are ~100 m wide and several km long, and lend evidence to stoping as an emplacement mechanism. The diking, stoped blocks, and lack of a ductile aureole are compatible with shallow batholith emplacement models.</p><p>
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Schroeder, Melissa Light. "Palynological reconstructions of Early Eocene flora of the Wind River Basin, Wyoming." Miami University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=miami1375541094.
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Thrasher, Bridget L. "Regional climate modeling studies of western North America under early Eocene conditions /." Diss., Digital Dissertations Database. Restricted to UC campuses, 2009. http://uclibs.org/PID/11984.
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Kickham, Julie C. "Structural and Kinematic Evolution of Eocene-Oligocene Grasshopper Extensional Basin, Southwest Montana." DigitalCommons@USU, 2002. https://digitalcommons.usu.edu/etd/6729.
Full textAbstract:
The Grasshopper basin of southwest Montana is a complex east-dipping graben containing five unconformity-bounded sequences of Tertiary sedimentary rocks. The Eocene-Oligocene basin lies within the northern Rocky Mountain Basin and Range province. Geologic mapping in five and a half 7.5 minute quadrangles indicates that at least three distinct phases of extension characterize the Cenozoic tectonic evolution of Grasshopper basin from approximately 46 Ma toMa.
The significant phases of extension in Grasshopper basin were phases 1 and 3. During the first phase of extension (46-27 Ma) the nonplanar Muddy-Grasshopper fault was initiated and 90% of the basin fill was deposited. At least 7 km of dip-slip displacement along this fault controlled the deposition of the Medicine Lodge beds (3.5 km thick) and development of a transverse fold train and a longitudinal anticline. The second phase of extension (late Eocene-early Oligocene) resulted in northwest-southeast trending extensional structures and was probably coincident with deformation along the Lemhi Pass fault (20 km to the southwest). The third phase of deformation (early Oligocene-middle Miocene) dismembered the once larger protobasin into smaller subbasins and tilted the northwest-dipping limb of the longitudinal anticline. The structures formed during this phase have north-south and northeast trends. Little sediment was deposited during phases 2 and 3. Overall >85% E-W extension accrued.
Extensional folds are common in Grasshopper basin and formed during all three phases of extension. One orthogonal fold set was recorded. Two-dimensional kinematic analysis of the longitudinal Bachelor Mountain anticline shows that this fold is a double-rollover that probably developed above a longitudinal ramp in the Muddy-Grasshopper fault. The transverse folds are the result of the changing strike of the downward-flattening Muddy-Grasshopper fault. A transverse syncline developed above a convex up part of the fault whereas a transverse anticline formed above a concave up part of the fault that reflects changes in the strike of the fault. Three-dimensional inclined shear probably created this geometry.