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Roigé, Taribó Marta. "Procedència i evolució dels sistemes sedimentaris de la conca de Jaca (conca d’avantpaís Sudpirinenca): Interacció entre diverses àrees font en un context tectònic actiu." Doctoral thesis, Universitat Autònoma de Barcelona, 2018. http://hdl.handle.net/10803/565902.
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La caracterització de l’evolució dels sistemes sedimentaris en conques d’avantpaís contribueix a desxifrar la història tectònica i erosiva de les seves àrees font. Els dipòsits clàstics de l’Eocè fins al Miocè de la conca Sudpirinenca constitueixen un exemple natural magnífic per investigar els canvis en els paleoambients, en les àrees font i en la composició dels sediments durant l’evolució de la conca.
Aquesta tesi presenta un estudi integrat sobre la procedència dels sistemes sedimentaris de la conca de Jaca, basat en l’anàlisi petrogràfic de gresos, el comptatge modal de conglomerats i l’anàlisi geocronològic d’U-Pb dels zircons detrítics. Aquesta metodologia s’aplica concretament en els dipòsits que representen els últims estadis de sedimentació turbidítica durant el Lutecià (Grup Hecho), i la seva evolució als sistemes deltaics que culminen amb la continentalització de la conca, durant l’Oligocè (Formació Campodarbe). Aquest canvi en els ambients sedimentaris va acompanyat d’una major reorganització en les xarxes de drenatge, la qual és objecte d’estudi en aquest treball.
S’estableix un sistema principal de drenatge axial durant la sedimentació del Grup Hecho procedent d’àrees font situades a l’est i localitzades en els Pirineus centrals. En canvi, els últims dipòsits turbidítics, corresponents al canal del Rapitán (Bartonià) són interpretats com els primers indicis de creació d’una àrea font situada al nord, provocada per l’activitat de l’encavalcament de Lakora/Eaux-Chaudes. El posterior reemplaçament de la sedimentació turbidítica per ambients deltaics i continentals (Formacions Belsué-Atarés, Sabiñánigo i Campodarbe) es caracteritza per la interacció dels sistemes de drenatge axial, procedents dels Pirineus centrals, i els sistemes de drenatge transversal, procedents de noves àrees font situades al nord, creades per l’activitat de l’encavalcament de Gavarnie. Aquestes noves àrees font estan formades pels materials mesozoics i paleozoics de la Zona Nord Pirinenca i pels dipòsits turbidítics anteriors, els quals són reciclats en el ventalls al·luvials de la conca. Fruit de l’activitat tectònica emergent al nord de la conca, durant l’Oligocè els sistemes de drenatge transversal s’acaben imposant als de drenatge axial, i evolucionen, sobretot de nord a sud, i d’est a oest, guanyant espai en la conca d’acord amb el sentit d’avançament de les estructures, provocant el desplaçament del sistema de drenatge axial cap a posicions més occidentals.
Finalment, s’estableix un últim estadi de rebliment de la conca de Jaca a finals de l’Oligocè i Miocè inferior, representat pels dipòsits al·luvials del ventall de San Juan de la Peña (Formació Bernués), els quals coexisteixen amb els ventalls de Luna i Huesca, situats a la conca de l’Ebre, registrant el reciclatge de la conca Sudpirinenca.
Amb tot, en aquesta tesi es fa palesa la necessitat d’integrar diferents tècniques d’anàlisi de la procedència, per tal de desxifrar senyals ambigües, que dificulten la caracterització de l’evolució dels sistemes sedimentaris, sobretot en contextos tectònics actius, on coexisteixen diverses àrees Font que evolucionen ràpidament en el temps.Characterization of the sediment routing evolution in foreland basins gives insights on the tectonic and erosional history of the source areas. The Eocene to Miocene clastic systems of the South Pyrenean basin are a good natural laboratory to investigate paleoenvironment, source areas and sediment composition changes during the progressive evolution of a basin. This thesis provides a multidisciplinary approach integrating sandstone petrography, clast point counting and detrital zircon U-Pb geochronology, applied in the Jaca basin sedimentary systems. This methodology is performed in the last turbiditic deposits from the Hecho Group, whose stratigraphic evolution from Lutetian deep-marine to deltaic and terrestrial environments during late Eocene-Oligocene times records a major tectonic and drainage reorganization in the active Pyrenean pro-wedge. A main axially drained system sourced from eastern areas, located in the central Pyrenees, is here characterized during the Hecho Group turbidite sedimentation. However, the last turbiditic deposits from the basin, known as the Rapitán turbidite channel (Bartonian), record the first sediment input sourced from new northern source areas, created by the activity of Lakora/Eaux-Chaudes thrust. The abandonment of the turbiditic sedimentation is replaced by deltaic to terrestrial environments (Belsué-Atarés, Sabiñánigo and Campodarbe Formations), which record the interplay of axially fed systems, sourced from the central Pyrenees, with transverse fed systems derived from new northern source areas uplifted by the activity of the Gavarnie thrust. These new source areas are composed by Paleozoic and Mesozoic materials of the North Pyrenean Zone, and by the former turbiditic foreland basin deposits that are recycled into the alluvial fan systems. During Oligocene times tectonics controlled the replacement of the axially fed systems by the transverse fed systems, from north to south, and from east to west, according to the main direction of progradation of the deformation. This situation resulted with the displacement of the axially fed system towards the western margin of the basin. The last stage of infill of the Jaca basin during Oligocene to early Miocene times consisted on the sedimentation of the alluvial deposits of the San Juan de la Peña fan (Bernués Formation), at the same time that alluvial sedimentation was initiated in the Ebro basin, by the Luna and Huesca which yielded to recycling of the former foreland deposits. This thesis highlights the importance of integrating different provenance techniques in order to resolve ambiguous provenance signals which hinder the characterization of the sediment routing evolution, chiefly in active tectonic settings, where diverse source areas can occur.
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Worthington, James, and James Worthington. "Paleozoic–Cenozoic Tectonics of Central Asia." Diss., The University of Arizona, 2017. http://hdl.handle.net/10150/625855.
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This dissertation investigates the evolution of continental orogenic systems in Central Asia during and between pre-collisional plate convergence (Cordilleran-style orogenesis), syn-collisional plate convergence (collisional orogenesis), and post-collisional tectonic processes within the scope of closing Paleo-Asian and Tethyan ocean basins. A brief introductory chapter outlines the scope and context of the research. Appendix A focuses on the Late Paleozoic closure of the Turkestan ocean basin and subsequent collision between the Karakum–Tarim and Kazakh–Kyrgyz terranes in the South Tian Shan, within the scope of the final amalgamation of the Mesoproterozoic–Permian Central Asian Orogenic Belt. Appendix B focuses on late Cenozoic syn-collisional exhumation of gneiss domes in the India–Asia collision, which is a component of the Triassic–recent Alpine–Himalayan orogenic belt. Abstracts of the results are provided in the respective appendices.
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Polhaupessy, Antoinette Adeleide. "Late Cenozoic palynological studies on Java." Thesis, University of Hull, 1990. http://hydra.hull.ac.uk/resources/hull:4634.
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This study is based on palynological investigations at three sites in Java: Bandung Lake, Trinil and Bumiayu. At Bandung Lake (Holocene) three cores were studied, while surface section samples were studied from Trinil in East Java (Middle Pleistocene) and Bumiayu in Central Java (Upper Pliocene). The Trinil site is well known for its hominid fossils.The pollen flora at each site is fully described and illustrated while the pollen record at each location is used to reconstruct their vegetational, environmental and climatic histories. An attempt has also been made to determine whether palynology can be used to assist in dating these deposits. At all three sites, the character of the local vegetation is better reflected than that of the regional vegetation.One of the Bandung sites (Rancaekek) was radiocarbon dated, suggesting deposition between 11,000 and 7,000 yr BP and represents a freshwater lake deposits. The lake gradually shallowed toward 7,000 yr BP, at which time it was drained. The regional pollen component suggests climatic amelioration at about 8,000 yr BP, possibly reflecting the maximum incoming of solar radiation experienced in the Northern Hemisphere about 9,000 yr BP.Studies at Trinil revealed a mosaic of forest and open vegetation growing on a lahar. The former climate at this locality was probably markedly seasonal, not unlike that of the present day. Palynology conclusively demonstrates that this sequence is Pleistocene rather than Pliocene in age. The palynological record at Bumiayu reflects a regressive sequence with lagoonal and freshwater lacustrine environments (Kalibiuk Formation) followed by freshwater fluvial deposition (Kaliglagah Formation). The climate during the deposition of this sequence was markedly seasonal. The data support an Upper Pliocene age for the Bumiayu sequence.Three taxa are shown to have become extinct in Java during the Plio-Pleistocene. These are Stenochlaena lamrifolia and S. areolaris, which become extinct at the end of the Pliocene, and Daczydium, which is thought to have become extinct during the Holocene.
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Clark, Marin Kristen 1973. "Late Cenozoic uplift of southeastern Tibet." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/29758.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2003.Includes bibliographical references.
Recent field work and DEM analysis show that remnant, local areas of a low-relief land scape (or "erosion surface") are geographically continuous across the southeastern Tibetan Plateau margin and can be correlated in order to define the maximum envelope of topogra phy of the margin itself. This observation contradicts earlier notions that the low-gradient plateau margin slope (i.e. the maximum elevation of the margin) is a product of landscape dissection and reduction by fluvial incision due to the presence of major rivers which drain this portion of the plateau and plateau margins. Although initial development of the erosion surface is likely diachronous, we propose that a continuous low-relief landscape existed at low elevations prior to uplift and long-wavelength tilt of the southeastern plateau margin. The modern altitude of the erosion surface provides an excellent datum for constraining the total amount of surface uplift of the southeastern plateau margin. The long-wavelength tilt of the surface across the plateau margin without major disruption mirrors the low-gradient decrease in crustal thickness across the plateau margin, which suggests that crustal thickening has occurred in a distributed manner. Because large-magnitude compressional structures of late Cenozoic age are lacking, we propose that crustal thickening beneath the southeastern plateau margin has largely been accomplished by preferential thickening the lower crust. Perched, relict landscape remnants that reflect slow erosion, low initial elevations and slow uplift rates contrast sharply with the rapidly eroding modern river gorges that incise the surface, indicating that the modern landscape is not in equilibrium. Surface remnants are preserved because incision of the fluvial system has been largely limited to major rivers and principle tributaries, and has not yet progressed throughout the entire fluvial network.
(cont.) This "transient condition" of the landscape in southeastern Tibet reflects the initiation of rapid bedrock incision into a developing plateau margin, and the altitude of the remnant erosion surface can also be used as a datum by which to measure the total amount of erosion since the beginning of plateau uplift. 2.1 Introduction The continent-continent collision between India and Eurasia is largely responsible for creating the Tibetan Plateau, the most extensive region of elevated topography on Earth [Figure 2.1]. The development of such an anomalously high landmass has been of interest to scientists in a broad range of disciplines ranging from lithospheric dynamics to the inter action between tectonics, climate and surface processes. Studies of the Tibetan Plateau have raised several first-order questions such as: 1) how is plate convergence accommodated in the continents and what are the relative contributions of continental subduction, uniform or differential shortening in the upper and lower crust, and lateral extrusion of rigid lithospheric blocks?; 2) how do spatial (or temporal) variations in crust and mantle rheology partition deformation throughout theorogen?; 3) does the convective removal of the mantle lithosphere contribute to surface uplift and high plateau elevation? ...
by Marin Kristen Clark.
Ph.D.
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Al-Hajri, Yasir Khalfan. "Quantifying cenozoic epeirogeny of West Africa." Thesis, University of Cambridge, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.614239.
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Wheeler, Paul John. "Cenozoic basin formation in SE Asia." Thesis, University of Cambridge, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.621934.
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Quaglio, Fernanda. "Taxonomia de invertebrados fósseis (Oligoceno-Mioceno) da ilha Rei George (Antártica ocidental) e paleobiogeografia dos Bivalvia cenozóicos da Antártica." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/44/44139/tde-25042008-153222/.
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As pesquisas apresentadas nesta dissertação integram o projeto CNPq - PROANTAR 550352/02-3 \"Mudanças paleoclimáticas na Antártica durante o Cenozóico: o registro geológico terrestre\", que estuda os depósitos cenozóicos da ilha Rei George em busca elucidação do histórico ambiental e climático desta região antártica. A evolução dos padrões de circulação marinha e atmosférica no Hemisfério Sul ocorreu em resposta ao isolamento geográfico e térmico da Antártica, resultado de sua separação da Austrália, no limite Eoceno/Oligoceno, e da América do Sul, no final do Oligoceno. Sob este aspecto, o estudo de organismos fósseis registrados nos depósitos cenozóicos da Antártica contribui para o entendimento das evoluções biológicas e ambientais ocorridas concomitantemente às mudanças paleogeográficas, oceanográficas e climáticas na região ao longo do Cenozóico. Frente à dificuldade de acesso, demanda logística e extensa cobertura de gelo, apenas uma pequena porção do registro geológico da Antártica está acessível para pesquisa. Afloramentos da ilha Rei George registram as mudanças climáticas e ambientais ocorridas do Oligoceno ao Mioceno, incluindo evidências do primeiro evento de glaciação perene no oeste do continente (Oligoceno). A despeito da abundância de fósseis nos estratos cenozóicos da ilha, são poucos os trabalhos taxonômicos com descrição sistemática detalhada de bivalves fósseis. O primeiro módulo do presente estudo apresenta a descrição taxonômica de invertebrados de depósitos cenozóicos aflorantes em duas localidades da ilha Rei George, Antártica ocidental. Da Formação Cape Melville (Mioceno), península Melville, foram descritos sete táxons de bivalves, incluindo seis espécies novas. Da Formação Polonez Cove (Oligoceno), Pico Vauréal, uma região previamente inexplorada paleontologicamente, foram descritos sete táxons de invertebrados (bivalves, braquiópodes, tubos de serpulídeos, briozoários e fragmentos de equinodermes), incluindo duas espécies novas. O segundo módulo corresponde à reunião dos gêneros de bivalves registrados em depósitos cenozóicos da Antártica. A análise do registro apontou para o conhecimento bastante incipiente sobre a diversidade de bivalves antárticos ao longo do Cenozóico. Além disso, a comparação entre gêneros de bivalves cenozóicos registrados na Antártica e Nova Zelândia revelou que a maior parte dos gêneros compartilhados está registrada em depósitos eocênicos, o que suporta o isolamento geográfico da Antártica e a redução do intercâmbio faunístico entre a Antártica e regiões periféricas após o Oligoceno. A análise do registro sugeriu um evento de dispersão intenso durante o Eoceno, e pequenos pulsos de dispersão após o Oligoceno. O padrão de distribuição dos táxons concorda parcialmente com as reconstituições de paleocorrentes disponíveis na literatura. A dispersão durante o Eoceno teria ocorrido da Antártica para a Nova Zelândia na direção do Atlântico para o Pacífico. Este evento de dispersão concorda com a hipótese de existência de conexões marinhas de plataforma rasa entre o oeste e o leste da Antártica (\"Passagem de Shackleton\") e da província Weddeliana do final do Cretáceo ao Eoceno. Os eventos de dispersão pósoligocênicos teriam ocorrido durante e após o estabelecimento da Corrente Circum-Antártica, não mais pela \"Passagem de Shackleton\", mas margeando a Antártica pelas bordas ocidental atlântica e oriental em direção à Nova Zelândia. A análise do registro dos bivalves cenozóicos da Antártica também concorda com a hipótese de glaciação perene a partir do início do Oligoceno na região leste do continente, e na metade do Oligoceno na região oeste, com temperaturas mais amenas que as observadas atualmente.The research presented in this dissertation comprised part of the CNPq - PROANTAR Project 550352/02-3 \"Mudanças paleoclimáticas na Antártica durante o Cenozóico: o registro geológico terrestre\", which studies Cenozoic deposits from King George Island in order to elucidate the environmental and climatic Cenozoic histories of this Antarctic region. Cenozoic evolution of marine and atmospheric circulation in the Southern Hemisphere occurred in response to the geographic and thermal isolation of Antarctica, which resulted from the separation of Antarctica from Australia, around Eocene/Oligocene boundary, and from South America, during the late Oligocene. Thus, study of fossil organisms from Antarctic Cenozoic deposits contributes to the understanding of biological and environmental evolutions that accompanied paleogeographic, oceanographic and climatic changes during the Cenozoic. As a result of the difficult access, logistic demand and extensive ice cover, only a small part of the Cenozoic Antarctic record is available for study. King George Island records climatic and environmental changes from the Oligocene to the Miocene, including evidence of the first full-scale glaciation (Oligocene) of West Antarctica. Despite the abundance of fossils in Cenozoic deposits of the island, taxonomic studies with detailed systematic descriptions of bivalves are very rare. The first section of this work consists of taxonomic descriptions of invertebrates from Cenozoic deposits cropping out in two localities of King George Island, West Antarctica. Seven taxa of bivalves, including six new species were described from the Cape Melville Formation (Miocene), at Melville Peninsula. Seven taxa of invertebrates (bivalves, brachiopods, serpulid tubes, bryozoans, and echinoderm fragments) were described from the Polonez Cove Formation (Oligocene), at Vauréal Peak, a site previously unexplored paleontologically. The second section presents the results of a survey of the Cenozoic fossil record of Antarctic bivalves. The analysis of the fossil record confirmed that the current knowledge about the Cenozoic diversity of the group is very scarce. Moreover, comparison of Cenozoic bivalve genera from Antarctica and New Zealand showed that the greatest number of shared taxa is recorded in Eocene deposits. This finding supports the geographic isolation of Antarctic and the drop in faunal interchange between Antarctica and periphery after the Oligocene. Analysis of the fossil record suggested an intensive dispersal event during the Eocene, and restricted pulses of dispersal from the Oligocene onwards. The distribution pattern of taxa provides partial support for available reconstructions of marine currents. Eocene dispersal would have occurred from Antarctica to New Zealand in Atlantic-Pacific direction. This dispersal event is consistent with the hypothesis of shallow marine connections between West and East Antarctica (\"Shackleton Seaway\"), as well of the existence of the Weddellian Province from the Late Cretaceous to the Eocene. Dispersal events following the Oligocene would have occurred during and after the establishment of the Circum-Antarctic Current, along the West-Atlantic and East margins of Antarctica towards New Zealand, and no longer through \"Shackleton Seaway\". These analyses also support the hypothesis of full-scale glaciation in West Antarctica from the early Oligocene onwards, and in East Antarctica since the mid-Oligocene, with warmer temperatures than today.
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Sapota, Tomasz. "Late Cenozoic Geoarchives from Lake Baikal, Siberia." Doctoral thesis, Uppsala University, Department of Earth Sciences, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-4552.
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Three long sediment cores (BDP-98 – 600 m, BDP-96 – 200 m and BDP-93 – 100 m) drilled in Lake Baikal (Siberia) have been studied with the aims of establishing an absolute chronology and reconstructing paleoclimatic and paleoenvironmental changes in the region. The location of the lake at relatively high latitude and continental interior and a thick continuous sedimentary archive that developed in a rift system tectonic setting provide unique material for this investigation. The cosmogenic isotope 10Be was used for dating and the results indicate time spans of 8 (+0.8\-0.6) Myr for BDP-98, 5.5 (±0.13) Myr for BDP-96 and >0.7 Myr for BDP-93. Two major sedimentary facies (deltaic and hemipelagic) are distinguished by textural geochemical and mineralogical data. Detrital mineral composition suggests negligible change in provenance during the period studied. Formation of authigenic minerals, such as framboidal pyrite, vivianite and siderite, reflects variable environmental conditions in the lake and climate change in the region. Biogenic silica content shows climatic influence, which is modified by the supply of detrital material and postdepositional alterations. 10Be dating, combined with lithological analysis of the sediments, makes it possible to place temporal constrains on climate cooling at the Miocene/Pliocene boundary (5 Myr ago) and at the Early/Late Pliocene boundary (3.6 Myr ago) as well as the beginning of the northern hemisphere glaciation at about 2.5–2.6 Myr ago. The regional east-west tectonic extension of south-east Asia, related to Tibetan Plateau uplift, was confined in the Baikal area to between about 7 and 5 Myr ago, with a rifting rate calculated at 7 mm year-1. Furthermore, the 10Be data suggest that geomagnetic field intensity strengthened around the Miocene/Pliocene boundary.
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Sterling, Nile Akel Kevis. "Cenozoic changes in Pacific absolute plate motion." Thesis, University of Hawaii at Manoa, 2003. http://hdl.handle.net/10125/7048.
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Using the polygonal finite rotation method (PFRM) in conjunction with the hotspotting technique, a model of Pacific absolute plate motion (APM) from 65 Ma to the present has been created. This model is based primarily on the Hawaiian-Emperor and Louisville hotspot trails but also incorporates the Cobb, Bowie, Kodiak, Foundation, Caroline, Marquesas and Pitcairn hotspot trails. Using this model, distinct changes in Pacific APM have been identified at 48, 27, 23, 18, 12 and 6 Ma. These changes are reflected as kinks in the linear trends of Pacific hotspot trails. The sense of motion and timing of a number of circum Pacific tectonic events appear to be correlated with these changes in Pacific APM. With the model and discussion presented here it is suggested that Pacific hotpots are fixed with respect to one another and with respect to the mantle. If they are moving as some paleomagnetic results suggest, they must be moving coherently in response to large-scale mantle flow.x, 73 leaves
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Kennan, Lorcan. "Cenozoic tectonics of the central Bolivian Andes." Thesis, University of Oxford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.306963.
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Rowley, Eleanor Jane. "Quantifying Cenozoic exhumation across the British Isles." Thesis, University of Cambridge, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.625018.
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Craig, Robert S. "Western Australian Late Cretaceous and Cenozoic brachiopoda." Thesis, Curtin University, 1999. http://hdl.handle.net/20.500.11937/2320.
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The research reported in this thesis focuses on Late Cretaceous and Cenozoic fossil brachiopods of Western Australia. Although the work is primarily taxonomic, it also includes biodiversity, distribution and some aspects of ecology of the brachiopods described.The most recent information on the anatomy, physiology and ecology of brachiopods is summarised at the beginning of the thesis.Identification of brachiopods is determined primarily on internal morphological features as brachiopods tend to be homomorphic, many species looking externally the same. The morphological features used in the identification of the brachiopods described within the thesis are defined.The fossil material studied has come from four sedimentary basins in Western Australia. The Carnarvon Basin contains Late Cretaceous and Cenozoic fossil material. The Perth Basin also has Late Cretaceous and late Cenozoic brachiopods The Bremer and Eucla Basin have Cenozoic deposits. The stratigraphy of the deposits containing the brachiopods is described.Until this study commenced, eight species had been described from Western Australia. This thesis describes fifty eight species including thirty new species, one new family and two new genera.In preparing descriptions of the new species it become evident that many of the species from the Southern Hemisphere were quite different to those found in the Northern Hemisphere. Their closest affiliation was with genera and species described from the Antarctic Peninsula. Four genera and one species from the Late Cretaceous deposits of Western Australia are common to the Late Cretaceous deposits of the Antarctic Peninsula. In the examination of the Tertiary material from the Carnarvon Basin, it also became clear that there was a strong correlation with Tertiary material from the Antarctic Peninsula. At least four genera are common to both deposits. Six brachiopod genera from the Middle Miocene deposits of the South Shetland Islands Antarctica are common to New Zealand. Nine genera, identified from the La Meseta Formation, Seymour Island, Antarctic Peninsula, are also common to New Zealand. These genera are also found in Australia. This evidence has led to the proposal that in the Late Cretaceous there was a common shelf environment from the Antarctic Peninsula to the north-west coast of Western Australia. In this area, which formed the high latitude southern circum-Indo-Atlantic faunal province, brachiopods evolved different genera and species than those in the northern hemisphere. Many then dispersed into northern areas of the Indian, Atlantic and finally Pacific Oceans.When the material from the Middle to Late Eocene of the Bremer and Eucla Basin was examined, five genera were found to be common to the Early Tertiary of the Carnarvon Basin. When comparing the species from the south-western basins and those from the south- east it was evident that similar species occur in the Middle to Late Eocene of the Bremer, Eucla, St Vincent and Murray Basins. There are some fifteen species in common. Many of these species then occur in the Late Oligocene south-eastern basins near Victoria and Tasmania as the gap between the Australia mainland and Tasmania began to open. One species that occurs in the Late Eocene of Western Australia is also described from the Late Oligocene of New Zealand.In considering the distribution of the Cenozoic brachiopods, genera first appear in the north-west of Western Australia and they then appear in chronological order in the south-western basins and south-eastern basins of South Australia, then the south-eastern basins of Victoria and Tasmania and then New Zealand. By the Late Eocene, there was a shallow marine connection between the Bight and the Tasman Sea. By the Late Oligocene this had widened and Australia was finally totally separated from Antarctica.The Proto-Leeuwin Current was responsible for the distribution of the brachiopods from the north-west of Western Australia to the southern coast. Possible mechanisms for the distribution of genera to New Zealand include rafting and an extended larval stage.It has been suggested that brachiopods in Australia are distributed according to the substrate on which they settle rather than any other factor. Using the information on the distribution of brachiopods in Western Australia throughout the Cenozoic this hypothesis is examined. It is suggested that avoidance of light in the photic zone and food availability with competition with bivalves are more important factors than substrate conditions.
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Craig, Robert S. "Western Australian Late Cretaceous and Cenozoic brachiopoda." Curtin University of Technology, School of Applied Geology, 1999. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=12043.
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The research reported in this thesis focuses on Late Cretaceous and Cenozoic fossil brachiopods of Western Australia. Although the work is primarily taxonomic, it also includes biodiversity, distribution and some aspects of ecology of the brachiopods described.The most recent information on the anatomy, physiology and ecology of brachiopods is summarised at the beginning of the thesis.Identification of brachiopods is determined primarily on internal morphological features as brachiopods tend to be homomorphic, many species looking externally the same. The morphological features used in the identification of the brachiopods described within the thesis are defined.The fossil material studied has come from four sedimentary basins in Western Australia. The Carnarvon Basin contains Late Cretaceous and Cenozoic fossil material. The Perth Basin also has Late Cretaceous and late Cenozoic brachiopods The Bremer and Eucla Basin have Cenozoic deposits. The stratigraphy of the deposits containing the brachiopods is described.Until this study commenced, eight species had been described from Western Australia. This thesis describes fifty eight species including thirty new species, one new family and two new genera.In preparing descriptions of the new species it become evident that many of the species from the Southern Hemisphere were quite different to those found in the Northern Hemisphere. Their closest affiliation was with genera and species described from the Antarctic Peninsula. Four genera and one species from the Late Cretaceous deposits of Western Australia are common to the Late Cretaceous deposits of the Antarctic Peninsula. In the examination of the Tertiary material from the Carnarvon Basin, it also became clear that there was a strong correlation with Tertiary material from the Antarctic Peninsula. At least four genera are common to both deposits. Six brachiopod ++genera from the Middle Miocene deposits of the South Shetland Islands Antarctica are common to New Zealand. Nine genera, identified from the La Meseta Formation, Seymour Island, Antarctic Peninsula, are also common to New Zealand. These genera are also found in Australia. This evidence has led to the proposal that in the Late Cretaceous there was a common shelf environment from the Antarctic Peninsula to the north-west coast of Western Australia. In this area, which formed the high latitude southern circum-Indo-Atlantic faunal province, brachiopods evolved different genera and species than those in the northern hemisphere. Many then dispersed into northern areas of the Indian, Atlantic and finally Pacific Oceans.When the material from the Middle to Late Eocene of the Bremer and Eucla Basin was examined, five genera were found to be common to the Early Tertiary of the Carnarvon Basin. When comparing the species from the south-western basins and those from the south- east it was evident that similar species occur in the Middle to Late Eocene of the Bremer, Eucla, St Vincent and Murray Basins. There are some fifteen species in common. Many of these species then occur in the Late Oligocene south-eastern basins near Victoria and Tasmania as the gap between the Australia mainland and Tasmania began to open. One species that occurs in the Late Eocene of Western Australia is also described from the Late Oligocene of New Zealand.In considering the distribution of the Cenozoic brachiopods, genera first appear in the north-west of Western Australia and they then appear in chronological order in the south-western basins and south-eastern basins of South Australia, then the south-eastern basins of Victoria and Tasmania and then New Zealand. By the Late Eocene, there was a shallow marine connection between the Bight and the Tasman Sea. By the Late Oligocene this had widened and ++
Australia was finally totally separated from Antarctica.The Proto-Leeuwin Current was responsible for the distribution of the brachiopods from the north-west of Western Australia to the southern coast. Possible mechanisms for the distribution of genera to New Zealand include rafting and an extended larval stage.It has been suggested that brachiopods in Australia are distributed according to the substrate on which they settle rather than any other factor. Using the information on the distribution of brachiopods in Western Australia throughout the Cenozoic this hypothesis is examined. It is suggested that avoidance of light in the photic zone and food availability with competition with bivalves are more important factors than substrate conditions.
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Casati, Rafael. "Caracterização tafonômica das concentrações fossilíferas da Formação Cape Melville, Grupo Moby Dick (Mioceno Inferior), Ilha Rei George, Antártica." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/44/44139/tde-19122007-101537/.
Full textAbstract:
Trabalhos objetivando a tafonomia de concentrações fossilíferas geradas em ambiente glacial ou periglacial são raros. Neste contexto, a presente dissertação realizou a caracterização tafonômica das concentrações fossilíferas da Formação Cape Melville, Grupo Moby Dick (Mioceno Inferior), Ilha Rei George, Antártica, tendo em vista a elucidação da gênese destes depósitos. Para tanto, dados relativos a um total de 534 espécimes foram obtidos nas camadas ricamente fossilíferas das quatro seções, denominadas Pingüineira (PRS), Hard Ground (HGS), Chaminé (CS) e Lava Crag (LCS), levantadas no topo da Península Melville entre Janeiro e Fevereiro de 2003. Destas, apenas a Seção PRS apresenta duas camadas fossilíferas distintas (PRS-C1 e PRS-C2). A fauna estudada é composta predominantemente por restos de moluscos bivalves. Restos menos abundantes de corais, caranguejos, gastrópodes e braquiópodes, além de icnofósseis, também estão presentes. A análise da composição taxonômica, ecológica e tafonômica permitiu identificar semelhanças entre as Seções PRS e HGS e entre as Seções CS e LCS. As seções PRS e HGS são compostas dominantemente por bivalves depositívoros da infauna rasa (Ennucula frigida, Enncula musculosa e Yoldia peninsularis), preservados preferencialmente com as valvas articuladas fechadas, porém fora da posição de vida, indicando remobilização da fauna pré-soterramento; a ausência de sinais de fragmentação, abrasão e incrustação indica que os bioclastos não foram afetados por processos bioestratinômicos químicos, físicos ou biológicos intensos. A ocorrência de bioclastos piritizados na Seção HGS é interpretada como resultante da decomposição dos organismos soterrados, ainda vivos, em ambiente anóxico. As assembléias das seções CS e LCS são constituídas dominantemente por bivalves suspensívoros da infauna profunda (Neilo (N.) rongelii), preservados preferencialmente com as valvas desarticuladas, indicando que os processos bioestratinômicos físicos foram mais atuantes, sendo, no entanto, raros os sinais de fragmentação e de outras assinaturas tafonômicas como incrustação e bioerosão. As valvas desarticuladas estão preservadas preferencialmente com a convexidade voltada para baixo indicando que os bioclastos foram colocados em suspensão e redepositados fora da posição de maior estabilidade hidrodinâmica; a orientação em planta destes bioclastos exibe direção preferencial, indicando atuação de correntes fracas e um maior tempo de exposição na interface água/sedimento; a ocorrência de raros restos de bivalves suspensívoros escavadores da infauna profunda (Panopea (P.) cf. P. regularis) e de caranguejos (Antarctidromia inflata) preservados em posição de vida é indicativa de que esta comunidade foi soterrada in situ por sedimentos em suspensão que trouxeram a tanatocenose de valvas desarticuladas. Os resultados obtidos no presente estudo reiteram a importância dos estudos tafonômicos e paleoecológicos no entendimento da dinâmica deposicional do passado, contribuindo com um grande conjunto de dados úteis na caracterização de ambientes glaciais e periglaciais.Works focusing on the taphonomy of fossil concentrations generated in glacial or periglacial environment are rare. In this context, the present dissertation carried out the taphonomic characterization of the fossil concentrations of the Cape Melville Formation, Moby Dick Group (Lower Miocene), King George Island, Antarctica, in order to elucidate the genesis of these deposits. To this end, data relative to a total of 534 specimens were obtained in the richly fossil layers of the four sections, called Pingüineira (PRS), Hard Ground (HGS), Chaminé (CS) and Lava Crag (LCS), investigated at the top of the Melville Peninsula between January and February of 2003. Of these, only the PRS Section presents two distinct fossil layers (PRS-C1 and PRS-C2). The studied fauna is mainly composed of remains of bivalve clams. Less abundant remains of corals, crabs, gastropods and brachiopods, as well as trace fossils, also are present. Taxonomic, ecological and taphonomic analyses allowed similarities to be identified between PRS and HGS and CS and LCS. PRS and HGS Sections are dominantly composed by shallow infaunal deposit-feeding bivalves (Ennucula frigida, Enncula musculosa Yoldia peninsularis), preserved preferentially with closed articulated valves, however out of life position, indicating remobilized fauna; the absence of signs of spalling, abrasion and incrustation indicates that the bioclasts were not affected by intense chemical, physical or biological bioestratinomic processes. The occurrence of pyritized bioclasts in HGS is interpreted as the result of decomposition of the entombed organisms, still alive, in an anoxic environment. The assemblages of CS and LCS Sections are dominantly constituted by deep infaunal suspension-feeding bivalves (Neilo (N.) rongelii), preserved preferentially with disarticulated valves, indicating that the physical biostratinomic processes were more operative; however there are few signs of spalling or other taphonomic signatures such as incrustation and bioerosion. Disarticulated valves are preferentially preserved convex down indicating that bioclasts were placed in suspension and redeposited in a position other than that of greatest hydrodynamic stability; the orientation of these bioclasts in plan view shows a preferential direction, indicating weak currents and a longer time of exposition at the water/sediment interface; the occurrence of rare remains of deep infaunal suspension-feeding bivalves (Panopea (P.) cf. P. regularis) and crabs (Antarctidromia inflata) preserved in life position is indicative that this community was entombed in situ by sediments in suspension that brought the thanatocenosis of disarticulated valves. The results obtained in the present study reiterate the importance of taphonomic and paleoecological studies for the understanding of the depositional dynamics of the past and contribute a great number of data useful in the characterization of glacial and periglacial environments.
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Masoud, Abdelmoniem Ahmed Mohamed. "Composition and age of Cenozoic volcanism in Libya." Thesis, University of Glasgow, 2014. http://theses.gla.ac.uk/5517/.
Full textAbstract:
Libya has five major Cenozoic volcanic provinces (Garian, Jabal Al Haruj al Aswad, Jabal Al Hasawinah, Jabal as Sawda and Jabal Nuqay) that have a surface area of approximately 66,000 km2. These volcanic provinces are dominated by alkali to mildly alkali basalts. The provinces are aligned NNW-SSE, typically occurring where NE-SW trending structural features intersect the main regional uplift structures. Small volumes of phonolites are associated with the basaltic volcanism at Garian and Jabal Al Hasawinah. Despite their size and relative accessibility the Cenozoic volcanic provinces of Libya have been rarely studied. In the first part of this thesis I report a new study of the petrology, geochemistry (major and trace elements, REE, Sr-Nd isotopes) and geochronology (40Ar/39Ar) of basalts and phonolites from the Garian volcanic province in north Libya. These analyses indicate that the plateau and late basalts are not distinct basalt types produced from melting of different mantle regions at different times as proposed by earlier studies. They are the product of fractional crystallisation of a common parent. There is little indication of crustal contamination. Trace element and REE data support an origin in 2 to 12 % melts of heterogeneous sub-lithosphere mantle. Trace elements and Nd and Sr isotopic composition of the Garian basalts overlap values measured in metasomatised peridotite xenoliths in the GVP. They are compositionally similar to Cenozoic volcanism of northern Libya (e.g. Jabal Al Haruj) and southern Italy (e.g. Etna and Pantelleria; European asthenosphere mantle reservoir), and they lack the influence of enriched mantle present in other North African Cenozoic basalt provinces. Compositional variation in the Garian province phonolitic magmas is dominated by extensive fractional crystallisation (50-83%) of plagioclase and alkali feldspars combined with an unusual style of assimilation (2-45%) of old upper crust typical of Pan-African shield. The new high precision age determinations of the phonolites suggest that they were produced over a very short period at ~8.1 Ma. This contrasts strongly with previous age determinations that were 40-50 Ma. In the second half of the thesis I report new Ar/Ar chronology measurements for extrusive and intrusive rocks all the major Cenozoic volcanic fields in Libya. The major pulse of basaltic volcanism in Garian in the north (from 6 to 2 Ma) overlaps in time in Jabal Al Haruj province in southern Libya. Jabal Al Hasawinah and Jabal as Sawda basalts were erupted significantly earlier (23-10 Ma). Dykes and plugs at all provinces imply basaltic volcanism started in Miocene, followed by periods of erosion. There is no systematic trend of time in Cenozoic basaltic volcanism of Libya. It appears to be related to reactivation of ancient structures during the passive rifting that has been produced in response to interaction of African and European plates since the late Mesozoic.
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Hodgson, Gillian Elizabeth. "Microfacies of the late Cenozoic southern North Sea." Thesis, University of East Anglia, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.480560.
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Hattum, Marco Willem Alexander van. "Provenance of Cenozoic sedimentary rocks of northern Borneo." Thesis, Royal Holloway, University of London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.423143.
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Hine, Nicolette. "Late Cenozoic calcareous nannoplankton from the Northeast Atlantic." Thesis, University of East Anglia, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.278144.
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Li, Qianyu. "Evolution and distribution of Cenozoic microperforate planktonic Forminifera." Thesis, Imperial College London, 1991. http://hdl.handle.net/10044/1/46887.
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Mackay, Laura Munro. "Cenozoic vertical motions in the North Atlantic region." Thesis, University of Cambridge, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.613816.
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Ma, Shing-ka'i George. "Petrology of mesozoic-cenozoic volcanic rocks in Northwestern Syria." Click to view the E-thesis via HKUTO, 2010. http://sunzi.lib.hku.hk/hkuto/record/B44136699.
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LlinaÌs, Agrasar Eduardo. "Evolution of cenozoic African crocodilians : biogeographic and palaeoenvironmental implications." Thesis, University of Bristol, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.289773.
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Aze, Tracy. "Cope's rule and macroevolution of Cenozoic macroperforate planktonic foraminifera." Thesis, Cardiff University, 2011. http://orca.cf.ac.uk/22350/.
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Abstract A comprehensive phylogeny of macroperforate planktonic foraminifer species of the Cenozoic Era (~65 million years ago to present) is presented. The phylogeny is developed from a large body of palaeontological work that details the evolutionary relationships and stratigraphic (time) distributions of species-level taxa identified from morphology (‘morphospecies’). Morphospecies are assigned to morphogroups and ecogroups depending on test morphology and inferred habitat, respectively. Because gradual evolution is well documented in this clade, instances of morphospecies intergrading over time have been identified, allowing the elimination ‘pseudospeciation’ and ‘pseudoextinction’ from the record and thereby permit the construction of a more natural phylogeny based on inferred biological lineages. Each cladogenetic event is determined as either budding or bifurcating depending on the pattern of morphological change at the time of branching. This lineage phylogeny provides palaeontologically calibrated ages for each divergence that are entirely independent of molecular data. The tree provides a model system for macroevolutionary studies in the fossil record addressing questions of speciation, extinction, and rates and patterns of evolution. Specifically for this thesis the phylogenies provide a statistically robust framework for testing Cope’s rule (the evolutionary trend towards larger body size along a lineage). Eleven case studies were selected at random from all possible Neogene lineages and the mean areas of ancestor and descendant populations were compared. Over 6000 measurements were taken from 30 lineages and the resulting data show that Neogene macroperforate planktonic foraminifera do not support Cope’s rule with only 48% of the ancestor-descendant population comparisons demonstrating an increase in mean area. The size analysis illustrates that the most robust method for testing Cope’s rule is to compare ancestor-descendant populations from the beginning and end of evolutionary lineages as these are the least affected by temporal sampling biases.
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Länje, Marcus. "Cenozoic history of North Atlantic deep sea carbonate preservation." Thesis, Stockholms universitet, Institutionen för geologiska vetenskaper, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-117984.
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Carbonate preservation in the oceans occurs at a depth called the carbonate compensation depth (CCD). The CCD is where the input rate of carbonate from the surface of the ocean is balanced by the dissolution rate. Factors controlling the CCD are the CO2 in the atmosphere, weathering, and productivity in the surface water, the depth of the lysocline and deep water currents (and their ocean circulation). Two previous studies have investigated the variation of the CCD through geologic time, one in the equatorial Pacific (Pälike et al., 2012) and the other compiled results from the Pacific, Atlantic and Indian Oceans (Van Andel, 1975). The project consisted of compiling a database of sediment lithologies for many more sites in the Atlantic since the compilation by Van Andel, 1975, and together with a subsidence model of the ocean crust the systematic variations of CCD could be investigated. The results show that the CCD varies both spatially and temporally in accordance with previous studies. The reconstruction of the CCD needs further analysis, and possibly data from the oldest drilling program, the Deep Sea Drilling Project (DSDP). One result that is very important is that this study includes a total of 91 sites in the Atlantic Ocean, far more than in any of the other two studies. Future work can build upon the already started database of sediment lithologies.
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Ma, Shing-ka'i George, and 馬興闓. "Petrology of mesozoic-cenozoic volcanic rocks in Northwestern Syria." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2010. http://hub.hku.hk/bib/B44136699.
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Sun, Yuanyuan, and 孙嫒嫒. "Cenozoic climatic and environmental changes in the Qaidam Basin." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/210238.
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Large discrepancies remain regarding the timing of Cenozoic paleoclimatic and paleoenvironmental transitions in the central Asia. The first order driving force behind these changes has been intensively debated. Global climate change, the uplift of Tibetan Plateau, and the evolution of Paratethys sea have been proposed as three major candidates. To understand the evolutionary history of climate and environment of the region and controlling factors responsible for these paleoclimatic and paleoenvironmental changes, a combined study utilizing multiple proxies, including microfossils, bulk carbonate carbon and oxygen isotopes, long chain alkenones, plant n-alkane-based indices (carbon preference index, average chain length and Paq) and compound-specific carbon and hydrogen isotopes of higher plant n-alkanes, was carried out on a long, continuous and well-dated section in Dahonggou, Qaidam Basin, northern Tibetan Plateau. A parallel study was also carried out in another relatively shorter section in the Xunhua Basin, northern Tibetan Plateau. Six intervals of paleoclimatic and paleoenvironmental transitions over an interval of ~35 Myr can be recognized in the studied sections, including Late Eocene-Early Oligocene gradual drying (prior to ~30 Ma), Middle Oligocene aridification (~30-26 Ma), Late Oligocene-Early Miocene wetting (~26-21 Ma), Early Miocene drying (~21-17 Ma), Middle Miocene climatic optimum (~17-13 Ma), and deteriorated climate since the late Middle Miocene (~13 Ma onwards). The reconstructed onsite C4 plant abundance including occurrence of C4 plants and their thriving and the followed decreasing, a sensitive indicator of available moisture level in the environment, agrees well with these intervals.
Microfossils and long-chain alkenones suggest that a relic sea existed in the Qaidam Basin during the Middle Miocene, thus falsifying any hypothesis of significant variations in elevations of northern Tibetan Plateau prior to the Middle Miocene. The relatively stable elevations since the Eocene and before the Middle Miocene of, respectively, the central-southern part and northern part of the Plateau reveals an insignificant role of Tibetan Plateau uplift in controlling the evolution of central Asian climate and environment during the early Cenozoic. However, the Middle Miocene marine transgression and the rapid plateau-scale uplift since the late Middle Miocene probably contributed to the Middle Miocene climatic optimum and the initiated aridification afterwards in the central Asia. A comparison of proxy records in the northern Tibetan Plateau with the global benthic oxygen isotope record suggests a tight relation between the climatic/environmental transitions in the central Asia and global climatic changes. This lends support to the hypothesis that global climate, by controlling the moisture supply to the continental interior, played the dominant role in the evolution of climate and environment of central Asia during the Cenozoic time.published_or_final_version
Earth Sciences
Doctoral
Doctor of Philosophy
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Galoukas, Stylianos Filippos. "Late Cenozoic ostracoda of Cyprus and their palaeoenvironmental interpretation." Thesis, University College London (University of London), 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283679.
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Jones, Stephen Marcus. "Influence of the Iceland plume on Cenozoic sedimentation patterns." Thesis, University of Cambridge, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.268681.
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Kaminski, Michael Anthony. "Cenozoic deep-water agglutinated foraminifera in the North Atlantic." Thesis, Massachusetts Institute of Technology, 1987. http://hdl.handle.net/1721.1/55312.
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Thesis (Ph. D.)--Joint Program in Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), February 1988.Vita.
Includes bibliographical references (p. 243-259).
by Michael Anthony Kaminski.
Ph.D.
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Hartley, Ross Alan. "Cenozoic transient convective uplift of the North Atlantic Ocean." Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.607889.
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Sharples, Alexander Gabriel William david. "Tectono-stratigraphic evolution of the Cenozoic Great Australian Bight." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/tectonostratigraphic-evolution-of-the-cenozoic-great-australian-bight(7025cc3d-1faa-4b0d-91d3-1bb514ee9237).html.
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The Great Australian Bight (GAB) is an extensive W-E striking continental margin basin that drifted northwards during the Cenozoic following rifting and separation from Antarctica in the mid/late Cretaceous. Seafloor spreading accelerated in the mid-Eocene and was associated with local volcanism. The mid-Eocene succession of the GAB is conspicuously mounded and separates a dominantly siliciclastic succession below from a fully marine carbonate succession above. The mounded succession was penecontemporaneous with major changes in global climate, oceanographic conditions and tectonic re-organization in the region, and thus may hold important clues as to the palaeo-environmental changes associated with these changes. The mid Eocene has so far only been described locally or in passing, usually by studies focused on either the siliciclastics below or the carbonates above. It was therefore chosen as a major focus point for the research project reported herein. Exploration activity in the GAB has been limited despite the presence of a working petroleum system and large target structures, but industry interest has increased over the past few years leading to 3D seismic surveys being acquired in the GAB. The focus for exploration is the Cretaceous succession beneath the relatively thin Cenozoic cover, which however, is still important in terms of shallow hazards and as overburden to the anticipated productive sections. As is often the case, the new 3D seismic data shows many overburden features in great detail and thus affords new insights to be gained that improve our understanding of the post-rift evolution of the marginThis thesis expands upon and reinterprets a pre-existing sequence framework in the Cenozoic GAB based from ODP Leg 182 results. A vast database of 2D and 3D seismic surveys has been integrated with exploration wells and borehole data and several surfaces have been calibrated to borehole and well constraints, then mapped to the maximum lateral extent across the available dataset. Surface mapping provided new insight into sequence deposition and palaeoenvironmental settings. Structure maps and thickness maps highlight key depocentre locations and trends over the Cenozoic GAB as well as stacked mass debris aprons. The newly discovered sequences raise new questions regarding trigger mechanisms in a-seismic areas and feed into industry geohazard perception models. The base surface of the Cenozoic framework hosts a plethora of mounded features across shelf and basinal section. All mounds within the dataset have been mapped. A set a bryozoan reef mounds have been interpreted lying parallel to the margin as linear complexes over 500 km. They coincide with the underlying siliciclastic delta clinoform breakpoints and provide insight into the changing palaeoenvironment at the 43 Ma mark, cessation of siliciclastics and regional marine transgression. Further mound mapping aided by 3D attribute extractions along the base Cenozoic unconformity led to the interpretation of a series of enigmatic igneous-based mounded features. The discoveries have been included in a comparative study, comparing all mounded features (igneous or carbonate) and contrasting their individual characteristics of geometry, seismic facies, dimension in order to understand mound origin and emplacement. A new grouping of mounds in the GAB has been established, the origin and emplacement mechanisms of which contribute to the global knowledge base.
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Testo, Weston. "Devonian origin and Cenozoic radiation in the clubmosses (Lycopodiaceae)." ScholarWorks @ UVM, 2018. https://scholarworks.uvm.edu/graddis/838.
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Together with the heterosporous lycophytes, the clubmoss family (Lycopodiaceae) is the sister lineage to all other vascular land plants. Given the family’s important position in the land-plant phylogeny, studying the evolutionary history of this group is an important step towards a better understanding of plant evolution. Despite this, little is known about the Lycopodiaceae, and a well-sampled, robust phylogeny of the group is lacking. The goal of this dissertation is to resolve the relationships among evolutionary lineages in the Lycopodiaceae and provide insight into the timing and drivers of diversification in the family.
First, to place the evolution of the family within a global and historical context, I generated a densely sampled, time-calibrated phylogeny of the family. I sampled 50% of the estimated 400 extant species in the Lycopodiaceae and used eight fossils to calibrate the age of major divergence events in the family and across the land-plant phylogeny. Further, we used a probabilistic biogeographic model to infer the historical biogeography of the family. Together, these analyses indicate that the Lycopodiaceae originated in the late Devonian, began its early diversification in the Carboniferous, and accumulated much of its extant diversity during the Cenozoic. From a geographical perspective, major cladogenesis events in the family’s history appear to be linked to the breakup of the Pangaean and Gondwanan supercontinents, with long-distance dispersal playing a role in the establishment of younger evolutionary lineages.
Second, I examined the drivers of diversification in the species-rich genus Phlegmariurus in the Neotropics. This clade includes an estimated 150 species and is most diverse in high-elevation habitats in the tropical Andes of South America. Using a time-calibrated phylogeny of the group and species distribution and niche data, I demonstrate a strong positive association between lineage diversification rates and the mean elevation of species’ distributions as well as a strong negative correlation between diversification rates and the size of species’ ranges. Further, we employ a paleoelevation-dependent diversification model to test for an association between the uplift of the Andes and diversification in the clade and demonstrate that speciation rates in Neotropical Phlegmariurus are positively associated with increasing elevations in the Andes.
Third, I use a phylogenetic framework to test the monophyly of morphology-based species groups in Neotropical Phlegmariurus. I demonstrate that most groups are not monophyletic, and that convergent evolution is widespread in the genus. We use ancestral character-state reconstruction methods for six morphological traits to elucidate patterns of trait evolution and to circumscribe new species groups. A total of eleven new monophyletic species groups are proposed and defined.
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Valverde, Pérez Ángel. "Numerical modeling of continental collision and intraplate deformation. Application to the Cenozoic geodynamic evolution of North Iberia." Doctoral thesis, Universitat de Barcelona, 2021. http://hdl.handle.net/10803/672478.
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This thesis aims at improving the current understanding of the geodynamic controls on tectonic deformation during plate collision, using the Cenozoic evolution of Iberia as a case scenario. Despite the vast efforts during the last decades, there is a limited understanding
today about what plate properties control the propagation of tectonic deformation towards the interior of tectonic plates. Meanwhile, the classic enigmas about the timing and the processes involved in the construction of the Iberian topography also persist: What is the origin of the high average elevation of the Iberian Peninsula? What is the quantitative contribution to topography induced by the intraplate tectonics of Iberia? How was this intraplate deformation in the middle of the Iberian microplate triggered?
To answer these questions, I first gathered information about the tectonic events in Iberia during the Cenozoic from previous structural tectonic and geodynamic modelling publications. Continental collision with Eurasia in the north first gave rise to the uprising of the Pyrenean and Basque-Cantabrian chains. Deformation subsequently jumped southwards and formed the elevation of the interior mountain ranges. Meanwhile in the southern margin, the subduction of the Tethys oceanic lithosphere due to the Africa-Iberia convergence gave rise to the Betics and opened the Alborán Sea. The underlaying hypothesis of this thesis is that this succession can be reproduced via a geodynamic model giving the appropriate initial conditions that are in reasonable agreement with the geological setting during the early-Cenozoic Iberia.
To this purpose, we carried out a series of high-resolution mechanical and thermomechanical numerical models with a state-of-the-art code named UNDERWORLD 2.0 (still under development at Univ. Melbourne). We first review fundamental ideas such as the patterns of deformation of the lithosphere predicted for converging continental margins, as well as the elevation of mountain ranges in a continental collision scenario. Then we investigate how the crustal deformation accommodates far from the continental margins, taking into
account the mathematical equations and physical laws that govern the thermal field and rock deformation.
Based on these, a series of mechanical numerical models are developed to explore the possible evolutionary scenarios after a continental collision. Two deformation end member models appear: double-vergence and crustal folding. While in the first one deformation concentrates near the axial collision zone where the orogen develops, in the second, deformation is transmitted farther from the initial contact between lithospheres. We compare these results with patterns of deformation seen in the Pyrenean mountain range as well as other natural scenarios where cortical folding occurs near a thrust failure like in the Zagros Chain in Iran.
This thesis then focuses on a series of high-resolution 2D numerical models for the North-Central area of the Peninsula. These models aim at linking the Cenozoic evolution of the Cantabrian chain to that of the Central System and the Duero basin. Here, deformation and failure consider creep-like behavior and plasticity in a viscoplastic rheology. We test the hypothesis of the presence of a detachment level within the Variscan basement, at the lower crust, of limited srength and thus capable of transmitting deformation towards the interior, potentially leading to the rise of the Central System. An alternative tested hypothesis is that the entire lithosphere folded in response to the convergence between Iberia and Eurasia.
Finally, we extend these 2D numerical models to the southern margin of Iberia to investigate how the approximation of Africa may have affected the distribution and timing of shortening in the different domains of the microplate, with particular emphasis on the topography and deformation of the Central System and adjacent basins.La presente tesis doctoral aborda el estudio de la evolución geodinámica de sistemas de colisión continental, usando como escenario de referencia la microplaca de Iberia durante el Cenozoico (últimos 65 millones de años). Pese al enorme esfuerzo acumulado por la comunidad geológica en este ámbito, los enigmas clásicos sobre la cronología y los procesos involucrados en la construcción del relieve y el subsuelo ibéricos persisten: ¿Cuál es el origen de la elevada topografía media de la Península? ¿Cómo ha sido construida su actual topografía como resultado de la peculiar posición de la microplaca tectónica de Iberia entre África y Eurasia? Para abordar estas preguntas, he recopilado información de estudios previos sobre episodios tectónicos desde el Cretácico Superior hasta la actualidad con especial atención a los intervalos relacionados con el choque continental con Eurasia que dio lugar al levantamiento de la cadena Pirenaica y Vasco-Cantábrica, la posterior elevación de las cadenas montañosas del interior y la posterior evolución del margen sur en relación con la aproximación entre África e Iberia. Para encontrar los mecanismos responsables de esta evolución, he diseñado una serie de modelos numéricos de alta resolución que simulan en 2D la deformación de la litosfera en límites de placa convergentes, utilizando uno de los programarios más evolucionados de la geodinámica internacional (Underworld 2.0; Univ. Melbourne). Este volumen empieza por tanto explicando las ecuaciones matemáticas y leyes físicas que gobiernan el modelo numérico, las relaciones entre los parámetros físicos y su importancia y sus limitaciones. Así, se han realizado una serie de modelos numéricos sintéticos en esta tesis para identificar los posibles escenarios evolutivos tras un choque continental donde aparecen dos modelos de deformación: doble vergencia y plegamiento cortical. Mientras que en el primero la deformación se concentra en torno a la zona de colisión donde se desarrolla un orógeno mediante fallas que buzan hacia la zona axial, en el segundo se transmite la deformación más lejos de la zona de colisión. Estos modelos sintéticos explican algunos rasgos de la deformación de la Cordillera Pirenaica y de la cadena de montañas de Zagros en Irán. Seguidamente, muestro otra serie de modelos numéricos termodinámicos 2D para la zona Norte-Centro de la Península. En este caso, los modelos tratan de explicar la evolución cenozoica de la cadena Cántabra junto con el Sistema Central y la cuenca del Duero en función de la viscoplasticidad adoptada para la roca. Se pone a prueba un hipotético nivel de despegue entre el basamento Varisco y la corteza superior que hubiera permitido transmitir esfuerzos hacia el interior formando el Sistema Central y la posibilidad de que toda la litosfera sufriera un plegamiento en respuesta a la compresión. Finalmente, estos modelos numéricos 2D se extienden hasta el sur Peninsular, examinando el papel de la frontera entre las litosferas Africana e Ibérica en la formación del Sistema Central y las cuencas adyacentes.
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Nelson, Faye Elizabeth, and University of Lethbridge Faculty of Arts and Science. "Late cenozoic magnetostratigraphy of Selkirk volcanics and associated sediments, west-central Yukon." Thesis, Lethbridge, Alta. : University of Lethbridge, Faculty of Arts and Science, 2006, 2006. http://hdl.handle.net/10133/357.
Full textAbstract:
Brunhes, Matuyama, Kaena and Mammoth age basaltic lava (Selkirk Volcanics - TQS) as
well as interbedded sediments were sampled in west-central Yukon Territory, Canada.
Paleomagnetic sampling of basalt mapped as TQS along a 370 kilometre transect
suggests that early eruptions of TQS occurred coevally over a significant distance to the
north of Fort Selkirk. Basal basalt at Ne Ch'e Ddhawa pre-dates continental glaciation in
Yukon and is older than the Fort Selkirk Vent (Lower Mushroom), previously thought to
be the oldest eruptive vent at Fort Selkirk. The high confining pressures required to form
pillow lava suggest subglacial eruptions at Mushroom section. An Early Pleistocene Fort
Selkirk glaciation sequence (till and outwash) was reversely magnetized and assigned to
the Late Matuyama chron between oxygen isotope stages 62 and 56 inclusive. A lateral
moraine on Ne Ch'e Ddhawa was reversely magnetized and therefore assigned to one of
the younger Pre-Reid glaciations.
ixi, 123 leaves : ill. (some col.) ; 29 cm.
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Hill, Robert S. "Evolution of the Australian flora in response to Cenozoic climate change /." Title page, contents and abstract only, 1997. http://web4.library.adelaide.edu.au/theses/09S.D/09s.dh6469.pdf.
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Williams, Gareth Anthony. "The role of tectonic inversion in the uplift and erosion of the St. George's and Bristol Channel basins, western UK." Thesis, University of Birmingham, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.288608.
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Franco, Ana Olivia Barufi [UNESP]. "Termocronologia por traços de fissão em apatitas na região do Arco de Ponta Grossa, entre os alinhamentos de Guapiara e São Jerônimo-Curiúva." Universidade Estadual Paulista (UNESP), 2006. http://hdl.handle.net/11449/92910.
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A evolução do Arco de Ponta Grossa, na região sudeste brasileira, durante o Meso-Cenozóico, apresenta uma estreita relação com os eventos tectono-magmáticos responsáveis pela abertura do Oceano Atlântico- Sul. A utilização do Método de Datação por Traços de Fissão em apatitas, nessa região, permitiu a identificação de cinco eventos térmicos, responsáveis pela estruturação dessa feição, a partir do Cretáceo. São eles: Evento A - Aquecimento em 130 Ma, relacionado ao evento de ruptura do Gondwana Sul-Ocidental e geração do Oceano Atlântico-Sul; Evento B - Resfriamento em 110 Ma, associado à reativação de antigas zonas de cisalhamento e/ou falhas geradas na ocasião do evento de ruptura do Gondwana Sul-Ocidental; Evento C - Aquecimento em 90 Ma, associado à um soerguimento regional, interpretado como alçamento de isógradas, provavelmente como reflexo do soerguimento do Arco de Ponta Grossa e conseqüente sedimentação correlativa (Grupo Bauru ls, no interior continental, e seqüência inferior da Formação Santos, na Bacia homônima), bem como de intrusões alcalinas; Evento D - Resfriamento em 60 Ma, correlacionado à um evento erosivo, que propiciou a formação de uma extensa superfície de erosão, neste caso a Superfície Sulamericana, amplamente registrada tanto na parte continental como na porção submersa adjacente ao Arco de Ponta Grossa (sob a forma de discordância regional na Bacia de Santos); Evento E - Resfriamento em 30/20 Ma, associado à atuação de ciclos erosivos, instalação de bacias tafrogênicas e, localmente, intrusões alcalinas.
The evolution of Ponta Grossa Arch, in southeastern Brazil, during Mesozoic-Cenozoic, seems to be related to the tectono-thermal events related to South Atlantic opening. The use of Apatite fission Track Method, in this region, allowed the recognition of five thermal events, responsible for the formation of this feature, since Cretaceous, which are: Event A - Heating event in 130 Ma, related to the Southeastern Gondwana break-up and the origin of South Atlantic Ocean; Event B - Cooling event in 110 Ma, associated to the shear zones reactivation and/or faults generated during Gondwana break-up; Event C - Heating event in 90 Ma, associated with a regional uplift, interpreted as uplift isotherms, probably as a reflection of Ponta Grossa Arch uplift and correlated sedimentation (Bauru Group ls, in continent and the inferior sequence of Santos Formation, in Santos Basin), and alkaline intrusions; Event D - Cooling event in 60 Ma, correspondent to an erosional event, that formed an extended erosional surface, in this case, Sulamericana Surface, registered both in continental region and in offshore portion (registered as a regional discordance in Santos Basin); Event E - Cooling in 30/20 Ma, related to erosional cycles, tafrogenic basins origin and, locally, alkaline intrusions.
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Vickery, Sara. "Cenozoic deformation in a plate-boundary zone, Marlborough, New Zealand." Thesis, University of Oxford, 1994. https://ora.ox.ac.uk/objects/uuid:590f1ea6-6d9e-4ed0-93ee-9d82e52e6be9.
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The Marlborough Fault System is a zone of dextral transpression in continental crust at the southern end of the Hikurangi subduction system between the obliquely convergent Australian and Pacific plates. Detailed mapping of an area of deformed Tertiary cover sequence on the down thrown side of the Kekerengu Fault (the Kekerengu- Washdyke study area) has revealed two phases of deformation, De and Dl. In the study area De consists of nine kilometre scale thrust faults cutting sediments derived from extra- and intra-basinal uplift. The timing of this episode is constrained by the age of the first clastic deposits and by a previously unidentified unconformity in this area of Late Miocene age. A clear sequence of Dl events is recognized deforming all earlier structures including Pliocene aged sediments. Although elsewhere in Marlborough a regional post-Pliocene ca. 20° clockwise block rotation has been previously identified, in the Kekerengu-Washdyke study area one site suggested no post-Pliocene rotation and another a large ca. 100° clockwise rotation. This lack of Dl rotation was unexplained and the large rotation attributed to localized Early Miocene deformation. Palaeomagnetic work carried out in this study has identified six more sites which contain this large rotation (average ca. 118+11°). The rotation therefore appears to be a regional event, likely to be a result of the location of Marlborough in the hinge zone at the southern end of the Hikurangi Margin. One site from dykes in basement rocks does not record this large rotation, indicating that the rotation occurred in upper layers detached from unrotating rock below by an unknown structure (such as a thrust fault), or that the rotation did not occur in this area. The large rotation is believed to have been achieved by pinning of the De thrusts to the south of the Marlborough region. The data suggests that the De thrusts in Marlborough were initially NW-trending and seaward, not landward-directed as was previously supposed. Palaeomagnetic work has also added to the evidence for a lack of Dl regional rotation on the downthrown side of the Kekerengu Fault. A previously unidentified second phase of Dl folding and 'bending' within the study area appears to have accommodated the regional rotation and suggests that the Kekerengu Fault acted as the eastern boundary of the Dl rotating block.
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Wagner, Frank Henry. "Cenozoic Extensional Tectonics Revealed Through Seismic Reflection Imaging, SE Arizona." Diss., Tucson, Arizona : University of Arizona, 2005. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu%5Fetd%5F1384%5F1%5Fm.pdf&type=application/pdf.
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McCune, Julian Glenn. "Cenozoic sedimentary evolution of the Helmville Basin, west-central Montana." CONNECT TO THIS TITLE ONLINE, 2008. http://etd.lib.umt.edu/theses/available/etd-05282008-101831/.
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Lin, Andrew Tien-Shun. "Cenozoic stratigraphy and tectonic development of the west Taiwan basins." Thesis, University of Oxford, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.393381.
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Petersen, Sierra Victoria. "Rapid Climate Change in the Cenozoic: Insights from Geochemical Proxies." Thesis, Harvard University, 2014. http://nrs.harvard.edu/urn-3:HUL.InstRepos:13064985.
Full textAbstract:
Studying the mean state and variability of past climate provides important insight into the dynamically coupled climate system, directly aiding projections of future climate. Reconstruction of past climate conditions can be achieved using geochemical proxies including the novel clumped isotope paleothermometer. In this thesis I use multiple proxies to study climate variability during the last glacial period and at the onset of Antarctic glaciation.
Greenland ice cores record repeated millennial-scale fluctuations in climate during the last glacial period known as Dansgaard-Oeschger (DO) cycles. We measure 18O of bulk sediment and planktonic foraminifera (Neogloboquadrina Pachyderma) in sediment cores from the North Atlantic to investigate fluctuations in sediment properties on the timescale of DO cycles. We find evidence of episodic deposition of carbonate ice-rafted debris near Iceland. Integrating these observations with published data and modeling studies, we propose a new hypothesis to explain DO cycles. We suggest that a large ice shelf in the Nordic Seas acted in concert with sea ice to set the slow and fast timescales of DO cycles. The ice shelf was periodically removed by subsurface warming with the timescale of shelf regrowth setting the duration of each interstadial.
We utilize the clumped isotope proxy to reconstruct the climate history during a key period of the Cenozoic - the onset of Antarctic glaciation. To facilitate this work, a new inlet is developed to streamline sample preparation and reduce sample size requirements. We decrease the required sample size from 5-8mg to 1-2mg per replicate, while still achieving external precision of 0.005-0.010o/oo, equivalent to previous methods. This new capability increases the range of possible applications for the clumped isotope paleothermometer, specifically in the field of paleoceanography. We apply the clumped isotope paleothermometer to thermocline-dwelling foraminifera (Subbotina angiporoides and Subbotina utilisindex) from the Southern Ocean core ODP689 across the Eocene-Oligocene transition. With the clumped isotope paleothermometer we separate the contributions of near- surface temperature change and ice sheet growth on the ~1o/oo increase in 18O observed in planktonic foraminifera from this site. We measure no change in temperature, and 0.8±0.2o/oo change in 18Osw, equivalent to 124-140% of the modern Antarctic ice sheet volume.Earth and Planetary Sciences
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Bevan, T. G. "A cenozoic stress history of southern England inferred from mesofractures." Thesis, University of Bristol, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.355136.
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Cocksworth, Graham. "Modelling plate driving forces for the present and the Cenozoic." Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.339730.
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Wilson, Jonathan William Peter. "Cenozoic epeirogeny of the Middle East and equatorial West Africa." Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.709049.
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Hosa, Aleksandra M. "Late Cenozoic extension in Limni Basin in northern Evia, Greece." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/55169.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2009.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 35-36).
The Aegean region has undergone several episodes of extensional deformation from early Miocene to present time. Among the structures that accommodate extension are faults that bound and cut sediments within young fault-controlled sedimentary basins. The objective of this study is to add to constraints on the history of within the upper plate of the Hellenic subduction zone. In particular, this study is aimed at mapping and, eventually, dating sediments and related normal faults in the Limni-Istiea basin of northern Evia. Field mapping in the southern portion of this basin reveals eight sedimentary units and suggests several periods during which steep relief was formed within and adjacent to the basin, interspersed with periods of deposition in fluvial and shallow lacustrine environment. The three sets of faults identified in the mapped area are consistent with the orientation of structures observed at the western end of the North Aegean trough system and within the Central Hellenic shear zone. The oldest faults are low-angle, north-south trending and east-dipping; younger structures are high angle, west-east or southwest-northeast trending and generally south-dipping; the youngest faults are high-angle, northwest-southeast trending and dipping to the southwest. The paleomagnetic analyses results show clockwise rotation of the Limni- Istiea basin by 18° during or after the last stages of extension within the basin.
by Aleksandra M. Hosa.
S.M.
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Swanson, Erika (Erika M. ). "Cenozoic extensional features in the geology of central mainland Greece." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/45789.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2008.Includes bibliographical references (leaves 16-17).
The Hellenides of Greece have undergone a series of extensional deformation events from early Miocene to present time. Two of the fault systems that accommodate this deformation in central Greece are the Itea-Amfissa detachment and the Parnassos detachment. The Itea-Amfissa detachment is known to have been active during Middle Miocene (Langhian and Serravallian time) from dating of marine sediments within the syn-tectonic hanging wall basin. The Parnassos detachment is probably younger, based on the Lower Pliocene sediments deposited in the hanging wall, but stratigraphically lower sediments are undated. The North Giona fault extends east-west from near the northern end of the Itea-Amfissa detachment to near the northern end of the Parnassos detachment. This steeply north-dipping normal fault probably truncates the Itea-Amfissa detachment, and approaches the Parnassos detachment in an area where the topography is low and highly irregular, suggesting that it may connect to and absorb some of the motion along the Parnassos detachment. Structural mapping in this area between the North Giona fault and the Parnassos detachment demonstrates that the limestone and flysch of the Parnassos nappe are folded without significant faulting. Folds occur in two orientations; the northwest-oriented structures are older and are probably related to nappe emplacement; the younger, east-west trending folds are probably related to Late Cenozoic extension. The lack of through-going faults indicates that the North Giona fault and the Parnassos detachment do not connect. Structural relations also show that the Parnassos detachment is younger than the east-west trending fold structures within the field area, and also probably younger than the North Giona fault.
by Erika Swanson.
S.M.
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Al, Kindi Suleiman. "A seismological study of cenozoic epeirogeny across the British Isles." Thesis, University of Cambridge, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.620694.
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Aldanmaz, Ercan. "Petrogenesis of Late Cenozoic collision volcanism in Western Anatolia, Turkey." Thesis, Durham University, 1998. http://etheses.dur.ac.uk/4658/.
Full textAbstract:
Western Anatolia exhibits a record of almost all stages of a collision event and its related magmatic processes. Following an Eocene continent-arc collision, Western Anatolia region experienced a complete cycle of thickening and orogenic collapse. The early stage of collision- related volcanism, which was most evident during the Early Miocene (<21 Ma), produced a considerable volume of lavas and pyroclastic deposits covering a broad compositional range from basaltic andesites to rhyolites. The volcanic activity continued into the Middle Miocene with a gradual change in eruptive style and rock compositions. The Middle Miocene activity, formed in relation to localised extensional basins and was dominated by lava flows and dykes of basalts to andesites composition. Both the Early-Middle Miocene rocks have calc-alkaline and shoshonitic character. The late stage volcanism, from 11.0 to 8.3 Ma, was marked by alkali basalts and basanites erupted along the localised extensional zones. The Early-Middle Miocene volcanic rocks exhibit enrichment in LILE and LREE relative to the HFSE (characterised by negative Nb and Ta anomalies) and are characterised by high (^87)Sr/(^86)Sr and low (^143)Nd/(^144)Nd (-ɛno) ratios. These characteristics indicate a mantle lithospheric source region carrying a subduction component inherited from a pre-collision subduction event. Perturbation of this subduction-metasomatised lithosphere by delamination of the thermal boundary layer is the likely mechanism for the initiation of the post-collision magmatism. Trace elements systematics suggest that the Early-Middle Miocene series underwent a hydrous crystallisation (dominated by pargasitic amphibole) in deep crustal magma chambers. Subsequent crystallisation in shallower magma chambers follows two different trends: (1) anhydrous (pyroxene + plagioclase-dominated; and (2) hydrous (edenitic amphibole + plagioclase + pyroxene dominated).Trace element and isotope modelling shows that the Early-Middle Miocene rocks have been affected by assimilation combined with fractional crystallisation processes, and that the effects of assimilation decrease gradually from the Early Miocene into the Middle Miocene. This indicates a progressive crustal thinning related to the extensional tectonics that prevailed from the latest Early Miocene onwards. In contrast to the Early-Middle Miocene rocks, the Late Miocene alkaline rocks are characterised by low (^87)Sr/(^86)Sr and high (^143)Nd/(^144)Nd (+ɛnd) ratios and have OIB-type like trace element patterns characterised by enrichment in LILE, HFSE and L-MREE, and a slight depletion in HREE, relative to the N-MORB compositions. REE inversion modelling indicates that these rocks formed by partial melting (with degrees of ~2 to -10%) of a spinel + garnet Iherzolite source. Trace element and isotopic systematics are consistent with decompression melting of an enriched mantle asthenospheric source.
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McAleer, Ryan Joseph. "Late Cenozoic Exhumation in a Transpressional Setting: Fairweather Range, Alaska." Thesis, Virginia Tech, 2006. http://hdl.handle.net/10919/43526.
Full textAbstract:
Deformation in southern Alaska is controlled by the accretion and partial subduction of the Yakutat terrane as margin-parallel motion transitions to subduction. Recent studies have shown that deformation in the St. Elias orogen, at the northern end of the terrane, accommodates a large portion of convergence, but deformation at the eastern and southern margins remains more poorly constrained. Rapid recent sedimentation (> 1cm/yr) and glacio-isostatic uplift rates (> 3 cm/yr) in the Fairweather corridor highlight short-term vertical deformation at the eastern margin; however, the relationship between these rates and long-term deformation is less well known. New low-temperature cooling ages are reported along the eastern flank of the St. Elias orogen, placing constraints on vertical deformation over the past few million years. Young cooling ages (< 3 Ma) occur in a broad zone, extending along the onshore length of the strike-slip Fairweather fault. These ages indicate that protracted convergence has been accommodated in the Fairweather corridor. Average (~1 mm/yr) and peak (~3 mm/yr) late Cenozoic exhumation rates are similar to rates to the north, and suggest that the orogen is actually boomerang-shaped in map view. If ~1 mm/yr exhumation has been steady, the onset of rapid exhumation is constrained to post-12 Ma, but likely occurred at 5 Ma with changes in climate and plate obliquity. Although cooling ages reveal no coherent regional pattern relative to known structures, they indicate the margin accommodates a significant component of pure shear and is slip-partitioned. The resolved magnitude of convergence in the Fairweather corridor also indicates that Yakutat terrane motion is rotated from Pacific plate motion, and likely requires significant slip on the Transition fault at the southern edge of the Yakutat terrane. Although million-year exhumation rates are rapid, they are slower than short-term rates related to deglaciation.Master of Science