Дисертації з теми "Proxy paleoenvironmental"
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Chawchai, Sakonvan. "Paleoenvironmental and paleoclimatic changes in northeast Thailand during the Holocene." Doctoral thesis, Stockholms universitet, Institutionen för geologiska vetenskaper, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-107185.
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Accepted. Paper 5: Manuscript.
Stephenson, Richard Javier. "Tropical land snails as precipitation proxies: Oxygen stable isotopes of shells from Trinidad Island." University of Cincinnati / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1563273765452653.
Noses, Spinola Diogo [Verfasser], and Peter [Akademischer Betreuer] Kühn. "Early Eocene paleosols on King George Island, Maritime Antarctica as a paleoenvironmental proxy / Diogo Noses Spinola ; Betreuer: Peter Kühn." Tübingen : Universitätsbibliothek Tübingen, 2018. http://d-nb.info/1198972327/34.
Lugo, Mendez Anastasia M. "By Proxy: A Radiocarbon Perspective on Prehistoric Mobility Using Summed Probability Distributions and Paleoenvironmental Reconstructions in Wyoming and Montana." DigitalCommons@USU, 2019. https://digitalcommons.usu.edu/etd/7447.
Carlson, Tessa Boe. "Volcanic Glass as a Paleoenvironmental Proxy: Comparing Preparation Methods on Ashes from the Lee of the Cascade Range in Oregon, USA." PDXScholar, 2018. https://pdxscholar.library.pdx.edu/open_access_etds/4472.
Newell, Sarah D. "An analysis of compound specific carbon isotopes of lipid biomarkers a proxy for paleoenvironmental change in the Maya lowlands of Peten, Guatemala /." [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0009584.
Kwiecien, Olga. "Paleoenvironmental changes in the Black Sea region during the last 26000 years a multi-proxy study of lacustrine sediments from the western Black Sea /." Potsdam : GFZ, 2009. http://d-nb.info/993233236/34.
Kwiecien, Olga. "Paleoenvironmental changes in the Black Sea region during the last 26,000 years : a multi-proxy study of lacustrine sediments from the western Black Sea." Phd thesis, Universität Potsdam, 2008. http://opus.kobv.de/ubp/volltexte/2008/1918/.
Aus Paläoumweltdaten lassen sich detaillierte Informationen über die spätquartäre Klimaentwicklung gewinnen. Für die kontinentalen mittleren Breiten ist das Gesamtbild der Klimaänderungen während dieses Zeitraumes aufgrund seiner Vielfältigkeit allerdings noch immer unvollständig. Eine ideale Loka-tion, das Muster und die Mechanismen der Klimaänderungen in Osteuropa und Kleinasien zu untersu-chen, ist das Schwarze Meer mit seiner bedeutenden Größe und seiner kontinentalen Lage. Gegenwärtig ist das südliche Einzugsgebiet des Schwarzen Meeres durch ein mediterranes Klima ge-prägt, während die nördlichen Regionen von zentral- bzw. nordeuropäischem Klima beeinflusst werden. Als im letzten Glazial der Meeresspiegel so stark sank, dass das Schwarze Meer vom Mittelmeer abge-trennt und zu einem großen, abflusslosen See wurde, waren der atmosphärische Niederschlag und der damit verbundene Abfluss die wesentlichen Steuerfaktoren für Sedimenteintrag und Wasserchemie des Schwarzen „Sees“. Deshalb liefert die Untersuchung der Sedimente des Schwarzen Meeres wichtige Informationen über die früheren Zusammenhänge sowie die Entwicklung von mediterranem und zentral- bzw. nordeuropäischem Klima. Das bedeutsamste Ergebnis meiner Doktorarbeit ist ein verbessertes Altersmodell für Sedimentkerne aus dem westlichen Schwarzen Meer; dieses erlaubt eine genauere Rekonstruktion der Entwicklungsge-schichte dieses Binnenmeeres und seiner Umgebung und ermöglicht einen fundierten Vergleich mit an-deren marinen und terrestrischen Archiven. Daten, die entlang eines N-S Transektes im westlichen Be-reich des Schwarzen Meeres erfasst wurden und auf einer gemeinsamen Zeitskala dargestellt werden, lassen die folgenden zusammenhängenden Entwicklungen im Becken und seiner Umgebung erkennen: Während des Glazials war der Feuchtigkeitstransport zum nördlichen Einzugsgebiet des Schwarzen Meeres aufgrund der südwärts verlagerten Polarfront vermindert, so dass Süßwasser und Sedimente vor-rangig aus dem südlichen Einzugsgebiet in das Becken gelangten. Die Rekonstruktion von Nieder-schlagsänderungen mit Hilfe von Schwankungen des terrigenen Eintrags zeigt, dass der regionale Nie-derschlag im Glazial stark von den Wasseroberflächentemperaturen des Mittelmeeres beeinflusst wurde und als Folge der Abkühlung während der nordatlantischen Heinrich-Ereignisse H1 und H2 abnahm. Im Gegensatz dazu blieb das Schwarze Meer während des Hochglazials hydrologisch relativ stabil. Die Sedimentzusammensetzung, Lithologie und δ18O-Werte von Ostracoden zeigen, dass erste signifi-kante Änderungen im Frischwasser- und Sedimenteintrag zeitgleich mit dem frühglazialen nordwärtigen Rückzug der ozeanischen und atmosphärischen Polarfronten um 16.4 cal ka BP auftraten. Der Schmelz-wassereintrag abschmelzender europäischer Eisflächen veränderte die Isotopenzusammensetzung des Wassers und erhöhte die Sedimentzufuhr aus den nördlichen Quellen. Während diese Änderungen auf ein bereits milderes Klima in Nordeuropa und im Mittelmeerraum hin-deuten, zeigt sich ein Anstieg der lokalen Temperaturen erst während des Übergangs von der Älteren Dryas zum Bølling/Allerød um etwa 14.6 cal. ka BP. Zu diesem Zeitpunkt führte ein wahrscheinlicher Anstieg der Wasseroberflächentemperaturen im Schwarzen Meer zu einem massiven Phytoplankton-wachstum, welcher die Ausfällung anorganischen Karbonats zur Folge hatte. Dieser biologisch ausgelös-te Prozess veränderte maßgeblich die Wasserchemie und spiegelt sich in simultanen Veränderungen der Elementzusammensetzung von Ostracoden und der Isotopenzusammensetzung von anorganisch ausge-fälltem Karbonat wieder. Beginnend mit dem Bølling/Allerød, durch die Jüngere Dryas Kälteperiode und die frühholozäne Erwärmung hindurch, deckt sich das Temperatursignal des Schwarzen Meeres mit den Niederschlags- und Temperaturänderungen des weiteren Mittelmeerraumes. Das Frühholozän war, ähnlich wie das Bølling/Allerød, durch das Einströmen salzhaltigen Meerwassers aus dem Mittelmeer gekennzeichnet (~9.5 cal. ka BP), welches die lakustrine Phase des Schwarzen Mee-res beendete und einen erheblichen Einfluss auf seine chemischen und physikalischen Wassereigen-schaften ausübte.
Krauß, Lydia [Verfasser], Frank [Akademischer Betreuer] Lehmkuhl, and Eileen Sandra [Akademischer Betreuer] Eckmeier. "Paleoenvironmental reconstruction of the last interglacial-glacial cycle of the quaternary in Central Europe applying a multi-proxy approach investigating loess-paleosol sequences / Lydia Krauß ; Frank Lehmkuhl, Eileen Sandra Eckmeier." Aachen : Universitätsbibliothek der RWTH Aachen, 2017. http://d-nb.info/1162450932/34.
Guida, Manrique Leydy Carolina. "Mécanismes contrôlant la séquestration du gadolinium, du rhénium et du sélénium dans des conditions de faible teneur en oxygène." Electronic Thesis or Diss., Université Grenoble Alpes, 2024. http://www.theses.fr/2024GRALU015.
Trace elements, despite their scarcity (less than 100 parts per million) on Earth, serve diverse purposes: some act as micronutrients, while others, known as critical metals, possess unique industrial and medical applications. In oxygen-deprived natural aquatic systems electron transfers involve biogeochemical reactions catalyzed by iron, sulfur and trace elements. Understanding their reactivity in these environments remains a challenge. My Ph.D. research focus on filling this knowledge gap concerning three specific elements (rhenium (Re), selenium (Se), and gadolinium (Gd)). They exist in various chemical aqueous species in water: monovalent anion (perrhenate, ReO4—), divalent anion (selenate, SeO42—and selenite, SeO32—) or cation (Gadolinium, Gd3+). Rhenium is a critical metal, while selenium is a bioessential element at low levels, and becomes toxic in higher concentrations. Gadolinium is a rare earth element and a critical metal as well, due to its wide use as a contrast agent in magnetic resonance imaging (MRI).These elements are most concentrated in marine sediments formed in oxygen-deprived environments. Common mineral phases include pyrite (FeS2) and magnetite (Fe3O4) depending on sulfide content in those environments, and origin (autogenic vs. detritic, e.g., from volcanic rocks) of the particles. My research, presented across four chapters, investigates surface reduction (Re(VII), Se(VI) and Se(IV)) and the sorption (Gd(III)) processes on/into magnetite and pyrite particles. Employing various analytical methods such as XAFS spectroscopy, STEM-EELS spectro microscopie and MC-ICP-MS, our study reveals distinct reactive pathways. Re(VII) reacts with sulfidic water to form Re(III, IV, V)2S7 nanoparticles, while at lower concentrations Re is reduced and incorporated into particles, in different pathways characterized by less isotopic fractionation with pyrite than with magnetite. We also show that pyrite nanoparticles reduce Se(VI) and Se(IV), down to surface Se(0) or structure Se(-I) depending on whether adsorption or co-precipitation occurs. Lastly, Gd substitutes for Fe(III) in magnetite nanoparticles up to 5% Fe substitution by Gd. We attempt to unify the affinity behaviour of these and other trace elements with anoxic Fe-bearing sediments in the light of the hard and soft acids and bases principle.The study provides new insights into the mechanisms that govern the sequestration of metals and metalloids in sedimentary settings. The significance of this research lies in its relevance to contemporary scientific and technological endeavours, particularly in understanding how processes in Fe and sulfidic systems work like trace elements, Fe and S mobility, mass balance in the global sedimentary cycles to the exploration, mining and recycling of potential repositories of metals. Furthermore, it enhances our current understanding of the use of palaeoenvironmental proxies to reconstruct the Earth's formation. Finally, this study also has implications for the treatment of nuclear waste and pollution, particularly in the management of selenium (Se) and gadolinium (Gd) contamination
Cecchet, Fernanda Aparecida. "Análise de fitólitos aplicada a reconstrução paleoambiental (vegetação e clima) na superfície incompletamente aplainada VI Campo Erê (SC) no pleistoceno tardio." Universidade Estadual do Oeste do Parana, 2015. http://tede.unioeste.br:8080/tede/handle/tede/63.
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Phytoliths are microscopic particles of silica, or biomineralizations, formed during the growth of the plant, through the absorption of dissolved monosilicic acid (H4SiO4) solute from the soil. Phytoliths remain preserved in soil under certain environmental conditions making them a great ally in paleoenvironmental reconstruction studies. In South-West Paraná and North-West Santa Catarina, where there were large areas of Araucaria moist forests (AMF), the Genesis and Evolution of Geomorphological Surfaces and Surface Formations research group (GPGESGFS) has carried out dedicated research using diverse biological proxies, including phytoliths, in order to understand the principal factors and processes which were active in the formation of the current relief and in the evolution of the landscape of this region. Considering the hypothesis of environmental changes (climate and vegetation) in the South of Brazil during the Pleistocene/Holocene, the present study has as its main objective understanding the environmental dynamic during the Late Pleistocene and Holocene, which may have acted on the evolution of the landscape of Campo Erê (SC), incomplete planation surface VI. The results obtained through routine physical and chemical analyses of the phytolith assemblage, the ratios of the stable carbon isotopes and 14C dating of the humin fraction, have enabled us to conclude that the soil studied in Campo Erê (SC), a typical distroferric red nitosol with humic A horizon, developed in situ through pedogenic evolution from the material of origin, basalt. Since the middle of the last glacial maximum (18.060-17.845 Years Cal. BP.) this profile developed beneath vegetation, possibly less leafy than the current vegetation, with a mixture of C3 (grasses, trees and bushes) and C4 (grasses) plants. This pattern of vegetation remained until the beginning of the Holocene (8.055-7.960 Years Cal. BP.) From the Middle Holocene on, there occurred an opening up of the vegetation, marked by greater participation of C4 grasses, possibly a campo sujo (a herbaceous layer with occasional small trees), shown as much by the isotopic signal as by the phytolith assemblage. This vegetation lasted until approximately 1.875-1.715 years Cal BP, once again becoming vegetation formed predominantly by C3 plant species of photosynthetic cycle, until the formation of the current AMF found in the study area. At no time were signs of dense tree formation detected, but instead leafy vegetation, which was at times more open and at others more closed. This characteristic is prominent in the vegetation of the south of Brazil, where extensive areas of AMF are surrounded by grasslands forming great mosaics on the landscape. All the climatic oscillations, however small, reflect the retreat or advance of this forest over grassland or vice-versa
Fitólitos são microscópicas partículas de sílica ou biomineralizações formadas devido à absorção do ácido monossílico (H4SiO4) dissolvido do soluto do solo durante o crescimento da planta. Os fitólitos ficam preservados no solo em determinadas condições ambientais tornando-se um grande aliado em estudos de reconstrução paleoambiental. No Sudoeste do Paraná e Noroeste de Santa Catarina, onde ocorriam grandes área de Floresta Ombrófila Mista (FOM), o Grupo de Pesquisa Gênese e Evolução de Superfícies Geomorfológicas e Formação Superficiais (GPGESGFS) tem se dedicado às pesquisas usando diversos proxies biológicos inclusive os fitólitos para compreender quais foram os principais fatores e processos que atuaram na formação do atual relevo e na evolução da paisagem nessa região. Considerando a hipótese de mudanças ambientais (clima e vegetação) no Sul do Brasil durante o Pleistoceno/Holoceno o presente estudo tem como objetivo principal compreender a dinâmica ambiental ao longo do Pleistoceno Tardio e Holoceno , que pode ter atuado na evolução da paisagem na região de Campo Erê (SC), superfície incompletamente aplainada VI. Os resultados obtidos através das análises físicas e químicas de rotina, de assembleia de fitólitos, as razões de isótopos estáveis de carbono e datações por 14C da fração humina, permitiram concluir que o solo estudado em Campo Erê (SC), um NITOSSOLO VERMELHO Distroférrico típico com horizonte A húmico, se desenvolveu in situ através de evolução pedogenética a partir do material de origem, o basalto. Desde meados do Ultimo Maximo Glacial (18.060-17.845 Anos Cal. AP.) este perfil se desenvolveu sob uma vegetação, possivelmente menos arborizada que a atual, com mistura de plantas C3 (gramíneas, árvores e arbustos) e C4 (gramíneas). Este padrão de vegetação se manteve até o inicio do Holoceno (8.055-7.960 Anos Cal. AP.). A partir do Holoceno médio ocorreu uma abertura da vegetação, marcada pela maior participação de gramíneas C4, possivelmente um campo sujo, evidenciada tanto pelo sinal isotópico, quanto pela assembleia fitolítica. Essa vegetação perdurou até aproximadamente 1.875-1.715 anos Cal AP, tornando-se novamente uma vegetação formada predominantemente por espécie de plantas de ciclo fotossintético C3 até a formação da atual FOM encontrada na área de estudo. Em nenhum momento detectou-se sinais de uma formação arbórea densa, mas sim uma vegetação arborizada que por vezes esteve mais aberta e por vezes mais fechada. Essa característica é eminente da vegetação do sul do Brasil onde extensas áreas de FOM são cercadas por campos formando grandes mosaicos na paisagem. Todas as oscilações climáticas, por menores que sejam, refletem o retrocesso ou o avanço dessa floresta sob o campo ou vice-versa.
Legge, Heiko-Lars [Verfasser]. "Calcareous nannoplankton of the Red Sea : a proxy for the reconstruction of the paleoenvironmental conditions during the late Quaternary / vorgelegt von Heiko-Lars Legge." 2008. http://d-nb.info/989376567/34.
Chou, Chien-Ju, and 周建儒. "Planktonic foraminifera rare earth element ratios as a new paleoenvironmental proxy - a precipitation intensity in Papua New Guinea during the past 363 thousand years." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/88122821522343162653.
國立臺灣大學
地質科學研究所
101
Characteristics of rare earth elements (REE) have been widely used as important tracers in earth sciences. Foraminiferal test REE signatures have been suggested to reflect ambient seawater conditions and serve as valuable proxies in paleoceanography and paleoclimatogy. Here I present a past 363 kyr planktonic foraminifer Globigerinoides ruber (G. ruber) REE record from sediment core MD05-2925 (9o20.61’S, 151o27.61’E, 1661 m water depth) collected from the Solomon Sea, Papua New Guinea (PNG). High significant correlation coefficients exist for all G. ruber REE/Ca time series. This foraminiferal REE/Ca time series is different from the Mg/Ca ratio-inferred sea surface temperatures and δ18O records. This inconsistency suggests that planktonic foraminiferal REE were not directly governed by changes in ice volume or thermal condition. Solomon Sea G. ruber REE/Ca time-series was dominated by 41-kyr obliquity and 23-kyr precession periodicities. An absence of significant relation of the G. ruber Mn/Ca and Fe/Ca versus Nd/Ca indicates that Fe-Mn oxides were completely removed after a clean procedure. The REE pattern diagram expresses two dominant sources of local water masses and the input from nearby terrestrial riverine discharge. PNG located at the southern border of the Intertropical Convergence Zone (ITCZ), delivers disproportionately large amount of suspended sediment fluxes to the adjacent oceans by seasonal precipitation. The nearby marine basins as receptacles of the transported terrestrial sediments can reflect past ITCZ precipitation. This regional G. ruber REE/Ca is an island-weathering signal modulated by rainfall, related to the different insolation gradients and regional insolation. In summary, Solomon Sea G. ruber REE content is considered to be a robust paleo-precipitation proxy over the PNG. This example opens a new potential of using foraminiferal REE records as a proxy of paleoclimatogy and paleoceanography.
Kwiecien, Olga [Verfasser]. "Paleoenvironmental changes in the Black Sea region during the last 26 000 years : a multi-proxy study of lacustrine sediments from the western Black Sea / vorgelegt von Olga Kwiecien." 2008. http://d-nb.info/989904148/34.
Yu, Jun-Qing [Verfasser]. "Lake Qinghai, China : a multi-proxy investigation on sediment cores for the reconstructions of paleoclimate and paleoenvironment since the marine isotope stage 3 / von Junqing Yu." 2006. http://d-nb.info/978348311/34.