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Ferdinand, Laurie. "La plaine alluviale de la Moyenne Garonne toulousaine au cours de l’holocène : apport d’une approche croisée archéologie et géomorphologie." Thesis, Toulouse 2, 2014. http://www.theses.fr/2014TOU20069/document.
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Sous le prisme de la pluridisciplinarité, la dichotomie entre anthropisation et environnement s’est réduite à mesure que de fortes interrelations dans les seuils d’évolution ont été démontrées. Les vallées fluviales constituent des supports d’observation privilégiés des relations hommes-milieux, et de nombreux fleuves ont fait l’objet de ce type d’étude ces dernières années. Le choix de la Garonne s’est imposé face au vide scientifique qui caractérise une grande partie du tracé au sein du Sud-Ouest de la France, en particulier la section moyenne. Ce travail se concentre donc sur l’étude des relations entre le peuplement et la basse plaine entre Toulouse et la confluence du Tarn depuis 10000 ans. La vallée atteint 25km de large à Toulouse et correspond à la première zone d’étalement des crues pyrénéenne, favorable à l’enregistrement des occupations passées et de la dynamique alluviale qui les a accompagnés. En l’absence de référentiel local, un cadre chronologique géomorphologique et archéologique a été mis en place pour l’Holocène à partir des travaux réalisés sur différents cours d’eau européens et continentaux. Ces deux volets ont ensuite été analysés distinctement sur la plaine de la Garonne à l’aide d’une méthodologie pluridisciplinaire. Les résultats montrent que l’occupation de la plaine alluviale est continue depuis le Néolithique, malgré une restitution biaisée par les travaux d’aménagement modernes et la taphonomie. Cette dernière est marquée par une forte mobilité du chenal de la Garonne et l’identification d’au moins deux épisodes d’incision au cours du 2nd l’Holocène et une nette diminution de l’alluvionnement depuis l’AntiquitéThrough the prism of multidisciplinarity, the dichotomy between environment and human impacts is reduced as strong interrelationships in thresholds have been demonstrated. The valleys are favored supports of human-environnement relations, and many rivers have been the subject of this type of study in recent years. The Garonne’s choice result of a scientific blank in the most part of the channel in the South West of France, especially the middle section. Therefore this work focuses on the study of the relationship between human occupation and the low plain from Toulouse to the confluence of the Tarn since 10000 years. The valley is 25km wide in Toulouse and is the first Pyrenean flood spreading area, enabling the recording of past occupations and the alluvial dynamic associated. Without local repository, geomorphological and archaeological chronological framework was established for the Holocene, based on works completed in European and continental channels. These two component were analyzed separately on the plain of the Garonne river with a multidisciplinary approach. The results show that the floodplain’s occupation is continuous since the Neolithic, despite restitution biased by modern development works and taphonomy. This aspect is characterized by a high mobility channel f the Garonne and the identification of at least two episodes of incision in the 2nd Holocene and a net sedimentation decrease since Antiquity
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Fernane, Assia. "Reconstitution des fluctuations holocènes en relation avec les changements climatiques et l'antropisation sur les côtes bretonnes à partir de bio-indicateurs fossiles (chironomidés, pollen et foraminifères benthiques)." Thesis, Brest, 2014. http://www.theses.fr/2014BRES0124/document.
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L’évolution du climat Holocène a fait jusqu’ici l’objet de très peu d’études au niveau de la Bretagne. Celles-ci, s’inscrivant dans un contexte à la fois paléo-environnemental et archéologique, présentent souvent un caractère local et ponctuel qui permet difficilement de replacer les changements paléoenvironnementaux observés dans un contexte climatique plus global. Pourtant, la Bretagne, par sa particularité géographique et son exposition océanique, constitue un milieu de prédilection pour l’étude du climat puisqu’elle est fortement exposée, à l’actuel comme ce fut aussi le cas par le passé, aux aléas climatiques typiques de l’Atlantique Nord (régimes de tempêtes notamment) induits par les changements de configurations atmosphériques et océaniques. De plus, la région Bretagne présente une grande diversité de milieux littoraux, avec la présence de rias, d’estuaires, de marais salants, etc. Or, les environnements côtiers sous influence fluviale sont des puits sédimentaires soumis à de forts taux de sédimentation qui offrent l’opportunité d’enregistrer les changements environnementaux passés sur des milliers d’années. Les milieux d’arrière-plage (dunes, lagunes, tourbières), abondamment présents dans la région, constituent ainsi des domaines protégés de l’érosion marine et renferment des remplissages sédimentaires ayant potentiellement enregistré l’évolution séculaire et/ou millénaire du littoral breton, avec très certainement l’empreinte de certains évènements hydrodynamiques majeurs, mais aussi des traces de l’occupation humaine, dont certains auteurs ont montré le caractère précoce et croissant depuis le mésolithique. Ici, nous nous proposons de conduire des reconstitutions paléoenvironnementales et paléoclimatiques à partir de plusieurs séquences sédimentaires prélevées autour du littoral breton, afin de mieux comprendre la réalité des forçages naturels et/ou anthropiques sur les écosystèmes analysés. Pour mener à bien notre étude, nous avons développé une approche paléoécologique multidisciplinaire impliquant plusieurs disciplines complémentaires : sédimentologie et pétrographie, palynologie (pollen et dinokystes) et micropaléontologie(foraminifères benthiques et Chironomidae). Au final, l’analyse des séquences sédimentaires fournit une vision très précise et complète des fluctuations climatiques et environnementales qui ont caractérisé le Nord-Ouest de la France durant la seconde partie de l’Holocène, i.e. depuis les 7000 dernières années. Le recoupement des données entre les différents sites étudiés (1 site Nord Finistère et 2 sites Morbihan),montre l’hétérogénéité spatiale des données paléoécologiques qui caractérisent le secteur. Alors que les séquences prélevées sur les côtes sud bretonnes enregistrent un signal d’anthropisation dès le Néolithique moyen, celle-ci n’apparaît qu’à partir de l’Age du Bronze sur les côtes nord bretonnes, en accord avec les données archéologiques. De plus, nos données montrent que la néolithisation ne s’effectue pas de façon continue mais montre des phases de régression autour de la transition Néolithique final - Age du Bronze, en lien très certainement avec des détériorations climatiques. En effet, les périodes de froid signalées sur le nord de l’Europe durant l’Holocène et caractérisées par des récurrences de tempêtes dans la région Bretagne, semblent synchrones avec les chutes des marqueurs d’anthropisation mais aussi avec les retraits des populations de la côte vers l’intérieur des terres tels que décrits par les études archéologiques depuis le Néolithique final. Ces résultats suggèrent un impact direct du climat sur les dynamiques de population et d’occupation des territoires depuis le Néolithique en BretagneNo
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Fadhlaoui, Sahbi. "Héritages holocènes et dynamiques morphologiques du bassin versant de l’oued Massengh et ses confluences avec les oueds Sbiba et el Hathob (Dorsale Tunisienne-Tunisie du centre ouest)." Thesis, Paris 4, 2017. http://www.theses.fr/2017PA040228.
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Cette thèse porte sur l’étude des paléoenvironnements et des dynamiques morphologiques holocènes dans le bassin versant du Massengh et de ses confluences avec les oueds Sbiba et el Hathob (Tunisie du centre-ouest). Après l’étude du cadre physique de l’évolution des environnements holocènes et actuels, la thèse se concentre dans un premier temps, sur la chronostratigraphie des héritages et des archives sédimentaires. La reconstitution des paléoenvironnements et de la morphogenèse Holocène est tentée, dans un deuxième temps. En dernier lieu, la thèse fait porter l’analyse sur l’évolution morphodynamique actuelle du milieu fluvial à l’échelle de l’espace de confluencesThis thesis focuses on the study of paleoenvironmental and Holocene morphological dynamics in the watershed Massengh and its confluence with the wadis and Sbiba el Hathob (Tunisia's center-west). After studying the physical part of the evolution of Holocene and current environments, the thesis focusesinitiallyon chronostratigraphy inheritances and sedimentary archives. The reconstruction of paleoenvironmentaland morphogenesis Holocene is attempted, in a second step. To summarize, the thesis studies in depth the currentmorphodynamic evolution of the fluvial environment across the space of confluences
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Costa, Renata Lima da. "Paleohidrologia do lago Acarabixi, médio Rio Negro, AM Durante o Holoceno." Niterói, 2017. https://app.uff.br/riuff/handle/1/3892.
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Conselho Nacional de Desenvolvimento Científico e Tecnológico
nstitut de Recherche pour le Développement
Universidade Federal Fluminense. Instituto de Química. Programa de Pós-Graduação em Geoquímica, Niterói, RJ
Sabendo-se que as condições hidrológicas de um sistema flu vial depende diretamente do clima regional, e que as mudanças climáticas do Holoceno atingiram várias regiões da Amazônia de diferentes formas, este trabalho visa r econstituir, através de estudos de sondagem lacustre, o cenário paleoambiental e as condi ções hidrológicas atuantes durante o Holoceno no lago Acarabixi, localizado na p lanície sedimentar do médio Rio Negro. A caracterização das unidades litológicas foi real izada através de medidas de densidade, teor em água, matéria orgânica, granulomet ria, e lâminas de material sedimentar bruto . A origem da matéria orgânica foi avaliada a partir da relação entre carbono e nitrogênio orgânicos e seus isótopos estáveis ( δ 13 C e δ 15 N), e de petrografia. A quantificação das frações minerais foi realizada atrav és de espectrometria de infravermelho, e a identificação através de análises de difração de raios X na fração argilosa. A cronologia foi realizada a partir de data ções radiocarbônicas ( 14 C) AMS. Os registros sedimentares de ambos os testemunhos analisados m ostraram a alternância entre ambientes de características deposicionais de maior e de menor energia hidrodinâmica. As diferenças apresentadas na sedimenta ção dos testemunhos estão relacionadas com a migração lateral do canal principal de um braço do Rio Negro que passa pelo Lago Acarabixi. Esses registros mostraram quatro fases de sedimentação: 9500-8100 14 C AP; 8100-7400 14 C AP; 7400-1600 14 C AP, e 1600 14 C AP–Presente. A ausência de registro sedimentar na terceira fase pelo test emunho ACA 02/03, está relacionada a fortes eventos de inundação, teriam remo vido o sedimento no testemunho ACA 02/03, que se localizava neste período m ais próximo do canal principal de corrente. A análise da matéria orgânica i ndicou origem pedogênica. Ela seria oriunda da lixiviação de solos podzólicos da bacia do Rio Negro, e transportada pelo Rio Negro e depositada junto com o sedimento no L ago Acarabixi. De modo geral, a planície de sedimentação estudada no Rio Negro demon strou ser um ambiente em que os centros de sedimentação variam ao longo do temp o. Estes centros de sedimentação estariam relacionados ao deslocamento latera l dos canais principais de correntes dos rios, além de seu preenchimento pelas ench entes. Podem ser reconhecidas duas fases neste preenchimento: uma fase de for te deposição com migração lateral dos canais até 8000 anos e uma fase de sedimentação mais lenta com características mais lacustres após 8000 anos AP
Knowing that the hydrologic conditions of a fluvial sy stem depends directly on the regional climate, and that the Holocene climatic chang es reached several areas of Amazonia in different ways, this work seeks to reconstitute , through studies of lacustrine survey, the paleoenvironment and the hydrologic condit ions active during Holoceno in the lake Acarabixi, located in the sedimentary plain of medium Rio Negro. The characterization of the litologics units was accomplished th rough density measures, % in water, organic matter, granulometry, and material she ets to silt up rude. The origin of the organic matter was evaluated starting from the relatio nship between carbon and organic nitrogen and δ 13 C and δ 15 N, and of petrografy. The quantification of the mine ral fractions was accomplished through infrared-espectrometry, and the identification through analyses of diffraction of rays X in the loamy fractio n. The chronology was accomplished starting from datings radiocarbônicas ( 14 C) AMS. The sedimentary registrations of both analyzed core showed the alternation among environmen ts from smaller and bigger hydrodynamic energy. The differences presented in the sedimentation of the core are related with the lateral migration of the main chann el of an arm of Rio Negro that goes by the Lago Acarabixi. Those registrations showed four sedimentation phases: 9500- 8100 14 C AP; 8100-7400 14 C AP; 7400-1600 14 C AP, and 1600 14 C AP-present. The absence of sedimentary registration in the third phase for the core ACA 02/03, is related to strong flood events, they would have removed the se diment in the core ACA 02/03, that was located closer of the main channel of current i n this period. The analysis of the organic matter indicated pedogenic origin. The organic matter would be originating from of the ‘ lixiviação’ of podzóls of Rio Negro basin, and transported by Rio Negro and deposited with the sediment in the Lago Acarabixi. In general, the sedimentation plain studied in Rio Negro demonstrated to be an environme nt in that the sedimentation centers vary along the time. These sedimentation cente rs would be related to the lateral displacement of the main channels of currents of the riv ers, besides it’s completion for the flooding. Two phases can be recognized in this comple tion: a phase of strong deposition with lateral migration of the channels to 8 000 years and a phase of slower sedimentation with more lacustrine characteristics after 8000 years AP.
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Engels, Mary S. "Holocene reef accretion: Southwest Molokai, Hawai'i." Thesis, University of Hawaii at Manoa, 2003. http://hdl.handle.net/10125/6999.
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Two reef systems off south Molokai, Hale O Lono and Hikauhi, show differences in modern ecosystem structure and Holocene accretion history that reflect the influence of wave-induced near-bed shear stresses on reef development in Hawaii. Both sites are exposed to similar impacts from southern, Kona, and trade wind swell, but differing wave impacts result from relative exposure to north swell. Analysis and dating of 10 cores from Hale O Lono reveal a back stepping reef ranging from ~8,100 cal yr BP (offshore) to ~4,800 cal yr BP (nearshore). A depauperate community of modern coral diminishes shoreward and seaward of~15 m depth due to wave energy, disrupted recruitment activities and physical abrasion. Evidence suggests a change from conditions conducive to accretion during the early Holocene to conditions detrimental to accretion in the late Holocene. Reef structure at Hikauhi, reconstructed from 14 cores, reveals a thick, rapidly accreting and young (maximum age ~900 cal yr BP) prograding reef. Modem live coral cover on this reef increases seaward with distance from the reef crest but terminates at a depth of ~20m where the reef ends in a large sand field. The primary limitation on vertical reef growth is accommodation space under wave base, not recruitment activities or energy conditions. This study suggests modem reef growth on the southwest comer of Molokai is controlled by wave-induced near-bed shear stress related to refracted North Pacific swell. Holocene accretion patterns here also reflect the influence of wave-induced near-bed shear stress from north swell. Other factors controlling Holocene reef accretion are relative sea-level and wave sheltering by Laau Point. Habitat suitable for reef accretion on the southwest shore of Molokai has shrunk throughout the Holocene.ix, 62 leaves
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Ouellette, Gilman Reno. "Late Holocene Paleoenvironmental Reconstruction in Barbados." TopSCHOLAR®, 2013. http://digitalcommons.wku.edu/theses/1285.
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Barbados is the easternmost island in the Caribbean region, and is uniquely situated between the Atlantic Ocean and Caribbean Sea. Being an isolated island with a karstified aquifer providing the majority of the nation’s water resources, Barbados has found itself in water scarce situations in recent years. In order to better understand natural shifts in groundwater recharge (which is determined by shifts in precipitation), longer records of precipitation are needed than are available from modern measurements. This study presents a paleoclimate reconstruction for the late Holocene on Barbados using stable and radiogenic isotope ratios in speleothem lamina as proxies. In addition, it introduces the use of novel mineralogical analyses using Raman spectroscopy and large chamber-scanning electron microscopy to supplement the oxygen isotope record. For the past 1,500 years, the speleothem record indicates average δ18O values near -4.1 0/00, maximum δ18O values around -3.2 0/00 that coincide with the Little Ice Age climate event, while minimum δ18O values around -5.3 0/00 occur during the Medieval Climate Anomaly. Raman spectral analysis shows a recent period of increased Mg substitution, which potentially represents anthropogenic changes to the island’s epikarst aquifer caused by European settlement and sugar cane cultivation on Barbados. Electron imaging revealed chemically distinct layers of detritus within the stalagmite sample, facilitating precise sampling for U-series dating while also providing some information on the nature of weathering on the island. Additionally, time series analysis of the isotope record indicates multidecadal and multicentennial periodicities that conform well to that of the Atlantic Multidecadal Oscillation exerting influence on rainfall variability at the decadal scale, and the Intertropical Convergance Zone modulating rainfall at the multicentennial scale. Collectively, these data provide a climate reconstruction for the island of Barbados that is useful for better understanding change in cyclic precipitation patterns, as well as non-destructive methods for speleothem analysis that complement the isotopic study, while allowing sample preservation.
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Brown, Fiona S. J. "Late Holocene environmental change at Castelporziano." Thesis, Loughborough University, 2010. https://dspace.lboro.ac.uk/2134/6752.
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The Mediterranean has long been recognised as an area that is particularly sensitive to climate change. It is also an area that has been impacted by human activity for millennia. Disentangling climatic and anthropogenic influences on the history of vegetation change in the Mediterranean remains an important challenge. As a contribution to this ongoing debate, this thesis explores the late Holocene environment of part of the coast in Central Italy using a multiproxy approach to investigate the archives of change preserved in dune slack deposits. Distinguishing between natural and anthropogenic signals presents a real challenge in most environmental reconstruction work; however, due to the extensive archaeological research carried out at Castelporziano, it is possible to examine human-environmental interactions in some detail. In order to understand these interactions part of the thesis examines how management has affected recent environmental changes and the current vegetation and whether there is a legacy of Roman landuse at the Castelporziano estate. The key findings of the thesis showed that dune slacks are suitable for palaeoenvironmental reconstruction with proxies such as plant macrofossils, ostracods, molluscs and bryozoans statoblasts. However, the pH and seasonality of the slacks meant proxies such as pollen were badly preserved or absent, and diatoms did not preserve due to the high levels of carbonate on site. Overall the results show the impact of the Romans on site in terms of localised eutrophication and increased fires, but with abandonment, came the formation of wet woodlands.
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Shaw, John. "Holocene coastal evolution, Co. Donegal, Ireland." Thesis, University of Ulster, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.252715.
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Taylor, Mark P. "Holocene sedimentation in River Severn catchments." Thesis, Aberystwyth University, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337496.
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Bruce, Alasdair Sutherland. "The Holocene evolution of the Fleet." Thesis, University of Greenwich, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.399695.
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Martin-Jones, Catherine Mariel. "Developing a Holocene tephrostratigraphy for Ethiopia." Thesis, Aberystwyth University, 2016. http://hdl.handle.net/2160/33b2e437-d8f5-4c28-848a-c55a105768b9.
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Explosive eruptions occurred throughout the Ethiopian Rift Valley during the Quaternary, depositing tephras that have provided crucial chronology for archaeological sites in eastern Africa. However, Holocene tephras are largely unstudied and the recent volcanic history of Ethiopia remains poorly constrained. The first < 17 ka regional tephrostratigraphy is presented here, constructed using sediments from seven Ethiopian lakes: Ashenge and Hayk (Ethiopian Highlands), Dendi and Hora (Yerer-Tullu Wellel Volcano Tectonic Lineament, YTVL) and Awassa, Tilo and Chamo (central Main Ethiopian Rift, CMER). A database of 2100 major and trace element single grain glass analyses will aid the future identification of these tephras at proximal and distal locations. Peralkaline rhyolitic tephras are dominant throughout the Ethiopian Rift. Tephras are more differentiated in the central Main Ethiopian Rift than those deposited in northern Ethiopia. The uniquely phonolitic-trachytic Dendi tephras are derived from volcanoes on the rift shoulders, where magma evolved under high pressure. Archives from the Ethiopian Highlands record < 17 ka distal volcanism from seven unknown volcanic centres in the Afar Rift. Eruptions occurred every <1000 years between 15:31:6 cal. ka BP. Different tephras were deposited in lakes Ashenge and Hayk, and they were not dispersed towards lakes further south. Tephras erupted from centres in the CMER are recorded in the Awassa, Tilo and Chamo archives. Glass compositions are indistinguishable from recent Corbetti eruptives. During < 10 ka, eruptions from Corbetti occurred every < 800 years and 6 eruptions were highly explosive. Two tephras are correlated between Tilo and Chamo (170 km SW of Tilo). However, eruptions from Corbetti are not recorded in archives from Ashenge, Hayk and Dendi. These findings demonstrate the potential for further study to construct a comprehensive tephra framework, enabling assessment of regional volcanic hazards. Further geochemical characterisation of regional volcanoes will constrain the sources of these tephras and their petrogenesis.
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Fletcher, William J. "Holocene landscape history of southern Portugal." Thesis, University of Cambridge, 2005. https://www.repository.cam.ac.uk/handle/1810/273436.
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To date, southern Portugal has been the focus of only limited palaeoecological research. In particular, the scarcity of dated pollen studies has meant that inferences regarding the vegetation history of the Algarve and related aspects of landscape evolution have had to be drawn from distant sites. Palaeoecological research has been hindered by the lack of suitable sites for pollen analysis. This thesis contributes to the understanding of Holocene palaeoenvironmental change in the Algarve region with new palynological data from intertidal, estuarine sediments. In a region without natural lakes, estuarine sediments deposited during the post-glacial marine transgression represent a valuable resource for pollen analysis. Presented in the thesis are the methods and results of sedimentary and palynological analyses of AMS radiocarbon dated sediment sequences from the estuaries of the Guadiana, Arade and Boina rivers. Sediment analyses, including loss-on-ignition, particle-size analysis and magnetic susceptibility, are used to characterise sedimentary units within the sequences and permit an interpretation of changing environments of deposition during the Holocene. The sedimentary analyses contribute to the understanding of the evolution of the Arade/Boina and Guadiana estuaries and changes in the littoral zone, and are critical to the interpretation of palynological material preserved in within the cores. Pollen analyses of the estuarine sediments provide detailed palaeoecological information regarding changes in local and wetland environments within the estuarine settings, and vegetation events in the wider landscape between c. 13,000 and 2000 cal BP. Critical to the analysis are both taxonomic precision and the rigorous discrimination of wetland and non-wetland taxa. Based on the new pollen records, this thesis provides the first account of Holocene vegetation history for the Algarve. Identified at the three sites is an early and mid-Holocene woodland vegetation characterised by Pinus, evergreen and deciduous oaks (Quercus spp.) and associated understorey shrubs and herbs. After c. 5000 cal BP, dramatic declines in arboreal pollen are recorded, associated with an increase in moor and heath taxa, notably Ericaceae and Cistaceae. The results permit a re-evaluation of the debated role of anthropogenic impact on the Algarve landscape. Finally, the results of both sedimentary and pollen analyses are placed in the wider regional context of the Iberian peninsula. Considered in the thesis are: a) the timing and nature of changes in coastal environments during the Holocene transgression, b) the impact of sea-level change on wetland environments, c) the characteristics of the early and mid-Holocene vegetation, and d) the evidence for major deforestation during prehistoric times.
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Mendes, Gérson Levi da Silva. "Caçadores-coletores na Serra de Paranapiacaba durante a transição do Holoceno Médio para o Tardio (5920-1000 anos AP)." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/71/71131/tde-25022008-161017/.
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Esta dissertação apresenta o resultado de um levantamento de sítios líticos caçadores-coletores no alto rio das Almas nos contrafortes ocidentais da Serra de Paranapiacaba. Dados sobre as indústrias líticas relacionadas são fornecidos sucintamente e comparadas às pesquisas desenvolvidas no Médio Ribeira por De Blasis (1988). Em acréscimo, esta Dissertação trata de estabelecer parâmetros para a compreensão da formação de sítios arqueológicos detectados em profundidade em porções de alta vertente, datados do Holoceno Médio. A continuidade de grupos caçadores-coletores na área de pesquisa é delimitada entre 5920 e 1000 anos AP e, em face a este período, tratamos de reconstruir os cenários sob transformação ambiental regional em a que estiveram submetidos esses grupos humanos e seus assentamentos. Nossa contribuição é desvincular os estudos sobre grupos caçadores-coletores do cunho hiper-determinista da tecno-tipologia lítica para uma discussão mais ampla que dialogue de forma transdisciplinar com a geomorfologia, a palinologia e a espeleologia.This thesis provides the results of an archaeological survey focused in hunter-gatherer settlements from Upper Almas valley, on the western side of Paranapiacaba Mountains. Dates from lithics analysis associated to these sites are compared with results from Middle Ribeira valley, developed by De Blasis (1988). In addition, this Thesis treats to establish frames of reference to understand the formation processes of archaeological sites settled during the Middle Holocene in high depth on high portions of the mountains. The hunter-gatherer continuity between 5920 and 1000 yr BP in the studied area is approached by a paleoambiental treatment: our additional goal is to reconstruct the scenarios of environmental transformations in which these human groups developed their History. Furthermore, this thesis provides an instance to reduce the technological approach over these groups, opening an ecosystem approach which includes dates from palinology, geomorphology and espeleology.
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Junior, Daniel Rodrigues do Nascimento. "Evolução sedimentar holocênica do delta do rio Tubarão, Estado de Santa Catarina." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/44/44141/tde-26072011-145300/.
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O delta do rio Tubarão, situado na costa centro-sul catarinense entre os municípios de Tubarão, Jaguaruna e Laguna, constitui raro exemplo de delta lagunar ativo no Brasil. Sua planície deltaica cobre área aproximada de 250km2, onde são encontradas evidências de migração de canais fluviais dadas por séries de truncamentos de antigos distributários, alguns ainda ativos. Dez testemunhos foram obtidos junto aos principais canais distributários do rio Tubarão, a partir dos quais foram realizadas análises de fácies, granulométrica, de minerais pesados, de teor de matéria orgânica e de relações químio-isotópicas, além de datações 14C. Também foram levantados acervos históricos de fotografias aéreas e de dados de prospecção mineral de subsuperfície. Cerca de 5000 anos atrás, na região de seu ápice, próximo ao rio tributário Capivari de Baixo, o delta do rio Tubarão ingressou numa antiga baía lagunar e ramificou-se em sete distributários principais que, desde seus momentos iniciais de migração, foram controlados por avulsões autogênicas rumo a antigas depressões do fundo da bacia receptora. Tais avulsões progradaram o delta inicialmente para SW, depois para ENE, e então para NNE, favorecendo a fragmentação da antiga baía lagunar em uma série de lagos e lagunas menores. Diante deste cenário dinâmico, sambaquis foram erigidos no entorno do sistema lagunar, constituindo importantes registros arqueológicos de interação entre evolução sedimentar e ocupação humana pré-histórica. O resultado das análises granulométricas indicou que a sedimentação deltaica, nas proximidades de encostas de morros, foi misturada com colúvio e/ou depósitos de fluxos gravitacionais, como evidenciado pela presença de intervalos texturalmente muito imaturos em alguns testemunhos. Em relação à análise de minerais pesados, o principal fator de controle nas variações da assembleia em depósitos de delta e de bacia é a proveniência sedimentar. Em termos mediatos, essa proveniência reflete fontes plutônicas e metamórficas (médio a alto grau) do Batólito de Florianópolis (e xenólitos associados) e do Complexo Granito-Gnáissico, e rochas arenáceas alteradas da Bacia do Paraná. Em termos imediatos, depósitos deltaicos destacam-se pela afinidade mineralógica com as areias do rio Tubarão, inferida sobretudo a partir da presença mútua de grãos alterados de cianita e estaurolita, enquanto que depósitos da bacia lagunar destacam-se por sua similaridade mineralógica com areias dos rios tributários Braço do Norte e Capivari de Baixo, neste caso principalmente pela presença de zircão. A matéria orgânica presente nos depósitos do delta e de sua bacia receptora resulta do aporte de fontes terrestres (fornecido pelos rios) e marinhas (trazido via desembocaduras lagunares), fato que é evidenciado pelos resultados de \'delta\'\'POT.13 C\', \'delta\'\'POT.15 N\' e razão \'C IND.ORG\'/\'N IND.TOTAL\'. Particularmente, nos sedimentos da bacia, variações entre diferentes tipos de matéria orgânica têm ocorrido ao longo do Holoceno, as quais são atribuídas tanto ao isolamento físico progressivo do sistema lagunar em relação ao mar aberto como por mudança climática regional (aumento destacado de precipitação). A análise isotópica de oxigênio (\'delta\'\'POT 18 O\') de conchas de moluscos em depósitos da bacia indicou enriquecimento relativo em \'ANTPOT.16 O\' durante o Holoceno. Este resultado, a exemplo daquele dos isótopos de carbono e de nitrogênio dos sedimentos, sugere isolamento gradual das águas lagunares em relação às de mar aberto.The Tubarão river delta, located on the centre-south coast of Santa Catarina State, among the municipalities of Tubarão, Jaguaruna and Laguna, is rare example of active lagoonal delta in Brazil. Its delta plain covers an area of about 250km2, where there are evidences of migration of fluvial channels in a set of truncations of ancient distributaries, some of these still in activity. Ten cores were acquired adjacent to the main distributary channels of the Tubarão river, from which analyses of facies, grain size, heavy minerals, organic matter, chemistry-isotope ratios, and radiocarbon datings were performed. Also, aerial photographies and data of subsurface mining were surveyed from historical collections. Thereabout 5,000 years ago, in the region of its apex, near Capivari de Baixo tributary river, the Tubarão river delta entered an ancient lagoonal bay and branched seven main distributaries. Since the beginning of its migration, these distributaries were controlled by autogenic avulsions towards ancient depressions in the bottom of the basin. Initially, these avulsions prograded the delta towards SW, afterwards to ENE, and then to NNE, favoring the fragmentation of the ancient lagoonal bay in a set of smaller lakes and lagoons. Faced with this dynamical scenario, shellmounds were erected surrounding the lagoon system, composing important archaeological records of the interaction between sedimentary evolution and prehistoric human occupation. The results of the grain size analysis showed that the deltaic sedimentation, in the vicinity of slopes of hills, was mixed with colluvium and/or gravity flow deposits, that is evidenced by the presence of texturally very immature intervals in some cores. The analysis of heavy minerals, by its turn, showed that the main controlling factor in the variations of its assemblage in deposits of delta and basin is the sedimentary provenance. In terms of mediate sources, this provenance reflects plutonic and metamorphic (medium to high grade) rocks of the Florianópolis batholith (including its xenoliths) and of the Granite-Gneiss Complex, and weathered sedimentary sandstones of the Palaeozoic Paraná basin. Regarding immediate sources, deltaic deposits stand out by its mineralogical affinity with sands of the Tubarão river, mainly by the mutual presence of weathered grains of kyanite and staurolite, whereas deposits of the lagoon have mineralogical similarity with the sands of Braço do Norte and Capivari de Baixo tributary rivers, especially in relation to the presence of zircon. The origin of the organic matter found in the deposits of the delta and in its lagoonal basin is both from sedimentary input of terrestrial sources (provided by rivers) and marine (brought via inlets), fact evidenced by results of \'delta\'\'POT.13 C\', \'delta\'\' POT.15 N\', and \'C IND.ORG\'/\'N IND. TOTAL\' ratio. Particularly, in the sediments of the basin, variations between different types of organic matter have occurred during the Holocene, and are attributed both to the progressive physical isolament of the lagoon system from the open sea, and by local climate change (pronounced augment of precipitation). The isotope analyses of oxygen (\'delta\'\'POT.18 O\') of molluskan shells from the deposits of the basin present relative enrichment in \'ANTPOT.16 O\' during the Holocene. This result, as well as the one from isotope analyses of carbon and nitrogen of sediments, suggests gradual isolation of the lagoonal waters of influence of waters from the open sea.
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Gambin, Belinda. "Vegetation history and climate dynamics in Malta : a Holocene perspective." Thesis, Aix-Marseille, 2015. http://www.theses.fr/2015AIXM4384.
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Cette thèse étudie la dynamique de la végétation Holocène pour Burmarrad dans le NW Malte et fournit une reconstruction paléoclimatique quantitative à base de pollen pour cet archipel méditerranéen situé au centre. Le record de pollen donne un nouvel aperçu l'échange végétation 7280-1730 cal BP qui correspondent bien avec other régional dossiers. La reconstruction du climat fournit également forte corrélation avec les sites du sud (en dessous de 40oN) de la Méditerranée. L'interprétation suggère un paysage initialement ouvert au début du néolithique, se développer en un dense Pistacia brousse ca. 6700 calBP. Depuis environ 4450 calBP le paysage devient de nouveau ouvert, coïncidant avec le début de l'âge du bronze sur l'archipel. Cette période coïncide avec une instabilité accrue du climat (entre 4500 et 3700 calBP) qui est suivie par une diminution progressive de la disponibilité de l'humidité de l'été à la fin de l'Holocène. Durant la période romaine début de l'occupation (1972-1730 calBP) le paysage reste généralement ouvert avec une augmentation modérée de Olea. Cette augmentation correspond à des preuves archéologiques pour la production de l'huile d'olive dans la région, avec l'augmentation des taxons cultivés des cultures et des espèces rudérales associés, ainsi que d'une hausse des cas d'incendies. Cette thèse propose également une synthèse des résultats d'un autre noyau (BM1) provenant de la même zone de chalandise, ainsi que les résultats d'une étude préliminaire de la pluie de pollen de surface moderne. L'archipel fournit des indications sur la végétation, les impacts humains et les changements climatiques dans un contexte de l'île au cours de l'HolocèneThis thesis investigates the Holocene vegetation dynamics for Burmarrad in north-west Malta and provides a pollen-based quantitative palaeoclimatic reconstruction for this centrally located Mediterranean archipelago. The pollen record from this site provides new insight into the vegetation changes from 7280 to 1730 cal BP which correspond well with other regional records. The climate reconstruction for the area also provides strong correlation with southern (below 40oN) Mediterranean sites. The interpretation suggests an initially open landscape during the early Neolithic, surrounding a large palaeobay, developing into a dense Pistacia scrubland ca. 6700 cal BP. From about 4450 cal BP the landscape once again becomes open, coinciding with the start of the Bronze Age on the archipelago. This period is concurrent with increased climatic instability (between 4500 and 3700 cal BP) which is followed by a gradual decrease in summer moisture availability in the late Holocene. During the early Roman occupation period (1972 to 1730 cal BP) the landscape remains generally open with a moderate increase in Olea. This increase corresponds to archaeological evidence for olive oil production in the area, along with increases in cultivated crop taxa and associated ruderal species, as well as a rise in fire events. This thesis also provides a synthesis with the results from another core (BM1) taken from the same catchment area, as well as results of a preliminary modern surface pollen rain study. The Maltese archipelago provides important insight into vegetation, human impacts and climatic changes in an island context during the Holocene
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Turner, Robert. "Late-Pleistocene to Holocence [i.e. Holocene] paleoseismic history of the Honey Lake Fault, northeastern California and northwestern Nevada /." abstract and full text PDF (free order & download UNR users only), 2006. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1440920.
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Thesis (M.S.)--University of Nevada, Reno, 2006."December, 2006." Includes bibliographical references (leaves 58-62). Online version available on the World Wide Web. Library also has microfilm. Ann Arbor, Mich. : ProQuest Information and Learning Company, [2006]. 1 microfilm reel ; 35 mm.
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Andersson, Sofia. "Late Holocene humidity variability in central Sweden /." Stockholm : Department of Physical Geography and Quaternary Geology, Stockholm University, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-36884.
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Diss. (sammanfattning) Stockholm : Stockholms universitet, 2010.At the time of the doctoral defence, the following papers were unpublished and had a status as follows: Paper 1: Submitted. Paper 3: Accepted. Paper 5: In progress. Härtill 5 uppsatser.
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Giesecke, Thomas. "The Holocene Spread of Spruce in Scandinavia." Doctoral thesis, Uppsala University, Department of Earth Sciences, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-4623.
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The Holocene spread of Picea abies in Scandinavia provides an excellent opportunity for detailed study of the dynamics of tree spread and population expansion. Early- and mid-Holocene macrofossil evidence for the presence of Picea abies in Scandinavia has questioned traditional interpretations of the timing and direction of its spread. This study aims to determine the pattern of the spread of Picea abies in Scandinavia from pollen and other data, to evaluate the significance of possible early outpost populations and to deduce possible factors that influenced the spread and population expansion of Picea abies in Scandinavia.
Palaeoecological investigations were carried out on the sediments of four small lakes in central Sweden to gain detailed insight into the dynamics of the spread. Holocene pollen diagrams with independent dating control were collected from Fennoscandia and adjacent areas to compare the timing of selected features of the Picea abies pollen curve. Computer models were used to test possible scenarios for the spread and Picea abies population expansion.
Picea abies entered the Scandinavian peninsula from the east at different times and by different pathways. Early-Holocene outposts can be discerned in pollen records from northwest Russia, eastern and northeastern Finland for the time before 9000 cal. BP. Pollen records from Sweden and Norway indicate small Picea abies populations after 8000 cal. BP. The mid to late-Holocene spread, which superficially resembles a front-like pattern, may in fact represent a wave of expanding populations. Disturbance through fire and human activity did not significantly influence the pattern of the spread. Changing climate parameters, slow adaptation and gene flow through seeds and pollen have to be considered as possible explanations for the late spread of the tree. Population dynamics and propagule pressure are likely to be important factors that shaped the spread of Picea abies.
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Mcilvenny, Jason Daniel. "Holocene evolution of Dunnet Bay, Caithness, Scotland." Thesis, University of Aberdeen, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.521338.
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Dunnet Bay in Caithness, Northern Scotland was chosen as a study site to look at the relationship between dune stability and climatic change during the late Holocene in Northern Scotland. The surviving drift deposits of Dunnet Bay consist of aeolian and organic soils overlying the shelly till which forms mounds and ridges beneath the overlying deposits. The surviving drift deposits have been deposited within the last 10,000 years. The oldest date acquired is from the lower inter-tidal peat which was dated to approximately 7,720–7,580 yrs BP. The aeolian sediment which makes up the bulk of the main dune ridge and a large percentage of the central links area is of very recent origin and was deposited rapidly during storm events in the Little Ice Age climatic event. An unconformity between the upper aeolian recent sands and older sediment was found. The unconformity occurs between approximately 250–1900 yrs BP and exists in the main dune sequence and links The depositional phases interpreted from the study can be associated with those found in other dune studies and proxy data. The timings of the depositional phases can be partially associated with levels of chloride found in the GISP2 core and storm circulation index data produced from a proxy ice core from Greenland (Mayewski & White, 2002), however some inconsistencies exist. These inconsistencies imply that the ice core record may not completely mirror timings of dune instability in Northern Scotland. Similar studies in the UK and around the North Atlantic basin show only partial correspondence with the transition timings at Dunnet. Coastal dune and sediment stratigraphy can therefore be seen as a low resolution localised record of coastal change of which climate plays a major role but not sufficiently consistent over regional areas to provide a clear regional pattern. A thin foraminifera rich shelly sand layer found beneath the inter-tidal peat may be the result of an extreme run-up event caused by the Storegga slides approximately 8,200 yrs BP. The thesis provides a detailed look at the development of the sedimentary history of Dunnet Bay.
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Daly, Julia. "Late holocene sea-level change around Newfoundland." Fogler Library, University of Maine, 2002. http://www.library.umaine.edu/theses/pdf/DalyJ2002.pdf.
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Fuller, Janice L. "Holocene forest dynamics in southern Ontario, Canada." Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.319318.
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Pearson, I. "Holocene evolution of the north Norfolk coast." Thesis, University of East Anglia, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.378907.
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The surtace and subsurtace Holocene deposits ot the macrotidal barrier coast ot north Norfolk. between Hunstanton and Wevbourne. have been investisated bv a coordinated studv ot sedimentarv and foraminiteral parameters. 14 distinct sedimentarv and vesetational areas (environmental units) are recognisable from aerial photographs, trom which a map of their spatial distributions has been produced. Barriers are both prograding (Holkham Gap) and eroding (Brancaster to Thornham) due to variations in sediment supply and land reclamation. Present models of sediment movement underestimate the offshore supply to the coast. In particular the input of sediment to the Holkham Gap area from a easterly offshore movement. Removal of fine sand to the offshore zone occurs at channel inlets although westerly spit development of Blakeney Point has created an embayment at Stiffkey where finer sands accumulate. Barrier formation observed at Holkham Gap indicates the emplacement and stabilisation of beach bars to be a major formational process. Sedimentarv parameter ranges delineate silt based units but show considerable overlap between sand-based units. Foraminiferal species assemblages delineate 4 significant cluster groupings also separating silt based units but amalgamating sand based units into one cluster group. The environmental unit determination of subsurface samples was supplemented bv stratigraphic relationship interpretations for sand based units. 9 subsur~ace environmental units have been separated. (i) back barrier sand and dune. (ii) peat. (iii) inter-tidal gravel, (iv) inter-tidal sand, (v) channel sand, (vi) inter-tidal silty sand, (vii) inter-tidal mud and marsh creek, (viii) lower marsh and (ix) upper marsh.
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Hazell, Zoe Jennifer. "Holocene palaeoclimate reconstruction from New Zealand peatlands." Thesis, University of Plymouth, 2004. http://hdl.handle.net/10026.1/1853.
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A selection of palaeoecological proxies were tested on two raised, ombrotrophic, restiad peat bog sites from the North Island of New Zealand. With varying degrees of success, peat humification, testate amoebae, plant macrofossil and charcoal analyses contributed to determining the palaeomoisture records from three cores on each site. Climatic inferences have successfully been made for the Waikato region, mid North Island, over the period between the Tuhua (6,130±30 14C years BP; 6,800-7,150 cal. years BP) and Taupo (1,850±10 14C years BP; 1,650-1,800 cal. years BP) tephras. 47 AMS radiocarbon ages contributed to the production of age-depth models. The peat humification records have a resolution of 20-30 years and are the first replicated records for this region. Whilst peat humification and charcoal were the most successful analyses, the limited plant macrofossil work has also shown potential. Testate amoebae analysis, however, was not appropriate for these particular sites due to extremely low fossil test abundances. From the peat humification record, the main palaeomoisture trend identified in all cores is a shift towards wetter conditions c.5,000-4,000 cal. years BP. This is thought to have resulted from stronger westerly circulation, driven by increasing temperature and pressure gradients across the Southern Ocean from equatorial to polar latitudes. This in turn is likely to have been due to an increasing differential between insolation received at these latitudes, ultimately forced by the precessional cycle. The 'Mid-Holocene Transition' to wet conditions appears to contradict previous work from New Zealand that infers a drier late Holocene. This apparent contradiction can, however, be reconciled by increasing seasonality that would also explain the rise in charcoal abundance following the Mid-Holocene Transition. Colder, wetter winters resulted from decreasing winter (June) insolation and stronger rain-bearing westerlies, causing a decrease in peat humification. Warmer, drier summers resulted from an increase in summer (December) insolation and caused increased regional burning. An intensifying ENSO signal at the mid-Holocene is also thought to be responsible for increased drought occurrence and weather extremes.
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Carroll, F. A. "The holocene environment of the Maltese Islands." Thesis, Queen's University Belfast, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.479274.
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Head, K. S. "Early Holocene cooling in the British Isles." Thesis, Queen's University Belfast, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.398100.
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Fairclough, Alison Jane. "Unsupported '2'2'6Ra chronology of Holocene lake systems." Thesis, University of Liverpool, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366509.
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Ranson, Simon David. "Modelling vadose diagenesis of holocene carbonate sands." Thesis, University of Bristol, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326765.
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Coley, Kirstin Helen. "Holocene environmental change on the Peruvian Altiplano." Thesis, Royal Holloway, University of London, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.500147.
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Johansson, Hans. "Towards a Holocene tephrochronology for the Azores." Licentiate thesis, Stockholms universitet, Institutionen för naturgeografi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-121896.
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The Azores is situated in the North Atlantic Ocean and is one of the most active volcanicregions in the Northern Hemisphere. The volcanic history of the islands is fairly wellknown and several explosive trachytic eruptions have been reported but the geochemicalcompositions of the glass component of the tephra as well as the dispersal oftephras to distal areas are less well known. The purpose of this study is twofold: (1) topresent major element geochemistry of the glass component from several historic aswell as prehistoric tephras, including the trachybasaltic Capelinhos AD 1957‐58eruption on the island of Faial, and the trachytic explosive eruptions of Sete Cidades(c. AD 1440), Fogo A (c. 5000 BP), Fogo AD 1563 and Furnas AD 1630 on the island ofSão Miguel; (2) to present a refined tephrostratigraphy for the island of Pico. Analyses ofmajor element geochemistry suggest that tephras from the three active stratovolcanoeson São Miguel can be separated in biplots showing e.g. FeOtot vs.TiO2 and FeOtot vs. CaO.The tephrostratigraphy of Caveiro bog on the island of Pico is based on a radiocarbondated core with eight tephra layers extending back to c. 7000 BP. All tephras are oftrachybasaltic/basaltic trachyandesitic composition except the oldest layer, which is ofbasanitic composition. An attempt was made to correlate the tephra record of Caveirobog with the previously investigated Lake Caveiro. A tephra‐based correlation betweenthe Caveiro bog and Lake Caveiro is not straightforward and only three tephras inCaveiro bog can possibly be correlated with tephras found in the sediments of LakeCaveiro.Proximal glass data from the Furnas volcano on São Miguel suggest that distal cryptotephrasfound in Ireland may have an origin in the Azores and not on Jan Mayen aspreviously has been suggested. The similarity of the proximal tephras on São Miguel anddistal tephras in Ireland is demonstrated by high similarity coefficients (>0.95) andbiplots showing major element composition also support a correlation between Azoreaneruptions and distal tephras in Ireland. Thus, trachytic tephras erupted from explosiveeruptions on the island of São Miguel may have a potential to contribute to theconstruction of a European‐wide tephrochronology framework.Trachytic tephras erupted from explosive eruptions on the Azores may be more widelydispersed than previously thought and may provide useful isochrones for correlation ofpaleoclimate archives in the north‐central Atlantic, North Africa and the Iberian regions.The trachybasaltic/basaltic trachyandesitic tephras erupted from cinder cones on PicoIsland are probably only useful for a local tephrochronology in the Azores region, andnot for a wider Atlantic or European framework.
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Novello, Valdir Felipe. "Reconstituição paleoclimática do holoceno recente com base em estalagmites da região central do Estado da Bahia." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/44/44142/tde-11052015-153510/.
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A partir de registros de \'delta ANTPOT.18 O\' e \'ANTPOT.13 C\' e das taxas de crescimento de espeleotemas precisamente datados pelo método U-Th foi possível reconstituir a paleopluviosidade dos últimos 3 mil anos da região central do estado da Bahia. Os registros de alta resolução (\'DA ORDEM DE\' 4 anos) propiciaram caracterizar a influência dos padrões atmosféricos e da temperatura da superfície do mar (TSM) observados atualmente nos oceanos Atlântico e Pacífico na paleoprecipitação da região. Através da comparação direta entre os dados de \'delta ANTPOT. 18 O\' da estalagmite TR5 (com resolução amostral de 6 meses) com estações de monitoramento pluviométrico da região, foi possível relacionar as variações do \'delta ANTPOT. 18 O\' do espeleotema com a variação da pluviosidade mostrando que, valores mais negativos no registro isotópico são representativos de maior precipitação e vice-versa. Essa relação está de acordo com o fator \"amount effect\", que atua na variação das razões isotópicas do oxigênio da chuva na região tal como foi identificado em estudos da série histórica de monitoramento das estações IAEA-GNIP e por simulações computacionais que mostram a variação dos valores de \'delta ANTPOT. 18 O\' na atmosfera. O registro paleoclimático mostrou que uma progressiva aridificação vem ocorrendo na região central da Bahia nos últimos 3 mil anos, acompanhando o aumento da insolação de verão. Nesse intervalo de tempo, foram encontradas sequências de eventos úmidos abruptos que ocorrem periodicamente em escala centenial. Entre esses eventos, destaca-se o que ocorreu entre \'DA ORDEM DE\' 822-642 A.C. que é coincidente com intervalo de extremo frio na Europa e com o período de mínimo solar detectado na variação da irradiância. Já, durante a Anomalia Climática Medieval (ACM) e a Pequena Era do Gelo (PEG) o registro mostrou condições secas próximas a detectadas atualmente. Através de análises estatísticas realizadas nas séries temporais obtidas a partir do registro paleoclimático das estalagmites, foi detectado uma periodicidade de \'DA ORDEM DE\' 65 anos correlata com a Oscilação Multidecenal do Atlântico (OMA) em todo o registro da parte central da Bahia. Influências decorrentes da TSM do oceano Pacífico mostraram-se presentes durante eventos abruptos e períodos anômalos úmidos e secos.We present the first high resolution (\'DA ORDEM DE\' 4 years) precipitation record from central portion of Bahia state, covering the last \'DA ORDEM DE\' 3000 yrs from \'ANTPOT. 230 Th-dated\' stalagmites oxygen isotope records. Our record shows abrupt fluctuations in rainfall tied to variations in the intensity of the South American summer monsoon (SASM), including the periods corresponding to the Little Ice Age (LIA), the Medieval Climate Anomaly (MCA) and a period around 2800 yr B.P. Unlike other monsoon records in southern South America, dry conditions prevailed during the LIA in the Nordeste. Spectral, wavelet and cross-wavelet analyses of our record detected several periodicities from multidecadal to centennial time scales, particularly centered on 65 and 210 years, which have been linked to Atlantic sea surface temperature (SST) variations and solar variability, respectively. Here we show that changes in SASM activity in the region are mainly associated with variations of the Atlantic Multidecadal Oscillation (AMO) and to a lesser degree caused by fluctuations in tropical Pacific SST. Comparisons between TR5 \'delta ANTPOT. 18 O\' stalagmite record (\'DA ORDEM DE\' 6 mouths resolution) with local meteorological station showed that variations in \'delta ANTPOT. 18 O\' speleothem composition are in agreement with variations in the amount of rainfall over central Bahia. The same correlation was also identified in computing simulations based on IAEA-GNIP monitoring stations data. The \'delta ANTPOT. 18 O\' speleothem record shows a clearly trend toward dry conditions in central Bahia since the last 3 thousand years in agreement with solar insolation curve. In addition, the \'delta ANTPOT. 18 O\' record od DV2 sample shows several sequence of wet event at centennial time-scale. Among these events we call attention to the event occurred at \' DA ORDEM DE\' 822-642 D.C., coincident with an abrupt cold event recorded in Europe and with a minimum of solar irradiance. In other hand during the MCA and the LIA the record shows dry conditions, close to current values.
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Ely, Lisa L. "Large floods in the southwestern United States in relation to late- Holocene climatic variations." Diss., The University of Arizona, 1992. http://hdl.handle.net/10150/191171.
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A regional synthesis of paleoflood chronologies on rivers in Arizona and southern Utah reveals that the largest floods over the last 5000 years cluster into distinct time periods that are related to regional and global climatic fluctuations. The fine-grained flood deposits used to reconstruct these flood histories selectively preserve evidence of only the largest events. Large floods were frequent on rivers throughout the region from 4.8-3.6 ka (¹⁴C yrs). In contrast, the period from 3.4-2.2 ka is marked by a significant decrease in the number of large floods on virtually all of the rivers. The frequency of large floods increased after about 2.2 ka, with particularly prominent peaks around 1 ka and after 500 yrs BP, separated by a sharp decrease between 600 and 800 yrs BP. The storms that generate large floods (≥ 10-year) in this region fall into three general categories: 1) winter North Pacific extratropical storms, 2) late-summer and fall storms that draw on moisture from recurved Pacific tropical cyclones, and 3) summer storms, mainly convective thunderstorms. Winter storms and tropical cyclones are associated with the very largest floods on the rivers with paleoflood records, and are the most probable causes of the late-Holocene paleofloods. Floods from both winter storms and tropical cyclones occur when deep mid-latitude troughs steer storm systems into the region. Composite anomaly maps of daily 700-mb heights and monthly sea-level pressure indicate that the winter floods are associated with a low-pressure anomaly off the California coast and a high-pressure anomaly over the Aleutians or Gulf of Alaska. Shifts in the locations of the low- and high-pressure anomalies over the North Pacific appear to control which subregions of the southwestern U.S. experience floods. Composite 700-mb anomalies during tropical cyclone floods show a similar pattern, with a variation to a blocking high-pressure anomaly in the central North Pacific and a low-pressure anomaly over the western U.S. There is a strong connection between the negative phase of the Southern Oscillation Index and the large floods associated with winter storms and tropical cyclones. Over the last 5000 years, the episodes of more frequent large floods coincide with cool, wet, neoglacial periods. Warm periods are times of dramatic decreases in the number of paleofloods. Although the floods record individual extreme storms, they cluster in times of generally moister conditions in the region. A clear positive relationship exists between floods and low-frequency variations in El Niño over the last 1000 years. Warm coastal sea-surface temperatures indicative of El Niño-like conditions are associated with more frequent large floods over at least the last 2000 years. The paleoflood records demonstrate centennial-scale variations in the conditions conducive to the occurrence of large floods in this region.
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Huckleberry, Gary. "Late-Holocene stream dynamics on the middle Gila River, Pinal County, Arizona." Diss., The University of Arizona, 1993. http://hdl.handle.net/10150/191174.
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An archival-stratigraphic investigation of the middle Gila River provides insights into late-Holocene channel behavior and flood-plain formation. Historical records detail changes in channel patterns that correlate with changing frequency of large floods, but channel sensitivity is also affected by factors such as flood seasonality, changes in sediment load, human disturbances, and internal thresholds. Because the frequency of large floods is the dominant factor in channel changes, radiocarbon-dated flood deposits in late-Holocene alluvial terraces allow for a reconstruction of prehistoric channel behavior. A period of reduced large flood frequency and channel stability 4,000-1,000 years BP separates periods of increased large flood frequency and channel instability 5,000-4,000 and 1,000-0 years BP. Transformations between braided and single channel morphologies affect the conveyance of floods and change the spatial characteristics of flood hazards. These channel dynamics are also important in analyzing changes in Hohokam-Pima irrigation technology and settlement patterns.
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Faure, Élodie. ""Hautes terres" : l'anthropisation des monts d’Aubrac et du Lévezou (Massif Central, France) durant l’holocène : approche palynologique des dynamiques socio-environnementales en moyenne montagne." Thesis, Toulouse 2, 2012. http://www.theses.fr/2012TOU20087/document.
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L’étude des interactions sociétés-milieux sur la longue durée, à l’origine de la construction des paysages de l’Aubrac et du Lévezou, a été menée à partir d’une démarche largement pluridisciplinaire dans laquelle la palynologie constitue l’outil principal. La constitution d’un référentiel actuel a conduit, dans un premier temps, à discriminer les principaux taxons polliniques représentatifs des activités humaines et d’en préciser la représentativité spatiale et fonctionnelle. L’étude multi-proxy de six séquences sédimentaires, étayées par 24 datations radiocarbones, a, dans second temps, permis de retracer l’histoire de la végétation et de l’anthropisation, notamment par l’identification des rythmes, des seuils et des ruptures durant l’Holocène. L’évolution des paysages en lien avec le développement des déboisements et des activités agricoles a pu être appréhendée à une échelle locale grâce aux apports combinés des pollens, des macrocharbons, des microfossiles non polliniques, de la confrontation avec les données archéologiques disponibles et de l’examen des sources archivistiques. Les premiers indices tangibles de fréquentation du massif de l’Aubrac apparaissent au cours du Néolithique moyen et les pratiques semblent se généraliser au Néolithique final sur l’Aubrac et le Lévezou. L’âge du Fer et le début de l’Antiquité marquent les premiers déboisements importants sur le plateau de l’Aubrac, concomitants d’une hausse de la pression agropastorale observée dans tous les sites. Enfin, les périodes médiévales et modernes contribuent à ancrer les formes du paysage esquissées aux époques plus anciennes. L’ensemble de ces dynamiques suggère avant tout l’importance des variabilités territoriales qui renvoient à des modes d’occupation temporaires jusqu’à l’âge du Bronze et à une grande mobilité des pratiques. Ces territoires présentent également des tendances communes qui répondent pour une part aux grandes trajectoires de colonisation des espaces montagnards. A l’examen de ces dynamiques d’anthropisation, le forçage climatique ne semble pas avoir été un facteur limitant et pourrait constituer un stimulus positif favorisant le développement de nouvelles stratégies adaptativesBased upon a multidisciplinary approach centered on palynology, the aim of our study was to better understand the long-term interaction in human/vegetation processes in the Aubrac and Levezou mountainous regions (Massif Central, France). In a first step, the relationships between present pollen deposition, vegetation and land-uses have been studied using a comparative approach. The main pollen taxa representative of human activities have been isolated and their spatial and functional representativeness have been assessed. Secondly, six sedimentary records, supported by 24 radiocarbon dates, have been studied with a multi-proxy approach combining pollen, macro charcoals, non-pollen palynomorphs, archeological and historical data. The analysis has allowed us to characterize vegetation history and local human impact on the landscape, in particular rhythms, breaks and thresholds concerning anthropisation’s dynamics According to our analysis, the first signs of human impact on the vegetation appear in Aubrac during the middle Neolithic period, while evidence of human activities seem to extent during the Late Neolithic. The Iron Age and early Antiquity periods are characterized by large scale deforestation correlated to the increase of the agro-pastoral pressure. Our analysis further suggests that the medieval and modern periods consolidate the types of landscape that have been created in earlier periods. The dynamics that have been highlighted in this study suggest an important degree of spatial variability of land use. The analyzed territories present common trends that correspond to colonization trajectories generally encountered in mountain areas. Relative to anthropisation’s dynamics, climate forcing seems to have not been a limiting factor for human settlements and may even have been a positive stimulus promoting the development of new adaptive land use strategies
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Edberg, Elin. "Environmental Development around Falun Copper Mineduring Late Holocene." Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-244313.
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The area at and around the Falun copper mine has always been of great interest. To begin with it was the valuable ore that drew people to the area. Now it is the historical, archaeological and environmental aspects that draw researchers from different fields of study to Falun. Peat cores were taken in several peatlands throughout an area extending toward about 2 kilometres to the west, southwest and south of the Falun mine. One core was selected for more extensive studies including plant macrofossil analysis, loss on ignition (LOI) and 14C – analysis. These methods are combined to give a picture of the environmental conditions at different periods in time, using plants and their preferred growth environment as an aid. The untouched environment changing into the well-known mining landscape that prevailed in the hey-day of the mine, with the change being the focal point, is the reason for this study.The cores presented in this thesis generally show lake areas drying up and transforming into peatlands, some peatlands may however have been formed in other ways. The location chosen for further studies is now almost transformed to a forest floor. This study provides a solid foundation for further studies as well as adds more information to existing knowledge. However, more research is needed to fully understand how the environment changed due to the opening of the mine.Området vid och runt Falu koppargruva har alltid varit av stort intresse. Till en början var det den dyrbara malmen som lockade människor till platsen. Numer är det de historiska, arkeologiska och miljörelaterade aspekterna som lockar forskare från olika forskningsfält hit. Torvkärnor togs från flera torvmarker inom ett område som sträcker sig ungefär 2 kilometer i väst-, sydväst-, och sydlig riktning från Falu gruva. En torvkärna valdes ut för mer omfattande undersökningar, dessa inkluderar växt-makrofossil-analys, LOI och 14C – analys. Dessa metoder kombineras för att få en bild av de rådande miljöförhållandena vid olika tidpunkter, genom att använda växters föredragna växtplats som hjälp. Det är hur den orörda naturen förändrats till det välkända gruvlandskapet som rådde under gruvans storhetstid, med förändringen i centrum, som är anledningen till denna studie.Torvkärnorna som visas i denna rapport visar i stort sett hur sjömiljöer torkat ut och förändrats till våtmarker, vissa våtmarker kan dock ha utvecklats på annat sätt. Den plats som valdes ut för vidare studier har idag nästan helt omvandlats till skogsmark. Denna studie ger en stadig grund för vidare studier och tillför viss information till den redan befintliga. Det behövs dock mer forskning för att fullt ut förstå de miljöförändringar som gruvdriften medförde.
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Rhodes, Aileen. "The Holocene palaeoclimatic history of Pine Lake, Alberta." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq28981.pdf.
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Murphy, Brent M. "Researching the early Holocene of the Maritime Provinces /." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ36157.pdf.
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Berger, Marit. "Modelling the early to mid-Holocene Arctic climate." Licentiate thesis, KTH, Turbulens, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-127870.
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In the recent past it has become evident that the Earth's climate is changing, and that human activity play a significant role in these changes. One of the regions where the ongoing climate change has been most evident is in the Arctic: the surface temperature has increased twice as much in this region as compared to the global average, in addition, a significant decline in the Arctic sea-ice extent has been observed in the past decades. Climate model studies of past climates are important tools to understand the ongoing climate change and how the Earth's climate may respond to changes in the forcing. This thesis includes studies of the Arctic climate in simulations of the early and mid-Holocene, 9 000 and 6 000 years before present. Changes in the Earth's orbital parameters resulted in increased summer insolation as compared to present day, especially at high northern latitudes. Geological data imply that the surface temperatures in the early to mid Holocene were similar to those projected for the near future. In addition, the geological data implies that the Arctic sea ice cover was significantly reduced in this period. This makes the early to mid-Holocene an interesting period to study with respect to the changes observed in the region at present. Several model studies of the mid-Holocene have been performed through the Paleoclimate Modeling Intercomparison Project (PMIP1 to PMIP3). The simulations have been performed with climate models of varying complexity, from atmosphere-only models in the first phase to fully coupled models with the same resolution as used for future climate simulations in the third phase. The first part of this thesis investigates the simulated sea ice in the pre-industrial and mid-Holocene simulations included in the PMIP2 and PMIP3 ensemble. As the complexity of the models increases, the models simulate smaller extents and thinner sea ice in the Arctic; the sea-ice extent suggested by the proxy data for the mid-Holocene is however not reproduced by the majority of the models. One possible explanation for the discrepancy between the simulated and reconstructed Arctic sea ice extent is missing or inadequate representations of important processes. The representation of atmospheric aerosol direct and indirect effects in past climates is a candidate process. Previous studies of deeper time periods have concluded that the representation of the direct and indirect effects of the atmospheric aerosols can influence the simulated climates, and reduce the equator to pole temperature gradient in past warm climates, in better agreement with reconstructions. The second part of the thesis investigates the influence of aerosol on the early Holocene climate. The indirect effect of reduced aerosol concentrations as compared to the present day is found to cause an amplification of the warming, especially in the Arctic region. A better agreement with reconstructed Arctic sea ice extent is thus achieved.Under senare tid har det blivit uppenbart att jordens klimat håller på att förändras, och att mänsklig aktivitet spelar en viktig roll för dessa ändringar. Ett av de områden där den pägäende klimatfärändringen har varit tydligast är Arktis: temperaturen vid ytan har ökat dubbelt så mycket här jämfört med det globala genomsnittet. Dessutom har man observerat en betydande nedgång i havsisens utbredning i Arktis de senaste decennierna. Simuleringar gjorda med klimatmodeller av forntida klimat är viktiga verktyg för att förstå de pågående klimatförändringarna och hur jordens klimat påverkas av ändringar i klimatsystemets drivningar. Denna avhandling består av studier av det arktiska klimatet i modellsimuleringar av tidig och mid-holocen, ca. 9 000 och 6 000 år före nutid. Förändringar i jordens bana kring solen resulterade i en ökad sommar-solinstrålning jämfört med nutid, särskilt vid höga nordliga breddgrader. Geologiska data antyder att jordens temperatur vid ytan under denna period kan jämföras med dem vi förväntar för den närmaste framtiden. Vidare indikerar geologiska data att havsisen i Arktisk var kraftigt reducerad under denna period. Detta gör tidig till mid-holocen till en intressant period att studera, med avseende på de förändringar som för närvarande har observerats i området. Flera modellstudier av mitt-holocen har utförts i de olika faserna av Paleoclimate Modeling Intercomparison Project (PMIP1 till PMIP3). Simuleringarna har utförts med klimatmodeller av varierande komplexitet, från atmosfärsmodeller i den första fasen, till fullt kopplade modeller med hög rumslig upplösning i den tredje fasen. I den första delen av denna avhandling undersöks den simulerade havsisen i de förindustriella och mid-holocen simuleringar som ingår i PMIP2 och PMIP3 ensemblerna. Modellerna simulerar mindre utbredning och tunnare havsis i Arktis i den senare PMIP ensemblen, men fortfarande återskapar inte modellerna generelt den havsisutbredning som de geologiska data indikerar. En möjlig förklaring till skillnaderna mellan den simulerade och rekonstruerade havsisutsträckningen kan vara att viktiga processer i klimatsystemet saknas eller inte är tillräckligt väl beskrivna i modellerna. Beskrivningen av atmosfäriska aerosoler och dess effekter på klimatet är en möjlig kandidatprocess. Från studier av forntida varma tidsperioder har man dragit slutsatsen att beskrivningen av aerosoleffekterna påverkar det simulerade klimatet. Bland annat kan man minska temperaturgradienten mellan ekvator och polerna i tidigare varma klimat, vilket bättre överensstämmer med temperaturrekonstruktioner. Den andra delen av avhandlingen undersöker påverkan av aerosoler på klimatet under tidig holocen. Den indirekta effekten som följer av lägre aerosolkoncentrationer i tidig holocen jämfört med i dag, visar sig orsaka en förstärkning av uppvärmningen, särskilt i det arktiska områet, vilket stämmer bättre med havsisrekonstruktioner från denna period.
QC 20130910
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Campbell, James Arthur McLeish. "Holocene palaeoenvironments of Guernsey and Alderney, Channel Islands." Thesis, Coventry University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.323575.
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TrifkovicÌ, Vuk. "Construction of space in early Holocene Iron Gates." Thesis, University of Oxford, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.422572.
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Meara, Rhian Hedd. "Geochemical fingerprinting of Icelandic silicic Holocene tephra layers." Thesis, University of Edinburgh, 2012. http://hdl.handle.net/1842/5834.
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The overall aim of this research project has been to develop a reference dataset of 19 Holocene silicic Icelandic tephra layers sourced from the Torfajökull, Askja, Katla, Öræfajökull and Hekla volcanic systems. The dataset comprises geochemical data (including major, trace and rare earth element data for bulk and glass phases collected by XRF, electron microprobe, ion probe and laser ablation ICP-MS) and physical data (including sedimentary logs, field photographs, distribution maps and GPS localities of reference sections). Results indicate that Icelandic volcanic systems show unique geochemical signatures which result from the systems proximity to the active rifting zone and the proposed upwelling mantle plume that underlies the island. Within individual volcanic systems, eruptions produce tephra with distinct geochemical characteristics, which allow for the independent confirmation of tephra identity. The identification and discrimination of tephra layers can in some cases be achieved using major element chemistry (e.g. Hekla, H1104 – H5) while other tephra layers can only be discriminated using trace element chemistry (e.g. Torfajökull, Landnám and Gràkolla). Certain tephra layers however show near-identical geochemistry and therefore discrimination is not possible (e.g. Hekla, HA, HB, HC, HM, HN, HX, HY, HZ) without the incorporation of other proxy data. Icelandic micro-tephra horizons are identified in soil, lacustrine and marine sedimentary sequences and are used for dating and correlation in Quaternary studies. Data collected for this project will facilitate reliable data comparison and tephra identification between proximal and distal localities across the North Atlantic region. The data may also contribute to the debate regarding the formation of silicic rocks within Iceland, particularly with regard to the Hekla central volcano. The geochemical data collected for this thesis shows distinct age-dependant geochemical sub-groups suggesting temporal sub-surface relocation of the Hekla magma source.
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He, Yuxin, and 何毓新. "Biomarker based holocene climatic reconstruction in Northwestern China." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/197088.
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Holocene hydrological changes in regions influenced by the mid-latitude westerly and the tropical/subtropical Asian monsoon differ from each other. The arid/semi-arid northeastern Tibetan Plateau, lying in between, is very sensitive to climatic changes. It thus becomes a climatologically important region to disentangle the interactions between the two circulations. Yet, limited high-quality Holocene paleoclimatic reconstructions are available in this region. This thesis presents multi-biomarker proxy records from lakes in the Qaidam Basin on the northeastern Tibetan Plateau to investigate the nature of Holocene climate variability.
Firstly, late-Holocene paired alkenone-based temperature (U_37^K' ) and moisture (%C37:4) records from Lake Gahai and Lake Sugan were reconstructed. Paired temperature and moisture records confirm the warm-dry (e.g. Medieval Warm Period) and cold-wet (e.g. Little Ice Age) periods on the arid northeastern Tibetan Plateau over the late Holocene, opposite to the warm-wet and cold-dry association in Asian monsoonal regions. The records also suggest substantially warmer and drier conditions during the Medieval Warm Period than the current warm period. Further, a possible link between solar forcing and natural climate variability (both temperature and moisture) during the late Holocene is found on the northeastern Tibetan Plateau.
This thesis also studied the late-Holocene grain size-based dust storm history from Lake Gahai to encode possible mechanism of dust storm interacting with hydrological parameters. Intensified dust storm events were identified in periods of 500 BC to 250 BC, 50 BC to AD 250 and AD 1100 to present. In multi-centennial to millennial scales, dust storm events might be caused by the intensified wind induced by strong westerlies or/and Asian winter monsoon. In multi-decadal to centennial scales, moisture and vegetation coverage might have impacted on the dust storm intensity and frequency.
Further, Holocene lake level history of Lake Gahai was reconstructed by multiple n-alkane and alkenone proxies. Combined biomarker results provide unambiguous evidence of relatively low lake level at 7-2 ka, probably lowest at ~6 ka. Considering the chronological uncertainty, Holocene lake level changes in this marginal region thus display a different pattern from either of the core regions dominated by the westerlies (anti-phase) and the Asian summer monsoon (out-of-phase). The temperature-induced evaporation in the arid marginal region could significantly affect regional hydrological balance, resulting in the discrepancy with the long-term decreasing trend in precipitation in Asian monsoon-dominated regions.
Lastly, n-fatty acid δD variation from Lake Hurleg over the past 10.5 ka was investigated. The C26 δD and C16 δD values can indicate water δD changes in terrestrial and aquatic sources, respectively. The heavier C26 δD values during cold and wet conditions suggest that terrestrial water δD changes might be caused by factors other than temperature and moisture, such as glacial melted water input and vegetation type change. The difference between C16 δD and C26 δD was used as an indicator of evaporation at the lake surface. At millennial timescale, less evaporation occurred during cold-wet periods in this region.published_or_final_version
Earth Sciences
Doctoral
Doctor of Philosophy
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Kaagan, Laura Mollie. "The horse in late Pleistocene and Holocene Britain." Thesis, University College London (University of London), 2000. http://discovery.ucl.ac.uk/1318059/.
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Until now, the horse was one of the few members of the British Late Pleistocene and Holocene fauna which had yet to be fully investigated. In this thesis, chronological, palaeoecological and morphological data based on direct investigations of British and European fossil and sub-fossil horses are presented. The time-frame encompasses the latest certain wild horses in Britain and continental Europe through to the early diversification of domestic types, and thus spans the interval from c. 15,000-2,000 years before present (BP). The gazetteers presented are the result of a thorough survey and intensive study of all relevant British (as well as selected continental) collections of fossil and sub-fossil horse material. Furthermore, the incorporation into this project of a radiocarbon accelerator dating programme has provided 45 new, direct horse dates from 31 British/Irish sites. A systematic review of all new and previously obtained dates reveals a complex pattern of chronological and geographical distribution for horses during the study interval. These data are interpreted with reference to known climatic and environmental events which are detailed. Further investigations are presented which reveal the ecological reactions of wild horses to underlying environmental factors such as climate change and vegetational succession. Questions of body size variability as well as taxonomic and relationship issues are addressed by means of a detailed morphological investigation. Cranial and postcranial measurements are employed to expose variation and diversification of size and form among wild and domestic animals of three key periods: Mid-Devensian, Late Glacial/early Post Glacial, middle to later Post Glacial. In addition, body size comparisons are made between British and continental horses for each episode. Finally, there is discussion of alternative ways of revealing relationships between ancient and modern horses. In particular, molecular evidence is reviewed with the aim of assessing its value to taxonomic, morphological and chronological studies
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Coulthard, Thomas James. "Modelling upland catchment response to Holocene environmental change." Thesis, University of Leeds, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364900.
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Lane, Adrian Francis. "Late Holocene environmental change at Butrint, southern Albania." Thesis, University of Sheffield, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.408302.
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Fossitt, Julie A. "Holocene vegetation history of the Western Isles, Scotland." Thesis, University of Cambridge, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.291744.
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Allison, H. M. "The Holocene evolution of Scolt Head Island, Norfolk." Thesis, University of Cambridge, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.372641.
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Tamo, Camille. "Late Holocene Environmental Change Across the Canadian Arctic." Thesis, Université d'Ottawa / University of Ottawa, 2019. http://hdl.handle.net/10393/38837.
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Lake sediment cores spanning the last 2000 years from four sites across the Canadian Arctic Archipelago (CAA) document the responses of terrestrial and freshwater ecosystems to regional climate variability. Biogenic silica (BSi) records in cores from Banks Island, NWT (Lake B503; 72.3245, -123.4036, 84 masl), Bathurst Island, Nunavut (PR01; 75.6497, -99.1144, 30 masl), Prince of Wales Island, Nunavut (SW08; 72.3177, -97.2678, 104 masl), and Ellesmere Island, Nunavut (CV03; 79.9211, -82.9348, 363 masl) were used to examine the relationship between diatom production and climate. A pollen record from Prince of Wales Island provided the first high-resolution July temperature reconstruction for the last 1000 years for the central CAA.
Dissolution was evident in three out of the four lakes; core SW08 contained no BSi above detection and cores CV03 and PR01 only contained values above detection in the uppermost sediments, suggesting that the preservation of biogenic silica (BSi) in the sediment is likely influenced by sedimentary carbonates. A BSi sequence from core B503 showed that diatom production was affected by climate changes such as the Medieval Climate Anomaly and the Little Ice Age.
The vegetation on southern Prince of Wales Island underwent marked transitions during the Little Ice Age and Medieval Climate Anomaly, which was mainly observed in the proportion of Cyperaceae and Poaceae. The mean July temperature reconstruction showed a long-term cooling from 1080-1915 CE with a sustained cold period from 1800-1915 CE prior to 20th-century warming. A synthesis of paleoclimate records from across the Arctic demonstrated that pollen-based reconstructions record both high and low frequency climate variability, when sampling resolution is sufficient, and can improve regional climate reconstructions.
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Githumbi, Esther Nyambura. "Holocene environmental and human interactions in East Africa." Thesis, University of York, 2017. http://etheses.whiterose.ac.uk/19515/.
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A multi-proxy approach analysing pollen, macro-charcoal, sediment characterisation and elemental profiles was used to develop palaeoecological records and reveal environmental changes since the late Pleistocene- Holocene transition period from Mau Forest and since the mid-Holocene from Amboseli. Mau Forest was characterised by diverse Afromontane forest taxa between �16,000 cal yr BP and �13,000 cal yr BP which decreased during the Younger Dryas. During the early Holocene, there was a slight increase in montane tree taxa and the main vegetation change noted during the Holocene was the increase in woody shrubs and herbs. The pollen, sediment characterisation and elemental profiles revealed that climatic variability was the main driver of forest composition change and periods of aridity and wetness were identified at�15,000, �13,400, �12,000 and �1200 cal yr BP where there was increased organic matter, sand, magnetic susceptibility with peaks in detrital elements suggesting periods of wetness. Four new Amboseli records dating from the mid Holocene (�5000 cal yr BP) revealed a predominantly dry environment characterised by localised wet and dry phases and fire activity. The spatial differences observed from the Amboseli records are attributed to hydrological variance as the swamps are all fed by ground water and the differential use by humans and wildlife. Kimana, Enkongu and Esambu swamps are Cyperaceae dominated; the pollen records indicate that Amboseli is a grassland savannah dominated by Poaceae, Acacia, Commiphora and Euphorbia. The pollen composition and abundance and charcoal concentration levels vary between the four Amboseli sites indicating localised drivers and controls of fire at each site. This long-term information is useful in the development of ecosystem management policies which are constantly being updated due to the evolving pressures caused by increasing populations and changing land use around the two ecosystems.
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Alizai, Anwar Hussain. "Holocene evolution of the Indus River and tributaries." Thesis, University of Aberdeen, 2011. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=202561.
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The Northwest Himalaya is a region of rapid rock uplift and a strongly erosive climate that allows the competing influences on drainage development to be assessed in the Indus River. This study used U-Pb zircon and K-feldspar Pb isotope analysis together with conventional heavy minerals to reconstruct flood plain drainage patterns from ~20 ka. Furthermore, clay mineralogy is used to reconstruct changes in chemical weathering. U-Pb ages for zircon grains from the Indus tributaries were compared with available bedrock data in order to constrain the source of the sediment reaching the Arabian Sea. The trunk Indus is typified by <200 Ma zircons, in contrast with >800 Ma in the eastern tributaries, eroded from Himalayan sources. A significant population of grains <200 Ma in Thar Desert indicates monsoon-related eolian transport from the lower Indus. Modelling of modern delta sand that is rich in >1700 Ma zircons contrasts with modern water discharge which is dominated by the trunk Indus indicating preferential Lesser Himalayan erosion before ~7 ka. Pb isotope compositions of K-feldspars were used as an additional provenance constraint. The eastern tributaries show a clear Himalayan provenance, contrasting with radiogenic grains in the trunk Indus. Thar desert sands show isotopic values that suggest significant erosion from Karakoram, consistent with the zircon dating, as well as heavy mineral data. In turn Holocene river sands from the western edge of the desert indicate increasing reworking from the dunes prior to ~4.5 ka, linked to climatic drying. XRD clay mineralogy shows increasing smectite in the delta at 13–7.5 ka, indicating stronger chemical weathering as the summer monsoon intensified. In contrast, the upper flood plains show evidence for increased chemical weathering after ~7 ka linked to the cessation of fluvial transport under the influence of a weakening monsoon.
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Commerford, Julie L. "Investigating North American grassland biogeography throughout the Holocene." Diss., Kansas State University, 2016. http://hdl.handle.net/2097/32798.
Full textAbstract:
Doctor of PhilosophyDepartment of Geography
Kendra K. McLauchlan
Throughout the Holocene, North American grassland vegetation has shifted in composition and spatial extent. However, it has been difficult to characterize these changes because the drivers—particularly climate, fire, topography, or grazing from large herbivores—operate at different spatial and temporal scales. Long-term archives such as lacustrine sediment cores, and the proxy records they contain, can help illustrate vegetation changes on relevant timescales. Yet, accurate interpretations of grassland vegetation composition from pollen (a common proxy used to infer vegetation of the past) remain limited by the number of calibrations of pollen and the drivers of vegetation change in modern conditions. This research addresses those gaps by evaluating grassland vegetation at different spatial and temporal scales in the context of modern and historical drivers. First, I reconstruct vegetation composition and diversity, fire activity, and erosion activity at a sub-regional scale over the last 9,300 years by analyzing pollen, charcoal, and magnetic data from a sediment core from a grassland lake in southern Minnesota. Second, I quantify the relationships between modern grassland pollen and fire, grazing, and topography at a fine spatial and temporal resolution, using pollen samples collected annually from traps at Konza Prairie Biological Station in the Flint Hills of Kansas. Finally, I synthesize modern pollen assemblages across the Great Plains to create a transfer function that quantitatively links precipitation and temperature with pollen. I apply this function to pollen data from the past to interpret the climate history of three sites across the Great Plains, including the aforementioned site in southern Minnesota. The results from this research suggest that grassland vegetation diversity remained relatively resilient to the climatic fluctuations of the Holocene, including the driest time at 5,000 yr BP. In addition, this work facilitates more informed interpretations of fossil pollen by effectively calibrating modern grassland pollen assemblages with their abiotic and biotic drivers.