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Palynological investigations into the early Quaternary and late Tertiary vegetation and climate of west Auckland, New ZealandByrami, Mairie January 2003 (has links)
This thesis presents a detailed late Tertiary and early Quaternary pollen record from two c. 40 m long sedimentary cores (the Patiki cores) from west Auckland. The cores consist of slightly to highly carbonaceous clays, with a thick sand incursion at mid-depth. The sediments below the sand incursion are aged through palynostratigraphy as mid-late Pliocene (Hautawan). The sediments above the sand incursion have numerous interbedded tephras, and are aged through a combination of Isothermal Plateau Fission Track dating, palaeomagnetism and orbital tuning to the marine oxygen isotope record as 1.0 – 1.4 Ma (MIS 28 - 45, Marahauan substage). The Tertiary pollen record portrays regional vegetation assemblages of extinct Nothofagus brassii-type species and modern-day podocarps, with local modern-day oligotrophic mire assemblages. A cool climatic phase is indicated by a period of dominance of an extinct member of the Proteaceae. However, the duration of this interval cannot be determined due to a lack of numerical age control for the record. The Quaternary pollen record consists of mostly extant pollen types. It shows multiple compositional shifts from Nothofagus-dominated to conifer-dominated regional vegetation, with local oligotrophic mire vegetation except for a fully aquatic phase at mid-depth (MIS 35). The primary axis score curve of a detrended correspondence analysis (DCA) of the pollen record was correlated to the marine isotope record, and shows that the Nothofagus-dominated intervals correspond to cool climate stages, while the conifer-dominated intervals correspond to warm stages. The strongest cool stage maximum is indicated at 12 - 13 m depth (MIS 34), where the vegetation consists of Fuscospora, Prumnopitys taxifolia and heath shrubs. The strongest warm stage maximum is indicated at c. 9 m depth (MIS 31) where the vegetation consists of Dacrydium forest. Astronomically forced climate change is an important driving force behind vegetation composition changes portrayed in the Quaternary pollen record. The majority of warm stage maxima inferred in the pollen record (conifer-dominated intervals) coincide with periods of maximum obliquity, and vice versa for inferred cool stage maxima (Nothofagus-dominated intervals). The modulating effect of eccentricity on precession is influential on the pollen record during MIS 31 and 34. The relationship between selected climate indicator taxa and calculated insolation values indicates that reduced seasonality in Auckland during warm climate stages favours Agathis, Dacrydium, Phyllocladus and Halocarpus, while increased seasonality during cool climate stages favours Nothofagus ‘fusca'-type, Nothofagus menziesii, and Prumnopitys taxifolia. In both situations the trees are probably responding to a combination of changes in mean global temperatures and seasonality, and reacting according to their own adaptive responses to astronomically driven climate change. The Quaternary pollen record contains plant mixtures that do not occur in New Zealand today, for example Agathis australis with Nothofagus menziesii, and Halocarpus bidwillii / biformis. The climate was probably cooler than it is in Auckland today, but never as cold as the last glacial maximum in Auckland when grasslands were present. Under more equable climatic conditions, with less extreme glacial and interglacial cycles, populations of comparably 'warm' and 'cool' climate taxa were probably able to shift throughout the region and mixed to a greater extent than is currently observed. The overall vegetation response to climate change (particularly above MIS 36) is analogous to that recorded in northern New Zealand in the late Pleistocene, and supports a negligible change in climatic preference of the main canopy species since the early Quaternary. The phytosociological idiosynchracies in the pollen record are not inconsistent with the known tolerance limits of the taxa involved, or with the individualistic nature of vegetation composition.
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History of Picea abies in west central Sweden : applications of pollen analysis to reveal past local presence of trees /Stedingk, Henrik von, January 2006 (has links) (PDF)
Diss. (sammanfattning) Umeå : Sveriges lantbruksuniv., 2006. / Härtill 4 uppsatser.
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Response of terrestrial palaeoenvironments to past changes in climate and carbon-cycling insights from palynology and stable isotope geochemistry /Heimhofer, Ulrich, January 2004 (has links)
Thesis (Sc.D.)--Eidgenössische Technische Hochschule Zürich, 2004. / Existe aussi en ligne (cf. lien) Available in PDF format via the World Wide Web.
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Middle to late eocene dinoflagellate cysts and fungal spores from the east coast of the Maracaibo Lake, Venezuela (biostratigraphy, palaeoecology and taxonomy) /Ramírez, Rafael A., January 2004 (has links) (PDF)
Thesis (Dr. rer. nat.)--Universität Tübingen, 2004. / Includes bibliographical references. Available in PDF format via the World Wide Web.
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Interactions Sociétés-Environnement en Macédoine orientale (Grèce du Nord) depuis le début de l'Holocène. : Approche multiscalaire et paléoenvironnementale. / Human-Environment relationships in eastern Macedonia (northern Greece) since the early Holocene. : Multiscalar and palaeoenvironmental approach.Glais, Arthur 19 May 2017 (has links)
Les perturbations environnementales enregistrées aujourd’hui dans le cadre du changementclimatique global exacerbent les craintes des sociétés quant au développement durable. Si l’impact desactions anthropiques sur les changements contemporains est désormais reconnu scientifiquement, lesspécialistes des sociétés anciennes et des géosciences se demandent si les changementsenvironnementaux d’origine naturelle ou anthropique n’ont pas déjà et à plusieurs reprises, affecté ledéveloppement des sociétés au cours des derniers millénaires. Les investigations menées, dans le cadrede cette thèse, proposent de contribuer à ce débat à partir de l’étude sur le temps long de la basse valléedu Strymon (Grèce du Nord) depuis le début de l’Holocène. L’enjeu est de comprendre les relationsqu’ont entretenues les sociétés avec leur environnement afin d’examiner les questions d’éventuelseffondrements culturels d’origine environnementale comme le suggèrent certains chercheurs pour la findu Néolithique ou l’Âge du Bronze, et celles des conséquences des actions des sociétés (néolithisation,conquête grecque, etc.) sur l’environnement et la durabilité de son exploitation. Pour dépasser les étudesde cas, nous proposons une approche géographique multiscalaire et géoarchéologique. Elle s’appuie surune étude des archives paléoenvironnementales combinant (1) une analyse géomorphologique et (2) uneanalyse palynologique des cours d’eau et des zones humides afin de renseigner les changementsenvironnementaux au plus près des lieux de vie des populations et de leurs pratiques agropastorales.Les résultats obtenus sont ensuite confrontés aux recherches archéologiques et historiques pourcomprendre les interactions Sociétés/Environnement de l’échelle de l’habitat à celle de la région étudiéeà différentes époques, et participer activement aux discussions multidisciplinaires sur la question. / Environmental disturbances recorded nowadays in global changes rise up society fears aboutsustainable development. Even if the responsibility of activities on contemporary changes is now wellknown,the specialists of past societies are still wondering if such environmental changes, either fromnatural or from anthropogenic origin, have not already affected societies development in last thousandsof years. This research project contributes to this debate on the base of long time study of Strymona lowvalley (northern Greece), from Early Holocene. The aim is to understand the relationships betweensocieties and environment by questioning the possibility of cultural collapses from environmentalorigin, and to examine the consequences of human activities (Neolithisation, Greek conquest, ...) onenvironment and his sustainability. To overcome case studies, we suggest a geographical andgeoarchaeological approach. Based on study of palaeoenvironmental archives which combinegeomorphological and palynological analyses of streams and wetlands. Our aim is to analyze the role ofagropastoral practices and climate events and oscillations on environmental changes, and on thedynamics of mosaic landscapes. Results will be compared with archaeological and historical researchesto understand the interactions between societies and their environment from sites to regional scale, fromthe Neolithic to Ottoman period and to take part actively to multidisciplinary discussions on this debate.
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Análise palinoestratigráfica e paleoambiental de Depósitos Aptianos-Albianos (Cretáceo Inferior) da Bacia do Espírito Santo, BrasilMichels, Fernando Heck January 2017 (has links)
A Bacia do Espírito Santo possui importantes campos de petróleo e gás em exploração, entretanto poucos trabalhos micropaleontológicos estão disponíveis para esta região uma vez que a maior parte deste conhecimento é relativo a relatórios internos de empresas de petróleo e gás. Este trabalho apresenta uma análise bioestratigráfica e paleoambiental de sucessões sedimentares do intervalo Aptiano-Albiano das formações Mariricu (Membro Itaúnas), São Mateus e Regência. A amostragem é derivada de dois poços (BES-01 e BES-02) perfurados na porção emersa da bacia. Dentre as 24 amostras, 18 revelaram assembleias palinológicas diversificadas, incluindo 51 táxons de plantas terrestres (23 de esporos e 28 de grãos de pólen), 4 táxons de algas (3 dinocistos e 1 alga clorofícea), bem como táxons não determinados de palinoforaminíferos, fungos, escolecodontes e acritarcos. Os grãos de pólen de gimnospermas são dominantes em ambos os poços, principalmente representados pela abundância e diversidade de Classopollis; outros gêneros de grãos de pólen e esporos ocorrem subordinados. A análise bioestratigráfica se baseou nos intervalos cronoestratigráficos de espécies-guias comparadas com biozoneamentos estabelecidos principalmente para a própria Bacia do Espírito Santo, como também para as demais bacias marginais brasileiras As amostras do BES-01 apresentaram idade Albiano inferior, enquanto para as amostras do poço BES-02 foi atribuída idades entre o Aptiano superior e o Albiano inferior (sem distinção). Os dinocistos e os palinoforaminíferos são restritos a alguns níveis do poço BES-01; a assembleia monoespecífica distinta do gênero Subtilisphaera representa o primeiro registro da Ecozona Subtilisphaera na Bacia do Espírito Santo, indicando a ocorrência mais ao sul desta ecozona nas bacias marginais brasileiras. Comparando a frequência da matéria orgânica particulada nas amostras (palinomorfos, fitoclastos e matéria orgânica amorfa), se interpretou o ambiente deposicional como uma região costeira ocasionalmente influenciada por transgressões marinhas. A palinoflora representa a fase final da Província Dicheiropollis etruscus/Afropollis documentada em várias bacias marginais no Brasil e na África, principalmente definida por elementos gimnospérmicos fortemente adaptados a condições climáticas quentes e secas. / The Espírito Santo Basin comprises important oil and gas fields, mostly in active exploration. However, few micropaleontological contributions are available for this region, once most part of its knowledge is concerning to internal reports of oil and gas companies. This work presents a biostratigraphic and paleoenvironmental analysis from an Aptian-Albian succession of Mariricu (Itaúnas Member), São Mateus and Regência formations. Sampling is derived from two wells (BES-01 and BES-02), drilled in the onshore portion of the basin. Among 24 samples, 18 revealed abundant and diverse assemblages of palynomorphs, including 51 taxa related to terrestrial plants (23 of fern spores, and 28 of gimnospermic pollen grains), 4 algae (3 of dinocysts and 1 chlorophicean), as well as no determined taxa of foraminiferal linings, fungi, scolecodonts and acritarch. Gimnospermic pollen grains are dominant in both wells, mainly represented by an expressive abundance and diversity of Classopollis; other gimnospermic pollen grains and pteridophitic spores are subordinate. Biostratigraphic assignments are based on the ranges of certain guide species compared with schemes mainly established for the Espírito Santo Basin, as well as to other Brazilian marginal basins The samples of BES-01 were defined as early Albian in age, whereas an age from late Aptian to early Albian (without distinction) was assigned for the samples of well BES-02. Dinocysts (mainly Subtilisphaera) and foraminiferal linings are restricted to certain levels of the well BES-01. A distinctive monospecific assemblage of the Subtilisphaera in some samples reflects the first record of the Subtilisphaera Ecozone in the Espírito Santo Basin, representing its most meridional occurrence in the Brazilian marginal basins. Comparing the frequency of palynological content in both wells (palynomorphs, phytoclasts and amorphous organic matter), the depositional environment is interpreted as a coastal area, episodically influenced by marine transgressions. The palynofloral content of the assemblages is assumed to represent the final stage of the Dicheiropollis etruscus/Afropollis Province, which is well documented in several marginal basins of Brazil and Africa, mainly defined by a gimnospermic elements, strongly adapted to warm and dry climate conditions.
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Reconstructing Holocene East Asian climate and oceanographic history of the northern South China Sea: high-resolution records of pollen, spores, and dinoflagellate cystsLi, Zhen 02 January 2019 (has links)
This study contributes to developing terrestrial and marine palynological indicators of winter or summer monsoon signals as well as oceanographic environments of the South China Sea (SCS). The high-resolution reconstructions of Holocene East Asian Monsoon (EAM) climate and oceanographic condition of the northern SCS provide insights into regional climate events in the western low-latitude Pacific Ocean and their impacts on local oceanography and ecology.
Sediment trap samples from the southwest Taiwan waters of the SCS in winter monsoon (March-April) and summer monsoon (July-August) seasons identify abundances of Pinus and Ulmus pollen as indicators of the winter monsoon whereas fern spores appeared to be indicators of the summer monsoon. The increased fluxes of dinoflagellate cyst (DC) taxa during summer are correlated with decreased sea-surface salinity (SSS) associated with nutrient-rich river inputs.
DC distributions across the SCS show that some taxa are good indicators of changes in sea-surface temperature (SST), SSS, water depth and chlorophyll-a (chl-a) concentrations associated with EAM and oceanographic conditions. In particular, the concenrations of Brigantedinium spp. and cysts of Protoperidinium together with Echinidinium spp. are positively correlatd with SST in January and SST in July, and chl-a concentrations, respectively, which are linked to past monsoon strength and primary productivity. In total, four high cyst concentration regions have been observed off southern Vietnam, Borneo, Hainan, and South China.
High-resolution palynological records from a sediment core in the northern SCS reflect several EAM climatic and oceanographic events over the last 12.5 kyr. A short-term Impagidinium decrease implied that the Taiwan Strait opened at ~11.7–11.0 cal kyr BP, with reduced Kuroshio Current influence when the East China Sea waters entered through the strait. Three Holocene relative sea-level stages were identified in the palynomorph records. The highest herb pollen abundances were observed before ~10.4 cal kyr BP, reflecting the shortest distance from the grassland sources on the exposed shelf at the low sea-level stand. High Brigantedinium and cysts of Protoperidinium abundances also indicate a near-shore environment. During ~10.4- ~6.8-6.0 cal kyr BP at the rising sea-level stage, fern spore abundances increased and DC abundances decreased. Consistently low total DC concentrations and high fern spore abundance were observed after ~6.8-6.0 cal kyr BP when the present oceanographic conditions were formed. Increased abundances of Pinus pollen reflected three strengthened winter monsoon intervals at ~5.5, 4.0 and 2.5 cal kyr BP under the present oceanographic conditions. The highest Dapsilidinium pastielsii abundances reflected the warmest interval at ~6.8-5.5 cal kyr BP of the northern SCS. / Graduate / 2019-12-13
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Análise palinoestratigráfica e paleoambiental de Depósitos Aptianos-Albianos (Cretáceo Inferior) da Bacia do Espírito Santo, BrasilMichels, Fernando Heck January 2017 (has links)
A Bacia do Espírito Santo possui importantes campos de petróleo e gás em exploração, entretanto poucos trabalhos micropaleontológicos estão disponíveis para esta região uma vez que a maior parte deste conhecimento é relativo a relatórios internos de empresas de petróleo e gás. Este trabalho apresenta uma análise bioestratigráfica e paleoambiental de sucessões sedimentares do intervalo Aptiano-Albiano das formações Mariricu (Membro Itaúnas), São Mateus e Regência. A amostragem é derivada de dois poços (BES-01 e BES-02) perfurados na porção emersa da bacia. Dentre as 24 amostras, 18 revelaram assembleias palinológicas diversificadas, incluindo 51 táxons de plantas terrestres (23 de esporos e 28 de grãos de pólen), 4 táxons de algas (3 dinocistos e 1 alga clorofícea), bem como táxons não determinados de palinoforaminíferos, fungos, escolecodontes e acritarcos. Os grãos de pólen de gimnospermas são dominantes em ambos os poços, principalmente representados pela abundância e diversidade de Classopollis; outros gêneros de grãos de pólen e esporos ocorrem subordinados. A análise bioestratigráfica se baseou nos intervalos cronoestratigráficos de espécies-guias comparadas com biozoneamentos estabelecidos principalmente para a própria Bacia do Espírito Santo, como também para as demais bacias marginais brasileiras As amostras do BES-01 apresentaram idade Albiano inferior, enquanto para as amostras do poço BES-02 foi atribuída idades entre o Aptiano superior e o Albiano inferior (sem distinção). Os dinocistos e os palinoforaminíferos são restritos a alguns níveis do poço BES-01; a assembleia monoespecífica distinta do gênero Subtilisphaera representa o primeiro registro da Ecozona Subtilisphaera na Bacia do Espírito Santo, indicando a ocorrência mais ao sul desta ecozona nas bacias marginais brasileiras. Comparando a frequência da matéria orgânica particulada nas amostras (palinomorfos, fitoclastos e matéria orgânica amorfa), se interpretou o ambiente deposicional como uma região costeira ocasionalmente influenciada por transgressões marinhas. A palinoflora representa a fase final da Província Dicheiropollis etruscus/Afropollis documentada em várias bacias marginais no Brasil e na África, principalmente definida por elementos gimnospérmicos fortemente adaptados a condições climáticas quentes e secas. / The Espírito Santo Basin comprises important oil and gas fields, mostly in active exploration. However, few micropaleontological contributions are available for this region, once most part of its knowledge is concerning to internal reports of oil and gas companies. This work presents a biostratigraphic and paleoenvironmental analysis from an Aptian-Albian succession of Mariricu (Itaúnas Member), São Mateus and Regência formations. Sampling is derived from two wells (BES-01 and BES-02), drilled in the onshore portion of the basin. Among 24 samples, 18 revealed abundant and diverse assemblages of palynomorphs, including 51 taxa related to terrestrial plants (23 of fern spores, and 28 of gimnospermic pollen grains), 4 algae (3 of dinocysts and 1 chlorophicean), as well as no determined taxa of foraminiferal linings, fungi, scolecodonts and acritarch. Gimnospermic pollen grains are dominant in both wells, mainly represented by an expressive abundance and diversity of Classopollis; other gimnospermic pollen grains and pteridophitic spores are subordinate. Biostratigraphic assignments are based on the ranges of certain guide species compared with schemes mainly established for the Espírito Santo Basin, as well as to other Brazilian marginal basins The samples of BES-01 were defined as early Albian in age, whereas an age from late Aptian to early Albian (without distinction) was assigned for the samples of well BES-02. Dinocysts (mainly Subtilisphaera) and foraminiferal linings are restricted to certain levels of the well BES-01. A distinctive monospecific assemblage of the Subtilisphaera in some samples reflects the first record of the Subtilisphaera Ecozone in the Espírito Santo Basin, representing its most meridional occurrence in the Brazilian marginal basins. Comparing the frequency of palynological content in both wells (palynomorphs, phytoclasts and amorphous organic matter), the depositional environment is interpreted as a coastal area, episodically influenced by marine transgressions. The palynofloral content of the assemblages is assumed to represent the final stage of the Dicheiropollis etruscus/Afropollis Province, which is well documented in several marginal basins of Brazil and Africa, mainly defined by a gimnospermic elements, strongly adapted to warm and dry climate conditions.
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Cenozoic terrestrial palaeoenvironemtal change : an investigation of the Petrockstowe and Bovey basins, south west United KingdomChaanda, Mohammed Suleiman January 2016 (has links)
The Petrockstowe and Bovey basins are two similar pull apart (strike slip) basins located on the Sticklepath – Lustleigh Fault Zone (SLFZ) in Devon, SW England. The SLFZ is one of the several faults on the Cornubian Peninsula and may be linked to Variscan structures rejuvenated in Palaeogene times. The bulk of the basins’ fill consists of clays, silts, lignites and sands of Palaeogene age, comparable to the Lough Neagh Basin (Northern Ireland), which is also thought to be part of the SLFZ. In this study a multiproxy approach involving sedimentary facies analysis, palynological analysis, stable carbon isotope (δ13C) analysis and organic carbon palaeothermometer analyses were applied in an attempt to understand the depositional environment in both basins. A negative carbon isotope excursion (CIE) with a magnitude of 2‰ was recorded at ~ 580 m in the siltstone, silty clay to clay lithofacies in the lower part of Petrockstowe Basin, with minimum δ13CTOC values of -28.6‰. The CIE spans a depth of 7 m. Palynological characteristics of this excursion are correlated with the Cogham Lignite in the southern UK, which is the only established PETM section in the UK, and other continental sections to test whether the palynology associated with this CIE can be used to date it. The age model proposed herein correlates the CIE to the Eocene Thermal Maximum -2 (ETM2; ~ 52.5Ma) event. Key pollen and spore assemblages found in the lower Petrockstowe Basin are Monocolpopollenites, Inaperturopollenites, Laevigatisporites, Bisaccate conifer pollen and Tricolporopollenites, which suggest an Eocene age, while those occurring in the upper part of the Petrockstowe and Bovey basins are Arecipites, Inaperturopollenites, Monocolpopollenites, Tricolporopollenites, Sequoiapollenites, and Pompeckjodaepollenites, which have suggested botanical affinities to modern tropical to sub-tropical genera signifying a climate that was frost-free at the time of sediment deposition. This assemblage further suggests that these sediments are Oligocene to middle Oligocene in age. In the upper part of the Petrockstowe Basin, reconstructed mean annual air temperatures (MAT) demonstrate a clear departure from the mean temperature of 24.5oC at 10 m to 19.5oC towards the top of the core, indicating a steady continuous decline similar to the temperature departures seen in the Solent Group in the Hampshire Basin, Isle of Wight, UK which has an established Eocene – Oligocene succession.
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Reconstitution de la végétation et du climat au cours du dernier interglaciaire à partir de la séquence pollinique du lac le plus ancien d'Europe : le lac Orhid (FYROM) / Vegetation and climate reconstruction during the last interglacial : the pollen record of Lake Ohrid (Republic of Macedonia) the oldest European lakeSinopoli, Gaia 21 December 2017 (has links)
Cette thèse est centrée sur les changements paléoenvironnementaux et climatiques survenus dans le période entre 130 et 70 ka (Dernier Complexe Interglaciaire), pour étudier la variabilité du climat à long terme sur l'environnement, sur la base des données de pollen à haute résolution provenant des sédiments du lac Ohrid (Albanie / F.Y.R.O.M), le plus ancien lac d'Europe. La reconstruction du climat obtenue à partir des données polliniques est basée sur un intervalle plus large, 160-70 ka.Le matériel pollinique provient des sédiments prélevés en 2013, dans le cadre du projet SCOPSCO (Scientific Collaboration On Past Speciation Conditions in Lake Ohrid) dont le carottage a été financé par l'ICDP (International Continental Scientific Drilling Program). Pendant la campagne de carottage, 6 carottes parallèles ont été prélevées à partir de l’épicentre du lac, obtenant une séquence composite extraordinaire de 569 m (DEEP).Les 247.8 m supérieurs de la carotte DEEP ont été datés et ils couvrent les derniers 637 ka. Nous avons amélioré le modèle d’âge pour le Dernier Complexe Interglaciaire et en particulier pour la transition entre MIS6 et 5, en comparant les données polliniques avec d'autres proxies de la carotte DEEP et de la Méditerranée. Cela rend le lac Ohrid extrêmement important car pour les autres enregistrements de la région Européenne, de telles contraintes chronologiques ne sont pas disponibles.L'analyse des premiers 200 m de la carotte DEEP, couvrant les derniers 500 ka, a été étudiée avec une résolution de 1,6 ka. La séquence a révélé une alternance entre des ouvertures forestières et périodes boisées reflétant une cyclicité glaciaires-interglaciaires comparable à celle de la stratigraphie des isotopes marins. Parmi les différents cycles glaciaires-interglaciaires, l’analyse pollinique à haute résolution du Dernier Complexe Interglaciaire montre l'alternance classique de périodes caractérisées par la forêt (interstades, périodes chaudes et humides) et la végétation ouverte (stades, et périodes sèches), ressemblant clairement à la succession végétale et climatique bien connue des autres séquences européennes.Concernant le Dernier Interglaciaire (ou Eémien, 128-112 ka), l'analyse pollinique et les reconstructions quantitatives climatiques basées sur ces dernières identifient trois phases clés : une phase initiale caractérisée par un réchauffement soudain (propagation des forêts mésophiles), puis une diminution des températures associées à des conditions humides (expansion de Carpinus betulus) et à la fin un établissement progressif vers des conditions froides et sèches jusqu'à la fin de Eemian à 112 ka, confirmant l’hypothèse déjà avancée par plusieurs études antérieures basées sur des séquences polliniques européennes , à savoir que l’Eemien n'était pas une période climatiquement stable.D’autres changements climatiques sont également visibles dans la région du lac Ohrid entre 112-70 ka et probablement liés à la succession d'événements froids enregistrés dans les carottes de glace du Groenland, associé à un affaiblissement de l’AMOC (Atlantic Meridional Overturning Circulation).Ce travail a permis de fournir une nouvelle séquence de référence pollinique pour le Dernier Complexe Interglaciaire en Europe. Ce travail a également permis de quantifier les paléoclimats pour la période 160-70 ka, encore peu étudiée en Europe, principalement dans le sud (<45 ° lat. N), où un seul enregistrement a été étudié pour toute la période, avec une résolution temporelle élevée.Sur la base de ces résultats, le lac Ohrid apparait comme un site clé pour l'étude des changements climatiques survenus à une échelle centenaire et millénaire dans une région de moyenne altitude entre les régions européennes et méditerranéennes, fournissant en outre des nouvelles informations sur la connexion entre les oscillations climatiques de la région méditerranéenne et de l'Hémisphère du Nord. / This thesis is focussed on the palaeonvironmental and climatic changes occurred during the period between 130 and 70 ka (Last Interglacial Complex), with the aims to investigate the long-term climate variability on environment, on the basis of high resolution pollen data from Lake Ohrid sediments (Albania/F.Y.R.O.M. border), the oldest lake in Europe. The climate reconstruction obtained from pollen data is based on a wider interval, 160-70 ka.The investigated pollen material comes from the sediments retrieved in spring 2013 in the frame of the project SCOPSCO (Scientific Collaboration On Past Speciation Conditions in Lake Ohrid) whose drilling was financed by the ICDP (International Continental Scientific Drilling Program). During the drilling campaign 6 parallel cores have been collected from the depocenter of Lake Ohrid obtaining an extraordinary composite sequence 569 m long (DEEP).The upper 247.8 m of DEEP core have been dated using tephrostratigraphic information and tuning of biogeochemical proxy data to orbital parameters and covers the last 637 ka. In the framework of this careful temporal establishment, an even more precise chronology for the Last Interglacial Complex, and in particular for the transition between MIS6 and 5, was obtained by comparing pollen data from the same period with other DEEP and Mediterranean proxies. This make Lake Ohrid extremely important because for the other records from Mediterranean and European area such chronological constrains are not available and so the chronologies are less precise.The pollen analysis results come from the uppermost 200 m of the DEEP core (covering the last 500 ka) and revealed a succession of non-forested and forested periods clearly connected with glacial–interglacial cycles of the marine isotope stratigraphy.Among the different glacial-interglacial cycle, the new high-resolution pollen stratigraphy of the Last Interglacial Complex shows the classical alternation of periods characterized by forest (interstadials, warm and wet periods) and open vegetation (stadials, cold and dry periods), clearly resembling the well-known vegetational and climate succession of other European records.Concerning the Last Interglacial (or Eemian, 128-112 ka, roughly equivalent to MIS5e), pollen analysis and climate quantitative reconstructions identify three key phases with a slight different timing, with an initial phase characterized by a sudden warming (propagation of mesophilous forests), then a decrease of temperatures associated with wet conditions (expansion of Carpinus betulus) and at the end a progressive establishment towards cold and dry conditions until the termination of Eemian at 112 ka, confirming what other previous studies on European records said, namely Eemian was not a stable period.Several abrupt events are in also identified, during the successive stadials and interstadials (Early Last Glacial), probably correlated to the succession of cold events recorded in the Greenland ice core records, associated to a weakening of the North Atlantic Meridional Overturning Circulation.This work provides a new pollen reference sequence for the Last Interglacial Complex in Europe and concerning climate reconstruction provides new information for a period (160-70 ka, from the last part of Riss Glaciation to the beginning of Würm Glaciation) still poorly investigated in Europe, mostly in the south (< 45° lat. N), where only one record has been studied for the whole interval, with high resolution time.According to my results, Lake Ohrid can be considered a key role site for the investigation of the climatic changes occurred in centennial and millennial scale in a region of mid-altitude between European and Mediterranean areas, providing furthermore new evidence for the connection between the Europe and Northern Hemisphere climate oscillations.
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