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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
161

Investigation of Neotectonic Activity within the Shallow, Unconsolidated Stratigraphy of the Pearl River Delta Area, Louisiana

Fischer, Dane 05 August 2010 (has links)
During the last half century researchers have suggested that active deformation driven by neotectonic activity has locally influenced areas of southeastern Louisiana in the form of wetland loss and coastal erosion. This study, within the Pearl River Delta Area of Louisiana, applied geomorphologic and stratigraphic methods of analysis to assess whether evidence of recent fault motion is present within the shallow, unconsolidated Holocene strata of the study area. Geomorphological historical change analyses focused on meander patterns, elongated water bodies and spatial changes in vegetation identify areas where fault motion may have recently occurred. The shallow stratigraphy was then investigated in these locations using vibracores and seismic reflection profiling. Facies relationships coupled with radiocarbon ages of select stratigraphic intervals led to the development of a detailed stratigraphic framework. Based on these relationships, data suggest that subsurface deformation, resultant of neotectonic activity, has recently occurred within the shallow, unconsolidated Holocene strata.
162

Progress In Constructing A Long Oak Chronology From The Central United States

Stambaugh, Michael C., Guyette, Richard P. 07 1900 (has links)
We describe methods and progress in developing the American Long Oak Chronology (ALOC), an effort to construct an oak tree-ring chronology from the Central US that spans the Holocene. Since 2000, we have collected and measured ring widths on over 550 pieces of subfossil oak (Quercus) wood. Over 330 oak samples have been radiocarbon dated, with ages ranging up to 14,000 cal yr B.P. A 1,093- year-long tree-ring record has been constructed from live and subfossil bur oaks (Q. macrocarpa Michx.) and swamp white oaks (Q. bicolor Willd.) growing along and buried in sediments of streams that flow through northern Missouri and southern Iowa, USA. Here we describe the ALOC for the period A.D. 912–2004 to demonstrate its dendrochronological value, display the material quality, and emphasize the importance of chronology construction. We also report on progress in developing older floating chronologies. The development of more long, multi-millennium chronologies will be an important contribution to dendroclimatology. These chronologies will be particularly useful to the Central US, a region with a continental climate and limited temporal depth of annually resolved paleorecords. Perhaps more critical is its location in the middle of one of the most important agricultural regions in the world.
163

The later Stone Age in the Southern Cape, South Africa, during the terminal pleistocene/early holocene with a focus on Klipdrift cave

Ryano, Kokeli Peter 30 January 2015 (has links)
A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy. Johannesburg, November 2014. / My analysis of the lithics, shellfish and tortoise recovered from layers dating to between 11.8 and 9.7 ka at Klipdrift Cave (KDC), De Hoop Nature Reserve, southern Cape, provides new information on the Oakhurst technocomplex. A re-analysis of a sample of lithic artefacts from Matjes River Rock Shelter (MRS) indicates many technological similarities, but also unexpected differences, highlighting the need for detailed contextualised studies that could reveal the complexity of the Oakhurst Industry. The lithic artefacts were analysed following a typo-technological approach. The KDC Oakhurst shares many characteristics typical of this technocomplex from the southern Cape, for example in the dominance of quartzite, irregular and unstandardized flakes, the occurrence of irregular cores and typical large side and end scrapers. It differs from most coastal Oakhurst sites in the more intensive exploitation of quartz, and the presence of a morphological blade component, especially in the lowermost layers. Shellfish remains were identified to species level in terms of minimum number of individuals (MNI) and weight. The two main species are Dinoplax gigas, dominating in the lower part of the sequence, between 11.8 and 11.1 ka and Turbo sarmaticus that is more numerous thereafter. These species provide the highest energy yield in terms of kilojoules, estimated at 667 511 kilojoules for both species combined. The species composition at KDC reflects changing environmental conditions that may relate to the effect of the Younger Dryas event, changing from a sheltered sandy bay to a habitat with more exposed rocks and less sand after 11.1 ka. T. sarmaticus opercula, Cymbula oculus shells and tortoise medio-lateral humeri were measured to investigate whether human predation pressure could have affected their size. Although the sizes of T. sarmaticus opercula show some decrease through time suggesting human predation pressure on these molluscs, there is also a possibility that environmental factors may have affected Turbo growth. The tortoise sizes at KDC, and some other Oakhurst sites, are similar to that of the Middle Stone Age (MSA) but the KDC data are iv inconclusive on whether intensive harvesting had an effect on average tortoise size.
164

Architecture for resilience: dialogues with place in the indigenous communities of Kuruman during the Holocene period

Maape, Sechaba January 2016 (has links)
A thesis submitted in fulfilment of the requirements for the degree of Doctor of Philosophy to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, 2016 / Since the latter part of the 20th century to the present, we have seen growing concerns about the potential collapse of socio-ecological systems due to climate change. On the other hand, palaeoenvironmentalists, archaeologists and anthropologists consistently point to evidence of how Homo-sapiens have survived within climate variability underpinned by an embodied/embedded relationship to their environments. Archaeological data shows how indigenous groups such as the Bushman have inhabited landscape features such as caves for longer than 10 000 years and thus survived through periods of climate variability. Another well researched element of Bushman life is their ritual practices. Given the low supply of livelihood resources within the contexts where such communities have survived, this study hypothesised a possible relationship between Bushman ritual practices and their long-term resilience when faced with variability. Using the Holocene habitation of the Wonderwerk Cave as the main case study, this study explored the relationship between people, place and ritual. Furthermore, the study applied phenomenology as the primary data collection method. The resultant first-person experience guided the researcher in engaging with secondary data from archaeology and ethnography. The study found that Bushman ritual practices such as trance constituted a critical adaptation tool in response to perpetually variable environments. Through such practices and their related tools such as art, space and myth, such communities managed to sustain a synchronised dialogue with place thus facilitating for ongoing dissolution of maladaptive behaviour. Another key finding is that our inability to change constitutes a key characteristic of our species today as we have been seduced into the trap of our deep psychic longing for existential continuity. The study argues for an architecture for resilience whose primary role would be to facilitate higher fluidity in our embeddedness to place and allowing for faster and trauma-free transitioning in synchronicity to our changing environments. In conclusion, the study finds that our own contemporary climate change has implications far beyond the techno-scientific understanding which has prevailed so far and is instead calling to be understood as an existential phenomenon to be primarily resolved through relevant/responsive ritual practices to facilitate our own transitioning and continued resilience. / MT2017
165

Kvartérní měkkýši Blanského lesa / Quaternary molluscs of Blanský les

Menšík, Jakub January 2018 (has links)
Rich mollusc assemblages preserved in two profiles of fossiliferous sediment in the Blanský les area, provided the evidence about the Late Glacial and Holocene in this region, which is one of the most faunistically known areas of Central Europe. Findings of Quaternary faunas are very rare in Southern Bohemia, so these two soil profiles near Český Krumlov are so important for understanding the postglacial succession of Central Europe. The fossil mollusc assemblages showed an early appearance of forest species, which dominated both sites from the Boreal till Subboreal. Forest development in the Holocene Climatic Optimum reached a maximum, due to the absence of Neolithic man. Steppe species almost completely disappeared during this period. The development of the Young Holocene was linked to a decrease of the forest on the first site and the deforestation of the second site, due to a combination of a humidity decrease and human impact. In addition, some southern elements involved in the postglacial colonization of Central Europe, were found there. A few of them were found in a much older deposit than expected.
166

Environmental change during the Holocene : A comparative multi-proxy study of landscape disturbances in Northern Sweden

Capel, Mégane January 2019 (has links)
Varved lake sediments were used to provide information on how a landscape is affected by disturbances of different scales, from global (i.e. climatic) to local (i.e. fires), as well as anthropogenic activities. Geochemical and pollen data, biogenic silica (bSi), lake-water total organic carbon (LWTOC) and chlorophyll a were used as proxies to infer past changes in lake-conditions. The goal was to evaluate the response to scale different disturbances and how it differs among sites. By comparing different lake records, it became possible to isolate the climatic signal from the effect of soil development and vegetation establishment, and differences emerging from different catchment characteristics. Climatic trends were reconstructed based on the pollen and geochemical data. The sediment records were then compared to identify the effect of each disturbance on individual lakes. One of the most prominent event observed was the immigration of spruce at about 3000 BP which considerably affected sedimentation trends. The presence of spruce within the catchment appears to promote the input of fine-grained material to the lakes. The timing and intensification of anthropogenic activities was established and it was possible to differentiate the effects of human disturbance from changes caused by natural processes such as climate or landscape vegetation cover changes. The results show that farming practices started earlier in more southern locations and that this timing is site-dependent. Two phases were identified, corresponding to the start of slash and burn farming and later to the expansion of agricultural practices, with a more profound transformation of the landscape.
167

As indústrias líticas do Holoceno no interior paulista: estudo de caso dos sítios Abrigo do Alvo e Bastos / The lithics industries of the Holocene in the state of São Paulo: a case study of the Alvo shelther and Bastos site.

Correa, Letícia Cristina 21 August 2017 (has links)
A arqueologia do Estado de São Paulo é um tema ainda pouco explorado nas pesquisas acadêmicas. Tal negligência pode ser justificada tanto pela constante transformação da paisagem quanto pelo próprio desconhecimento de seu alto potencial informativo. Essa dissertação tráz resultados inéditos para dois sítios localizados na região de Rio Claro, porção centro-leste do estado. Foram trabalhados os sítios: Abrigo do Alvo - que como o próprio nome sugere encontra-se em contexto abrigado - com duas cronologias bem estabelecidas, sendo a ocupação mais recente em torno de 1.170 cal AP e a mais antiga em 7.500 cal AP; e o Bastos - sítio a céu aberto - com a idade mais recente em 7.650 cal AP e a mais antiga em 12.640 cal AP. O objetivo da pesquisa foi o de caracterizar o conjunto artefatual dos dois sítios considerando os materiais líticos associados apenas à datação do Holoceno Médio, tendo como referencial teórico o conceito de Cadeia Operatória. Os resultados, quando comparados, mostram que esses grupos caçadores-coletores que habitaram o interior paulista no mesmo período, não compartilhavam características tecnológicas em comum, indicando grupos culturalmente distintos. / The archaeology of São Paulo State is a subject not fully explored in academic research. Such state of the art can be justified both by the constant transformation of the landscape and by the lack of knowledge of its high information potential. This dissertation brings new data from the Rio Claro region, central-eastern portion of the state. Two sites have been worked: Alvo Rockshelter with two well established occupations, the most recent around 1,170 cal AP and the oldest around 7,500 cal AP; and Bastos - am open air site - with the most recent chronology at 7,650 cal AP and the oldest at 12,640 cal AP. The aim of this research was to characterize the assemblages of the two sites considering the lithic materials dated from the middle Holocene, having as theoretical reference the concept of Châine Opératoire. The results, when compared, show that these hunter-gatherer groups that inhabited the interior of São Paulo in the same period did not share common technological characteristics, indicating culturally distinct groups.
168

Variações paleoambientais e paleoclimáticas durante o holoceno no Rio Grande do Norte a partir do estudo de registros geoquímicos de sedimentos de lagos e cavernas / Paleoenvironmental and paleoclimatic variations during the Holocene at Rio Grande do Norte inferred from studies about sediment geochemistry of lakes and caves

Utida, Giselle 22 January 2016 (has links)
A porção norte da região Nordeste do Brasil é uma das áreas mais interessantes para estudo dos mecanismos e processos relacionados à variação de pluviosidade dos trópicos, pois a maior parte da precipitação anual está associada à migração meridional da Zona de Convergência Intertropical do Atlântico (ZCIT). O clima no Nordeste sofreu alterações durante o Holoceno, no entanto, as interpretações paleoclimáticas são ainda muito controversas devido a pequena quantidade de estudos. De forma a contribuir para a discussão sobre mudanças paleoclimáticas e paleoambientais do Nordeste brasileiro, este estudo realizou análises geoquímicas, micropaleontológicas, biogeoquímica e de isótopos de deuterium e carbono em sedimentos lacustres e guano, e análises de isótopos de oxigênio e carbono em espeleotemas do Holoceno Médio e Tardio. Os estudos da Lagoa do Boqueirão sugeriram que sua formação ocorreu devido a dinâmica fluvio-eólica, que resultou em barramentos dos canais fluviais durante o período úmido do Holoceno. A transição entre o sistema fluvial e lacustre, que marca o barramento, foi definido em torno de 4.500 anos BP pela substituição de espículas de esponjas, tipicamente fluviais, pelas diatomáceas lacustres, predominantemente Mastogloia smithii var. lacustres. Foi demonstrado que a formação e as flutuações da profundidade da Lagoa do Boqueirão não estavam associadas a precipitação regional. As variações paleoclimáticas da Lagoa do Boqueirão e da Caverna do Trapiá puderam ser acessadas através dos dados de \'delta\'D em ácidos n-alcanóicos de 28 carbonos, produzidos por vegetação terrestre e macrófitas aquáticas, e dados de \'\'delta\'POT.18\'O dos espeleotemas. Valores mais positivos (negativos) desses isótopos indicaram que durante o MCA (LIA) a região apresentava condições de seca (umidade), devido ao posicionamento mais ao Norte (Sul) da ZCIT, que migrou em direção ao Hemisfério mais aquecido de acordo com a correlação observada com a Oscilação Multidecadal do Atlântico (OMA). A porção norte do NEB apresentou paleoclima diferente em relação ao da porção sul do NEB durante o LIA, que estava seco devido ao deslocamento da Zona de Convergência do Atlântico Sul (ZCAS) mais para sul, assim como a ZCIT, que não afetou a porção sul do NEB. Mudanças paleoambientais foram também definidas com base na idade de sequências sedimentares clásticas datadas por LOI e pelos depósitos de guano em condutos de cavernas em Felipe Guerra-RN. A deposição de sedimentos terrígenos na caverna Urubu entre 7 to 4 ky B.P. cave foi cronologicamente associada a clima mais úmido, o que é apoiado pelo baixos valores de \'\'delta\' POT.18\'O values de espeleotemas. Esse período também foi marcado pelo aumento da contribuição de de carbono orgânico do solo como indicado por valores mais baixos de \'\'delta\'POT.13\'C dos mesmos espeleotemas. Uma transição abrupta para clima mais seco pode está associada ao final da sedimentação clástica na caverna por volta de 4.2 ky devido a interrupção do fluxo do rio subterrâneo e completa erosão do solo ao redor da caverna. A erosão do solo é ressaltada por altos valores de \'\'delta\'POT.13\'C dos espeleotemas próximos aos da rocha encaixante (~0 %0). Estes resultados demonstraram uma relação entre preenchimento sedimentar da caverna Urubu com a formação e erosão de solo na sua volta. Esse aumento de aridez, particularmente nos últimos três mil anos na região, foi também importante para preservação de depósitos de guano sobre os sedimentos clásticos, visto que esse material é bastante solúvel. As idades das camadas de guano foram utilizadas para definir períodos de alta ocupação das cavernas por morcegos entre 1730 and 677 cal. anos A.P. e 200 cal anos A.P. até o recente. Durante o evento MCA houve redução na acumulação de guano que levou a um hiato deposicional por conta que o clima seco desfavoreceu a sobrevivência dos morcegos na região. A acumulação de guano voltou a ocorrer a 200 anos atrás, provavelmente porque a população de morcegos foi reestabelecida, devido a clima mais úmido. / The northern sector of Nordeste of Brazil (NEB) is one of the most interesting regions to study mechanisms and processes related to fluctuations tropical rainfall, as the majority of annual precipitation is associated to the meridional migration of Intertropical Convergence Zone (ITCZ). Climate in NEB changed during the Holocene, although paleoclimatic interpretations are still controversial due to small number of studies. This study contribute to the discussion about paleoclimatic and paleoenvironmental changes of NEB by using geochemistry, micropaleontological, biogeochemistry and deuterium and carbon isotope analyses in lacustrine sediments and bat guano, and also speleothem isotope records from middle to late Holocene. Studies from Boqueirão Lake suggested that its formation occurred due to the fluvio-eolian dynamic, which resulted in blockage of fluvial channels during the holocenic humid period. Transition between fluvial and lacustrine system recorded the barrage formation and was defined around 4,500 years BP and suggested by the substitution of fluvial sponge spicules to lacustrine diatoms, mainly Mastogloia smithii var. lacustres, preserved in sediments. These data demonstrated that depth fluctuations of Boqueirão Lake were not associated to local precipitation accumulation. Paleoclimatic changes were reconstructed from Boqueirão Lake and Trapiá Cave based on \'delta\'D of n-alkanoic acids of 28 carbons, which are produced by terrestrial vegetation and macrophytes, and from \'\'delta\'POT.18\'O of speleothems. More positive (negative) isotope ratios indicate persistent dry (wet) climatic conditions during the MCA (LIA) there, due to a north (south) displacement of ITCZ. This climate system migrated toward the warmest ocean according to the correlation with Atlantic Multidecal Oscillation (AMO). The northern portion of the NEB (nNEB) presented different paleoclimate conditions when compared to the southern NEB portion (sNEB) during the LIA. LIA in sNEB was dry due to the displacement of the South Atlantic Convergence Zone (SACZ) to a southernmost position. Paleoenvironmental changes were attested by determining the age of clastic sequences filling cave conduits dated by OSL method and also by radiocarbon in bat guano. The deposition of terrigenous sediments in Urubu cave from 7 to 4 ky B.P. cave was chronologically associated with more humid climate indicated by low \'\'delta\'POT.8\'O values in speleothems. In addition, this period was marked by increased contribution of organic carbon from soil indicated by negative values of \'\'delta\'POT.13\'C of the same speleothems. An abrupt transition to dry climate was indicated by the end of clastic sedimentation at about 4.2 ky because interruption of underground river flow and complete erosion of soil surrounding the cave as indicated by abrupt enrichment of \'\'delta\'POT.13\'C values of speleothems, reaching values similar to the carbonate bedrock (~0 %o). These data demonstrated the relationship between the sedimentary filling of the Urubu Cave and the formation and soil erosion in the region. These predominant dry conditions during last three millenniums in the region were also important for preservation ofbat Guano deposits above terrigenous sediments. The chronological data of guano was also used to indicate two periods of high accumulation associated with intense occupation of caves by bat colonies between 1,730 and 677 years cal BP and 200 cal years BP until recently. During the MCA occurred a reduction in guano accumulation until a complete hiatus, because dry conditions did not favor bats survival. Guano deposit accumulated again only 200 years ago, when the population of bats restored with stabilization of relatively humid conditions.
169

Folhas fósseis do Ribeirão da Mata: uma abordagem florística e anatômica para caracterização do paleoambiente do Holoceno Médio de Lagoa Santa, MG / Fossil leaves from Ribeirão da Mata: a floristic and anatomical approach to characterize the paleoenvironment of the mid-Holocene at Lagoa Santa, MG

Nakamura, Celina 08 April 2011 (has links)
A região cárstica de Lagoa Santa (MG) apresenta uma das evidências de ocupação humana mais antiga das Américas, datada do final do Pleistoceno e início do Holoceno. Um intenso registro arqueológico é observado nos períodos compreendidos entre 10.000 a 8.000 anos AP (antes do presente) e 2.000 a 1.000 anos AP. No período intermediário (Holoceno Médio) observa-se nos sítios arqueológicos uma minimização da representação desses vestígios. Autores denominaram esse período de \"Hiato do Arcaico\" que sugeriria que essas populações teriam emigrado por conta de eventos de seca na região, corroborados por dados provenientes da palinologia. O sítio paleontológico RMT-1, situado na região, pertence à bacia do Ribeirão da Mata e contém sedimentos de natureza aluvial datados entre 5.800-4.500 anos AP. e 2.500-1.500 anos AP. Neles estão contidos restos vegetais (pólen, lenho e folhas fósseis). O presente trabalho teve como objetivo principal identificar taxonomicamente assembléias fósseis de folhas por meio da morfologia com a finalidade de reconhecer com quais características fisionômicas atuais essa assembléia mais se assemelharia. As análises de similaridade confrontadas com 47 listas florísticas do Brasil demonstraram que houve alta correlação com Florestas Estacionais Semideciduais e formações de Cerrado. Não foi possível confirmar nem refutar a hipótese do \"Hiato do Arcaico\" já que não houve a presença de taxa que representariam exclusivamente um clima marcadamente seco, entretanto, sugere-se uma estacionalidade nas formações vegetais mais pronunciada ou uma associação fisionômica diferente das vegetações atuais expressadas por mosaico vegetacional. / The karst region of Lagoa Santa (MG) has one of the most ancient evidences of human occupation in Americas, dated from the end of the Pleistocene and beginning of the Holocene. An intense archaeological register is observed in periods between 10.000 to 8.000 years BP (before present) and 2.000 to 1.000 years BP. In the intermediary period (mid-Holocene) a decrease on the representation of these remains could be observed in the archaeological sites. Authors called this period \"Archaic Gap\" which suggests that these populations have migrated due to drougth events in the region that are corroborated by data from the palinological studies. The paleontological site RMT-1, situated in the same region, belongs to the basin of the Ribeirão da Mata and contains sediments of alluvial nature that are dated from 5.800-4.500 years AP. to 2.500-1.500 years BP. In these sediments plant remains (pollen, wood and fossil leaves) were found. The present study aims to identify fossil assemblages of leaves through the morphology to recognize which present physiognomy is closer to the assemblage. The analyses of similarity faced this assemblage with 47 floristical lists from Brazil, and demonstrated that there was a high correlation with semi-decidous stationary forests and cerrado. It was not possible to confirm neither to refute the hypothesis of the \"Archaic Gap\" since there was no observed taxa that could represent exclusively a markedly dry climate However, a more pronounced seasonality in the plant formations or a physiognomic association different from the present vegetational mosaics are suggested.
170

Variações de produtividade da porção oeste do Atlântico Sul ao longo dos últimos 15 mil anos a partir de estudo quantitativo de nanofósseis calcários / Productivity changes of the western South Atlantic region during the las 15,000 years based on quantitative study of calcareous nannofossil

Ferrarese, Heliane Bevervanso 14 April 2010 (has links)
O objetivo do presente estudo foi estimar as possíveis variações na produtividade das águas superficiais da porção oeste do oceano Atlântico Sul ao longo dos últimos 15.000 anos, contribuindo para a melhor compreensão das variações oceanográficas ocorridas na região no decorrer deste tempo. Foram realizadas análises quantitativas de nanofósseis calcários em um testemunho da Bacia de Santos, a partir da técnica de decantação aleatória. Isótopos estáveis de carbono e oxigênio em rocha total e teor de carbonato de cálcio também foram utilizados para interpretações sobre paleoprodutividade. A produtividade primária das águas superficiais apresentou variações ao longo dos últimos 15.000 anos. Variações no aporte continental e na profundidade da termoclina/nutriclina devem ter influenciado as condições das águas superficiais da região, e conseqüentemente, a produtividade dos cocolitoforídeos. Estimou-se que a produtividade da camada fótica superior tenha diminuído desde o início do Holoceno. Anterior a este período, uma maior contribuição continental teria propiciado condições mais favoráveis ao desenvolvimento dos cocolitoforídeos que habitam as camadas mais superficiais do oceano. / The aim of this study consisted in estimate possible changes on southwestern Atlantic Ocean surface water productivity for the last 15.000 years, contributing to a better understanding of oceanographic changes that occurred along this time. Quantitative calcareous nannofossils analyses were carried out on a Santos Basin core using the random settling technique. Bulk carbon and oxygen stable isotopes and calcium carbonate content were also used for paleoproductivity interpretation. Primary productivity of surface waters presented variation along the last 15.000 years. Variations in continental contribution and thermocline/nutricline depth must have influenced the surface water conditions and therefore coccolithophorids productivity. Upper photic zone productivity was estimated and seems to have diminished since early Holocene. Prior to this time, a major continent contribution would have provided more favorable conditions for the development of the coccolithophorids that inhabit the upper layers of the ocean.

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