Long-term palaeo-climatic conditions have primarily been interpreted from ocean marine sediments and ice cores. Few middle and low latitude continental records exist that provide insight into continental response to climate change over time. This research offers new chronologies on a variety of low latitude continental deposits from the Southern High Plains, and demonstrates their importance as palaeo-environmental archives. These chronologies extend the existing Southern High Plains palaeo-environmental record from the historic period to the late-middle Pleistocene, and provide an important basis from which to examine landscape response to late Quaternary climate change. This study demonstrates the applicability of optical dating procedures to well-bleached sedimentary features, such as lunettes, lacustrine material, tufa, and coversands. The precision and accuracy of the technique permits the detection of historic depositional events, whilst the range of the dating technique extended the chronology to the middle-late Pleistocene. The physical isolation of the Southern High Plains from its surrounding areas for the last 1.6 Ma has preserved a record of past climatic fluctuations within the aeolian and fluvio-lacustrine sediments. This research has demonstrated that the Southern High Plains landscape is sensitive to periods of less effective moisture, causing reactivation during historic drought periods (e.g. 1930s "Dust Bowl" event). Coversands and small playa lunettes were active during glacial and interglacials. This suggests that these features are sensitive to smaller scale climatic fluctuations that result in reduced effective moisture for the region during both glacial and interglacial periods. Large lake lunettes were inactive during the Wisconsin glacial. During this same period, active lacustrine and tufa deposition occurred; this offers evidence of greater effective moisture for the Southern High Plains, which resulted in regional recharge. The record of climate change preserved in the lunettes, lacustrine material, tufa, and coversands has provided insight into the response of this dynamic landscape to climatic fluctuations and has been employed for the reconstruction of the palaeo- environmental history of the Southern High Plains. An understanding of landscape response is important in light of the future of the Southern High Plains environment as global temperatures increase, and is critical to a complete evaluation of continental response to climatic change.

Late Quaternary is an important period for paleoclimate study due to the boom of human civilization and thus its influence on climate conditions of the present interglacial period. In this study, a 52 m long borehole was drilled in a coastal embayment of Fujian, China, within which a thick marine layer from 16.05 to 32.60 m is found. Bulk organic geochemical analyses, containing total organic carbon content (TOC), carbon isotope ratio (δ13C), alkenones and n-alkanes, were analyzed for the whole core. Organic carbon isotope ratios (δ13C) of the sediment layers vary between -22.1‰ and -32.9‰, with higher values in the two marine sequences and lower in the two aquatic sequences. In the thick marine sequence, the δ13C is relatively stable, and it becomes gradually enriched from the base upwards and depleted rapidly at the top, indicating a full cycle of marine transgression and regression. The n-alkanes exhibit a similar trend, with several indexes, i.e., maximum concentration (Cmax), carbon preference index (CPI), average chain length (ACL), terrestrial-aquatic ratio (TAR), Paq and C31/(C29+C31). These results suggest the control of EAM and sea-level change in the sedimentary processes. Analysis on alkenones shows sea surface temperature (SST) variations as well as sea-level oscillations in the study site. / published_or_final_version / Earth Sciences / Master / Master of Philosophy

Orientadores: Sérgio Furtado dos Reis, Sergio Ivan Perez / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-25T14:03:24Z (GMT). No. of bitstreams: 1 Costa_CarolinaLemesNascimento_M.pdf: 1856991 bytes, checksum: 0333e9b5415ace1df307eb389ef0260c (MD5) Previous issue date: 2014 / Resumo: Mudanças climáticas são fenômenos responsáveis por influenciar dinâmicas de populações ao longo da história evolutiva das espécies. Quando mudanças no clima ocorrem de maneira abrupta suas consequências podem ser refletidas na distribuição, no tamanho e na persistência das populações sob o efeito destas mudanças. O Quaternário foi uma época caracterizada por mudanças climáticas rápidas e intensas. Estimar a demografia histórica de populações nesta escala de tempo é uma forma de avaliar como flutuações no clima influenciaram populações ancestrais. Dados genéticos nos permitem recuperar informação sobre o tamanho populacional em escalas de tempo amplas e buscar associações entre flutuações no tamanho das populações e variações no clima. A demografia histórica de populações do peixe de água doce Poecilia vivipara habitantes da planície Quaternária do norte do Rio de Janeiro foi estimada com o objetivo de avaliar se fenômenos em escalas de tempo ancestrais deixaram uma assinatura no genoma dos indivíduos de populações contemporâneas. Subsequentemente, foi avaliado se as assinaturas genéticas são reflexo de respostas populacionais às variações climáticas intensas ocorridas no Quaternário. Para estimar a demografia histórica de P. vivipara, utilizou-se o método Skyline-Plot Bayesiano (BSP), sendo o gene mitocondrial citocromo b o marcador molecular analisado. A dinâmica populacional ancestral de P. vivipara revelou uma mudança de regime nos últimos 75 mil anos, que pode estar associada direta ou indiretamente às variações climáticas do Quaternário. Flutuações no nível do mar, geradas pelas mudanças climáticas do Quaternário, podem estar relacionadas com as flutuações no tamanho populacional de P. vivipara. Estudos incluindo outras regiões do genoma e com maior detalhamento sobre variações climáticas locais podem contribuir para gerar estimações mais confiáveis da história populacional de P. vivipara e sua potencial relação com eventos climáticos / Abstract: Paleoclimatic changes are responsible to influence population dynamics through the evolutionary history of species. When climatic changes occur suddenly its consequences can be reflected in the distribution, size and persistence of populations. The Quaternary was a time of massive climatic changes. The estimation of the demographic history of populations at such timescales allows the assessment of how climatic fluctuations have influenced ancestral populations. Genetic data are available and allow recovering information about population sizes in wide timescales and searching for associations between population size fluctuations and climatic change. The historical demography of freshwater fish Poecilia vivipara populations inhabiting the Rio de Janeiro Northern Quaternary Plain was estimated aiming to evaluate if phenomena in ancestral timescales leaves a signature in the genomes of its modern representatives. Subsequently, we evaluate if the genetic signatures are the result of population responses to massive climatic changes occurred in Quaternary. The Bayesian Skyline-Plot (BSP) was utilized to estimate the demographic history of P. vivipara, with the mitochondrial gene cytochrome b as molecular marker. The ancestral population dynamics of P. vivipara revealed a regime change in the last 75,000 years, which can be direct or indirectly associated to Late Quaternary climatic variations. Sea level fluctuations, generated by Quaternary climatic changes, could be related to population size fluctuations of P. vivipara. Studies including other genome regions and with more details about local climatic variations can create more reliable estimations of the P. vivipara population history and its potential relationship with climatic events / Mestrado / Biodiversidade Animal / Mestra em Biologia Animal