Carregant...
Fitxers
Tipus de document
TesiVersió
Versió publicadaData de publicació
Llicència de publicació
Si us plau utilitzeu sempre aquest identificador per citar o enllaçar aquest document: https://hdl.handle.net/2445/173445
Ultra-high resolution environmental and climatic reconstruction using oxygen and carbon isotopes of diatom frustules
Títol de la revista
Autors
ISSN de la revista
Títol del volum
Resum
[eng] Calcareous microfossils are not always present in marine or lacustrine sediments owing to unfavourable ecological or post-depositional conditions. These non-carbonated sediments sometimes contain abundant biogenic silica, rendering them suitable for studies of stable isotopes. For this reason, considerable progress has been made in the study of biogenic silica using isotopes in recent years. Diatom isotopes are increasingly being used for palaeoenvironmental reconstructions in lacustrine sedimentary records. Tropical proxy records offer valuable insights into past climate and environmental changes of the Earth and into possible future climate change scenarios. Research into tropical regions has therefore become a key issue among palaeoclimatologists. Influenced by the tropical circulation in the north, and by the mid-latitude westerlies in the south, the Central Andes are an ideal site to study past variations of atmospheric circulation systems. Thus, the Andean Altiplano has become a key region for the study of late Quaternary climate change in South America. Sedimentary records of high-altitude Andean Altiplano lakes usually preserve an excellent centennial- to millennial-scale record of effective moisture fluctuations and source changes during the Late Glacial and Holocene despite the fact that the interpretation is not always straightforward. Oxygen and carbon isotope analyses in carbonates (δ18Ocarbonate and δ13Ccarbonate) and δ13Cbulk have been successfully used to reconstruct the hydrological responses to climate change in different Andean lacustrine systems to date. No attempt, however, has been made to use δ18Odiatom and δ13Cdiatom despite the fact that they are usually the best preserved fossils in the sedimentary record of the Andean Altiplano lakes. For this reason, the aims of the PhD Thesis are twofold: a) to explore the possibilities that the study of δ18Odiatom and δ13Cdiatom can offer in palaeoenvironmental reconstructions, and b) to carry out high- and ultra-high resolution environmental and climate reconstructions in the Andean Altiplano during the Late Glacial- Early Holocene transition using these stable isotopes. The thesis focuses on new and poorly documented fields where δ18Odiatom and δ13Cdiatom can successfully be applied to lacustrine sediments. It shows how stable isotopes from diatom silica may be used a) to highlight the importance of reconstructing the different evolutionary stages of lake ontogeny given that climate derived palaeohydrological signals can be distorted by changes in lake morphology b) as a main proxy in ultra-high resolution moisture balance reconstructions forced by fluctuations in the intensity of the ENSO and solar activities c) to reveal the major biogeochemical processes that give rise to the formation of rhythmites, and finally d) to reconstruct the regional environmental evolution at centennial-to-millenial time scales.
Descripció
Matèries (anglès)
Citació
Citació
HERNÁNDEZ HERNÁNDEZ, Armand. Ultra-high resolution environmental and climatic reconstruction using oxygen and carbon isotopes of diatom frustules. [consulta: 29 de novembre de 2025]. [Disponible a: https://hdl.handle.net/2445/173445]