168 research outputs found

    Influence des activités de l'homme sur le cycle hydrométéorologique

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    Lake levels in the southern Bolivian Altiplano (19°-21°S) during the Late Glacial based on diatom studies

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    This study is focused on the endorheic Uyuni-Coipasa Basin located in the southern Bolivian Altiplano. Stratigraphical and fossil diatom studies based on a detailed radiocarbon chronology revealed six phases in water-level changes and paleosalinity variations. At 15,430 +- 80 yr B.P., lacustrine conditions settled in the southern Bolivian Altiplano. A saline lake, characterized by benthic meso-metasaline species, reached +4 m altitude above the present bottom of the basin. After 15,430 +- 80 yr B.P. the level rapidly rose to + 27 m, as suggested by a tychoplanktonic mesoline flora. Between 14,500 years and 13,000 years, finely lamited sediments at + 32 m contained successively a dominance of epiphytic mesosaline to hypersaline species and tychoplanktonic oligosaline diatoms, indicating weak fluctuations in water-level and salinity. At 13,000 years, strong changes in the diatom flora occurred: epiphytic oligo-hypersaline diatoms were replaced by planktonic meso-polysaline species. They indicate a deep salt lake (the lake level reached + 100 m). After 12,j000 yars, the lake level abruptly dropped, as suggested by fluviatile sediments with a benthic mesopolysaline diatom flora. The main lake was replaced by shallow saline ponds. A wet pulse occurred at 11,400 years, characterizad by low water level ( + 7 m) and high salinity. This lacustrine phase remained until 10,400 yr B.P. These data indicate changes in Precipitation minus Evaporation (P-E). Our regional interpretations are based on a comparison with the available data on the northern (Lake Titicaca) and southern (Lipez area) Bolivian Altiplano and on the northern Chilean Altiplano (Atacama Desert). (Résumé d'auteur)

    Palaeomagnetic stratigraphy of pliocene continental deposits of the bolivian Altiplano

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    Les dépots fluviolacustres post-Miocène de l'Altiplans bolivien ont été échantillonnés sur une section de 400 m. dans les bassins de la Paz et de Ayo Ayo. Leur étude permet d'établir un schéma magnétostratigraphique pour des interprétations chonostratigraphiques

    Hugues Faure, 1928–2003: The unique adventure of his life

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    Hugues Faure was not only one of the greatest pioneers of the study of the Quaternary and a man of outstanding personality, with the highest integrity, an uncommon strength of character, with a lot of kindness and generosity, but also a man who made his dreams, conceived in the inhospitable solitudes of the Sahara, come true. He was very young when he chose his way: barely 10 years old and his passion for geology already filled his life. It was in Africa, a continent he discovered at his earliest years as a field-geologist, and deeply loved, that he nursed and matured many of his most stimulating ideas on Quaternary environmental change. It was in the desert that he built up his exceptional personality and found his truth, which finally allowed him to accomplish his destiny. Hugues Faure was born in Paris, on the 11th March 1928, the son of a jeweller. The comfortable circumstances of the family were darkened by his father's death when Hugues was only 3 years old. As a consequence of this sad event, Hugues used to spend in England most of his school holidays far from his family. Then during World War 2, he lived the exodus on the roads of France, cycling under the bombs, with his dog in his basket. He was 12 years old, and it was the end of his youth. His passion for earth sciences had began before the age of ten, when he started collecting flint and fossils from the chalk of the Paris Basin, and decided to stop playing piano, so as to devote himself to Geology. Hugues graduated in Mathematics from Lycée Jacques-Decour in 1948, and in Sciences from the Faculté des Sciences de Paris Sorbonne in 1949. On the same year he enrolled as a geologist of the “France of Overseas”, then as a hydrogeologist at the French Geological Survey (BRGM) (1949–1963), so as to work in Africa
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