15 research outputs found
La dernière transition glaciaire/interglaciaire des Andes tropicales sud (Bolivie) d'après l'étude des variations des niveaux lacustres et des fluctuations glaciaires
Get PDFUne comparaison entre les variations des niveaux lacustres dans le bassin de Uyuni-Coipasa et les fluctuations glaciaires dans la Cordillère Orientale montre que les lacs et les glaciers ont simultanément enregistré les changements des précipitations. Un intense maximum lacustre (environ 13-12 14C ka BP) a eu lieu aux latitudes tropicales sud de la Bolivie, 4 000 à 6 000 ans avant le maximum lacustre de l'Afrique nord-équatoriale. (Résumé d'auteur
La dernière transition glaciaire/interglaciaire des Andes tropicales sud (Bolivie) d'après l'étude des variations des niveaux lacustres et des fluctuations glaciaires
No full textUne comparaison entre les variations des niveaux lacustres dans le bassin de Uyuni-Coipasa et les fluctuations glaciaires dans la Cordillère Orientale montre que les lacs et les glaciers ont simultanément enregistré les changements des précipitations. Un intense maximum lacustre (environ 13-12 14C ka BP) a eu lieu aux latitudes tropicales sud de la Bolivie, 4 000 à 6 000 ans avant le maximum lacustre de l'Afrique nord-équatoriale. (Résumé d'auteur
Plant succession in a forest on the Lower Northeast Slope of Serra Geral, Rio Grande do Sul, and Holocene palaeoenvironments, Southern Brazil
No full textThe study of plant succession provides information on vegetation dynamics of a region and, therefore, improves our understanding of the natural trends of present ecosystems. With this objective, plant succession based on palynology of a sediment profile in a swamp forest was studied on the Lower Northeast Slope of Serra Geral, Rio Grande do Sul. Samples were treated with HCl, HF, KOH and acetolysis; slides were mounted in glycerol-jelly. For each sample a minimum of 500 grains of pollen + pteridophyte and bryophyte spores was counted and other palynomorphs were counted in parallel. Tilia and Tilia Graph software were used to construct percentage and concentration diagrams, with three 14C datings. The results show a local water reservoir in the beginning of the Holocene (± 9800 yrs. BP), creating a herbaceous plant marsh by hydrosere. The initial colonization of the marsh by trees occurred about 8800 yrs. BP, with tropical species from the Coastal Plain migrating in an east-west direction. Afterwards, there was a dry phase between 7000-5000 yrs. BP. The second appearance of regional tree species began at about 5000 yrs. BP, resulting in the present forest and in the west-east migration of tropical species from interior lowlands, like this one, to re-colonize the coast after the last marine regression
The carbon isotope record in soils along a forest-cerrado ecosystem transect: implications for vegetation changes in the Rondonia state, southwestern Brazilian Amazon region
No full textHolocene palaeoenvironmental evolution in the São Paulo State (Brazil), based on anthracology and soil δ13C analysis
No full textVegetation history in western Uganda during the last 1200 years: a sedimentbased reconstruction from two crater lakes
No full textSpatial distribution of palynomorphs in the surface sediments of the Lagoa do Campelo lake, North region of Rio de Janeiro State, Brazil
No full textGymnosperm pollen grains from the La Veteada Formation (Lopingian), Paganzo Basin, Argentina: biostratigraphic and palaeoecological implications
No full textInterfacial properties of amphiphilic systems on the basis of natural polymers—chitin derivatives
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