Astronomical Forcing of Contrasting Rainfall Changes in Tropical South America between 12,400 and 8800 cal yr B.P.

Martin, Louis; Bertaux, Jacques; Corrège, Thierry; Ledru, Marie Pierre; Mourguiart, Philippe; Sifeddine, Abdelfettah; Soubiès, François; Wirrmann, Denis; Suguío, Kenitiro; Turcq, Bruno

doi:10.1006/qres.1996.1866

Cited by 133 publications

(96 citation statements)

References 23 publications

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“…This means that the record presented here started at the beginning of the Holocene, at the Pleistocene/Holocene boundary, when climate was recorded as humid, similar to present. This agrees with the main picture established for Venezuela and also for savanna areas located northward the ITCZ (Martin et al 1997). In Mapire core, the Early Holocene humid period lasted from 10,225 yr BP to 7,800 interpolated yr BP.…”

Section: Comparison With Other Records From Venezuela and Northern Sosupporting

confidence: 90%

Contribution to Early Holocene vegetation and climate history of Eastern Orinoco Llanos, Venezuela, from a paleoecological record of a Mauritia L.f. swamp

Leal

Pérez²,

Bilbao³

2011

Acta Amaz.

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A palynological analysis of an organic paleosol found at 150-125 cm depth in a Mauritia swamp from the Eastern Orinoco Llanos is presented. The 25 cm pollen record summarizes the vegetation history during the Early Holocene, from 10,225 to 7,800 calendar yr BP. The vegetation was characterized by a Poaceae marsh, where Asteraceae, Melastomataceae, Schefflera-type and Phyllanthus were the most abundant shrubs and trees. Pollen-types richness was lower than that recorded today in similar environments, and Mauritia pollen was absent. Results suggest that climate was as humid as present during the beginning of the Holocene, with a decreasing trend in humidity from around 8,000-7,000 yr BP, in coincidence with the beginning of the "Early-Mid-Holocene Dryness" that affected deeply the Amazon Basin and neighboring areas. Dry climatic conditions could have existed in the study site until the Mid-Late Holocene when a Mauritia swamp developed, and humid conditions similar to present established. Main climate phases inferred in our study site fit well with regional trends recorded in other places located north Amazon Basin. However, conclusions are still limited by the lack of additional Quaternary records in the Orinoco Llanos area, avoiding regional correlations. KEYWORDS: Orinoco Llanos, Mauritia swamp, Early Holocene, paleoclimate, Early-Mid Holocene Dryness.Contribuição para a história da vegetação e clima durante o Holoceno Temprano do Llanos Orientais do Orinoco, Venezuela, a partir de um registro paleoecológico de um pântano Mauritia L.f. RESUMORealizou-se uma análise de pólen amostrada em paleossolos orgânicos, entre 150-125 cm de profundidade, em um pântano Mauritia os lhanos do Orinoco. O registro de pólen dessa amostra resumiu a história da vegetação durante o Holoceno Temprano, entre 10,225-7,800 cal. anos AP. A vegetação durante esse período foi caracterizada por um pântano de Poaceae, com maior abundância de arbustos e árvores de Asteraceae, Melastomataceae, tipo-Schefflera e Phyllanthus. Encontrou-se que a riqueza de tipos polínicos no Holoceno Temprano foi menor do que a riqueza atualmente encontrada em ambientes similares; o pólen de Mauritia esteve ausente de todas as amostras. Os resultados deste estudo sugerem que o clima durante o início do Holoceno foi úmido, semelhante ao clima atual. Houve também uma tendência de diminuição de umidade entre 8,000-7,000 anos AP, o que coincidiu com o início da "seca do Holoceno Temprano-Médio". Esta seca afetou profundamente a Bacia Amazônica e áreas adjacentes, persistindo no local de estudo até o Holoceno Médio-Final, período em que surgiram o pântano Mauritia e as condições climáticas atuais. Fases climáticas principais deduzidas se encaixam bem com as tendências regionais registradas em outros lugares localizados ao norte da Bacia Amazônica. No entanto, as conclusões ainda são limitadas pela falta de novos registros quaternários na área lhanos do Orinoco, evitando correlações regionais. PALAVRAS-CHAVE: lhanos do Orinoco, Mauritia pântano, Holoceno Tempra...

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Section: Comparison With Other Records From Venezuela and Northern Sosupporting

confidence: 90%

Contribution to Early Holocene vegetation and climate history of Eastern Orinoco Llanos, Venezuela, from a paleoecological record of a Mauritia L.f. swamp

Leal

Pérez²,

Bilbao³

2011

Acta Amaz.

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“…Martin et al (1997) suggests that during the mid-Holocene, the ITCZ was located farther north than its present-day position (Fig. 1) this would produce a summer rainfall deficit and increased winter precipitation; in short greater seasonality.…”

Section: ±500 14 C Yr Bpmentioning

confidence: 97%

“…One of the main mechanisms used to explain moisture shifts is fluctuations in the Southern Oscillation and the migration of the ITCZ (Martin et al, 1997). Martin et al (1997) suggests that during the mid-Holocene, the ITCZ was located farther north than its present-day position (Fig.…”

Section: ±500 14 C Yr Bpmentioning

confidence: 99%

Pollen-based biome reconstructions for Latin America at 0, 6000 and 18 000 radiocarbon years ago

et al. 2009

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Abstract. The biomisation method is used to reconstruct Latin American vegetation at 6000±500 and 18 000±1000 radiocarbon years before present (14C yr BP) from pollen data. Tests using modern pollen data from 381 samples derived from 287 locations broadly reproduce potential natural vegetation. The strong temperature gradient associated with the Andes is recorded by a transition from high altitude cool grass/shrubland and cool mixed forest to mid-altitude cool temperate rain forest, to tropical dry, seasonal and rain forest at low altitudes. Reconstructed biomes from a number of sites do not match the potential vegetation due to local factors such as human impact, methodological artefacts and mechanisms of pollen representivity of the parent vegetation. At 6000±500 14C yr BP 255 samples are analysed from 127 sites. Differences between the modern and the 6000±500 14C yr BP reconstruction are comparatively small; change relative to the modern reconstruction are mainly to biomes characteristic of drier climate in the north of the region with a slight more mesic shift in the south. Cool temperate rain forest remains dominant in western South America. In northwestern South America a number of sites record transitions from tropical seasonal forest to tropical dry forest and tropical rain forest to tropical seasonal forest. Sites in Central America show a change in biome assignment, but to more mesic vegetation, indicative of greater plant available moisture, e.g. on the Yucatán peninsula sites record warm evergreen forest, replacing tropical dry forest and warm mixed forest presently recorded. At 18 000±1000 14C yr BP 61 samples from 34 sites record vegetation reflecting a generally cool and dry environment. Cool grass/shrubland is prevalent in southeast Brazil whereas Amazonian sites record tropical dry forest, warm temperate rain forest and tropical seasonal forest. Southernmost South America is dominated by cool grass/shrubland, a single site retains cool temperate rain forest indicating that forest was present at some locations at the LGM. Some sites in Central Mexico and lowland Colombia remain unchanged in the biome assignments of warm mixed forest and tropical dry forest respectively, although the affinities that these sites have to different biomes do change between 18 000±1000 14C yr BP and present. The "unresponsive" nature of these sites results from their location and the impact of local edaphic influence.

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“…13,000}10,000 BP) there is a sudden increase in temperature and rainfall, and most lake levels rise around 12,500 BP, especially in the tropics (Martin et al, (1997) showed a valuable concept on astronomical forcing of South American rainfall). There is a short, cold interval between 11,000 and 10,000 BP (Younger Dryas stadial), locally also somewhat drier, and 10,000 BP is the beginning of the Holocene.…”

Section: The Last Glacial Climatic Sequencementioning

confidence: 99%

Neogene and Quaternary history of vegetation, climate, and plant diversity in Amazonia

Hammen

Hooghiemstra

2000

Quaternary Science Reviews

276

120

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Astronomical Forcing of Contrasting Rainfall Changes in Tropical South America between 12,400 and 8800 cal yr B.P.

Cited by 133 publications

References 23 publications

Contribution to Early Holocene vegetation and climate history of Eastern Orinoco Llanos, Venezuela, from a paleoecological record of a Mauritia L.f. swamp

Contribution to Early Holocene vegetation and climate history of Eastern Orinoco Llanos, Venezuela, from a paleoecological record of a Mauritia L.f. swamp

Pollen-based biome reconstructions for Latin America at 0, 6000 and 18 000 radiocarbon years ago

Neogene and Quaternary history of vegetation, climate, and plant diversity in Amazonia

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