Thermoluminescence dating and chemistry of quaternary sodic alluvial soils in the Venezuelan savanna

Vaz, Joaquim; García‐Miragaya, J.

doi:10.1016/0341-8162(92)90025-7

Cited by 8 publications

(6 citation statements)

References 7 publications

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“…Fluvisols and Gleysols were cored under gallery forests and grasslands flooded by clearwater rivers. Vaz & García‐Miragaya (1992) found solonetzised soils under gallery forests of the Rio Orituco in the savannas of Venezuela, whereas Gehler (1985) classified Solonetz under grass‐and woodland in the floodplains of the Rio Yacuma in Bolivia.…”

Section: Discussionmentioning

confidence: 99%

Relationship between vegetation and environmental conditions in the northern Pantanal of Mato Grosso, Brazil

Zeilhofer¹,

Schessl²

2000

Journal of Biogeography

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Summary This paper analyses the relationship between the distribution of tropical floodplain vegetation and environmental factors such as the soil types, their physical‐chemical properties and inundation dynamics in the northern Pantanal of Mato Grosso, Brazil. Fifty‐four soil profiles of the four principal geomorphologic units of the lowland were classified into twenty‐one units of the FAO‐UNESCO system and related to eight vegetation formations. Under the deciduous and semideciduous woodland and forest formations on flood free riverbanks and relict dunes Arenosols, Solonetz and Alisols dominate. Inundation forests grow on a large variety of soil groupings such as Alisols, Solonetz, Fluvisols, Gleysols and Cambisols, mainly on fluvial deposits. Under the grassland formations of periodically flooded spreadings and depressions Planosols, Acrisols, Alisols, Fluvisols, Arenosols and Cambisols were cored, while Gleysols are common on swamps bearing Thalia geniculata or Cyperus giganteus. Canonical Correspondence Analysis was applied to study the influence of monitored environmental factors on spatial distribution of vegetation formations. Water regime and soil texture were found to define the grassland‐forest boundaries as well as the transition between different grassland formations and between seasonal as well as evergreen forests.

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Section: Discussionmentioning

confidence: 99%

Relationship between vegetation and environmental conditions in the northern Pantanal of Mato Grosso, Brazil

Zeilhofer¹,

Schessl²

2000

Journal of Biogeography

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“…This phase, also recorded recently in new sites at Gran Sabana (Montoya et al 2009), was recorded as a drier than present period in Mapire core between 7,800 and 2,200 yr BP at level B (Figure 2) when pollen preservation in sediments stopped, suggesting that sediments could have dried out repeatedly in the sampling site during a longer and stronger annual dry season. An arid phase of such magnitude was also evidenced by the occurrence of sodic alluvial soils studied by Vaz and García-Miragaya (1992) in the Central Orinoco Llanos (location shown in Figure 1), with Early to Mid-Holocene ages. Such Early to Mid-Holocene dry phase was also recorded at the Llanos Orientales of Colombia from 9,700-5,800 yr BP in Laguna Angel, Sardinas, Carimagua, El Piñal and Chenevo (Behling and Hooghiemstra 1998;Behling and Hooghiemstra 1999;Berrío et al 2002), and also in northwestern Brazil, and in general at the Amazon Basin, as is supported by Pessenda et al (2001), and by Mayle and Power (2008), among others, encompassing the period between 8,000 to 4,000 yr BP.…”

Section: Comparison With Other Records From Venezuela and Northern Somentioning

confidence: 62%

“…Furthermore, the occurrence of extremes climates which had a substantial impact on vegetation and landscape is supported by the presence of paleodune fields in the Western Venezuelan Llanos, dated at 36,000 and 11,600 year before present (hereafter abbreviated as yr BP) (Roa 1979;Vaz and García-Miragaya 1989, location shown in Figure 1), and the sodic alluvial soils dated at 8,700 to 4,000 yr BP, found in the central Venezuelan Llanos (Vaz and García-Miragaya 1992, location shown in Figure 1). Fossil dunes, as well as sodic soils could have been shaped during very arid periods, when strong changes on annual rainfall, maybe synchronous with glacial/interglacial cycles and with the Pleistocene/Holocene boundary occurred (Hooghiemstra and Van der Hammen 1998).…”

Section: Introductionmentioning

confidence: 96%

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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“…Some authors suggest a slightly drier climate compared with today (e.g. van der Hammen et al, 1992a, b;Vaz and García-Miragaya, 1992), but they give no information about the late glacial cooling. The view of Bush et al (1990, p. 343) that further climatic reconstructions modeling the temperature of the lowland American tropics should incorporate a probable cooling of ca.…”

Section: Discussionmentioning

confidence: 99%

The Mera site revisited: Ice-age Amazon in the light of new evidence

Heine

1994

Quaternary International

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The Mera site is the only fossil pollen and forest bed radiocarbon dated 33-26 ka BP in tropical lowland Amazonia. Here I conclude, from the study of the geology, geomorphology and paleopedology of the Mera site area, as well as from new 14 C and U/Th age determination of the organic layers, that the pollen sections are not of last glacial age but of Middle Pleistocene age, at least. No evidence of last glacial age has been found for the Mera fossil forest beds. The data from the Mera sites, therefore, should neither be used for climate reconstructions of the last glacial maximum, nor for disputing the refugial theories.

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Thermoluminescence dating and chemistry of quaternary sodic alluvial soils in the Venezuelan savanna

Cited by 8 publications

References 7 publications

Relationship between vegetation and environmental conditions in the northern Pantanal of Mato Grosso, Brazil

Relationship between vegetation and environmental conditions in the northern Pantanal of Mato Grosso, Brazil

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

The Mera site revisited: Ice-age Amazon in the light of new evidence

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