Amazonia during the last glacial

doi:10.1016/0031-0182(94)90178-3

Palaeogeography, Palaeoclimatology, Palaeoecology

Volume 109, Issues 2–4, June 1994, Pages 247-261

https://doi.org/10.1016/0031-0182(94)90178-3 Get rights and content

Abstract

New data on the vegetational history and Quaternary geology of Amazonia permit an improved reconstruction of past environments in Amazonia during the last glacial period. Although limited, data from Rondonia, Carajas and Guyana show that, in certain areas, savanna-type vegetation and savanna forest had replaced the rain forest during the late Pleniglacial (ca. 22,000–13,000 yr B.P.). The Amazonian forest may have been split up into one major west Amazonian and several other medium-size forest areas. This suggests a decline in rainfall of 500 to 1000 mm (a reduction of 25 to 40%). Temperatures may also have been 2° to 6°C (4±2°C) lower than today, possibly substancially influencing Amazonian vegetation. During the humid middle Pleniglacial (55,000–26,000 yr B.P.), rivers carried a lot of water and sediment, resulting in the deposition of lower terrace sediments with one dry interruption around 40,000 yr B.P. (Carajas and Katira). In Carajas, there is evidence of dry periods ocurring at about 40,000 yr B.P., and during the early Pleniglacial (ca. 60,000 yr B.P.). Rivers carried little water and incised into the low terrace sediments during the dry late Pleniglacial. Water levels rose during the late glacial (13,000–10,000 yr B.P.) or at the beginning of the Holocene (10,000 yr B.P.). Sedimentation in (and of) the present inundation valleys commenced after that.

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During the Pleistocene, long-term trends in global climate were controlled by orbital cycles leading to high amplitude glacial-interglacial variability. The history of Amazonian vegetation during this period is largely unknown since no continuous record from the lowland basin extends significantly beyond the last glacial stage. Here we present a paleoenvironmental record spanning the last 1800 kyr based on palynological data, biome reconstructions, and biodiversity metrics from a marine sediment core that preserves a continuous archive of sediments from the Amazon River.
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Mangroves are key ecosystems which respond to global changes in tropical and subtropical regions worldwide. We describe late Holocene mangroves that established close to the southernmost limit (28°S) for this type of ecosystem in South America. Our findings are based on a ¹⁴C dated core obtained from Babitonga Bay, Santa Catarina State, Brazil (26°12′S, 48°33′W). Analysis of palynology, sedimentary facies, isotopic and elemental data shows that mangrove establishment took place ~500 yrs. B.C.E., following an increase in humidity, and expanded further during the Roman Warm Period and at the end of Dark Age Cold Period. Mangrove and precipitation proxies records appear to be sensitive to rainfall patterns imposed both by the expansion/retraction of the Intertropical Convergence Zone and also the interaction with the South Atlantic Subtropical Anticyclone which affects coastal region due to sea surface temperature variations.
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Citation Excerpt :
During the LGM, the humidity was reduced and the temperature was between 2° and 6 °C below modern values (van der Hammen and Absy 1994; van der Hammen and Hooghiemstra 2000; Cohen et al., 2014). Thus, an intensified aridity toward the end of the late Pleistocene was estimated in Madeira river region (Rossetti et al., 2017), whereas savanna expansion was proposed for Katira site related to a dry climatic phase between 26 and 13 ka BP (van der Hammen and Absy, 1994). On the other hand, in localities of Amazonas and Rondônia border, the carbon isotopes of soil organic matter suggest that these regions were still covered by forest vegetation between 17 to 9 ka BP (Freitas et al., 2001).
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Amazonia during the last glacial

Abstract

Climatic Change

Arg. Zool. S. Paulo

A palynological study of Holocene sediments in the Amazon basin

Some paleoecological data from Rondonia, southern part of the Amazon Basin

Acta Amazonica

Mis en évidence de quatre phases d'ouverture de la forêt dense dans le sud-est de l'Amazonie au cours des 60.000 derniéres années

C.R. Acad. Sci., Paris, Ser. II

Tectonic and climatic controls on Late Quaternary sedimentary processes in a neotectonic intramontane basin (The Pitalito Basin, South Colombia)

Tectonic and climatic controls on Late Quaternary sedimentary processes in a neotectonic intramontane basin (The Pitalito Basin, South Colombia)

A long record of climatic and vegetation change in lowland Panama

Veget. Sci.

Late Pleistocene temperature depression and vegetation change in Ecuadorian Amazonia

Quat. Res.

The surface of the Ice-Age Earth

Science

Amazon diversity in light of the paleoecological record

Quat. Sci. Rev.

The late Quaternary climate of the western Amazon basin

Ecuatorial Atlantic deep-sea arkosic sands and Ice-age aridity in tropical South America

Bull. Geol. Soc. Am.

Precipitation distribution over central and western tropical South America

Climanálise

Modeling the Ice-Age climate

Science

Speciation in Amazonian forest birds

Science

Vegetational and climatic history of the high plain of Bogotá, Colombia: A continuous record of the last 3.5 million years

Late Pliocene-Pleistocene high resolution pollen sequence of Colombia: an overview of climatic change

Quat. Int.

Quaternary sediments of the Upper Amazon lowlands of Brazil

Biogeographica

Modifications de la vegetation du Brésil Central entre la derniére epoque glaciere et l'interglacial actuel

C.R. Acad. Sci. Paris, Sér. II

Forest changes in the Amazon basin during the last glacial maximum

Nature

Palaeogeography and palaeoclimatology

Palaeoclimates in Central and South America since 18,000 BP based on pollen and lake-level records

Quat. Sci. Rev.

A pollen core from the Hacienda Lusitania

Pro Calima