A proposed Pleistocene/Holocene lake in the Amazon basin and its significance to Amazonian geology and biogeography

Recent studies have described widespread statigraphic units of Late Pleistocene and Holocene age in the western part of the Amazon Basin. The recognition of deltaic sedimentation in the uppermost these units near Rio Branco, Brazil, at a modern elevation of approximately 500 feett leads to the conclusion that this area was situated on the edge of a large Amazonian lake that existed in the recent past when Andean tectonism caused active downwarping of the western edge of the Amazon Basin. The ramifications of this "Lago Anazonas" hypothesis extend into every area of modern Amazonian geology and biology.

PALEOENVIRONMENTAL MODEL FOR THE LATE CENOZOIC OF SOUTHWESTERN AMAZONIA: PALEONTOLOGY AND GEOLOGY

Our study provides paleontological and geological data substantiating a paleoenvironmental model for the upper Miocene-Pliocene of Southwestern Amazonia. The extensive Late Tertiary sediments of The Solimões Formation, outcropping in Southwestern Amazonia, were deposited by a complex megafan system, originating in the high Peruvian Andes. The megafan system was the sedimentological response to the Andean Quechua tectonic phase of Tertiary age, producing sediments that fdled the foreland basin of Southwestern Amazonia. Occurrences of varied vertebrate fossil assemblages of the Huayquerian-Montehermosan Mammal age collected in these sediments support this interpretation. The fauna includes several genera and species of fishes, reptiles, birds, mammals and appears to be one that could have lived in or near a riverine habitat. In the Late Pliocene, the megafan system became inactive as a result of the influence of the Diaguita Tectonical Phase.

Journal of researches into the natural history and geology of the countries visited during the voyage of H.M.S. Beagle round the world, under the command of Capt. Fitz Roy, R.N.

(1873 printing)

The Annals and magazine of natural history; zoology, botany, and geology being a continuation of the Annals combined with Loudon and Charlesworth's Magazine of Natural History.

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The Annals and magazine of natural history; zoology, botany, and geology being a continuation of the Annals combined with Loudon and Charlesworth's Magazine of Natural History.

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The Annals and magazine of natural history; zoology, botany, and geology being a continuation of the Annals combined with Loudon and Charlesworth's Magazine of Natural History.

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The Annals and magazine of natural history; zoology, botany, and geology being a continuation of the Annals combined with Loudon and Charlesworth's Magazine of Natural History.

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The Annals and magazine of natural history; zoology, botany, and geology being a continuation of the Annals combined with Loudon and Charlesworth's Magazine of Natural History.

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The Annals and magazine of natural history; zoology, botany, and geology being a continuation of the Annals combined with Loudon and Charlesworth's Magazine of Natural History.

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Magazine of natural history and journal of zoology, botany, mineralogy, geology and meteorology.

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The Annals and magazine of natural history; zoology, botany, and geology being a continuation of the Annals combined with Loudon and Charlesworth's Magazine of Natural History.

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The Annals and magazine of natural history; zoology, botany, and geology being a continuation of the Annals combined with Loudon and Charlesworth's Magazine of Natural History.

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The Annals and magazine of natural history; zoology, botany, and geology being a continuation of the Annals combined with Loudon and Charlesworth's Magazine of Natural History.

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