Quaternary geology of the Amazonian Lowland |
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| Authors: | Georg Irion Jens Müller Jose Nunes de Mello Wolfgang J Junk |
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| Institution: | (1) Forschungsinstitut Senckenberg, Schleusenstrasse 39a, D-263B2 Wilhelmshaven, Germany;(2) Lehrstuhl für Geologie Technische Universität, München, Lichtenbergstr. 4, 85748 Garching, Germany;(3) Instituto National de Pesquisas da Amazonia (INPA), BR-6900 Manaus/Brasilien, Brazil;(4) Max-Planck-Institut für Limnologie AG Tropenökologie, Postfach, 165, D-24302 Plön, Germany |
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| Abstract: | The Quaternary history of the Amazon lowlands is characterized by deposition of sediments of Andean provenance and by the influences of changing sea levels. Areas well above the present water tables were not reached by Pleistocene high-water stages. These areas have been intensively weathered since the Tertiary, forming hard lateritic weathering horizons. These weathering horizons are best explained by the relatively constant, humid tropical climate throughout the Quaternary. In the western Amazonian Lowland, flood plains corresponding to the different Pleistocene sea-level heights were formed. During low sea level, erosion in the drainage areas increased and the water levels of the central Amazon River system were lowered. Valleys drowned and lakes formed in the lower reaches of rivers and creeks during high sea-level stages. These lakes (ria lakes) remained in the valleys with rivers having a low sediment load. Seismic profiling (3.5 kHz) in some of these lakes clearly showed deposits of the three last periods of Quaternary high sea-level stages. |
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