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The impact of Quaternary sea level changes on the evolution of the Amazonian lowland
Author(s) -
Irion Georg,
Müller Jens,
Morais Jáder O.,
Keim Gertrud,
de Mello Jose Nunes,
Junk Wolfgang J.
Publication year - 2009
Publication title -
hydrological processes
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.222
H-Index - 161
eISSN - 1099-1085
pISSN - 0885-6087
DOI - 10.1002/hyp.7386
Subject(s) - amazon rainforest , tributary , amazonian , quaternary , coring , geology , siltation , hydrology (agriculture) , glacial period , floodplain , erosion , water level , sea level , oceanography , geomorphology , sediment , geography , paleontology , ecology , engineering , mechanical engineering , drilling , cartography , geotechnical engineering , biology
Coring and acoustic surveying (3·5 kHz) in both rivers and lakes in Central Amazonia provide additional insights into the Late Quaternary hydrological and sedimentological development of the Amazon River and its tributaries. Erosion and accumulation phases were found to be linked to Quaternary sea level changes. The low sea level phase during the last glacial maximum caused deep incision of the Amazon River and erosion in major tributaries such as the Rio Negro, 1500 km upstream from the Amazon mouth. A 3·5‐kHz profiling suggests a lowering of the water level by at least 30 m at Manaus. During that phase, the slope of the Amazon valley must have increased, resulting in an increase in bed load transport capacity. The subsequent sea level rise caused a backwater effect far upstream, with silting up of the Amazon valley and the tributary inflows. Former river systems changed into Ria lakes. The floodplains of the Amazon River, the várzea, were formed approximately 5000 years ago when the sea level approached its present‐day level. Copyright © 2009 John Wiley & Sons, Ltd.