Abstract

JARAMILLO JUSTINICO, ALEXIS; PARRA SANCHEZ, LUIS NORBERTO  and  RANGEL-CH., J. ORLANDO. Geomorphology and stratigraphy of the Quaternary formations in the Colombian Amazon rain forest region. Caldasia [online]. 2013, vol.35, n.2, pp.429-464. ISSN 0366-5232.

The shape and stability of Recent sedimentary sequences (neoformation) in the Amazon basin depend on the Amazon river 's annual flood cycle. The Leticia-Tabatinga Terrace is one of the sedimentary sequences not affected by the current annual flood cycle. Its age has been estimated between 8000 and 10000 years AP., although its modeling was likely generated in the tardyglacial, about 14000 years A.P. The Leticia-Tabatinga Terrace is covered by the formation Iça and is the highest of the geological units that retain the original flat morphology. Other sedimentary materials have been accumulated as channel deposits, which are associated with drains and have been dated nearly 8,600 years A.P. Lakes associated with canangucha palms (Mauritia flexuosa) are also found in the terrace, particularly in areas with differential erosion, a relatively recent phenomenon (about 530 years A.P). Among recognizable geologic units associated with areas affected by the river's annual flood cycle are the systems of swamps and lagoons of Yahuarcaca and Zapatero. This formation is estimated to be between 240 and 150 years A.P. and is bordered by La Milagrosa , which is submerged during high precipitation levels. Also recognized as product of neoformation are a number of landforms of alluvial systems, such as sand bars, channels, drain channels connecting rivers or rivers to lakes. The landforms and materials of neoformation are young and highly dynamic due to constant landscape modeling caused by the river's flood annual cycle, which is influenced by climatic change.

Keywords : Geomorphology; Amazon; Quaternary Stratigraphy; Terraces.

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