Loess-Paleosol-Sequences in South America

KRÖHLING, DANIELA M.

Handbook of Pedology

Springer Verlag

Lugar: Berlin; Año: 2021;

The large alluvial basins of South America (the Orinoco, Amazon and Paraguay-Paraná) have responded to changes in global climate during the Late Cenozoic. Loess deposits provide long-term terrestrial archives for reconstructing the succession of climates and the environmental changes that occurred in the continental interior. Dust accumulation in the extensive plains was influenced by different surficial geomorphic processes occurring in the Andes and in the lowlands. Quaternary loess-paleosol sequences provide one of the longest and most complete terrestrial records of glacial-interglacial cycles. Palaeosols in these sequences indicate a period of warmer and/or moister conditions between cold and/or arid phases of loess accumulation related to glacial stages. Pleistocene loess and loess-like deposits in the Chaco-Pampas plain are the thickest and most extensive. The glacially-derived Pampean Eolian System in Central Argentine plains is the most representative Quaternary eolian system of South America. Also loess units in Argentina were described in the W Chaco plain, in some of the pre-Andean valleys of the N Pampean Ranges, in the highland plains of the Pampean Ranges of Córdoba and San Luis, and along the E Andean piedmont of Mendoza. Other loess/loess-like/paleosols sequences occur in the Chaco area of Bolivia and Paraguay, in the S of Brazil and in Uruguay. Non-classical occurrences of loess are the tropical loess in NE Argentina, SE Brazil, E Paraguay and N Uruguay; the North trade-wind loess of the Orinoco Llanos of Colombia and Venezuela, the South trade-wind loess of NE Brazil, the volcanic loess of the Ecuadorian Andes (N Ecuador and S Colombia) and of the Central Valley of Chile, and the loess generated by continental anticyclones in the Chaco-Pampa Plain (Argentina, Bolivia, Paraguay) and neighbouring areas of Brazil and Uruguay. The different parent materials, also with the geomorphological characteristics and the climatic configuration of South America, is reflected in the complex pattern of modern soils. The Last Glacial Maximum loess units are the parent material of the largest area of chemically fertile soils in South America. A synthesis of the main Quaternary loess/paleosols sequences of South America is presented in this chapter.