Morphostructural trends of the Amazonian regions of Peru: the effect of neotectonics on fluvial changes and upland wetland boundaries

Abstract:

The Amazonian regions of Peru are discussed within the context of current knowledge on recent Andean tectonics and their impact on river drainage. The structural framework of the Subandean Zone consists of the Subandean Thrust and Fold Belt (STFB) West which crops out mostly in the Upper Foothills, and the Subandean Tilted Block Zone (STBZ) East which is concentrated mainly in the Lower Foothills. The main rivers which cross the STFB are antecedent or superimposed, but the secondary drainage channels conform to these structures and are subsequent. The STBZ river basins run parallel to the structure contour. The rivers showing active meander belts (Maranon, Ucayali and Tapiche) are drained by white (silty) water from the Andes. Watersheds are drained by stable black water (from organic acids) streams with underfit patterns like the Samiria and Pacaya rivers. The underfit pattern is interpreted as the abandonment of formerly active large streams of white water. The position in the depression of the black water streams suggests successive shiftings of the Maranon and Ucayali rivers respectively northward (50km) and southeastward (100km) during the recent time, probably the Holocene. Neotectonic data as well as data from earthquake focal mechanisms are compared to the present morphostructural scheme of the area, and discussed in term of Quaternary tectonic evolution. -from English summary

Año de publicación:

1992

Keywords:

Fuente:

scopus