Profiles across the Peru-Chile trench

Abstract

Three general types of profile across the Peru-Chile Trench are shown: trench with gently basined topography, trench with smooth flattish floor, and trench with abrupt topography. Differences in trench shape are ascribed to differences in agents and rates of sedimentation. Production of plankton whose skeletons might accumulate as bottom sediment is reasonably uniform along the length of the area examined, therefore differences in sedimentation must be associated with available supply from the South American continent. Presumably the supply would be greater north of the Chilean desert because more streams reach the sea and in some places, such as near Talara, Peru, the coastal sediments are less resistant than the volcanics along much of the Chilean coast. If the trench is not the same age throughout its length, then the arguments for different sedimentary environments do not necessarily explain differences in bottom topography, nor from profiles alone is it possible to say which end of the trench is younger; however a progressively growing earth flexture must then be assumed. Topographic features such as subsidiary trenches to the side of the main trench, grabens and horsts, and submarine canyons are described.