Their clearly defined floodplains are a marked contrast to the splaying pattern of ancient paleochannels. This mosaic shows the sinuous Rio Taquari emerging from the escarpment just west of the town of Coxim. Note the splaying pattern of paleochannels developed to the southwest of the Rio Taquari. Crosscutting relationships indicate a succession of channel abandonment on the fan surface. This occurs because of decreasing mean annual flow and increasing flow variability in the downstream direction.
Water is lost by infiltration into the sandy fan sediments underlying the river.
This recharge feeds an extensive ground- water system that is directed toward the Paraguay River 200 km to the west. The pronounced differences in channel patterns for this region probably resulted from Quaternary climatic change. During the glacial conditions that characterized much of the Quaternary, the climate of this region likely changed from its present tropical savanna conditions to semiarid conditions. Stream regimens probably changed from their present uniformity to ephemeral conditions characterized by rare but intense floods that carried immense loads of sand washed from adjacent slopes. The sediment-charged streams deposited their load on the immense fans along the Pantanal escarpment.