The conditioning features of ditches processes at the sedimentary structures of the peripheral depression in Rio Grande do Sul

Abstract

Aiming to define the conditioning features responsible for the different erosion processes actuating at the drain heads between Jacuí and Ibicuí rivers - at Peripheral Depression in Rio Grande do Sul, we analysed the geologic/geomorphologic aspects defining a set of marks due to the relief evolution, in which the details are presented as interfluvial depressions - pseudokarstic forms, rill erosion and large burrows, all of them interlaced to the hydrodynamic system. Based on a cartographic chart, satellite images, structural analysis of the sedimentary components and the examination of the hardness presented by several samples of water collected at, approximately, 15 and 48 meters deep, we verified the existence of complex surface structures (approximately 30 meters deep) associated to the apparently simple topographic forms (hills with ample areas of captivation and long ramps), geological events as fault lines and the stratigraphic arrangement of the sedimentary materials. These are the predisposing elements of the erosion forms here analysed, showing that the origin of these forms is beyond the anthropogenic action scale, becoming necessary the realization of systematic interconnected stratigraphic and surface geometry studies. Key-Words: erosion factors, burrows, landscape evolution.