Regional dissection volume in central Amazonia sedimentary plateau mapped from SRTM-DEM

Abstract

Fluvial incisions are the prevailing source of short-range topographic variations in central Amazonia plateau, organized in patterns of varying degrees of dissection. Dissection was estimated from a DEM (digital elevation model) and computed as the volume of sediment removed by fluvial erosion relative to the area of terrain units. The elementary input for regional integration was the local depth, calculated by regional-residual relief separation techniques. The top sedimentary surface, used as the regional reference for subtracting the original DEM, was reconstructed by filling the fluvial incisions with the use of maximum filter followed by smoothening. Terrain units were established with segmentation of elevation data from the reconstructed top sedimentary surface, to delineate extensions of sedimentary deposits over the plateau without the influence of the modern fluvial incisions. The size of the terrain units was constrained by the extent of a repeated downstream variation pattern of local dissection data within the individual drainage systems. Numerical and spatial distribution of dissection volume intervals in the study area were consistently grouped in at least four descriptive patterns, sketched into contiguous regions subordinate to the sedimentary plateau. Results were generally consistent with published geological information, despite providing elements for occasional revision and further detailing.