Characterization of the Sediment Routing System of the Argentine Las Peñas Thrust From ASTER Imagery Interpretation and DEM Terrain Analysis

In an arid region north of Mendoza, Argentina active structures of the Precordilleran fold and thrust belt control sedimentation in the proximal Andean foreland basin. Initiation of new thrust faults and along-strike growth of fault-propagation folds drives uplift of hanging-wall source areas. Drainage basin initiation and development in the Las Peñas thrust hanging-wall triggers erosion of sediment, controlling transport and depositional mechanisms in the associated alluvial fan system. Alluvial fans are classified as either sheetflood or debris-flow fans based on the areally dominant process responsible for producing the sediment wedge as recorded in the surface character and morphology of the fans. Traditionally, information about these systems has been directly measured using manual methods such as ground surveying and visible image interpretation. This study implements remote sensing with ASTER spectral data and derived topographic data to characterize both fan surfaces and drainage basins. AST14DMO data include fourteen ASTER Level-1B calibrated nadir looking radiance bands at 15-m (VNIR), 30-m (SWIR) and 90-m (TIR) resolution. AST14DMO also includes the ASTER 30-m Digital Elevation Model (DEM) derived from stereoscopic data from the VNIR sensor. These bands were used in rule-based classification implemented in statistical software. The classification was used for mapping and measuring the patterns and spectral characteristics of fan surfaces. TIR and VNIR explanatory variables in decision trees highlighted differences in fan environmental variables including soil conditions, sediment size, and vegetation (moisture, roughness, and composition) indicative of process and rate of deposition on alluvial fans. Terrain Analysis conducted with the ASTER 30-m DEM focused on morphology of the drainage basin sector of the sediment routing system. Drainage basin characteristics including areal extent, slope, aspect, hypsometric curves, and bedrock geology were identified and compared. The information was used to interpret transport and depositional mechanisms within the system, as well as identify source materials and possible ranges of fluid-sediment concentrations for each basin. The geometry of the developing Las Peñas thrust controls attributes of both drainage basin source areas, and alluvial fan depositional environments as shown by their variation along the fault. The techniques and setting of this study inform interpretations of processes active in modern systems that are applicable to ancient systems on Earth and elsewhere.