Tectonic and lithologic controls on the landscape adjustment along the eastern terrain of the Mae Tha fault, northern Thailand

Abstract

Understanding the interaction between tectonics, climatically-driven surficial processes, and bedrock erodibilityprovides insight into how the landscape develops over space and time. Although numerous active faults, lithologicand climatic variability control the landscape across Northern Thailand, the influence of these factors on thespatial adjustment of a dynamic landscape is largely unknown. In the study, we focus on lower-order channelsdeveloped across the eastern terrain of the Mae Tha fault, in which spatial variability in rock mass quality and faultcharacteristics strongly control the landscape. We combine topographic data analysis from channel profiles andgeologic field observations to determine variations in bedrock watershed characteristics and any linear structuresacross the site. Our results reveal that channels in the northern and central zones of the terrain are relatively steeperbecause a west-dipping fault controls them with less fracture density of granite. Channels in the south, however,are less steep as an oblique-slip fault governs their profiles with a higher fracture density of bedrock. Moreover,channels flowing across different lithologic bedrocks exhibit steeper channel profiles than channels developed inuniform lithology. Our study highlights the use of topographic adjustment as one of the efficient tools to describethe dynamics of active deformation on the landscape over space and time. According to the mutual analysis, ourfinding suggests that lithologic resistance and spatial differences in fault lineaments ultimately control charactersof channel profiles and overall landscape topography.