[H-CG21] Earth surface processes related to deposition, erosion and sediment transport

[HCG21-P11] Grain-Scale Microtextural Evidence of Sediment Transport Mechanisms in the Kinu River, Japan: A preview

*Wenzhao DONG¹, Hiromi Itamiya², Toshihiko Sugai¹ (1.Department of Natural Environmental Studies, Graduate School of Frontier Sciences, The University of Tokyo, 2.National Research Institute of Police Science)

Keywords:Quartz microtexture, Fluvial sediment, Subaqueous energy, Environmental interpretation

Quartz, a highly weathering-resistant mineral, preserves microtextural signatures imparted by sediment transport and depositional processes. This study employs scanning electron microscopy (SEM) in low-vacuum mode to systematically analyze grain morphology and surface microtextures of quartz particles from modern channel deposits along the Kinu River, Kanto Plain, Japan. Eleven mechanical and three chemical microtextural features were identified. Mechanical features (e.g., conchoidal fractures, arcuate steps, V-shaped percussion cracks) exhibited higher frequencies at upstream sites and near the Kinu-Tone River confluence. A pronounced concentration of mechanical textures at the Ta-Kinu River confluence suggests localized turbulence enhances particle collisions through high-energy hydraulic conditions. Two sampling sites displayed subdued mechanical features but elevated frequencies of chemical textures (e.g., oriented etch pits, solution pits), likely linked to reduced flow velocities and anthropogenic influences. Grain morphology analysis revealed a strong linear correlation between higher roundness (R) and solidity. Principal component analysis (PCA) of microtextural data highlighted three principal components: PC1 (25.93%) dominated by conchoidal fractures, arcuate steps, V-shaped percussion cracks, and subparallel linear fractures (interpreted as high-energy mechanical impacts); PC2 (20.92%) characterized by straight steps and graded arcs (suggestive of unique high-energy shock events); and PC3 (18.34%) associated with chemical dissolution features. Ternary plots of normalized microtextural frequencies demonstrated no systematic downstream trends but effectively discriminated between sites based on hydraulic energy regimes. Notably, microtextural signatures proved sensitive to localized transport dynamics, distinguishing depositional environments even within 500-meter intervals (e.g., channel sediments vs. adjacent dunes). This study highlights the utility of quartz microtextural analysis in reconstructing sediment transport pathways, identifying anthropogenic impacts, and assessing hydraulic energy variations at fine spatial scales. These insights are critical for sediment provenance studies, river management strategies, and mitigating human-induced alterations in fluvial systems.