Use of composite fingerprinting technique to identify sources of fine-sediment deposited in a reservoir

Geochemical fingerprinting was used to identify the sources of fine sediments derived from three types of contrasting lithological zones and deposited in a reservoir in a medium-sized catchment over the past 60 years. The impact of grain-size sorting on the source of fine sediments in the reservoir was investigated. Overall, the fine sediment sources identified in the sediment cores indicated changing trends in sediment contribution from the three types of lithological zones during the past 60 years. Although the granite zone covers half of the catchment, has thicker soils, is more prone to soil erosion, and has been subjected to more human disturbance than the limestone and shale zones, it only provided 25% of the fine sediment in the cores. The limestone and shale zones, on the other hand, account for 23% and 15% of the catchment, respectively, but produce 42% and 33% of the fine sediment in the cores. This is due to grain-size sorting in the reservoir system during downstream sediment transit and deposition. These data show that grain-size sorting has had a significant impact on the sediment source. This study provides new insight into the source of sediments deposited in a reservoir system from different lithological zones at the scale of a medium-sized catchment across multi-decadal periods.