Proportional relationship between the flux of catchment-fluvial segment and their sedimentary response to diverse bedrock types in subtropical lacustrine rift basins

Abstract

Abstract Sedimentary features of a source-to-sink (S2S) system produce distinct responses to diverse bedrock types (i.e., silicate and carbonate rocks) in the catchment; these majorly influence the sediment flux, volume, and grain size in the sink area. By comparing a modern S2S system of Holocene Erhai Lake Basin (ELB) (in southwestern China) and an ancient S2S of Eocene western Offshore Bohai Bay Basin (OBBB) (in eastern China), we investigated the differences and proportional ranges among sandy sediment flux (Qf) and sediment discharge (Qs) from catchment associated with diverse bedrock types in a humid and subtropical lacustrine rift basin by combining with the Google-topographic-map, BQART-model, and seismic-geomorphology analysis. Based on geomorphological and 3D visualization analysis, we identified the differences among multiscale catchment-fluvial segments and their sedimentary responses in S2S systems, and then extracted parameters of catchment-unit area (A), catchment relief (R), and total sediment discharge (Qs, calculated by BQART model). Furthermore, we analyzed sediment-dispersal patterns and sandy sediment fluxes in the nearshore (Qf) using regional geologic data, outcrops and the Google Earth database in the Holocene ELB, and using seismic geomorphology in the Eocene western OBBB. Finally, quantitative analysis of the modern and ancient S2S segments was used to investigate the total sandy sediment flux (Qf), which is supplied by >60% of the entire sediment discharge (Qs) for catchments with silicate bedrocks (e.g., metamorphic rock and granite), while the ratio Qf/Qs corresponding to carbonate bedrocks is less than 30%. Additionally, the ratio Qf/Qs for catchments with mixed silicate carbonate bedrocks ranges between 30% and 60%. These results not only provide a new perspective for investigating sandy sediments in a subtropical lacustrine rift basin, but also yield implications for better understanding of continental S2S system theory for diverse bedrock types.