Diagnostic Sediment Indicators In The Late Cenozoic Sediments, The Yangtze River Coast, China-A Special Reference To River Channelization Into The Sea

The Yangtze River is 6, 400km long from Tibetan plateau to the East China Sea and its drainage basin area is more than 1, 800, 000km2, accounting for one-fifth of China national territory. In the drainage basin located are many highlands, hills, intermountain valleys and plains, accompanied by pleasant climate and abundant natural resources that have supported largely economic growth and human societal advancement. Morphological processes of the Yangtze basin have been closely associated with the formation and evolution of Yangtze water system, regarding its significant theoretic importance and long-term economic plan. Moreover, the Yangtze Channelization into sea is closely related to the topographic reversal of the eastern China continent, and to the formation of East China Sea.The fluvial topographic evolution can be recorded as finger-print in its drainage basins sediments, which are transported from sediment sources to sink. The major concern about the long-term river evolution arisen by many geomorphologists is given to the provenance sediment affected by coupling tectonic and paleoclimate interaction, highlighting sediment tracer to the sink basin. This has become an intensive geomorphological study of the Yangtze River, since its sediment that has been brought to the estuary contains unique sedimentological and mineralogical signal from the upper Tibetan plateau.In the present study, there are 118 sediment samples taken from one sediment borehole (Pd) of 354.5m long and of late Cenozoic age. These samples were analysed for heavy mineral. Additional fifty-five (55) sediment samples were taken from the borehole for magnetic test. Meanwhile, the present study has discerned the information of rocks (metamorphic, intrusive and igneous) and minerals distribution in the Yangtze River drainage area from geological maps and previous research results, especially Hypersthene occurrence in the borehole sediment in relation to the Emeishan basalt in the upper Yangtze basin. In the past years, our research teammates also tested 335 samples of borehole Pd for grain-size and 63 samples for clay minerals, and numerous data on heavy minerals, pollens and dating data were collected from many another sediment boreholes. Strata information of the study area was summed up from more than 100 late Quaternary boreholes. These, together, form the present study database. Based on laboratory experimental results and data synthesis, our attempt was made to aim at evidence of the Yangtze River channelization into the East China Sea, which thereby highlights a new insight into the Yangtze River evolution.