The incision of the Sanmen Gorge marks the birth of the modern Yellow River,but its timing varies from the late Miocene-early Pliocene to the late Pleistocene(~0.15 Ma),and the suggested forcing mechanisms vary from t...The incision of the Sanmen Gorge marks the birth of the modern Yellow River,but its timing varies from the late Miocene-early Pliocene to the late Pleistocene(~0.15 Ma),and the suggested forcing mechanisms vary from the uplift of the Tibetan Plateau to global climate change.Here,we report sedimentologic,geochronologic,and provenance data from a drill core near the Sanmen Gorge,the last gorge along the main course of the Yellow River.Our results indicate that typical river channel deposits,with detritus from the Ordos Block in the upstream regions,started to accumulate in the Sanmen Gorge at~1.25 Ma.When integrated with river terrace evidence from the upstream and downstream regions,the results provide robust evidence that the final integration of the modern Yellow River occurred at~1.25 Ma,consistent with the beginning of the Mid-Pleistocene transition(MPT).We propose that the accelerated lowering of eustatic sea level during the MPT may play as important a role as tectonism in driving the birth and evolution of the modern Yellow River.展开更多
Red tides are abnormal ecological phenomena, which bring lots of damage in China every year. Research on detecting red tides is necessary. Water color will change abnormally while red tides bloom out, i.e. the absorpt...Red tides are abnormal ecological phenomena, which bring lots of damage in China every year. Research on detecting red tides is necessary. Water color will change abnormally while red tides bloom out, i.e. the absorption and scattering characteristics of waters will appear different. With these varieties, algorithms can be developed to retrieve water constituents from spectral reflectance. Furthermore, red tides detection methods can be applied with retrieval chlorophyll concentrations. Though absorption characteristics of waters play important parts in bio-optical algorithms development of ocean color remote sensing, no stable useful absorption coefficients of waters can be used in the high frequency red tides areas of the East China Sea.During 2002～2005 we have performed 11 cruises and done a lot of measurements in the research areas. After analyzing multi-years in-situ data, we have drawn the absorption relations of waters as follows:Good correlations have been contained when analyzing the relationships among different absorption bands of phytoplankton pigments. Taking both 440 nm and 675 nm as reference bands together, the simulation results attained much closest to in-situ measurements. The relationships between absorption coefficients and concentrations of chlorophyll-a have also been indicated. With 440nm or 675 nm as the reference bands, good results have shown with correlations 0.915 and 0.938 respectively.After 400 nm is taken as the reference band, mean spectral slope has been specified as 0.0102 nm-1 with regard to suspended sediment absorption and 0.0173 nm-1 about CDOM absorption.展开更多
基金supported by the Fundamental Research Funds for the Central Universities,China(lzujbky-2021-ey12)the National Natural Science Foundation of China(42072211)+1 种基金the Second Tibetan Plateau Scientific Expedition and Research Program(STEP)(2019QZKK0602)the National Non-Profit Fundamental Research Grant of China(IGCEA 2008)。
文摘The incision of the Sanmen Gorge marks the birth of the modern Yellow River,but its timing varies from the late Miocene-early Pliocene to the late Pleistocene(~0.15 Ma),and the suggested forcing mechanisms vary from the uplift of the Tibetan Plateau to global climate change.Here,we report sedimentologic,geochronologic,and provenance data from a drill core near the Sanmen Gorge,the last gorge along the main course of the Yellow River.Our results indicate that typical river channel deposits,with detritus from the Ordos Block in the upstream regions,started to accumulate in the Sanmen Gorge at~1.25 Ma.When integrated with river terrace evidence from the upstream and downstream regions,the results provide robust evidence that the final integration of the modern Yellow River occurred at~1.25 Ma,consistent with the beginning of the Mid-Pleistocene transition(MPT).We propose that the accelerated lowering of eustatic sea level during the MPT may play as important a role as tectonism in driving the birth and evolution of the modern Yellow River.
文摘Red tides are abnormal ecological phenomena, which bring lots of damage in China every year. Research on detecting red tides is necessary. Water color will change abnormally while red tides bloom out, i.e. the absorption and scattering characteristics of waters will appear different. With these varieties, algorithms can be developed to retrieve water constituents from spectral reflectance. Furthermore, red tides detection methods can be applied with retrieval chlorophyll concentrations. Though absorption characteristics of waters play important parts in bio-optical algorithms development of ocean color remote sensing, no stable useful absorption coefficients of waters can be used in the high frequency red tides areas of the East China Sea.During 2002～2005 we have performed 11 cruises and done a lot of measurements in the research areas. After analyzing multi-years in-situ data, we have drawn the absorption relations of waters as follows:Good correlations have been contained when analyzing the relationships among different absorption bands of phytoplankton pigments. Taking both 440 nm and 675 nm as reference bands together, the simulation results attained much closest to in-situ measurements. The relationships between absorption coefficients and concentrations of chlorophyll-a have also been indicated. With 440nm or 675 nm as the reference bands, good results have shown with correlations 0.915 and 0.938 respectively.After 400 nm is taken as the reference band, mean spectral slope has been specified as 0.0102 nm-1 with regard to suspended sediment absorption and 0.0173 nm-1 about CDOM absorption.
