Yang Shouye

Research on preservation and enrichment mechanisms of organic matter in muddy sediment and mudstone

Using multidiscipline methodologies, the differences in preservation and enrichment mechanisms of organic matter (OM) in muddy sediment and mudstone are investigated. In clay fractions, concentrations of TOC and chloroform bitumen “A” are significantly higher than those in coarser fractions. This indicates that clay minerals (CM) play an important role in enriching OM. The content of chloroform bitumen “A” increases obviously in the clay fraction, which reveals that dissolvable OM is the main composition of coalesce with clay minerals. Furthermore, TG and DTA data show that OM enrichment mechanisms and preservation forms have multiplicity. Several exothermic peaks in the DTA curves demonstrate that muddy sediment and mudstone contain a number of bioclasts and amorphous OM besides dissolvable OM. Through analyzing with XRD and DTA after mudstone samples were pretreated, the conclusions can be arrived at. Firstly, CM interlayer space of XRD curves and exothermic peaks of DTA curves both change as temperature increases. Secondly, the changes of CM interlayer space and exothermic peaks are concordant and stable around 350°C. All these are the features that OM enters CM interlayers to form stable organo-clay complexes. Therefore, the combination format of OM with CM is not only surface adsorption, partial OM enters CM interlayers to form stable organo-clay complexes. Finally, through the research on OM preservation forms and enrichment mechanisms in muddy sediment and mudstone, the hydrocarbon-generation processes and the global carbon cycle and budget can be explained.

Monazite age spectra in the Late Cenozoic strata of the Changjiang delta and its implication on the Changjiang run-through time

The Late Cenozoic strata are 313 m thick, revealed by the drilling core PD-99 in the south Changjiang delta. Monazite chemical dating shows that 350–500-Ma monazites predominate in the Pliocene and 100–275-Ma monazites in the Quaternary, indicating a great change of their provenance. The first presence horizon of monazites younger than 25 Ma is just above the Matruyama/Gauss boundary (~2.58 Ma), whch is exactly when uplift of the Tibetan Plateau began to influence deposition in the East China Sea. Variations in contents of monazites younger than 25 Ma can be divided into two sections. The Early-Middle Pleistocene with less <25 Ma monazites corresponds with rapid uplift of the Tibetan Plateau, and the Late Pleistocene with more <25 Ma monazites parallels the peak uplift of the Tibetan Plateau. This study demonstrates that chemical dating of monazites in the river-mouth strata is a useful method to explore changes of river drainage basins, and deconvolute multistage tectonic and magmatic activity histories in the provenance areas.

Regional variation of sediment load of Asian rivers flowing into the ocean

Study of Asian major rivers discharge to the ocean reveals variations of their water discharges and sediment loads, and local characteristic of river sediment concentrations. On the basis of this, the Asian rivers can be divided into three regions: Eurasia Arctic, East Asia, Southeast and South Asia Region. The Eurasia Arctic Region is characteristic of the lowest sediment concentration and load, while the East Asia Region is of the highest sediment concentration and higher sediment load, and the Southeast and South Asia Region yields higher sediment concentration and highest sediment load.

Characteristic elemental compositions of the Yangtze River and Yellow River surface sediments and their geological background

Significant differences are noticed in major and trace element compositions between the Yangtze River and the Yellow River surface sediments. The former sediments are rich in some major elements such as K, Fe, Mg, Al, and most of the trace elements which show wide variations in element concentrations, whereas the Yellow River sediments only have higher Ca, Na, Sr, Ba, Th, Ga, Zr, Hf contents and show slight variations in element contents. In the Yangtze River Basin are widely distributed intermediate-acid igneous rocks and complicated source rocks together with strong chemical weathering which determine the elemental compositions of the Yangtze River sediments, while the elemental compositions of the Yellow River sediments are decided by the chemical composition of loess from the Loess Plateau and intense physical weathering. Cu, Zn, Sc, Ti, Fe, V, Ni, Cr, Co, Li and Be can be used to distinguish the Yangtze River sediments from the Yellow River sediments and be treated as tracers for both the sediments to study the processes of their mixing and diffusion in the coastal zones of China.