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

作　　者：Yokoyama Kazumi 

机构地区：[1]Department of Geology, National Science Museum, Tokyo, Japan

出　　处：《Science China Earth Sciences》2005年第10期1718-1727,共10页中国科学（地球科学英文版）

基　　金：supported by the National Natural Science Foundation of China(Grant Nos.40176022,40276018 and 40476028).

摘　　要：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.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 pre-dominate 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.

关 键 词：delta  monazite  electron microprobe  chemical dating  formation of the Changjiang  UPLIFT of the Tibetan Plateau. 

分 类 号：P534.6[天文地球—古生物学与地层学] P597.3[天文地球—地质学]