澜沧江云南德钦古水一带第四纪堰塞湖的沉积特征及其环境意义

在云南省西北部德钦县古水一带深切的澜沧江河谷中,发现了一套第四纪湖相沉积物,以纹层状粘土、粉砂质粘土和粉砂的互层组合为特征,构成了第三和第四级阶地的基座.笔者对该湖相剖面进行了U系、孢粉和若干地球化学指标的分析测试,并以这些结果讨论了古湖的形成时代和成因,以及古湖堆积时期的古植被和古气候.剖面顶部、中部和中下部粘土的U系法年龄测定结果分别为52.3±3.4 ka、64.2±5.6 ka和81.9±6.5 ka,说明古水古湖形成于晚更新世早中期的末次间冰期晚期和末次冰期的早冰阶与间冰阶早期,很可能是大型冰川(如下游的明永冰川等)或巨量的冰水沉积物堰塞了澜沧江河谷而造成的结果.

"Yangtzedonta is Undoubtedly a Junior Synonym of Xianfengella" is to be Queried

In 2005,the Acta Geologica Sinica(in English edition,vol.79,no.6) contemporaneously issued two articles respectively by Yu Wen and Qian Yi on the topic of whether Yangtzedonta and Xianfengella are synonymous or not.The topic has long been debated and caused a wide concern as well.By examining in detail the holotype specimen of Yangtzedonta primitiva Yu by Yu Wen in 1985 with the Cat.no.84430,and the specimen of Xianfengella described by Qian Yi in 2001 with the Cat.no.125018~125022,the both stored in the Nanjing Institute of Geology and Palaeontology,the Chinese Academy of Sciences.The close observation suggests that the holotype specimen of Yangtzedonta primitiva Yu,1985 with Cat.no.84430 is a small shelly fossil with unique morphological characteristic and developed with peculiar posterior hinge structure.Although Qian Yi announced that more well preserved specimens in analogous with the holotype specimen of Yangtzedonta primitiva Yu with Cat.no.84430 and complete shell are at his disposal,he has never illustrated any of his specimens with similar posterior hinge structure as seen in the holotype of Yangtzedonta primitiva Yu.Indeed,he has confused the real differences in the morphological characteristics and the size of shell between the holotype of Yangtzedonta primitiva Yu and Xianfengella by illustrating a sketch drawing which is neither the original nor the real morphological characteristics.Therefore the author has to raise a query to the conclusion made by Qian as "Yangtzedonta is undoubtedly a junior synonym of Xianfengella" and "the holotype of Yangtzedonta primitiva Yu,1985 which is just the cracked and contorted specimen of Xianfengella prima described by Qian."