摘要
据上、下粉砂层在剖面上出现的位置、黄土—古土壤地层层序、^(14)C、热释光(TL)和裂变径迹年龄以及古地磁测量结果,兰州九洲台黄土仅仅是距今140—150万年以来才沉积而成的,因而距今220—240万年以来形成的结论不能成立.
The thickness of Jiouzhoutai loess section of Lanzhou is 318.2m which is the thickest loess section in China and in the world.The upsand loss and low-sand loess marker beds are respectively at 103.5 to 127.0 meters and at 45.0 to 52.5 meters high, which shows that the loess section was formed at 1.35 Ma ago and aeolian-loess began to deposit at about 140 Ma ago.The B / M boundary and Jaramiuo normal event are located at 135.0m and at 75.5-92.0m high, which means that the loess section should be formed at 1.30 Ma. Also there are thirty-four palaeosols among which the first eight layers of palaeosols are so called the first Wucheng palaeosol group formed at 1.48 Ma So the profile was formed at 1.40-150 Ma.The fission tract age of gypsum samples collected at profile bottom and at 5.0m high are respectively at 1.48Ma and 1.45 Ma. Therefore, the eaolianloess of Jiouzhoutai loess profile began to deposit at about 1.30 Ma and Alluvial-loess began to deposit at about 1.40-1.50 Ma.
出处
《沉积学报》
CAS
CSCD
北大核心
1989年第3期105-111,共7页
Acta Sedimentologica Sinica
基金
国家自然科学基金项目
