| 滇池湖盆第四系沉积相、古地磁和孢粉的初步研究 |
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| THE STUDY ON THE SEDIMENTARY FACIES,PALEOMAGNETISM AND PALYNOLOGY OF QUATERNARY SEDIMENTS IN DIANCHI LAKE BASIN, YUNNAN |
| Dianchi Lake Basin is a Cenozoic fault basin controlled by rift systemin S-N direction. The bedrock of the lake basin consists of mainly Palaeozoic strata, on the top of which is usually a layer of lateritic residuum. TheCenozoic sediments are about 500 m thick on average, with a maximum morethan 1000 m. These sediments are predominantly of lacustrine facies, whichare composed mainly of gray, greenish gray mud, silty mud, silt, sand andsandy gravel, intercalated with about 7-20 lignite beds. Abundant nonmarinefossils have been found from these sediments. The Cenozoic strata from theupper lignite downwards were referred to as the Late Tertiary deposits inthe past. A comprehensive study has been on two cores, the core TK-15 and Tk-9in the northeastern side of Dianchi Lake. As a result the following facieshave been recognized in the sediments: shore sandgravel, shore sand, shallow lake siltmud and carbonaceous mud-lignite facies of lake-marsh environments, and sandgravel, sand, siltmud and carbonaceous mud facies of riverand deltaic environments. The paleomagnetic data obtained from the two cores show that theseCenozoic strata have a general positive polarity, corresponding to the BrunhesNormal Epoch. There are also five short reversal events on the positive background, named tentatively as DA, DB, D_1, D_2 and D_3 downwards, correla-table with those of the magnetic stratigraphic sections of Biwa Lake corein Japan and V20-108 in the Pacific Ocean. This suggests that all Cenozoicsediments in the two cores are of Middle-Late Quaternary age. Also the palynology data show Quaternary characteristics. The representative sporopollen components are mainly Quercus,Pinus, Abies and Picea ofwooden plant, and herbs of Gramineae, Persicaria, Compositae, Umbelliferaeand so on. The Quaternary sporo-pollen sequence can be divided into sixstages with different assemblages, which witnessed a periodic variation ofcold and worm climate. The same conclusion was reached by the study onthe surface texture of quartz in the sediments. The quartz sand surface textures in layers containing cold climatic type of pollen assemblage show ice-wornfeatures. |
| LUO Jian-ning,XIAO Yong-lin,ZHUANG Zhong-hai,CHEN Le-yao,SU Jun-zhou,ZOU Pei-xin.1983.THE STUDY ON THE SEDIMENTARY FACIES,PALEOMAGNETISM AND PALYNOLOGY OF QUATERNARY SEDIMENTS IN DIANCHI LAKE BASIN, YUNNAN[J].Acta Geoscientica Sinica,5(2):65-78. |
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