四川盆地紫色岩风化成土的研究

RESEARCH INTO SOIL FORMATION FROM PURPLE ROCK WEATHERING IN SICHUAN BASIN

对四川盆地7个主要地层组的紫色泥页岩研究结果表明,除难风化的飞仙关组页岩外,年风化崩解厚度平均达1.5～4cm,并具有季节动态变化,高温多雨的7、8、9月崩解量占全年的60％以上。岩块风化成土率(<2mm)和化泥率(<0.25mm),除飞仙关组页岩外,每年达20～50％和2～14％以上,3年分别达50～95％和3～20％以上。遂宁组紫色泥页岩具有较高的成土率和较低的化泥率。

Field observation and natural—weathering—simulating experiments were conducted to investigate the development of siol formation from purple mud stone. The field observation showed that with the exception of the mud stone of T_1f that is hard to weather, the mean annual physical weathering thickness for all the other purple mud rocks was in the range of 1.5 to 4 cm. The amount of weathering of mud stone from July to September accounted for over 60% of the total amount in a year owing to the effects of high temperature and plentiful rainfall. The simulation experiments gave similar results, in which 'soil forming ratio' and 'fine particle forming ratio' were defined as the percentage of <2mm and <0.25mm soil particles, respectively. The soil forming ratio and the fine particle forming ratio of weathering mud stone were estimated to be 20—50% and 2-14% in a year and 50—95% and 3-20% in three years. The purple mud stone of J3s showed a high soil forming ratio but a low fine particle forming ratio. As was observed in the field, the hard mud stone of T_1f was an exception.