红土·黄土·全球变化

华南热带区红土的分期及其时间序列和红土中的古环境记录及其与全球变化的关联是华南第四纪研究中的两大重要问题。本文重点讨论了多旋回的红土－沉积系列和红土－火山岩系列的时代及其环境记录所反映的华南气候、构造环境变迁的多旋回性,并指出红土系列也是全球变化的良好信息载体之一,华南环境变迁的多旋回性与黄土－古土壤系列、冰碛系列以及河－湖相系列所记录的全球变化的多旋回性振荡有某种程度的相似性。准周期为０．８Ｍａ、０．４Ｍａ、０．１－０．０８Ｍａ和０．０４－０．０２Ｍａ的环境变化在不同地区、不同时段有不同的反映。

RED SOIL, LOESS AND GLOBAL CHANGE

Red soil areas in the tropical and subtropical zones of South China play a veryimportant role in Quaternary environmental research of China because some sectionsconsisting of volcanic rocks, sediments and red soils remain almost intact.In this article, we suggest a concept of "red soil sequence", which can be defined as a general continuous profile which has its time-scale and is built by a certain alternation of red soils and other materials including sediments or volcanic rocks.There are two main types of red soil sequences to be identified in the Leizhou Peninsula: red soil-sediment sequence and the red soil-volcanic rock sequence.The red soil-sediment sequence consists of seven main cycles, of which four cycles fall in the Zhanjiang Formation (Q1), two cycles in the Beihai Formation (Q,)and one cycle in the Basuo Formation (Q2). In the Zhanjiang Formation, the upper part of each cycle consists of variegated clay (weathered red clay) and the lower part of silt, sand and gravels. All the Zhanjiang Formation can be dividedinto 23-25 secondary sedimentary cycles. In the two cycles of the Beihai Formationeach consist of silt-sand-gravel layers and the middle contains a lot of tektites withan age of about 0.70 Ma.B.P. The Basuo Formation consists mainly of sand sediments.Prom the sedimentary rate, it is estimated that the possible ages of the bottoms ofthe seven main cycles are 0.03-0. 127, 0.452, 0.859, 1.274, 1.605, 2.001 and 2.440 MaB. P. and that the lasting time of each cycle is about 0.4Ma.The red soil-volcanic rock sequence contains volcanic rocks of several stagessuch as the Shimaoling volcanic stage, the Huguangyan volcanic stage and the LatePleistocene volcanic stage. This sequence recorded nine to twelve cycles since EarlyPleistocene.The study of red soil and paleoenronment was carried out on the basis of analyses of geochemistry, palynology, paleomagnetism, clay minerals and organic geochemistry. The red soil is higher in Al,Ga and Fe and lower in Si,Mg and S thanother in sequences. It contains a lot of xylophyta and less than 7% herbs. Kaolinite, halloysite, gibbsite, montmorillonite and geothite are its clayey component, inwhich the molecular proportion of SiO₂/Al₂O₃ are 1.51 to 4.60. The natural remanent magnetizations (NRM) of the red soil are 3.157×10^-3 to 9.966 ×10^-2(A/m).On the whole, most of indexes analyzed indicate that the red soil was. formed in ahot and damp climate.The seven main cycles in the red soil-sediment sequence in South China arecorrelatable with the seven sandy-loess cycles and the seven stages of drainage evolution in North China. The multilayers of volcanic rocks in the red soil-volcanicrock sequence may correspond to some units in the loess-paleosol sequence. Similarevents happened in the west part and the east part of Chinese continent and theTaiwan Island of China as well as Europe and other continents. Therefore, the redsoil sequence recorded a lot of information of global change, too, and the periods of0.8,0.4,0.1-0.08 and 0.04-0.02Ma can be found in red soil areas. In this article,finally, we propose the new concept of "climato-tectonic coupling system" as a model for describing the global change