古土壤的分类系统及其在地质学中的应用领域

CLASSIFICATION OF PALEOSOLS AND THEIR GEOLOGIC APPLICATIONS

古土壤是近年来沉积学研究领域的一个热点。古土壤就是形成于过去地貌上的土壤,是暴露在地表的沉积物或岩石经过物理的、生物的和化学的改造形成的,一般形成于很长的地貌稳定期,记录了地层间断或不整合,蕴含着丰富的有关古气候、古植被、古地貌、沉积环境状况的信息,并且是指示地层时代的"化石"。古土壤对恢复地质历史时期古植被与古环境、古气候提供了新的途径,是地层划分、对比的重要标志,并且可用以重建沉积盆地古地貌。古土壤的识别可以根据野外宏观标志、室内微观特征来进行,但是古土壤学家还没有解决古土壤的分类问题,我们对国际上流行的几种古土壤分类方案进行评述,认为古土壤的分类应该根据不同的应用目的采用不同的分类方案,而且在一个分类系统的组名中可采用形容词的组合作为修饰语。

Paleosol is one of researching crazes of sedimentary field recently. A paleosol or fossil soil is a soil that formed on a landscape of the past. Paleosols form because of physical,biological,and chemical modifications of sediment or rock exposed at the earth surface, and because of lengthy episodes of land- scape stability,so they can eventually indicate existence of stratigraphic diastem or unconformity,and can offer information of paleoenvironment, paleoclimate, paleovegetation, paleomorphology, and sedi- mentary environment state and be a fossil instructing stratigraphic time. Paleosols are used to recon- struct ancient vegetation and climates,even to estimate ancient mean annual precipitation（MAP）and mean annual temperature（MAT）. Paleosols are also helpful in stratigraphic studies and in stratigraph- ic correlations. The studying of paleosols provides a new beneficial way for reconstructing paleomor- phology of sedimentary basin. Criteria for recognizing these paleosols have been extensively described, but classifying them has proved more complicated. This paper discusses several classification systems and gives some advice to paleosols classification.