元谋盆地古红土的土壤发生学特征及古环境意义

Pedogenetic Properties and Paleo-environmental Implication of Paleo-Krasnosems in the Yuanmou Basin

选择元谋盆地不同发育年代形成的古红土,探讨了古红土的发生学特性。研究表明,在气候上更有利于早期形成的古红土发生强烈的风化淋溶作用,同时,晚期形成古红土气候湿热程度下降,成土时间也短,故土壤中硅淋溶较弱,铁铝富集程度不强。利用古红土发生学特性,可以推断出元谋盆地从晚新生代的湿热气候经暖干气候演化至现代的干热气候。

By discussing the types and pedogenetic properties of paleosols, great geological events and environmental change can be deduced to reconstruct paleo-environment. The paleo-krasnosems formed in different periods were selected in the Yuanmou Basin to deal with the field morphological and micro-morphological features, composition of clay minerals, chemical properties, iron oxides, and mechanic composition in the paleo-krasnosems. The paleo-climate favored, stronglg, weathering and leaching in the paleo-krasnosems developed in early stage, while silicon was leached weakly and iron and aluminumwere accumulated in the paleo-krasnosems formed in the late stage due to the precipitation and heat decreasing in paleo-climate as well as short pedogenetic time. Furthermore, some pedogenetic properties changed, as influenced intensively by modern soil-formation because of long-term exposing on earth surface.By comprehensively analyzing the pedogenetic properties of the paleo-krasnosems in the Yuanmou Basin,it was concluded that the variation in soil-forming processes and degree among the paleo-krasnosems were developed in different geological times. However, the pedo-environments in various periods might be inferred by use of pedogenetic properties as the paleo-krasnosems developed from the same or similar type of parent materials. Since the late Cenozoic, the climate was transmitted from hot and humidity via warm and dry to hot and dry in modern time.