摘要
将岩石学研究方法引入三趾马红粘土研究中，利用薄片系统观察、电镜扫描、Ｘ－射线衍射、粒度分析及化学分析手段，对红粘土的岩石学、微结构及形态学进行较为细致的研究。结果表明，各粘土层下部的沉淀层系成壤过程中钙质从上部土壤中淋滤并向下迁移再沉淀的结果。土壤中粘化层的光性定向粘粒及淀积铁质粘胶膜的发育程度受古气候及淋滤作用强度的控制。红粘土形成过程中主要为干旱、半干旱－半湿润气候的草原疏林环境，也有湿润气候的森林环境出现。
The reasonably interpretation of the genesis of the Late Neogene red clay has attracted increasingly attention due to its importance for better understanding of problems such as the evolution of the Quaternary paleoclimate and the Paleomonsoon.Several opinions have been documented.But a more systematic petrologic study on red clay has not been reported. Recently we have made a careful field observation and conducted a systematic study on petrology,microtexture and morphology,geochemistry on several red clay sections in different parts in the middle reaches of the Yellow River,using thin section,SEM,X-ray diffraction,particle size and geochemical analysis.Field and laboratory studies show that the pedostratigraphic structure in different red clay sections can be fairly well correlated although they are located over far distances and the texture,mineral components exhibit an obvious homogeneity in different places.Our studies also found that preferentially oriented optical clay films are common in red clay.They mainly occur along the walls of pores and cracks as flowing colloid or as rim films around framents. They were formed during soil forming process and fheir development is controlled by paleoclimate.The developed optical caly films in red clay indicate a warm,wet forest climate accompanied by an intensely leaching process,while undeveloped ones imply an arid or semiarid prairie environment coupled with slight leaching.Our studies also show that calcareous concretion layer beneath the red clay horizon is an illuvial horizon which was resulted from eluviation of calc form the upper clay and by its migration and reperecipitation during pedogenic process of the red clay,impluing a warm and wet climate with intensely leaching. The Hipparion red clay was formed domintly under an arid-semiarid prairie environment with subhumid-humid forest climate alternative.This climatic pattern was probably related with the paleogeographic pattern that Qing-Zang Plateau had elevated to a height that could blocked the warm and wet paleomonsoon blowing from the Indian Ocean to northe China.The variation of the climate and differentiation of temperature among red clay layers became greater after about 6.0Ma,this also attributed to the deteriorated climate resulted in accelerating elevation rate of Qing-Zang Plateau.Taking the Hipparion red clay in Ridge Wangdaifu,Fugu,norther Shaanxi province as an example,its formation experienced four main climatic cycles,according to the petrology,texture and micromorphological features as well as geochemical characteristics of the red clay.Each cycle initiated with arid or semiarid climate and ended with humid or subhumid climate.
出处
《沉积学报》
CAS
CSCD
北大核心
1999年第2期214-220,共7页
Acta Sedimentologica Sinica
基金
中科院西安黄土与第四纪地质国家重点实验室资助项目
关键词
黄河中游
三趾马红粘土
古气候
岩石学
middle reaches of the Yellow River Hipparion red clay Paleoclimate
