| 黄河中游三趾马红粘土的岩石学研究及古气候意义--以陕西府谷老高川三趾马红粘土剖面为例 |
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| 引用本文： | 罗静兰,张云翔.黄河中游三趾马红粘土的岩石学研究及古气候意义--以陕西府谷老高川三趾马红粘土剖面为例[J].沉积学报,1999,17(2):214-220. |
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| 作者姓名： | 罗静兰 张云翔 |
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| 作者单位： | 西北大学地质系 |
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| 基金项目： | 中科院西安黄土与第四纪地质国家重点实验室资助项目 |
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| 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。府谷老高川三趾马红粘土剖面记录了四个大的气候旋回
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| 关 键 词： | 黄河中游 三趾马红粘土 古气候 |
| 收稿时间： | 1998-02-03 |
Petrologic Study on the Late Neogene Hipparion Red Clay in the Middle Reaches of the Yellow River and Implications for Climatic Evolution |
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| Institution: | Department of Geology,Northwest University,Xi' an 710069 |
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| Abstract: | The reasonably interpretation of the genesis of the Late Neogene red clay has attracted increasingly attention due to its importance for better understan ding of problems such as the evolution of the Quaternary paleoclimate and the Pa leomonsoon.Several opinions have been documented.But a more systematic petrologi c study on red clay has not been reported. Recently we have made a careful field observation and conducted a systematic stu dy on petrology,microtexture and morphology,geochemistry on several red clay sec tions in different parts in the middle reaches of the Yellow River,using thin se ction,SEM,X-ray diffraction,particle size and geochemical analysis.Field and lab oratory studies show that the pedostratigraphic structure in different red clay sections can be fairly well correlated although they are located over far distan ces and the texture,mineral components exhibit an obvious homogeneity in differe nt 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 a s flowing colloid or as rim films around framents. They were formed during soil -forming process and fheir development is controlled by paleoclimate.The develo ped optical caly films in red clay indicate a warm,wet forest climate accompanie d by an intensely leaching process,while undeveloped ones imply an arid or semia rid 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 migr ation and reperecipitation during pedogenic process of the red clay,impluing a w arm and wet climate with intensely leaching. The Hipparion red clay was formed domintly under an arid-semiarid pr airie environment with subhumid-humid forest climate alternative.This climatic p attern was probably related with the paleogeographic pattern that Qing-Zang Plat eau had elevated to a height that could blocked the warm and wet paleomonsoon bl owing from the Indian Ocean to northe China.The variation of the climate and di fferentiation of temperature among red clay layers became greater after about 6. 0Ma,this also attributed to the deteriorated climate resulted in accelerating el evation rate of Qing-Zang Plateau.Taking the Hipparion red clay in R idge Wangdaifu,Fugu,norther Shaanxi province as an example,its formation experi enced four main climatic cycles,according to the petrology,texture and micromor phological features as well as geochemical characteristics of the red clay.Each cycle initiated with arid or semiarid climate and ended with humid or subhumid c limate. |
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