CLAY MINERALOGY AND ITS APPLICATION TO PALEOENVIRONMENTAL RECONSTRUCTION

Component,assemblage,content and crystalization of clay minerals in sediments can reflect cold-warm cyclical changes of climate and their sedimentary environments.In recent years,clay mineralogy is regarded as a valuable tool for reconstructing ancient environmental conditions and becomes an efficient method of source tracing.Firstly,the authors introduce various methods for studying clay minerals,such as X-ray diffraction (XRD),scanning electron microscope (SEM),transmission electron microscope (TEM),electronic probe microanalyzer (EPM),energy dispersive X-ray spectroscopy (EDS),thermoanalysis,infrared (IR) spectroscopy,chemical analysis,isotope analysis,and M ssbauer spectroscopy,and make comments on their advantages and shortcomings,Secondly,clay minerals are considered as indicators of acid alkali water medium,hydrodynamic environment,paleoclimate and trace source.Finally,clay minerals used in marine,loess and lacustrine paleoenvironmental reconstructions are reviewed.
Variations of clay mineralogy are in agreement with results from paleontology (e.g.pollen),oxygen isotope,and diatom,indicating it is useful proxies for paleoclimate.However,original clay mineralogy also depends on climate,topography,lithology,tectonic activity,and some other factors of the source area.Therefore,care should be taken on the interpretation of clay mineralogy.We have to consider the impacts of erosion,transportation,tectonics,relief,hydrology,paleoflow and post-depositional transformation on the mineralogy.With new techniques and methods,integrated studies on a variety of other paleoenvironment proxies such as physical indicators (e.g.particle size,magnetic susceptibility,color),chemical indicators (e.g.elements,isotopes) as well as paleontology (e.g.pollen,diatoms,ostracods),will help clay minerals play an increasingly important role in paleoenvironment reconstruction.