Abstract:

The earth’s isostasy,of which the final outcome will be the earth itselfbecoming an ideal spheroid with concentric sphere structure and uniform den-sity in each sphere or layer,is a unified movement of the earth as a wholeand its interior spherical layers.The asthenosphere is the outermost sphereof the earth,in which the material can flow.Therefore,isostasy in the up-per part of the earth mainly occurs between the lithosphere and the astheno-sphere.This means that the top surface of the asthenos phere can be consi-dered as a surface of isostatic adjustment.Apart from isostasy,there arestill other movements which may disturb and destroy the isostasy,such asmantle diapirs and compression or tension of the lithosphere.Sedimentary ba-sins form and develop through new isostatic adjustment under the conditionthat the isostatic state somewhere in the upper part of the earth has beendestroyed.According to the initial cause of inducing subsidence of the basin and towhat extend the isostasy has occurred in the course of basin development,the author divides basins into three categories:the first,caused by sedi-ment-loading,is named sediment-induced basin;the second,by structure,is named structure-induced basin;and the third,not only caused but alsocontrolled its development by structure,is named stucture-controlled basin.Under the last has case,the isostasy is insignificant.Moreover,the writerhas discussed the mechanisms of their formation respectively.Finally,on the basis of the features of the basin development,the authorproposes and discusses the problem of the maturity of basins.