EVOLUTION AND MECHANISM OF FORMATION OF THE STRUCTURAL SYSTEM IN THE LONGMENSHAN AREA

In the light of the time sequence, spatial distribution and characteristics of the stress field, the Cathaysian structures in the Longmenshan area may be classified from older to younger into the Old Cathaysian （pre-late Sinian）, Paleocathaysian （late Sinian-Middle Triassic）, Mesocathaysian （Late Triassic-E- arly Cretaceous） and Neocathaysian （Late Cretaceous-early Tertiary） structural systems. The characteristics of these structural systems, their activities since the Neoid （late Tertiary-Quaternary） and their compounding and conjunction with other structural systems are discussed. Then from the generation, devel- opment and evolution of the stress field of various structural systems, the author demonstrates the inheritance of the latitudinal and longitudinal structural systems, the shifts of the orientation of the Cathaysian structural systems in various geological periods, which reflects the mode and orientation of the local or regional dynamic action and the model of its regular changes during a struc- tural movement. From this, the mode of crustal movements, the regularity governing the change in their direction and their relations with the rotation axis of the earth and equator are inferred, and the inner connection of the crustal movements and the changes in the rotational velocity of the earth is induced. This is of theorectical and practical significance for the analysis and study of the regularities of geological structures and their evolution.