GEODYNAMIC TYPES AND MECHANISMS OF TRANSPRESSIONAL BASINS

The transpressional basin is not only one of the widespread basin types but also an important petroliferous basin type in the world.A reasonable classification and the discussion of formation mechanism of transpressional basins will be helpful for petroleum geology study and exploration potential evaluation.Based on the study of basin structure and hydrocarbon exploration,it is put forward in this paper a basic classification scheme of the transpressional basins.According to transpression time and its relation to basin formation,the transpressional basins can be basically classified into the proto-and the post-transpressional ones.Then,according to plate tectonic settings,transpression mechanism and transpressional force magnitude,the transpressional basins can be further classified into many secondary types.Based on the geodynamic settings of transpressional basins,it is analyzed in this paper their formation mechanisms and structural features.The tectonic background of transpressional basins is quite different from which of the extensional or trans-extensional basins.The transpressional basin has been predominantly resulted from oblique compression,such as oblique compression plate boundary,transform plate boundary and the peripheral area of collisional orogens.The formation mechanism of post-transpressional basin is much more complicated than that of the proto-transpressional basin.The oblique-compression between plates,the accretion of micro-terranes,and the plate rotation,etc.can accordingly give rise to the formation of transpressional basin.