CHARACTERISTICS AND TECTONIC SETTING OF TECTONO-STRESS FIELD OF ORDOS BASIN

Abstract

On the basis of observation of a great number of joints, faults, folds in the field and classification of the formation sequences of structures, the paleo-tectonic stress fields of the Ordos Basin were studied by taking into account the plate dynamics background of formation and evolution of the Ordos Basin and the previous achievements made in this field. The directions of the major tectonic stress fields for the basin are NNE-SSW and SN respectively during the Caledonian movement, and this was resulted from the northward subduction of the Qinling ocean basin and its collision with the North China plate since late Ordovician. During the Indosinian movement, the directions of the major tectonic stress fields are along NW-SE, NNE-SSW and SN, which were basically resulted from the collision between the Qiangtang block, a part of the Tethyan dynamic system, and the Eurasian plate. During the Yanshanian movement, the direction of the major tectonic stress field is NW-SE, and this is obviously resulted from the collision between the paleo-Pacific continental plate and the Eurasian plate. During the Himalayan movement, the stress direction becomes NNE-SSW, and this is a result of the collision between both present Pacific plate and Indian plate with the Eurasian plate.