PROCESS OF LARGE SCALE FOLD FORMING IN THE CRUST SEDIMENTARY LAYER

Based on the finite element method of three dimensional visco-elastic variation in the orthotropic foliated shells proximity, where shells are in quasi stationary loading process, the authors carried out, modeling of large scale fold forming processes in the crust sedimentary layer. The presented method allows us to calculate heterogeneities of the considered geological structures of both geometrical and rheological character. As a result, it is found, that fold velocities growth and fold forms forming depend on sedimentary rocks fracturing degree and on the deviation of the constringent geotectonic forces from horizontal direction, as well as on forms and sizes of the sedimentary rocks contortion areas. Consequently, sedimentary rocks fracturing degree leads to decreasing of the folds growth velocities. Deviation of the constringent geotectonic forces from horizontal direction also leads to their decreasing. Anticlinoriums and synclinoriums forming processes, and also velocities of these processes greatly depend on forms and sizes of the sedimentary rocks contortion areas. Moreover, anticlinoriums forming process is typical for contortion areas of big sizes. As the contortion area size decreases in the direction of compressing forces to some characteristic value, anticlinorium growth velocity decreases to zero, and qualitative transition to synclinoriums forming process takes place. Besides, as the respective contortion area size decreases, synclinorium growth velocity increases from zero to some maximum value, and then decreases to zero. In the case of anticlinoriums forming, sedimentary contortion area sizes in transversal direction relatively to geotectonic forces action do not effectively influence the process velocity. But In the case of synclinoriums forming, sedimentary contortion area size shortening leads to decreasing of the process velocity. The obtained information can be used for orogeny processes explorations as well as large geostructures forming and changing processes.