Abstract

For the first time data are given on the planetary fracturing of Kopetdag, and its important role is demonstrated in the formation of the principal types of relief of that mountainous country.

On the basis of the planetary fracturing concept the questions of its disjunctive tectonics, the development of fold structures, the system of frontal faults along the northern foothills, etc., are treated in a new light.

The concept of planetary jointings is proposed which supplements that of planetary fracturing, and which is not synonymous with the concept of tectonic blocks. As distinct from the latter, which have only local significance, planetary jointings, like planetary fractures, are developed throughout the Earth’s crust and are characterized by well defined morphology.

Principal morphological types established in the geologic sections of Kopetdag’s strata are outlined. Their dimensions vary within an extremely wide range and are determined by the frequency of fractures of different orders. The morphology of jointings is determined by the spatial position of planetary fractures (bounding their lateral faces) and the surfaces in the sedimentary cover which separate stratigraphic units of different rank each having a different density of fractures from those units above or below.

The relationships that have been revealed between topographic relief and the systems of planetary fractures (predominantly diagonal) testify to the fact that many types of relief formerly classified as morphosculptural are actually geostructural. The exogenous processes play only the role of a preparing factor, but they have no genetic significance in the morphology of relief whose basic features are determined by the shape of planetary jointings, their spatial position, composition and structural character.

Lithologo-petrographical and lithologo-stratigraphical jointings of various shapes and dimensions are distinguished with whose exogenous preparation is associated all the diversity of geostructural relief.

The presence of planetary fracturing in the course of evolution of geostructural relief on the limbs of denuded folds determines the inversion of its positive and negative forms, the cyclic displacements of erosion cutting, etc. An example is given of such a process in the case of exogenous preparation of rhomboid jointings in inclined strata.