The density of sedimentary complexes of the Carpathian-Pannonian region (generalization)

Abstract

An extensive analysis of the available information on the density of themain tectonic elements of the Ukrainian Carpathians is given in connection with the need for further construction of a three-dimensional gravity model. The density was studied both from cores of reference, exploration, crelius and deep exploration wells, and from samples taken from numerous outcrops. In the Ukrainian Carpathians, there is a change in the density of rocks depending on the age, lithological composition and depth of occurrence. Local metamorphism plays a significant role in the increase in density. It is shown that in the Bilche-Volitsky Nappe of the Precarpathian Trough, a discontinuous change in the density of clays with increasing depth is more often observed, which is caused not by a static load, but by the geological conditions of the formation of the region: by tectonic processes and a change in sedimentation and denudation processes, which cause residual compaction. According to the analysis of available data, the density of molasse and flysch strata within the Borislav-Pokutsky and Sambir Nappes at depths of 1000 m and more practically does not change, and an increase in the density of Pokuttya rocks is associated with a decrease in the porosity of rocks by 2—5 % and is due to the degree of their metamorphism. Analysis of a large amount of data showed a very complex nature of the density distribution in the Folded Carpathians and its dependence, mainly, on porosity. For different stratigraphic subdivisions of the Skiba Nappe, there is a general tendency to an increase in density with depth (in most cases, unevenly), which is most clearly manifested in the Stryi series of deposits.In the Transcarpathian Trough, the change in density with depth depends on the ratio of clay, tuffogenic and sandy material in the rock. Sedimentary and igneous rocks in the upper part of the section of the Vygurlat-Gutinskaya volcanic ridge are not differentiated in density, which can be explained by the high densities of sedimentary rocks, on the one hand, and a decrease in the density of igneous rocks due to their decompaction, on the other. In the stratigraphic complexes of the Solotvino and Mukachevo Depressions, the density varies over the area. For the first time, based on generalized data on the density of rocks of different age groups of the sedimentary complex for the folded region of the Ukrainian Carpathians, a diagram of the distribution of the average density for each structural-facial zone has been drawn up. An increase in density from north-east to south-west is shown. It is concluded that the density of the Precarpathian and TranscarpathianTroughsis much lower than the density of the rocks of the Folded Carpathians.