Density heterogeneity of the Earth’s crust of the Black Sea megadepression and adjacent territories from three-dimensional gravity modelling. 1. Regional density distribution at different depths.
Аннотация:This paper presents a comprehensive analytical review of the various approaches to the gravity modelling of the Earth’s crust of the Black Sea and adjacent territories. It is shown that even in using the same thickness of sedimentary layers whose total gravitational effect makes a considerable contribution to the observed field the results of different authors do not coincide and in some cases contradict each other. The reason is that every researcher uses ad hoc reference density and a method of reducing the calculated curves. Therefore, an unified three-dimensional density model of this region was first developed that significantly increased the reliability of the geological interpretation of the modelling results. In additional the spatial distribution of density was first used for the Maykop Series, the Eocene- Pliocene, and Cretaceous deposits that allowed us to obtain principally new data on the heterogeneous structure of the main horizons of the sedimentary cover. An analysis of the density distribution of the consolidated crust revealed anomalously weakened and compacted areas in the shelf zones. A pattern was constructed for the distribution and depth to the basement of dislocated sediments. The density of rocks was also calculated on this surface. The granitic, granitic-diorite, dioritic and basaltoid types of the crust were identified that for the first time made it possible to delineate the areas of different composition in the present - day consolidated crust of the entire study region. A decrease in crustal basicity was unveiled in the direction from the deep-water basins to the northwestern, western, and southern offshore zones. On the shelf local density inhomogeneities were at the base of the basalt layer, which are indicators for penetration of basic and ultrabasic intrusions into the crust.
