The work is the first generalization of the results of the study of microspangiofauna (isolated spicules of siliceous sponges), their systematic composition, stratigraphic and lateral distribution in Jurassic and Cretaceous deposits of platform Ukraine. For the first time for Jurassic and Cretaceous deposits of the studied region a detailed monographic description of 67 morphospecies of spicules of sponges belonging to 30 morphogenus, 8 morphofamily was carried out. Of these, 38 morphospecies of spicules of sponges from Jurassic and Cretaceous deposits on the territory of platform Ukraine are described as new.
The author establishes and characterizes the spicules of sponges complexes from Callovian, Oxfordian, Albian and Cenomanian deposits of platform Ukraine, determines their systematic and quantitative composition. Peculiarities of the distribution of sponges of spicules morphospecies in the studied sediments have been established and a gradual change in the composition of sponges of spicules morphospecies complexes has been traced both in separate sections and in different structural-facial zones. The stratigraphic distribution of each of the identified morphospecies of sponges of spicules was traced. Complexes of spicules of siliceous sponges containing morphogenus characteristic of Callovian, Oxfordian, Albian and Cenomanian deposits of the western, central and eastern regions of platform Ukraine have been established. This gives rise to the use of isolated siliceous sponge of spicules for stratification of sediments at stages and substages levels, especially carbonate-free strata depleted into orthostratigraphic fauna groups.
The results of comparison of Jurassic and Cretaceous deposits of the territory of Volyn-Podillya, Ukrainian Shield and Dniprо-Donetsk depression by spicules of sponges are given. The analysis of the systematic composition of the identified complexes of sponges of spicules is carried out, their general and distinctive features are established. According to the established complexes of spicules of sponges in Jurassic and Cretaceous deposits, a lateral change of their composition in similar age deposits was traced. According to the systematic composition of the complexes and the presence of common morphospecies in them, as well as the characteristic morphospecies of spicules of sponges, analogues of the similar age deposits have been established. The expediency of using spicules of sponges for interregional correlations is substantiated. According to the obtained data, the spicules of sponges complexes from the Lower Callovian and Middle Callovian deposits of the Dniprо-Donetsk depression and Kaniv dislocations correlate well. The identified differences in the composition of the complexes are explained by some features of the conditions of existence of sponges (depth, temperature, nature of the seabed, etc.), as well as the presence of endemic species of sponges. In the Lower Cenomanian sediments of the western slope of the Ukrainian Shield, Kaniv dislocations and the north-western part of the Dniprо-Donetsk, complexes of spicules of sponges have been established, in which common characteristic morphospecies have been identified, which give grounds to consider the studied sediments to be similar age.
