FEATURES OF THE SPATIAL-TEMPORAL SPREADING OF THE BENTHOUS MACROFAUNA OF THE PLATFORM UKRAINE DURING THE LATE CRETACEOUS ERA

Abstract

The spatio-temporal spreading of benthic macrofauna (Bivalvia, Gastropoda, Brachiopoda, Echinodea) of platform Ukraine during the Late Cretaceous epoch is highlighted. The analysis of the systematic composition of macrofossils and their taxonomic component during the Late Cretaceous allows us to state a close correlation between the diversity of its various systematic groups both within individual regions of platform Ukraine and between related groups within most of the study area. The maximum values of systematic diversity of Bivalvia, Gastropoda, Brachiopoda, and Echinodea are observed in two time intervals: the Middle - early Late Cenomanian and the Late Campanian – Еarly Maastrichtian with clear correlative peaks in species numbers for all faunal groups throughout the epoch. The minimum values of systematic diversity are recorded during the Cognacian – Early Campanian. The abundance, systematic diversity, and habitats of the main benthic macrofauna groups were controlled mainly by the type of substrate, which depended on the nature of sedimentation. At the beginning of the Late Cretaceous (Early-Middle Cenomanian), the formation of silicate rocks, represented by quartz-glauconite sands, pebbles and sandstones, which contributed to the formation of hard and loose substrates, was predominant. In the Turonian, Cognac, Santonian, Campanian and partially Maastrichtian ages, carbonate formation processes played a significant role in sedimentation with the accumulation of thick layers of writing chalk, limestone and marl and the formation of silty and, partially, loose substrates. The hard substrate, represented by sandy-gravel-pebble and sandy-shell-detritus sediments, contained up to 30% of the macrofauna taxonomic composition. Up to 65% of the macrofauna species lived on a loose substrate composed of sandy-lime, sandy marl, flinty sandy carbonate sediments and mossy foraminiferal silt, and only about five percent on a silty substrate composed of foraminiferal-pytonel coccolithic silt. The patterns of lateral spreading of paleobiocomplexes are reflected in the maps of the territorial distribution of communities during the Late Cretaceous epoch. Clarification of the spatial and temporal features of the spreading of benthic macrofaunal complexes of the Platform Ukraine during the Late Cretaceous is a necessary component of further biostratigraphic constructions.