卷 31, 编号 4 (2023)

The paper presents the results of studying the taxonomic composition of ammonites of the family Cardioceratidae in the Bathonian of northern Siberia in the range of distribution of the last representatives of the genus Arcticoceras and the first representatives of the genus Catacadoceras to solve the problem of distinguishing between the Middle and Upper Bathonian. The incorrectness of all previous identifications of the Middle Bathonian species Arcticoceras cranocephaloide Callomon et Birkelund, 1985 based on the northern Siberian material has been established. These determinations were mainly based on Late Bathonian ammonites belonging to the species Catacadoceras barnstoni (Meek, 1859) or the form characterized by a narrow umbilicus and described herein as Cat. aff. barnstoni. An updated zonal scale of the Middle–Upper Bathonian of Siberia based on ammonites is proposed, which is recommended for use both in the regional stratigraphic schemes of the Jurassic deposits of Eastern (Middle) Siberia and in the Boreal (Siberian) zonal standard of the Bathonian Stage. The extreme importance of preserving an auxiliary biostratigraphic subdivision in this scale, the Cat. barnstoni Beds, is noted, which is due to the wide distribution and abundance of the index species in Siberian sections, as well as its significance for the correlation of the lower part of the Upper Bathonian of northern Canada, northern Siberia, Franz Josef Land and East Greenland. In addition, two intervals, namely interval with Cat. aff. barnstoni and interval with Cat. perrarum, are fixed as benchmarks, which are useful for the rapid age estimation and correlation of the Upper Bathonian deposits in Arctic sections within the upper part of the Cat. barnstoni Beds.

New radiolarian data from the type section of the middle Cenomanian Pseudoaulophacus lenticulatus Zone located on the northern and southern slopes of the Sel’-Bukhra Mountain section (southwestern Crimea) are reported. The Pseudoaulophacus lenticulatus Zone radiolarians have been studied and analyzed in this section for the first time. Five species previously unknown in this region have been found here. Lithology of the lower part of the upper Cenomanian Triactoma parva Zone from the southern slope of the Sel’-Bukhra Mountain section is reported. Both Pseudoaulophacus lenticulatus and Triactoma parva Zones have more than 60% species distributed in the Tethyan Superrealm.

The article presents the results of a comprehensive (diatom and spore-pollen analysis and ¹⁴C-dating) study of the Holocene bottom sediments of a lake located on the coast of the Kandalaksha Bay of the White Sea near the mouth of the Keret River. Three stages in the development of the lake basin have been identified: marine, transitional, and lacustrine. Diatom assemblages characteristic of each facies are given. The indicator value of pollen, spores and non-pollen palynomorphs for identifying marine, transitional and freshwater sedimentation conditions is noted. A decrease in sea level was established at the turn of 7200 calendar years ago. The change of the marine environment of sedimentation to the lacustrine was recorded approximately at the turn of 6700 calendar years ago. For a given time, the position of the coastline of the sea is shown within the studied coast. The data of spore-pollen analysis were used for relative dating of post-glacial deposits. Vegetation was reconstructed from the end of the early Holocene to the present.