New paleontological and lithological data characterizing the upper boundary of the Chekurovskii Formation are considered for the stratoregion located in the lower reaches of the Lena River, northern Siberia. We propose to accept this boundary at the bottom of a sandy bed with pebbles, considering the latter to be basal sandstones of an overlying transgressive sequence. Taking into account ammonite records, we can conclude that the boundary corresponds to a level within the Upper Bathonian Catacadoceras barnstoni Zone. The predominantly silt–sized sediments lying above (uppermost Bathonian? – Lower Callovian) can be treated an analogue of a lower part of the Innokent’evka Formation recognized in adjacent facial region.
New data on the litho-and biostratigraphy of the Jurassic/Cretaceous (J/K) boundary interval of the lower reaches of the Lena river, at the Cape Chekurovka and Cape Chucha, are presented. Volgian-Valanginian interval of the Chekurovka section is represented by Buolkalakh and Kigilyakh formations and corresponds to beds with Buchia fisheriana, beds with B. unschensis, beds with B. okensis and B. volgensis, beds with B. volgensis, beds with B. volgensis and B. tolmatschowi and beds with B. keyserlingi. Volgian-Valanginian interval of the Chucha section is represented by Chonoko, Khairgass and Kigilyakh formations and corresponds to beds with B. unschensis, beds with B. volgensis and B. okensis, beds with B. volgensis and B. tolmatschowi and beds with B. keyserlingi.
An analysis of the current state of research in the field of Boreal-Tethyan correlation of the Middle Jurassic marine sediments of Siberia is given. Further perspectives are closely related to the obtaining and mutual coordination of the results of bio- and chemostratigraphic, biofacial and biogeographical studies of the Middle Jurassic of Siberia and adjacent territories, and is thus expected to reveal a set of calibrated markers (traces of biotic and abiotic events) that will contribute for interregional and global correlations.
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