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.