Paleotectonic Setting of the Accumulation of Middle Jurassic Deposits in the Northeastern Flange of the Nagondzha Terraine (Ulakhan-Sis Ridge)

The age of the Middle Jurassic deposits of the Ulakhan-Sis Range is corrected to the Bajocian–Middle Bathonian. Three terrigenous units are identified that formed at a single stage of sedimentation in the shelf part of the sedimentary basin associated with an active volcanic arc under conditions of gradual uplift of the Ulakhan-Tas block of Paleozoic limestones of the Omulevka terrane. The calclithite composition of the upper sequence was recognized, which is a reliable marker of the beginning of the thrusting process in the Bajocian–Middle Bathonian associated with terrane amalgamation, which ended with the formation of the Kolyma–Omolon superterrane. The formation of the Kolyma–Omolon microcontinent was complete by the beginning of the Late Jurassic, which is confirmed by the absence of Upper Bathonian and Callovian deposits in the section.