Changing ichnofossil composition in the Callovian–Oxfordian sediments of the West Siberian basin as a reflection of sedimentation cyclicity

We summarize the results of the integrated lithologic and ichnofacies studies of the Callovian–Oxfordian sediments in the West Siberian sedimentary basin on the basis of core samples from more than 200 wells. In the sections of various structurefacies zones, ten ichnofossils of the ichnofacies Skolithos, Cruziana, and Zoophycos have been identified and spatial variations in the species composition of ichnofacies assemblages have been traced. It has been found that lateral and vertical variations in the ichnofossil distribution agree with the regional structural patterns of the Vasyugan Horizon and are related to the Callovian–Oxfordian cyclic turnovers of the basin depositional systems.