Eustatic signals in the Jurassic and Lower Cretaceous (Neocomian) depositsof the West-Siberian sedimentary basin

A transgressive-regressive (T-R) curve for the Jurassic and Lower Neocomian of the West-Siberian sedimentary basin was constructed on a detailed chron ostratigraphic basis. This curve is compared with the quantitative eustatic curve for the Russian and Siberian Platforms, constructed earlier by D. Sa hagian et al. for the Middle Jurassic-Cretaceous from sedimentation and bio stratigraphic data, and with the curve constructed by B. Haq et al. This co mparison permitted recognizing eustatic signals from local T-R events. Nine teen significant T-R events are distinguished in the Jurassic-Neocomian: tw o - in the Early Jurassic, three - in the Middle Jurassic, four - in the La te Jurassic, and ten - in the Neocomian. Most of the T-R cycles are well co rrelated with the eustatic curves. The increase in the frequency of sea lev el fluctuations is explained by reduction of the regressive <shoulder>> of cycles with time. Significant T-R events in the Jurassic and Neocomian were traced far beyond West Siberia, both in the adjacent regions and on other continents of the Northern Hemisphere. These are Kiterbyut T-event (Early T oarcian), Vymsk-Leontievsk T-R event (Bajocian), Central-Vasyugan R-event ( Middle Oxfordian), Bazhenovka T-event (Late Kimmerigian-Volgian), and five T-R events in the Valanginian. A <<through>> sequence-stratigraphic analysi s has been carried out for the Jurassic and Neocomian petroliferous series of the West-Siberian sedimentary basin. The series was divided into sequenc es of second and third ranks, which has allowed some contradictions between the existing stratigraphic and sedimentation models to be overcome.