Lower Cretaceous foraminifera of the northern part of Middle Siberia (Central Taimyr and lower reaches of the Olenek River): biostratigraphic and biofacies analyses

By the analysis of foraminifera distribution in the Lower Cretaceous sections of the Luktakhskaya-4 well (Central Taimyr) and natural outcrops in the lower reaches of the Olenek River, we identified a sequence of five biostratons: Gaudryina gerkei, Trochammina rosaceaformis zone (KF1, middle Boreal Berriasian); Valanginella tatarica, Recurvoides obskiensis zone (KF2, uppermost Boreal Berriasian - Valanginian); Cribrostomoides infracretaceous, Cribrostomoides sinuosus zone (KF4, upper Lower Valanginian - lowermost Hauterivian); beds with Cribrostomoides concavoides, Trochammina gyroidiniformis (KF5, lower Hauterivian) (based on [1, 2]). The paper presents the biofacial study results of the Early Cretaceous basin in the northern part of Central Siberia. The authors reconstructed foraminifer communities of the Boreal Berriasian ([1], =Ryazanian stage [3]), Valanginian and lower part of the Hauterivian of the Enisei-Khatanga Strait (Central Taimyr), and the southern end of the North Siberian Sea (lower reaches of the Olenek River). Their evolution mechanisms were discovered. The succession of bionamic zones was determined.