Palaeoenvironments and palaeoceanography changes across the Jurassic/Cretaceous boundary in the Arctic realm: case study of the Nordvik section (north Siberia, Russia)

• Published in: Polar Research
• Main Authors: Victor A. Zakharov, Mikhail A. Rogov, Oksana S. Dzyuba, Karel Žák, Martin Košt’ák, Petr Pruner, Petr Skupien, Martin Chadima, Martin Mazuch, Boris L. Nikitenko
• Format: Article in Journal/Newspaper
• Language: English
• Published: Norwegian Polar Institute 2014
• Subjects: Biodiversity; stable isotopes; J/K boundary; Arctic Realm; palaeoceanography; Environmental sciences; GE1-350; Oceanography; GC1-1581; Arctic; Pacific; Polar Research; Siberia
• Online Access: https://doi.org/10.3402/polar.v33.19714; https://doaj.org/article/97bb5ba64e3c4536a931357ee98b1812

The Jurassic/Cretaceous transition was accompanied by significant changes in palaeoceanography and palaeoenvironments in the Tethyan Realm, but outside the Tethys such data are very scarce. Here we present results of a study of the most complete section in the Panboreal Superrealm, the Nordvik section. Belemnite δ18O data show an irregular decrease from values reaching up to +1.6‰ in the Middle Oxfordian and from +0.8 to −1.7‰ in the basal Ryazanian, indicating a prolonged warming. The biodiversity changes were strongly related to sea-level oscillations, showing a relatively low belemnite and high ammonite diversity during sea-level rise, accompanied by a decrease of the macrobenthos taxonomical richness. The most prominent sea-level rise is marked by the occurrence of open sea ammonites with Pacific affinities. Peak abundances of spores and prasinophytes correlate with a negative excursion in organic carbon δ13C near the J/K boundary and could reflect blooms of green algae caused by disturbance of the marine ecosystem.