|mhorn||Дата: Tuesday, 25.03.2014, 16:45 | Сообщение # 1|
|Zakharov V.A., Rogov M.A., Dzyuba O.S., Žák K., Košt’ák M., Pruner P., Skupien P., Chadima M., Mazuch M., Nikitenko B.L. (2014) Palaeoenvironments and palaeoceanography changes across the Jurassic/Cretaceous boundary in the Arctic realm: case study of the Nordvik section (north Siberia, Russia) // Polar Research 2014, 33, 19714,http://dx.doi.org/10.3402/polar.v33.19714 |
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.
Middle Jurassic - Lower Cretaceous ammonites & aptychi