Sea-level and climatic controls on Aptian depositional environments of the Eastern Russian Platform
Abstract On the basis of a high-resolution chronostratigraphic framework of the Eastern Russian Platform, a comparison between Late Barremian–Aptian global and regional sea-level trends was performed. The detailed evaluation of the long-term (3rd order) Aptian sea-level cycle results in the recognition of sea-level and climate as controlling factors on depositional environments in the basin. The rising part of the Aptian sea-level cycle lasted from the Deshayesites tenuicostatusis Zone to the Deshayesites deshayesi Zone, and transgression is responsible for the local development of anoxia on the Eastern Russian Platform. The Lower Aptian bituminous shales and sheeted calcite concretions associated with the Eastern Russian Platform are interpreted as being a regional manifestation of Oceanic Anoxic Event OAE 1a. The Late Aptian “cold snap” that occurred during the Early Cretaceous greenhouse world coincided with a simultaneous global and regional sea-level lowstand, peak shallowing of the basin, and the almost complete absence of sediments due to subaerial exposure in the studied region. The global distribution of the lowstand gives clear evidence for sea-level fluctuations, and intrinsic climate control on sequences in the study area.