Palaeoceanographic significance of the Tethyan 'Livello Selli' (Early Aptian) from the Hybla Formation, northwestern Sicily: biostratigraphy and high-resolution chemostratigraphic records

High-resolution micropalaeontological and chemostratigraphic records for the Hauterivian-Aptian succession outcropping at Calabianca (NW Sicily) provide new insight into the palaeoclimatic and palaeoceanographic evolution of the Tethys Ocean. Calcareous nannofossil and planktonic foraminiferal biostratigraphy together with delta(13)C chemostratigraphy allowed the identification of a hiatus in the Barremian and a major one including most of the Upper Aptian, the entire Lower Albian and part of the Middle Albian. The Livello Selli equivalent was identified on the basis of lithology and well constrained by calcareous plankton biostratigraphy as well as by the delta(13)C curve. The multi-proxy record from the Calabianca section is consistent with previous documentation of Tethyan sections, and others worldwide. Early Aptian global events, such as black shale deposition, nannoconid crisis, C isotopic negative spike and positive excursion associated with the OAE1a, increase in abundance of leupoldinids and clavate hedbergellids are superimposed on local/regional events, being strictly related to climate changes and increased runoff. Based on micropalaeontological results and geochemical proxies (Ba, P, V, Ni), the Livello Selli equivalent is interpreted as a high-productivity event associated with variable but overall anoxic/dysoxic conditions in the lower water column. The onset of new physical, chemical and biological conditions in the oceans and of the mid-Cretaceous greenhouse climate are interpreted as consequences of the superplume episode. (C) 2002 Elsevier Science B.V. All rights reserved.