New advances in the stratigraphy of Aptian oceanic anoxic events (Castro Urdiales, Basque-Cantabrian Basin, Spain)

• Published in: Cretaceous Research
• Main Authors: Fernández Mendiola, Pedro Ángel, Pérez Malo, Joanaitz, Owen, Hugh G., García Mondéjar, Joaquín
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 2023
• Subjects: black shale; Aptian; oceanic anoxic events; volcanism; Basque-Cantabrian basin; North Atlantic
• Online Access: http://hdl.handle.net/10810/60292; https://doi.org/10.1016/j.cretres.2022.105430

The Aptian sedimentary deposits of the Castro Urdiales area in north Spain record an episode of disoxia/anoxia which postdates Oceanic Anoxic Event 1a (OAE 1a). Carbonate platform and overlying facies are analysed for stratigraphy, sedimentology, total organic carbon and carbon isotopes. Lower Aptian shallow-water limestones are covered by deeper-water marlstones and organic-carbon-rich black lutites of lower to upper Aptian, ranging from Dufrenoyia furcata Zone to Cheloniceras (Epicheloniceras) martinioides Zone. Biostratigraphy and chemostratigraphic calibration are based on ammonites, carbon isotopes and total organic carbon analyses, revealing consistency with the global Aptian reference framework. The Castro Urdiales black-shale levels of the lower to upper Aptian transition together with their encasing series are correlated with other Aptian sections of the Basque-Cantabrian Basin (northern Spain) and southeastern France. The Castro Urdiales black shales are correlated with the Aparein Level of the eastern Basque-Cantabrian Basin. Prior to this oxygen deficient episode, glauconite-and-ostreid facies were also deposited under oxic conditions during the Gutiolo volcanic event of the Basque-Cantabrian Basin. This volcanism correlates in part with the Cretaceous superplume eruptions of Ontong Java, Manihiki Plateaus and the North Atlantic opening as a result of increasing seafloor spreading rates. This study is a contribution to the Basque Government Research Project IT-930-16 and the Research Group IT-1602-22 of the Basque University System. This investigation has also been supported by the University of the Basque Country (UPV/EHU) under grant number PIF18/105.