The Aptian sedimentary deposits of the Castro Urdiales area in north Spain record an episode disoxia/anoxia which postdates Oceanic Anoxic Event 1a (OAE 1a). Carbonate platform and overlying facies are analysed for stratigraphy, sedimentology, total organic carbon isotopes. Lower shallow-water limestones covered by deeper-water marlstones organic-carbon-rich black lutites lower to upper Aptian,...