The Cretaceous paleo-ocean has experienced multiple phases of Oceanic Anoxic Events (OAEs), characterized by organic carbon enrichment, geochemical indicator anomalies and fossil assemblage changes. It includes three events, namely OAE 1, OAE 2 and OAE 3.
Click here for original story, Study shows first record of oceanic anoxic event 1b in Jiuquan Basin section
Source: Phys.org