Oceanic anoxic events and plankton evolution: Biotic response to tectonic forcing during the mid‐Cretaceous

Mid‐Cretaceous (Barremian‐Turonian) plankton preserved in deep‐sea marl, organic‐rich shale, and pelagic carbonate hold an important record of how the marine biosphere responded to short‐ and long‐term changes in the ocean‐climate system. Oceanic anoxic events (OAEs) were short‐lived episodes of organic carbon burial that are distinguished by their widespread distribution as discrete beds of black shale and/or pronounced carbon isotopic excursions. OAE1a in the early Aptian (∼120.5 Ma) and OAE2 at the Cenomanian/Turonian boundary (∼93.5 Ma) were global in their distribution and associated with heightened marine productivity. OAE1b spans the Aptian/Albian boundary (∼113–109 Ma) and represents a protracted…