Uranium isotope evidence for two episodes of deoxygenation during Oceanic Anoxic Event 2

Significance Past “Oceanic Anoxic Events” (OAEs) represent important carbon cycle perturbations that offer the opportunity to study Earth’s response to extreme climate warming. A fundamental limitation for understanding OAEs is quantifying the timing and total extent of ocean anoxia. We present a quantitative account of global redox conditions for OAE 2 (∼94 million years ago), using a high-resolution record of uranium isotopes combined with a...