Fig. 7: Environmental interpretations across Ocean Anoxic Event 2 (OAE2).

Summary figure showing environmental interpretations for the Mentelle Basin, Site U1516, during OAE2. Δ13C interpreted as local increased CO₂ in the surface waters – either as a result of higher atmospheric CO₂ levels or increased upwelling. δ¹³C_(carbonate) and δ¹³C_{(benthic foram)} composite show similar trends prior to OAE2, and during phases A and B. After the low carbonate horizon, there is an offset between the two, possibly caused by a change in the dominance or abundance of different planktic groups. Hg relative to total organic carbon (Hg/TOC) data show sporadic enhanced volcanism prior to OAE2, with the first large Hg/TOC signal occurring at OAE2 onset, corresponding with a negative shift in δ¹³C for both bulk and composite benthic foraminiferal records. Another large spike in Hg/TOC corresponds with the start of enhanced fluvial runoff, demonstrated by K/Al and εNd data³⁷. Productivity is enhanced over OAE2, and remains high during phase C, despite the apparent recovery in δ¹³C_(carbonate). A particularly intense period of productivity over the low carbonate horizon is suggested by high levels of biogenic silica (BSi)⁵².