Geochemistry and δ¹⁸O G.ruber records of sediment cores MP50PC, MP39PC and MP37PC

During sapropel formation, enhanced levels of primary productivity occurred in the surface waters and oxygen-depleted conditions in the bottom-waters for all sites. Conditions for sediment and bottom-water below ~1.4km water depth were sulphidic throughout S1, but for intermediate depth (775m) were anoxic only during the first part (S1a). Bottom-water oxygenation interrupted S1 formation at water depths down to ~1.4km, during two brief episodes, at 8.2 and 7.4 cal.ka BP.

From the 7.4 cal.ka BP ventilation onward, the transition to more oxygenated bottom-water conditions was more progressive for the intermediate water depth site (775m) than for the deeper sites. Conditions remained fully oxic for all water depths following the S1-MarkerBed ventilation event. Possibly the onset of continuously oxic conditions started slightly earlier at intermediate depth (775m; 6.6±0.3 cal.ka BP) than at greater depths (1358m, 1908m; 6.0±0.3 cal.ka BP).