Productivity and sea-surface temperature changes recorded during the late Eocene–early Oligocene at DSDP Site 511 (South Atlantic)

• Environmental changes are investigated at DSDP Site 511 during the Eocene–Oligocene.
• A progressive but significant sea-surface temperature cooling (8 °C) is recorded.
• A primary productivity increase occurred concomitantly, proving upwelling conditions.
• Results support the influence of Antarctic Circumpolar Current since the EOT.
• Alkenone-based SSTs are reliable as they are consistent with other SST proxies.

This study investigates paleoenvironmental changes during the Eocene–Oligocene transition (EOT) at Deep Sea Drilling Project (DSDP) Site 511 (South Atlantic), as inferred from lipid biomarker (long-chain diols, alkenones) and calcareous nannofossil accumulation rates, as well as changes in sedimentation regime (i.e. relative contributions of total organic carbon-TOC-, calcium carbonate, and biogenic silica). Sea-surface temperatures (SSTs) reconstructed from the alkenone unsaturation index UK′37 indicate a progressive but significant cooling (~ 8 °C) from 34.5 Ma to 33.6 Ma, consistent with estimates derived from other temperature proxies (TEX86; δ18O) at the same site and for the same time interval. This cooling is associated with a marked increase in primary productivity, as indicated by high accumulation rates of biogenic silica, TOC, alkenones, long-chain diols, and calcareous nannofossils. Together, these results are consistent with an enhancement of upwelling conditions favorable to the development of siliceous organisms at DSDP Site 511, possibly induced by the Oi-1 glaciation in Antarctica that occurred during this period.