Diagenetic behavior of barite in a coastal upwelling setting

Multiproxy data from ODP Hole 1017E (Point Conception, California) provide an excellent opportunity to examine the behavior of barium, within a well‐characterized sedimentary system. Barium excess is generally considered to be a productivity proxy; however, in nearshore environments, Ba excess records can be compromised by both sediment provenance and barite remobilization. For the last 60 kyr, ODP Hole 1017E exhibits significant changes both in primary productivity driven by coastal upwelling and in the sediment redox chemistry of underlying sediments. Significant barite enrichment occurs at an active diagenetic front that marks the boundary between sulfate‐rich and sulfate‐poor pore waters. This boundary also intersects a sediment facies change from deposition of relatively coarse‐grained sediment before 35 ka to an interval of fine‐grained, organic‐rich sediment after (i.e., Interstadial Event 8). Changes in diffusion rates associated with the sediment facies change cause a strong but misleading correlation between a mobile zone of barite enrichment and rapid climate change. Thus, within the Ba excess record at ODP Hole 1017E is a history of redox chemistry that has corrupted the paleoproductivity record of Ba biogenic .