An Assessment of xsBa Flux as a Paleoproductivity Indicator and Its Water‐Depth Dependence in the Easternmost Equatorial Pacific Ocean

Abstract

We present the first regional-scale records of biogenic Barium (xsBa) fluxes in the Panama basin of the eastern-equatorial margin of the Pacific Ocean in order to assess xsBa as a paleoproductivity proxy. Measurements of xsBa from 13 cores that range in water depths from about 700 to 3,000 m show an increase in 230 Th-normalized xsBa mass accumulation rates (MARs) with increasing water depth during both marine oxygen isotope stages (MIS) 1 and 2. The correlation of xsBa MARs with depth are strong despite differences in bulk sediment MARs and differing degrees of sediment redistribution. We interpret the increasing xsBa with water depth as likely due to the continued decomposition and remineralization of falling and/or resuspended biogenic particles. xsBa does not seem to be affected by diagenetic sulfate reduction in most of the cores. Calculated estimates of xsBa preservation in the sediment pile are high and fluctuate between 45% and 52% throughout the last 25 kyr. Although xsBa fluxes can be a robust indicator of paleoproductivity, caution is needed if (a) there is evidence of sulfate reduction in sediments being analyzed, and (b) one is trying to quantify differences in paleoproductivity among sites that are located at different depths in the water column.

Bentho‐Pelagic Decoupling: The Marine Biological Carbon Pump During Eocene Hyperthermals

“…In other words, barite accumulation might be impacted by the transfer efficiency, or the fraction of carbon exported from the base of the photic zone that is exported further down, out of the mesopelagic zone at its base. If the amount of marine pelagic barite forming in decaying organic matter, and the accumulation of marine pelagic barite in deep‐sea sediment, increases with increased rates of remineralization or microbial respiration in the water column below the photic zone (see e.g., Singh et al., 2020), then barite accumulation might represent the “sequestration flux” of organic carbon in the oceans rather than the “export flux” (Figure 1).…”