Equatorial Pacific productivity and dust flux during the mid-Pleistocene climate transition

We present a helium isotope record for core TT013-114PC from the central equatorial Pacific (140°W, 4°N, 4432 in water depth) spanning a period of 1 million years. We focus on the time interval from 560 to 800 kyr, largely coinciding with the mid-Pleistocene climate transition (MPT) when the dominant period of the Earth's climate variability shifted from 41 kyr to 100 kyr. The terrigenous ⁴He concentrations from our study correlate very well with published titanium concentrations in this core strongly supporting the use of terrigenous ⁴He as a monitor of continental dust. Normalizing titanium and terrigenous ⁴He concentrations to ³He suggests that the dust supply during the MPT was approximately 30% lower compared to the subsequent period (560-100 kyr). The ³He-normalized barium, aluminum and phosphorus concentrations, trace elements with a predominantly biogenic source in these sediments, are relatively constant. This is in contrast to previous studies that reported an apparent rise of titanium-normalized productivity proxies. Rather than a significant increase in productivity during the MPT, we conclude that the dust flux to the central equatorial Pacific was reduced and that the export productivity was approximately constant during this period of climate reorganization.