Biogenic sedimentation in the equatorial Pacific: Carbon cycling and paleoproduction, 12–24 Ma Academic Article uri icon

abstract

  • The equatorial Pacific is an important part of the global carbon cycle and has been affected by climate change through the Cenozoic (65Ma to present). We present a Miocene (12-24Ma) biogenic sediment record from Deep Sea Drilling Project (DSDP) Site 574 and show that a CaCO3 minimum at 17Ma was caused by elevated CaCO3 dissolution. When Pacific Plate motion carried Site 574 under the equator at about 16.2Ma, there is a minor increase in biogenic deposition associated with passing under the equatorial upwelling zone. The burial rates of the primary productivity proxies biogenic silica (bio-SiO2) and biogenic barium (bio-Ba) increase, but biogenic CaCO3 decreases. The carbonate minimum is at∼17Ma coincident with the beginning of the Miocene climate optimum; the transient lasts from 18 to 15Ma. Bio-SiO2 and bio-Ba are positively correlated and increase as the equator was approached. Corg is poorly preserved, and is strongly affected by changing carbonate burial. Terrestrial 232Th deposition, a proxy for aeolian dust, increases only after the Site 574 equator crossing. Since surface production of bio-SiO2, bio-Ba, and CaCO3 correlate in the modern equatorial Pacific, the decreased CaCO3 burial rate during the Site 574 equator crossing is driven by elevated CaCO 3 dissolution, representing elevated ocean carbon storage and elevated atmospheric CO2. The length of the 17Ma CaCO3 dissolution transient requires interaction with a slow part of the carbon cycle, perhaps elevated mantle degassing associated with the early stages of Columbia River Basalt emplacement. © 2012 by the American Geophysical Union.

author list (cited authors)

  • Piela, C., Lyle, M., Marcantonio, F., Baldauf, J., & Lyle, A. O.

citation count

  • 13

publication date

  • April 2012