Project Details
Projekt
Diatoms, radiolarians and the Cenozoic Silicon and Carbon cycles
Applicant
Dr. Johan Renaudie
Subject Area
Palaeontology
Oceanography
Oceanography
Term
from 2015 to 2018
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 279867559
Modern marine planktonic diatoms have, as silicon biomineralizers and primary producers, a significant impact on both the Silicon and the Carbon cycle: there are at the same time the main silica and carbon exporter to the deep-sea. However, at the beginning of the Eocene, radiolarians were the main silica exporter and diatoms were only a rare, geographically-constrained group. Prior studies have highlighted two main events in the Cenozoic history of diatoms and radiolarians. The first one near the Eocene-Oligocene boundary is a diatom diversity and abundance peak during which they took over radiolarians for control of the marine silicon cycle. The second one occurred during the Middle Miocene and witnessed a complete spatial reorganization of the biogenic opal deposition pattern as well as a sustained rise in diatom diversity and abundance. Both events are coeval with known shifts in atmospheric pCO2 as well as shifts in strontium and osmium isotopes (indicative of changes in the silica weathering pattern). In this new project, I propose to measure siliceous microfossils absolute abundance on a variety of DSDP-ODP-IODP sites spanning the last 55 Myr and covering the different geographical zones highlighted in a pilot study on Cenozoic diatom deposition patterns. With these timeseries in hand, I intend to disentangle the causal relationships between diatoms and Cenozoic climate shifts, as well as to determine what made diatoms outcompete radiolarians and how diatom biogeography changed so drastically during the Cenozoic. Finally, biogenic opal being the only output of the marine silicon cycle and weathering its main input, I will be able to estimate from the measured time-series a global biogenic opal accumulation rate and, consequently, estimate the Cenozoic history of silica weathering intensity.
DFG Programme
Infrastructure Priority Programmes
