Articles | Volume 13, issue 21
Research article
02 Nov 2016
Research article |  | 02 Nov 2016

Quantifying the Cenozoic marine diatom deposition history: links to the C and Si cycles

Johan Renaudie

Abstract. Marine planktonic diatoms are, today, among the world's main primary producers as well as the main organic carbon exporter to the deep sea despite the fact that they were a very minor component of the plankton at the beginning of the Cenozoic. They are also the main silica exporter to the deep sea, thus balancing global chemical weathering. This study reviews their global Cenozoic depositional pattern in order to understand the modality and the context of their rise to dominance, but also to understand how diatom evolution affected the Cenozoic functioning of the ocean's biological pump. After two short-lived major abundance peaks near the Eocene–Oligocene boundary and in the late Oligocene, diatom abundance in sediments shifted in the middle Miocene to globally higher values which have largely persisted to the modern day. These quantitative findings provide support for the hypothesis according to which diatoms, through their ecological role in the ocean's biological carbon pump, have contributed to the Cenozoic changes in atmospheric carbon dioxide pressure and consequently to changes in the global climate state. Additionally, correlations between diatom abundance peaks and shifts in seawater strontium and osmium isotopic composition hint at a strong control of the silicate weathering on diatom deposition.

Short summary
Marine planktonic diatoms are today both the main silica and carbon exporter to the deep sea. However, 50 million years ago, radiolarians were the main silica exporter and diatoms were a rare, geographically restricted group. Quantification of their rise to dominance suggest that diatom abundance is primarily controlled by the continental weathering and has a negative feedback, observable on a geological timescale, on the carbon cycle.
Final-revised paper