Secular Distribution of Biogenic Silica through the Phanerozoic: Comparison of Silica‐Replaced Fossils and Bedded Cherts at the Series Level

Biosilicification Drives a Decline of Dissolved Si in the Oceans through Geologic Time

“…In a systematic review of the literature Schubert et al (1997) determined that a large bias exists in the early literature because poorly preserved specimens have been neglected as taxonomists required well-preserved material to do their work, skewing microfossil-based attempts at reconstructing the Si cycle. Kidder and Erwin (2001) made qualitative estimates of the relative importance of Si burial through the Phanerozoic and assumed that plankton would be more effective than benthic sponges at removing DSi from the ocean. They hypothesized that once radiolarians arrived on the scene, their relative contribution to BSi production quickly dwarfed that of siliceous sponges.…”

“…They further hypothesized that diatoms have dominated the ocean Si cycle since the late Jurassic ( Figure 1B). But in truth, the extent to which these putative changes in sponge and radiolarian abundance/distribution changed oceanic DSi concentrations (Schubert et al, 1997;Racki and Cordey, 2000;Kidder and Erwin, 2001), and the extent to which they were themselves influenced by reduced DSi availability are not really known.…”

“…A key issue to resolve is the extent to which global average river inputs of DSi could have changed due to plant-stimulated weathering (Moulton and Berner, 1988) for a given atmospheric concentration of pCO 2 . Although the enhancement of silicate weathering by plants is expected to transiently increase the supply of DSi to the oceans, available data do not show an increase in numbers of chert deposits with the rise of plants (Kidder and Erwin, 2001). What has not been previously considered in the effect of plants on weathering, is the evolution of plants that accumulate phytolith BSi (Hodson et al, 2005), also allowing for more BSi accumulation on the continents (Struyf and Conley, 2012).…”

“…Although Kidder and Erwin (2001) argued that there were large-scale changes in radiolarian and sponge abundances during the Paleozoic (Figure 1B), Siever (1991) suggested that the geologic record does not support the occurrence of widespread siliceous sediments and thus did not affect DSi in the global oceans ( Figure 1A). More importantly, Maliva et al (1989) argue that nodular chert formation predominated in the Paleozoic and was the result of DSi diffusion into sediments from the essentially infinite reservoir in the overlying water because there was insufficient biogenic precipitation.…”

“…From Schneider and Boston (1991) by permission of The MIT Press. (B) Qualitative interpretation of the relative role of the importance of radiolarians, sponges and diatoms present in the fossil record though geologic time (Redrawn from Kidder and Erwin, 2001). Reproduced with permission ©2001, The University of Chicago Press.…”