Biogenic silica and chert in the Pacific Ocean

Site U1332

“…Pieces of porcellanite contain clay minerals, microcrystalline quartz, opaques, and calcite, as well as biogenic shells and fragments from radiolarians and foraminifers. Sediments from Sites U1331 and U1332 appear to document the silicification process in clay-rich horizons near basement, which will likely extend the findings of Moore (2008).…”

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“…Sites where Eocene sediments were recovered were located within 2° latitude of the paleoequator at the time of first sediment accumulation, so evidence of equatorial upwelling might be expected in the assemblages. The absence of siliceous microfossils is likely a result of dissolution associated with hydrothermal flow of the crust (Moore, 2008a).…”

“…at a scale where orbital forcing can be resolved. Combined with seismic reflection data (Lyle et al, 2006 following in the vein of Mitchell et al (2003) and synthesized with earlier drilling (e.g., Moore et al, 2002Moore et al, , 2004Lyle et al, 2005;Moore, 2008a), we can reconstruct equatorial Pacific history with high confidence and substantially improve upon work from the early stages of DSDP and recent ODP legs.…”

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

“…The interpretation that DSi saturation occurred in bottom waters above chert nodule formation has been questioned (Ritterbush et al, 2015) with Moore's (2008) alternative explanation for chert formation as mobilization of amorphous hydrothermal deposits in deeper sediments, which removes chert nodules as indicators of DSi concentration through time. This brings into question an important tenant by Maliva et al (1989) regarding chert deposition reflecting DSi concentration in the water column.…”