. The Earth beneath the sea : History . 5 10 15 m mole/I. Interstitially dissolved SiOo —> Fig. 21. Monosilicate in interstitial solution at various depths of the core Capricorn 38 BP, South Pacific. The interstitial solution was separated from the sediment by adding a known mass of fresh sediment (with separately determined water content) to a measured volume of filtered sea-water with a low and known silica content. After dispersion, the suspension was centrifuged, and an aliquot of the supernatant liquid was passed through a membrane filter and analyzed colorimetrically. (From Arrhenius
. The Earth beneath the sea : History . 5 10 15 m mole/I. Interstitially dissolved SiOo —> Fig. 21. Monosilicate in interstitial solution at various depths of the core Capricorn 38 BP, South Pacific. The interstitial solution was separated from the sediment by adding a known mass of fresh sediment (with separately determined water content) to a measured volume of filtered sea-water with a low and known silica content. After dispersion, the suspension was centrifuged, and an aliquot of the supernatant liquid was passed through a membrane filter and analyzed colorimetrically. (From Arrhenius and Rotschi, 1953.) continents (cf. Fig. 1). The instability of silica in the interstitial water of the sediment causes continuous dissolution of the siliceous fossils after deposition; the silicoflagellates disappear first, followed by diatoms, then radiolarians, and finally even the robust sponge spicules. Part of the dissolved silica reacts to form authigenic aluminosilicates observed as overgrowths in partly dissolved siliceous skeletons (see below). In some cases reprecipitation of the silica as opal takes place, resulting in thin flakes of this mineral along the bedding planes in phosphorite, or in laminae of chert, observed to occiu' at depth in pelagic
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