If present stream discharge and dissolved load are assumed to be representative of the geologic past, and if the volume of the oceans has remained essentially constant, many problems arise concerning the disposal of the constituents brought into the oceans by streams. Two of these problems relate to silica and bicarbonate.

The amount of dissolved silica delivered to the oceans in 10⁹ years, if precipitated chemically or biochemically as SiO₂, would produce a much greater volume of sediment than is observed in the geologic column. The bicarbonate ion transported to the oceans either must be recycled through the atmosphere as CO₂, or removed in calcareous sediments. Yet the precipitation of carbonate minerals, with concomitant loss of CO₂ to the atmosphere, leaves about 40 per cent of the HCO₃- unaccounted for.

These two problems can be solved by assuming that a small but significant fraction of the suspended load of streams consists of weathered aluminosilicates, probably poorly crystalline, that react with silica and bicarbonate prior to deposition, by reactions of the type: Al-silicate + SiO₂ + HCO₃^- + cations = cation-Al-silicate + CO₂ + H₂O.

Reactions of this type can be considered "reverse weathering," and are representative of chemical changes commonly considered to take place after deposition.

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