Distribution of opal and quartz in surface sediments from the subtropical southeastern Pacific (Table 1)

The opal distribution resembles that of primary productivity in the surface waters, except along the Peruvian and northern Chilean coasts, where dilution reduces opal values. The distribution pattern of quartz represents both eolian and fluvial transport.

Quartz distribution extends out as a tongue in the same direction and position as the prevailing southeast trade winds. Along the South American coast, high quartz concentrations are found in patches near shore and decrease rapidly seaward.