Although calcareous organisms are abundant in temperate waters of the southern California continental borderland, CaCO₃ is a relatively minor constituent of the sediments. Noncarbonate dilution provides only a partial explanation. Estimating rates of particulate CaCo₃ mass transfer to or from that

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water volume in the borderland bounded above by the air-sea interface and below by the sediment-sea interface clarifies the situation.

Carbonate deposition (output) totals approximately 125 × 10¹⁰ g/yr. The major carbonate mineral is Mg-calcite_(<4), with some Mg-calcite_(<4), aragonite, and dolomite. Noncarbonate dilution totals about 800 × 10¹⁰ g/yr.

Other mechanical transfer is primarily river input (15 × 10¹⁰ g/yr) of Mg-calcite_(<4) and some dolomite. Neither aerial nor ocean current transfer affects the budget significantly.

Biologic transfer involves primarily input of CaCO₃. Foraminifera produce about 250 × 10¹⁰ g/yr of Mg-calcite_(>4) and aragonite. Production of 400 (g/m²)/yr by macrobenthos in shallow, hard-bottom areas is comparable to tropical, nonreef production rates.

Chemical transfer involves solution (output) of about 200 × 10¹⁰ g/yr CaCO₃ on basin floors. Apparently all carbonate minerals except dolomite undergo solution.

These input and output estimates balance to within about 10%.

Rivers entering the borderland supply only enough dissolved calcium for 30% of the CaCO₃ deposited.

Of the CaCO₃ input to the borderland, over half dissolves, the remainder is deposited. The CaCO₃ deposition rate is sufficient to extract some dissolved calcium from seawater flowing through the borderland.

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