ABSTRACT

The transfer of particulate CaCO₃ to or from the water mass of the Southern California Continental Borderland can be described by means of a budget. The sum of mechanical plus biological plus chemical transfer must equal zero if the system is one of steady state.

Deposition of CaCO₂ on the basin floors, on the slopes, and on the shelf totals 125 10¹⁰ g/yr. River supply of particulate CaCO₂ totals 16 10¹⁰ g/yr. No other mechanical transfer processes are quantitatively significant.

Biological production of CaCO₃ includes approximately 40 10¹⁰ g/yr by macrobenthos of the shallow rocky shelf, 34 10¹⁰ g/yr by other macrobenthos, 247 10¹⁰ g/yr by planktonic plus benthic foraminifera, and 25 10¹⁰ g/yr by other organisms.

Chemical transfer includes solution of 200 10¹⁰ g/yr CaCO₃. The CaCO₃ transfer terms sum to zero, within the limits of error.

The carbonate minerals present include Mg-calcite_(<0.04), Mg-calcite_(>0.04), aragonite, and dolomite. All carbonate minerals other than dolomite show evidence of solution. Most of the Ca deposited in Borderland sediment is derived from ocean waters flowing through the Borderland rather than from river water input.

Water associated with the O₂ minimum is important in dissolving particulate CaCO₃. The shallow water precipitation and intermediate water solution may be an important process of dissolved Ca relocation from one water mass to another.