Holocene accumulation rates of calcite in the Panama Basin: Lateral and vertical variations in calcite dissolution

Abstract

Study of calcite accumulation rates in the Holocene section of 28 sediment cores from the Panama Basin region, eastern equatorial Pacific, suggests that calcite accumulation is controlled primarily by lateral and vertical variations in dissolution rates. Low accumulation rates within the central western trough and within 250 km of the continental shelf suggest, respectively, the effects of low calcite supply from surface water and enhanced dissolution due to oxidation of an increased flux of organic matter from the surface water. Elsewhere calcite accumulation rates decrease linearly with depth according to a gradient of 3.3 g/cm 2/1000 yrs/km. ΔpH calculations using hydrographic data from a station in the basin indicate that the seawater below 200 m is undersaturated with respect to calcite and that the hydrographic lysocline (Morse and Berner, 1972) occurs between 300 and 1900 m. The pattern of accumulation below the high-productivity regions can be explained by the lysocline model of calcite dissolution. Linear extrapolation of the inferred dissolution curve to the surface yields an average annual surface input of 50–110 g calcite/m 2.