Significantly large concentrations of suspended matter, especially calcites, are found at some locations in the Deep Pacific, particularly at the depth of the Pacific Benthic Thermocline. These particle-rich layers cannot be explained by simple classical settling processes nor by resuspension of the underlying sediment. A theoretical approach based on these data, on the hydrodynamic characteristics of the regional circulation and on some known physical and chemical parameters, leads us to postulate two possible mechanisms: the settling of large particles from surface waters and their preferential disaggregation at some specific depth, particularly at the Pacific Benthic Thermocline depth; or alternatively, the resuspension at those depths of old calcareous sediments from the flanks of East Pacific Rise associated with a horizontal advective diffusive transport mechanism. New chemical and electron-microscope analyses of GEOSECS samples give rise to the conclusion that the resuspension mechanism is the most probable. A simple model based on this mechanism, using our calcite concentrations at the PBT depth implies that the calcium carbonate flux arising from this source ranges between 5 × 106 and 5 × 108 tons per year. The erosion intensity and the quantity of calcium carbonate contained by the rises or the seamounts, must be large enough to maintain this flux. Those two constraints have been successfully tested.