Erosion of sediment at two sites within the siliceous-clay province of the northeast equatorial Pacific is investigated by examining radionuclide, radiolarian and percent smectite profiles of three cores. A numerical model of the sediment is presented that examines the effect of various particle rain rates, erosion rates and biological mixing parameters on these profiles. 230Th, because of its longer half-life, is a more sensitive tracer of erosion than231Pa. Because the input of these radionuclides into the sediment is not well defined however, conservative tracers, such as the percent smectite of the clay fraction and fossil radiolarians are used to constrain the rate of sediment recycling. Dissolution of radiolarians though can greatly affect the interpretation of the observed biostratigraphy.

The dried, powdered samples (approximately 0.5 g) were dissolved in a mixture of nitric, perchloric and hydrofluoric acids to which 233Pa, 232U, and 238Th spikes were added. The nuclides were precipitated with iron hydroxide, taken up in 8N HCl and further separated.