PREFERENTIAL DIFFUSION OF CL-35 RELATIVE TO CL-37 IN SEDIMENTS OF KAUBAY, HALMAHERA, INDONESIA

Kau Bay, a 470-m-deep basin, is separated from the Pacific Ocean by a shallow, 40-m-deep sill. During the last glaciation this sill was abov e sea level, and the bay turned into a freshwater lake. After glaciati on, the sea level rose and the bay turned saline again. Since then, ch loride from the newly formed saline sediments diffused into the freshw ater sediments. As the sedimentation rate was constant throughout the Holocene it is relatively easy to model the chloride concentration in the sediment pore water. The diffusion coefficient of Cl-35 is slightl y higher than the diffusion coefficient of Cl-37, thus variations in d eltaCl-37 were expected in the pore water. Because the pore-water hist ory of Kau Bay is well known it was possible to use deltaCl-37 variati ons to determine the diffusion coefficient ratio (D35/D37) for the two stable isotopes of chlorine. It was found that this ratio is 1.0023 i n the pore water from sediments in this bay.