IRIDIUM CONCENTRATION AS AN ESTIMATOR OF INSTANTANEOUS SEDIMENT ACCUMULATION

Ir concentrations and mass accumulation rates from nine deep-sea cores , one from the Atlantic Ocean and eight from the Pacific Ocean, were c ompiled to evaluate a new technique for determining mass accumulation rates, The technique is based on the large difference of the high Ir a bundance in extraterrestrial matter versus the low Ir contents in terr estrial material, Assuming a constant flux of cosmic matter, this diff erence leads to high Ir concentrations in slowly accumulating sediment s, versus low Ir concentration in rapidly accumulating sediments. The method is independent of stratigraphic control, and does not require k nowledge of age of the deposit, We note that Ir concentrations in some slowly accumulating sediments are of the same order of magnitude as s ome of those reported for the Cretaceous-Tertiary boundary event.