Atmospherically transported volcanic glass in deep-sea sediments: development of a separation and counting technique

Abstract

A new method to separate fine, disseminated volcanic glass from deep-sea sediments and to measure its accumulation rate is described. Separation is by use of heavy liquids with an efficiency that ranges from 45 to 85% with increasing particle size. The size distribution of the bulk sediments and weights of selected volcanic glass size ranges are measured using a Coulter Counter and Cahn Electrobalance. A scanning electron microscope and a high-power transmitted light microscope have been used to estimate the volcanic glass load of the 11- to 1-μm size range. The reproducibility of results from split samples is between 0·10 and 6·5%. The precision is generally higher for those samples containing larger amounts of the fine volcanic glass (36-11 μm). A 6-cm 3 wet sediment volume, with 2-cm vertical extent, representing from 2000 to 6000 years of depositional time, is an ideal sample size for this separation and counting system.