(super 32) Si dating of marine sediments from Bangladesh.

Abstract

Appropriate dating tools are essential for paleoenvironmental studies. Cosmogenic (super 32) Si with a half-life of about 140 years is ideally suited to cover the dating range 30-1000 years. Here we have applied scintillation spectrometry for detection of natural (super 32) Si to date marine shelf sediments. High detection efficiency, combined with stable background, allows for the detection of extremely low (super 32) Si specific activities found in such sediments with counting rates below one count per hour. For a sediment core from the Ganges-Brahmaputra delta (super 32) Si dating yields mean sedimentation rates of 0.7+ or -0.2 cm/yr for 50 to several hundred years BP and 3.1+ or -0.8 cm/yr for the past 50 years. The four-fold increase of the sedimentation rate over the past 50 years may reflect increased sediment loads in the rivers due to increasing human colonization within the rivers' drainage basins.