32Si dating of marine sediments from Bangladesh

Appropriate dating tools are essential for paleoenvironmental studies. Cosmogenic Si-32 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 Si-32 to date marine shelf sediments. High detection efficiency, combined with stable background, allows for the detection of extremely low Si-32 specific activities found in such sediments with counting rates below one count per hour. For a sediment core from the Ganges-Brahmaputra delta Si-32 dating yields mean sedimentation rates of 0.7 +/- 0.2 cm/yr for 50 to several hundred years BP and 3.1 +/- 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.