Mineralogy of the silt fraction in surficial sediments from the outer continental shelf off southeastern New England

The silt-sized heavy mineral assemblage, which is predominantly detrital, has been concentrated in this fraction by hydraulic factors and ranges between 11.8 wt. % of the silt fraction in the sandy sediments near Georges Bank to 3.4% in the clayey silt deposit south of Martha's Vineyard. By contrast, the sand fraction averages only 1.5% heavy minerals. Lateral variability within the silt-sized heavy mineral assemblage is considerable. Zircon and ilmenite abundances progressively decrease from east to west on the continental shelf off southeastern New England. Conversely, abundances within the amphibole and the epidote groups increase from east to west.