Sand from the southern New England shelf is a mixture of three sand types, each characterized by quartz grains with distinctive morphologies. The first sand type consists of well-rounded and equant grains derived from Tertiary and Cretaceous coastal plain strata which have been smoothed and rounded by chemical and mechanical processes; sands of this type are found in significant quantifies in both the relict fluvial sediment of the middle and outer shelf and in the Recent sediment of Rhode Island Sound, but not in the glacial sediment of the inner and middle shelf. The second sand type consists of highly angular and elongate grains which were transported to the area by glaciers and subsequently reworked in subaqueous environments; this sand type is found in abundance in the relict glacial moraine and outwash plain sediment of the inner shelf and in the palimpsest sediment of the middle shelf to the west of the relict glacial deposits, but is not generally found in appreciable quantities in the relict fluvial sediment of the middle and outer shelf except in the westernmost part of the study area. A third sand type, heretofore unrecognized in these strata, consists of grains derived from sedimentary rocks exposed in late Paleozoic and Mesozoic basins of southern New England. This sand type is found in appreciable quantities in both relict and Recent fluvial sediment on the entire shelf and in the relict glacial sediment of the inner shelf, indicating that the glacial sediment also was derived from the southern New England area. The patterns of distribution of these three sand types reflect the paleogeography of the shelf during the late Pleistocene; the resolution of well-defined paleogeographic features by a morphological study of surficial sediment indicates that throughout most of the study area, modern sediment transport processes acting on the shelf have not yet destroyed the provenance record imprinted upon the shelf during the late Pleistocene.