Summary

The U.S. Geological Survey, in cooperation with the Massachusetts Office of Coastal Zone Management, compiled previously published seismic-reflection, bathymetric, acoustic backscatter, and sea-floor sediment sample and photograph data to investigate the surficial and shallow subsurface geology of Vineyard and western Nantucket Sounds. The results are a series of composite geophysical maps with nearly full sea-floor coverage, and detailed interpretive maps of the surficial geology and shallow geologic framework of the sounds. Each of the interpretive maps contributes new insight into the geologic framework and sedimentary environments of the sounds at a resolution that was previously impossible because of a lack of high-resolution geophysical data. The shallow geologic framework and surficial geology is a complex and variable distribution of sediments and geomorphic features that can be primarily attributed to the advances, occupations, and retreats of Wisconsinan glaciation and to reworking and deposition during the Holocene transgression. Glacial, marine, and terrestrial processes have acted on this region since the late Pleistocene, resulting in a complex geologic history and a heterogeneous sea-floor character. Glacial sediments within the entire region are locally overlain by Holocene fluvial, estuarine, and marine sand and mud.