Seismic reflection and magnetic measurements made over the last ten years in Long Island Sound have been combined with earlier seismic refraction data and with geological data on the surrounding land to provide details of the Pleistocene history of the area.
Long Island Sound is at present shallow and the bottom is of low relief. Reflection data indicate the presence of relief on the order of many hundreds of feet beneath the bottom. The combined geophysical data indicate that the relief is in the primarily Cretaceous cover over the basement in the Sound and is related to the Pleistocene glaciation of the area. This conclusion is supported by correlations with surface geology and physiography and with data from boreholes.
The magnetic measurements can be interpreted to support the suggestion of Sanders (1963) that the Triassic of Connecticut extends beneath the Sound at least as far as the north shore of Long Island.