A Cretaceous-Tertiary boundary (K/T) section with a 6-cm-thick spherule layer with shocked minerals and elevated iridium values was recovered in November 1996 in the Bass River Borehole (New Jersey Coastal Plain Drilling Project, ODP Leg 174AX). Above the spherule layer small clay clasts, containing calcite-replaced tectites and Cretaceous foraminifera and dinoflagellates, occur in the lower 10 cm of the Danian. This interval of clay clasts is a marker for the K/T in outcrops and other boreholes where a spherule layer is absent. The clasts are interpreted as ripups that were transported by tsunami activity shoreward from a deeper part of the Maastrichtian sea floor. Evidence from the New Jersey shelf is consistent with a major tsunami at the K/T boundary. Olsson and Wise (1987) showed that a long hiatus with missing Maastrichtian and upper Campanian strata was encountered in exploration and stratigraphic test wells in the Baltimore Canyon Trough beneath the New Jersey continental margin. DSDP Site 605 located east of the Baltimore Canyon Trough at the foot of the New Jersey continental slope terminated in the upper Maastrichtian (Abathomphalus mayaroensis Zone) indicating that the hiatus is confined to the outer continental shelf and upper slope. The area of the hiatus encompasses at least 30,000 square kilometers of the Maastrichtian outer continental shelf and upper slope and may represent a giant slump scar. A tsunami triggered by seismic shaking from the Chicxulub impact at this area would have reached the New Jersey Coastal Plain in less than 1/2 hour. Surface seismic waves generated from the K/T impact at Chicxulub, Yucatan would have arrived in a little less than 10 minutes, about the time of the arrival of the ejecta-vapor cloud. The fact that the Bass River clay clasts contain replaced tectites indicates that the tsunami took place after deposition of the tectites and that the two events closely followed one another.