The youngest period of volcanism at the lower Nicaraguan Rise/Hess Escarpment in the vicinity of Sites 1001 and 152 occurred at about 81 Ma. The basalts are tholeiitic and generally similar to MORB in composition, although the comparatively low incompatible element concentrations (at the same MgO concentrations) in the Site 1001 glass may signify derivation from either a more depleted mantle source or higher degrees of partial melting. The volcanism at this site is part of the continuing widespread submarine volcanism in the region that postdates the initial 90-Ma eruptions of the Caribbean oceanic plateau.