Magnetic and seismic surveys were carried out in the Blake—Bahama Basin. The magnetic survey delineates low-amplitude anomalies in the Jurassic quiet zone that can be correlated with anomalies found elsewhere in the western North Atlantic (M26, M27 and M28). A spreading rate of 2.25 cm/yr was derived from anomalies M22 through M25 and extrapolated into the Jurassic, giving a Callovian age for M26 and M27 and Bathonian for M28 (150, 154 and 159 m.y., respectively). The seismic survey traces the major sedimentary horizons and basement in the vicinity of DSDP site 391. Sonobuoy data were used to convert reflection time to depth for correlation with the drilling results. A deep reflector not penetrated at site 391 is designated as horizon D. Basement at site 391 lies 1800 m subbottom, just within reach of the drill. Extrapolation of the sedimentation rate estimated for the lower 400 m of the drill hole yielded age estimates of 156 m.y. for horizon D and 160 m.y. for basement.