The basement structure and acoustic stratigraphy of Jurassic sedimentary rocks within the western Atlantic Jurassic magnetic quiet zone north of lat. 31°N have been examined in multichannel and single-channel seismic reflection profiles. East of the Blake Spur magnetic anomaly, the basement relief is dominated by northwest-trending ridges and troughs associated with fracture zones. The only prominent basement features paralleling the magnetic lineations generated by seafloor spreading are west of the Blake Spur magnetic anomaly. A large scarp, downdropped to the west, is parallel with and just west of the Blake Spur magnetic anomaly. Both the scarp and the Blake Spur magnetic anomaly are present only south of lat. 36°N. Three flat-lying conformably acoustic hori ons have been identified within the Jurassic sedimentary rocks below horizon ß. The uppermost horizon, J₁, onlaps oceanic basement in the vicinity of magnetic anomaly M-23 (age 142 m.y.). The next lower horizon, J₂, is west of and terminates against the scarp associated with the Blake Spur magnetic anomaly (inferred age 165 m.y.). The lowest horizon, J₃, extends from the East Coast magnetic anomaly halfway to the Blake Spur anomaly. Sedimentation rates for the sedimentary units below these three horizons are estimated at 18 m/m.y. between horizons J₁ and J₂, and greater than 300 m/m.y. for the units below horizon J₂.