Analyses of slant stacks of synthetic record sections generated from velocity models for ophiolites by the reflectivity method show that even 90-km-long refraction lines having a 10-Hz source and a 1-km intertrace spacing barely distinguish between fine-scale crustal structures which are of current interest. Such data are sufficient, however, to distinguish between yound and old oceanic crust. Tripling the spatial sampling period degrades the quality of the synthetic slant stacks for this temporal frequency content. A major implication of the study is that most currently available field data, being sparser and poorer in quality (due to both noise and instrument responses), offer little hope of resolving thin low-velocity layers or small changes in velocity gradients by using newly proposed inversion techniques based on slant stacking. Last, a simple, first-order correction to a downward continuation algorithm, namely, the inclusion of the phase shift caused by postcritical reflection at each ray parameter, is proposed.