Figure F20. (A) Methane, ethane, and propane concentrations (ppmv) and (B) C₁/C₂ ratio vs. depth as obtained by the headspace technique, analyzed by the GC3 (FID 1) for Hole 1148A. Solid vertical bar = interval of ethylene presence, open square = depth interval and approximate concentration of C₄ and C₅, FID = flame ionization detector.