Three-component (P, SH, and SV) expanding spread profiles (ESP), common-midpoint profiles, and sparse three-dimensional P wave data were collected over an unusually strong midcrustal reflector, the Surrency Bright Spot (SBS), in southeastern Georgia. Shear wave reflections from the SBS at 10.9 s (16 km depth), and possibly from the lower crust at 18.3 s (29 km depth), were recorded but required substantial source effort (stacking) and were too weak for reliable reflectivity measurements. Reflections on the ESPs delineate a 1.5-km-thick Atlantic Coastal Plain section whose seismic properties (Vp=2.53 km/s, Vs=1.51 km/s, Vp/Vs=1.67) are consistent with quartz-rich sandstones and siltstones, sitting atop a 15-km-thick upper crust (Vp=6.38 km/s, Vs=3.25 km/s, Vp/Vs=1.96), which in turn overlies a 15 km-thick lower crust of slower material (Vp=6.02 km/s, Vs≈3.26 km/s, Vp/Vs≈1.84). The velocity inversion may result from underthrusting of upper crustal rocks during suturing of Florida to North America. Amplitude-versus-offset analyses, combined with an earlier reflection polarity test and waveform modeling, indicate that the SBS originates from a thin (~80--120 m), high-impedance layer, most likely a mafic dike or tectonically emplaced ultramafic body. ¿ American Geophysical Union 1993