A study of two mid-crustal bright spots from southeast Georgia (USA)

Two high-amplitude reflections, or "bright spots', occur on COCORP line Georgia 16 at a record time of 5.9s, corresponding to nearly 16km depth. The first is the "Surrency Bright Spot' (SBS), an exceptionally bright antiformal reflection, and the second is the "Reedy Creek Reflection' (RCR), which lies 5km to the south and resembles the south half of a diffraction. The RCR is also imaged on a crossline, Georgia 18, as a relatively symmetric antiformal reflection. These reflections coincide with the Brunswick magnetic anomaly, thought to mark the late Palaeozoic Alleghanian suture. These results, combined with recent evidence that the SBS is a reflection from a high-velocity thin layer, suggest that the SBS and the RCR might be reflections from ultramafic slices emplaced within the Alleghanian suture zone during collision or from mafic sheets intruded into the suture zone during subsequent rifting. -from Authors