Three example seismic profiles near Drayton Island show several different types of geologic characterization present within the St. Johns River Valley. Karst development in the underlying limestone is accompanied by fluvial-type incised channels, occupying areas of subsidence caused by the loss of material at depth. Profile A-A’ shows relatively mature karst development in the limestone, represented by the red dashed line at 30 to 45 m (92 to 148 ft). Gamma log profiles from four wells surrounding the northern portion of Lake George (P-0410, V-0346, M-0149 and M-0021; Index Map D) show a highly fluctuating upper contact to the Ocala Limestone. Depths to limestone range from greater than -61 m (-200 ft) below sea level southwest of Drayton Island, to -30 m (-100 ft) to the west, to -15 m (-50 ft) at the lake’s eastern shoreline. The variability and range are consistent with the contact represented by the red dashed line on profiles A-A’ and B-B’. In profile A-A’, a fluvially-incised channel (light brown line) appears to reside over one of the more pronounced depressions in the karst surface. Multiple incisions appear within the channel (orange line) with fill (purple lines). Channel development was apparently terminated and a planing surface (green line) is overlain by a more recent depositional event (solid red lines). This sequence can be correlated to spikes in the gamma counts at -12 m (-40 ft) below sea level (P-0410, V-0346 and M-0149), suggesting a fluvial source, possibly a Pleistocene flooding surface and estuarine deposition, as seen elsewhere within the St. John’s Offset (Brooks and Merrit, 1981). These low-angle reflections are also truncated (dark blue line) and what appear to be recent, riverine deposits occupy the nearsurface of the profile. On the right side of the profile there appears to be another drop in the limestone surface which is also occupied by a channel incision (green lines), but most of this feature is obscured by noise in the seismic record.