Print this pageA 1-km high-resolution shallow seismic reflection survey was conducted over Sapelo Island, Georgia, to image the shallow stratigraphy of the island.
The principal goal was to test the extent to which features associated with sea-level fluctuations over the past 45 million years are preserved and are resolvable by shallow seismic reflection profiling techniques; specific targets for imaging included the Pleistocene-Holocene contact, and horizons within the Miocene and Oligocene.
A 24-channel acquisition system was used to produce 12-fold CDP coverage. Receivers were single 100-Hz geophones; the source was a 12-gauge "buffalo gun" firing shotgun blanks. Shotpoint and geophone spacings were 4m. A 64-Hz low-cut filter yielded frequencies well above 200-Hz on field records, providing a minimum vertical bed resolution (quarter wavelength criterion) of about 2m.
Preliminary results reveal strong reflection events between 50ms and 200ms on deconvolved sections putting the expected yield of subsurface stratigraphic information to a depth of at least 150m to 200m.
Seismic facies analysis will involve detailed waveform modeling of true relative amplitude CDP stacked sections. Synthetic seismograms will be generated using the reflectivity method which generates all multiples and converted phases.
A final correlation of the CDP stacked sections with previously acquired drill-hole information and single-channel profiles will be made to establish the stratigraphic framework of Sapelo Island and its relationship to neighboring islands.
AAPG Search and Discovery Article #90925©1999 AAPG Foundation Grants-in-Aid