Mapping Buried Metallic Objects And Titaniferous Placers In The Mississippi Sound, Gulf Of Mexico

Recent experiments with a marine induced polarization (IP) streamer system have shown<br>that it can find and map titaniferous placers on and beneath the sea floor (Wynn and Laurent,<br>1998) and facies changes in the substrate beneath sandy shoals (Wymr and others, 1998). Close<br>examination of profile data acquired in the Mississippi Sound, however, shows that the system<br>can also detect certain conductive, polarizing objects that are buried beneath the sea floor and not<br>discernible with conventional bathymetry. The streamer system is designed to detect<br>polarizeable materials down to at least 6 meters below the sediment-water interface. The recent<br>data show broad phase-shift (IP) anomalies along the east side of Cat Island, off the coast of<br>Biloxi. MS. Dark, titaniferous sands can be seen in dissected benches and berms on the island’s<br>coastline, reinforcing the conclusion that the IP system is mapping the ilmenite-rich (FeTiO,)<br>sediments reported in shoals there (Foxworth, 1962). Interspersed in these data, however, are<br>several narrow electrical anomalies of two kinds: resistivity, and resistivity-IP anomalies. Both<br>kinds show pronounced drops in the already-low resistivity, and several of these also have<br>coincident phase-shift anomalies. The polarizing objects observed are -10 to 20 meters across,<br>but the IP anomalies can be seen - 20 to 40 meters laterally from their centers. The sources of<br>these anomalies are probably man-made in origin, buried under a veneer of modern sediments.<br>We speculate that these are shipwrecks, sunken buoys or parts thereof, lost and later buried (in<br>water now about 3 meters deep) by Hurricane Camille, which passed through the area in 1969.<br>We cannot, however, preclude emplacement and burial at an earlier time.