Magnetic Detection of the Emanuel Point Shipwrecks, Pensacola, Florida, United States

This study presents the results, interpretations and recommendations of close-order magnetometer surveys of the early Spanish Emanuel Point (EP) shipwrecks in Pensacola, Florida. The vessels were a part of the Tristán de Luna expedition and wrecked during a hurricane in 1559. These wrecks were likely salvaged to some extent, and taphonomic processes have reduced their concentrations of iron. When compared with the magnetic anomalies associated with other colonial shipwrecks, the EP shipwrecks have low intensities and extents and exhibit distinct morphologies. Because of these unique characteristics, existing guidelines and recommendations for locating shipwrecks with magnetometers are problematic. Based on the observed data, we present new recommendations for reconnaissance surveys with the intent of locating similar shipwrecks or when similar shipwrecks might be encountered. These recommendations include survey lane spacing of 10 m or less, maintaining the sensor at low altitudes and including multicomponent anomalies in selection criteria for visual identification. Although this study focuses on investigations in North America, it has broader implications for shipwreck reconnaissance around the world.