A Geophysical Investigation Of A Sugar Cane Plantation, St. Croix, U.S. Virgin Islands: Using Multiple Techniques To Assess A Complex Industrial Site

An archaeological geophysical investigation was conducted at Estate Whim Plantation Museum<br>(Whim) February 25 to March 5, 1999. Whim is the only preserved and publicly open site<br>on St. Croix that offers a guided interpretation of lifeways and processes associated with the island’s<br>historical role in the sugar trade from the 1 sth to the early 20th centuries. During its operation<br>Whim was not only a plantation, but also housed a factory for on-site cane processing. The plantation<br>and factory were worked by slaves until 1848. While many features remain standing, the<br>original slave village and factory have been buried up to a depth of three meters.<br>Three geophysical techniques were used to assess potential excavation sites. These were:<br>Magnetics (Total field), DC resistivity (square array); and ground penetrating radar (GPR).<br>Ambient noise levels were high due to soil inhomogeneity. The industrial site also contained<br>a complex firebrick foundation with an extremely strong magnetic and resistivity signature which<br>masked more subtle structural features. Low amplitude boundary features were revealed by converting<br>measured resistances to transverse anisotropy plots. The magnetics data required more intensive<br>processing. Removal of an upward continued dataset served as a high pass filter. This was<br>reduced to the pole and converted to pseudogravity sections to perform a horizontal derivative.<br>The GPR survey was performed using 200 MHz antennas; lower than those typically used at archaeological<br>sites. Removal of the average trace from a line and band-pass filtering, indicated numerous<br>shallow diffraction events and discontinuous surfaces not apparent in the raw data.<br>The data from all three techniques were combined to produce maps to assess the site. Processing<br>did not appear to introduce significant artifacts. Interpretation of anomalies (e.g. foundations,<br>firebrick, etc.) proceeded with much greater confidence due to multiple technique results.<br>Several sites within the factory were chosen for excavation in August of 1999, based in-part on the<br>geophysical results. Compared to excavation results, transverse anisotropy and magnetics had<br>been reliable indicators of potential excavation sites. GPR’s service as an interpretive tool was<br>heightened after excavation.