The Toltec site, 3LN42, consists of a multiple mound complex of over 100 acres enclosed by an earthen embankment. Several culture periods are represented, although ceramics from excavations to date indicate that major occupation and mound construction occurred during the Late Baytown and Coles Creek periods, roughly A.D. 600 to 1000. The 1980 magnetometer survey at Toltec was a pilot feasibility study with survey coverage limited to selected areas of the site. Nine test blocks were laid out in areas that would yield information on a variety of archeological and soil contexts-some known, others unknown. The survey was divided into three phases. Phase I consisted of surveying each block and a 10 m area around it with a metal detector. This enabled us to screen the locations of historic metal trash as well as the potential anomalies produced by this material. Phase II consisted of some experimental work with a differential mode gradiometer based on the design of Steponaitis and Brain (1975). Our success with this instrument, however, was primarily limited to the relocation of our old, 1978/79 excavation units, and was, at best, inconclusive. Phase III of the magnetic survey consisted of a 1.5 day survey contract by a team under the direction of Dr. John Weymouth of the University of Nebraska Physics Department. Block priorities were established and a grid interval of 1 m was selected. Two Geometric (Model G816) proton magnetometers with digital readout capacity were used at a sensitivity interval of 1/4 gamma. Due to certain time restrictions and field conditions, only 7 of the original 9 blocks were surveyed for a total of 1550 sq m.

Four magnetometer blocks were selected for excavation in 1980. The blocks selected were 5, 7, 8, and 9 at the base of Mound B, Mound E, RSA-B (Mound S), and Mound G, respectively. In Blocks 7, 8, and 9, 15 out of the 16 units excavated showed a direct correlation between the number of artifacts by weight recovered in the submound midden/A horizon surface and the relative degree of higher or positive gamma values. Off-mound areas in Blocks 5 and 7 show a very precise correlation between the magnetic contour and mapped distribution of artifacts within a midden soil. Used with permission.

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