The scale of application of geophysical methods in archaeology has been quite limited in comparison to exploration geophysical surveys employed in engineering, hazardous-waste, ground-water, oil and gas, and mineral research. Archaeogeophysical projects have been directed toward discovering or detailing archaeological features that are generally smaller in scale and occur over a relatively smaller range of sizes than the features of interest in exploration geophysics. It is suggested that the interplay of scale of application with both research orientation and limitations of the geophysical methods has worked to constrain the use of geophysical technology in archaeology. By expanding the scale of archaeogeophysical research beyond the traditionally defined discrete archaeological feature, archaeologists can more fully exploit the potential of this technology. The use of geophysical methods to investigate both broad- and small-scale archaeological phenomena and the problems and prospects of such research are illustrated with data from the Cahokia Mounds State Historic Site in southwestern Illinois.

Multiple varve counts over common intervals in four parallel cores permit estimation of the precision of the Elk Lake varve chronology. At the 95% confidence level, the imprecision of the counts averages 12%. External evidence and comparison of independent varve counts suggest that the accuracy of the varve chronology is well within this limit. Magnetic susceptibility is shown to be an exceptional tool for determining stratigraphic correlations, allowing unambiguous matching of all cores used.

Comparison of the bulk magnetic properties of the Elk Lake sediments with varve thickness and sediment density suggests that most of the magnetic carrier in the sediments is allochthonous to the lake. An exception may be the fine-grained magnetite in the upper three meters of section. Correlation of the Elk Lake directional record with the records from Lake St. Croix and Kylen Lake demonstrates the accuracy of the Elk Lake varve chronology.