Included are explanations and interpretations of the models, as well as assumptions and methods for creating contour maps and 3D displays for each construction stage. Reed, Bennett, and Porter Model Figure 12. Washington University sponsored solid core drilling to determine the internal structure of Monks Mound. To confirm the accuracy of the cores a test excavation was dug around core 1 to a depth of 6.03 meters. In this excavation a series of limonite bands were discovered.
Limonite consists of secondary hydrated iron oxides that form as a precipitate.
Reed, Bennett, and Porter in their analysis gave an explanation of limonite's role. In the Cahokia region, there exist sediments with high iron content, and in other mound and habitation excavations we have observed that these bands of limonite not only have formed on living surfaces, but that they outline vertical prehistoric excavations and, in a few instances, cut across both types of surfaces. Limonite can form through oxidation on an exposed surface, or it can be carried in solution, by water, down through the earth and deposited on the face of a soil change. It can form rapidly under proper conditions. With this information two assumptions were made to create the construction stages.