Figs. 3, 9. Garnavillo member of Guttenberg formation. Shown on columnar section as basal member of Guttenberg formation. Underlies Glenhaven member (new); overlies Spechts Ferry formation or where Spechts Ferry is absent, the Strawbridge member (new) of Quimbys Mill formation. Age is Middle Ordovician.
[Notable exposures in Dixon-Oregon area, northern IL.]
[GNC remark (ca. 1966, US geologic names lexicon, USGS Bull. 1200, p. 1473): In copy of guidebook used by compiler [G.C. Keroher], in figure 3, the name Glenhaven had been crossed out and the name Garnet written in. However, in figure 9, the name Garnet had been used to replace the name Garnavillo. Since compiler had no way to determine what changes, if any, had been made in other copies of the guidebook, it was impossible to be certain which names should be retained.]

Source: US geologic names lexicon (USGS Bull. 1200, p. 1473).