. Bulletins of American paleontology. . Text-figures 18 and 19.—Photographs to illustrate difference in quality of the outcrop of the upper part of the Cerro Gordo Member of the Lime Creek Formation at Bird Hill (Locality 31, Appendix). Figure 18 was taken in August of 1967 when stratigraphic sequence was clearly exposed, with the basal Ampluporu limestones of the Owen Member present at the extreme top of the outcrop. Figure 19 was taken in June of 1986 and illustrates the amount of slumping present, and resultant deterioration of the outcrop, where no fossils could be collected in place. is s
. Bulletins of American paleontology. . Text-figures 18 and 19.—Photographs to illustrate difference in quality of the outcrop of the upper part of the Cerro Gordo Member of the Lime Creek Formation at Bird Hill (Locality 31, Appendix). Figure 18 was taken in August of 1967 when stratigraphic sequence was clearly exposed, with the basal Ampluporu limestones of the Owen Member present at the extreme top of the outcrop. Figure 19 was taken in June of 1986 and illustrates the amount of slumping present, and resultant deterioration of the outcrop, where no fossils could be collected in place. is shown extending from M. N. Zone 9 at the base (Lower Juniper Hill Member) to Zone 12 at the top of the Owen Member. The Owen Member (with its brachiopods placed in the Elita inconsueta and lo- watrypa owenensis zones) comprises almost all of Zone 12 of Klapper (1989), along with the up- permost part of the Cerro Gordo Member (the Elita inconsueta Zone). The Cyrtospirifer whitneyi Zone, to- gether with the underlying Doitvillina arciiata Zone and Nenostrophia thomasi Zone are correlated to Zone 11 (with the exception of the basal portion of the latter). For details of this biostratigraphic zo- nation of the Frasnian of Iowa, the reader is referred to the excellent summary by Day (1996, pp. 277-290). The base of the Famennian Stage occurs somewhat higher in the Devonian sequence in northern Iowa, at the base of the overlying Sheffield Formation (Witzke and Bunker, 1996, p. 319). FIELD CONDITIONS The greatest part of field work for this study was done in the summers of 1967 and 1968; both strati- graphical, including description of stratigraphic sec- tions, and paleontological, collecting faunas. Addition- al collecting was done in 1970. Most collections dur- ing this time were made in place in the stratigraphic subdivisions shown in stratigraphic sections, with large collections of fossils from float only made in the Rockford Brick and Tile Company's piles of stri
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