The intent of this project is to map and analyze orientations of large orthocone cephalopods in the Late Ordovician Kimmswick Formation to determine whether they indicate traceable current directions. The Kimmswick Formation is a medium-to-coarsely-grained crystalline limestone which is highly fossiliferous, with bedding varying from massive to cross-bedded, and ranging from 10-30 meters in thickness in the project region. Numerous orthocone cephalopods (of the genera Endoceras and Cameroceras) can be observed within the lower Kimmswick in several locations in Northeastern Missouri, especially near Imperial and Frankford. A total of 21 orientations along a six-kilometer corridor near Imperial have been collected to date. While not a sufficient sample for statistically significant analysis, these measurements, taken together with other field observations, indicate a bimodal distribution of orientations at this locality (with similar patterns observed at other localities). In addition, the orthocones show a consistent preference for generally easterward apical alignment. Nearly all of these measurements have been collected from a single massive bed, herein titled the Kimmswick Nautiloid Bed (KNB), which can be correlated across outcrops against the underlying shaley House Springs K-Bentonite Bed. While cephalopods are known in the Kimmswick faunal lists, they are not common; they appear to be restricted to specific beds, such as the KNB; and their orientations have hitherto not been analyzed. The Kimmswick Formation is conventionally understood to represent a carbonate platform, with a relatively calm depositional environment. Preferential orientation of orthocone fossils may be indicative of a more energetic depositional environment for the Kimmswick than commonly supposed. More research is needed to accumulate a larger set of orthocone orientations, to study the grading of other fossil debris within the KNB, and to establish stratigraphical correlation of the KNB with the cephalopod-bearing Kimmswick bed in Frankford and other more distant localities.
