Relative sea-level changes during Middle Ordovician through Mississippian deposition in the Iowa area, North American craton

The Tippecanoe and Kaskaskia cratonic megasequences in the Iowa area are subdivided into a succession of third-order transgressive-regressive (T-R) depositional cycles of ~1 to 3 m.y. duration. Cratonic deposition in the Iowa area is categorized into two broad-scale facies groupings, each dominated by shallowing-upward patterns: 1) an inner shelf with shallow subtidal to peritidal facies, and 2) a middle shelf dominated by subtidal facies. Relative changes in sea level, as documented in the cycles, are considered primarily to reflect eustatic patterns, but local variations in subsidence history and sedimentation rates complicate interpretations of the eustatic signal. Minor modification of certain sequence stratigraphic paradigms that were developed originally for continental margin settings is suggested for application to the Iowa cratonic cycles.