Devonic Chronology in Iowa

The most important geological discovery in Iowa in recent years is the revelation that our Devonic deposition is not what it was long thought to be, that is, contemporaneous with the Devonic sedimentation of the East, or New York standard column. Instead of the two widely separated sections being of the same age, as always regarded, our Iowa Devonic rocks turn out to be very much younger than New York rocks. The two stratal successions appear now to have been laid down in altogether different geosynclines, and our western rocks were formed largely out of the ruins of the Eastern rocks. To be sure, our Iowa Devonics were long known to recline in marked unconformity upon Siluric and Ordovicic strata. But in southeastern Missouri, recently, Devonic strata continuous with our Cedar Valley limestones rest in conspicuous erosional unconformity upon the western extension of the New York Hamilton formation. So in Iowa, our so-called Hamilton is obviously not the New York Hamilton by any means, as so long so confidently regarded, a fact indicative of a hiatus much wider than heretofore suspected. Fortunately most of the fossils occurring in the Iowa Devonic rocks have been described as different from those of the New York Hamilton and now our organic forms urgently need to be analyzed anew