SEES:7000 Colloquium - Thursday, 10/22/26, 3:30pm, 255 MacBride Hall

SEES Distinguished Alumni Presentation - Dr. Brian Witzke, "An Iowa Geology Retrospective: the Crucial Role of Stratigraphy"

The University of Iowa has been a center of excellence in sedimentary geology, biostratigraphy and paleontology for many decades, and stratigraphic investigations have been at the core of so many studies here at Iowa. A large group of distinguished alumni confirm that they came to study at Iowa because of that well-deserved reputation. I was one of those fortunate students. The study of the geology and paleontology in the Iowa area and the cratonic heartland has remained the focus of my professional career since those wonderful days in grad school. My role as a geologist at the Iowa Geological Survey and University has been primarily as a stratigrapher, helping to unravel and define Iowa’s fascinating stratigraphy and depositional history. I have been extremely fortunate over the years to have worked with an incredible group of friends and colleagues (academia, students, government, industry) on a multitude of stimulating projects on the stratigraphy, paleontology, structure, and hydrogeology in the Iowa area spanning strata from the Precambrian to Quaternary. Some of these projects will be briefly reviewed. My reflections on over fifty years of research verify the indispensable role that stratigraphy has played in all of these studies. The development of a well-defined stratigraphy for the Paleozoic-Mesozoic bedrock and surficial Quaternary section for Iowa and surrounding areas proved to be essential for local and regional studies in hydrogeology, resource evaluation, and geologic mapping. Furthermore, the Iowa stratigraphic section provides an unmatched regional and global reference for Paleozoic paleontology, biostratigraphy, eustatic sea-level change, carbon isotopic perturbations, and more. The Iowa Quaternary stratigraphic section provides an unequaled record of multiple continental glaciations and climate change.

Accurate stratigraphic correlations are essential for so much of what we do in geology and paleontology. My concluding comments are intended to raise a cautionary warning about the need to critically evaluate published stratigraphic correlations for consistency and accuracy. Miscorrelations can introduce major errors in our interpretations of earth history, but integrative studies and new correlation tools can eventually correct those errors. At times, based primarily on the cited conclusions of a few influential studies, a consensus “bandwagon” of uncritically evaluated lithostratigraphic, biostratigraphic, or chronostratigraphic miscorrelations can become entrenched in the literature. The inertia of that consensus can spread through scores of subsequent research projects and publications. However, in some cases that consensus is later demonstrated to be in error. A few examples of such errors are outlined for Upper Jurassic and Lower Cretaceous strata of the Western Interior, part of my ongoing stratigraphic research. Widely-cited ages and unwarranted stratigraphic extrapolations in the current literature for portions of this stratigraphic interval have propagated egregious miscorrelations that span an astounding 15 to 20 million years. Buyer beware.