John Isbell's Research
Dr. Isbell is a clastic sedimentologist and sequence stratigrapher who works with glacial, glaciomarine, fluvial, deltaic, and shallow marine sediment and sedimentary rocks deposited in foreland, rift, piggyback, and cratonic basins. He currently works on rock exposures in Antarctica, Argentina, Australia, South Africa, the Falkland Islands, the western United States, the Appalachian Mountains, and in Wisconsin. His work focuses on understanding environmental changes that occurred during critical intervals in Earth History. These include (1) the late Paleozoic Ice Age (LPIA) and the ensuing Permian-Triassic greenhouse (359 to 199 million years ago) and (2) the transition from the Cretaceous to the Tertiary prior to and following the extinction event (145 to 55 million years ago).
The LPIA represents the last complete transition from an icehouse to a greenhouse Earth. Both the LPIA and the current Cenozoic Ice Age share several important features: 1) both occurred during times of low atmospheric CO2, 2) both ice ages were bi-polar, 3) both were/are represented by long duration glaciation, and 4) both occurred during times when complex ecosystems characterized Earth. Therefore, the LPIA is an important ancient analog for understanding future environmental changes. Dr. Isbell currently works on understanding the environmental and biotic changes that occurred during and after the LPIA with Dr. Margaret Fraiser (Assistant Professor of Geosciences at UWM), Dr. Carlos Oscar Limarino (Univ. of Buenos Aires), Dr. Isabel Montañez (Univ. of California-Davis), soon to be Dr. Erik Gulbranson (Univ. of California-Davis), Dr. Sergio Marenssi (Univ. of Buenos Aires), Dr. David Elliot, (The Ohio State University), Dr. Molly Miller (Vanderbilt Univ.); Dr. Edith Taylor (Univ. of Kansas), Dr. Thomas Taylor, (Univ. of Kansas), Dr. Christian Sidor (Univ. of Washington), Dr. Douglas Cole (Counsel for Geosciences, South Africa), Dr. Derek Briggs (Yale Univ.), Dr. Octavian Catuneanu, (Univ. of Alberta), Dr. Chris Fielding (Univ. of Nebraska), and Dr. Tracy Frank (Univ. of Nebraska).
Another critical interval in Earth history that Dr. Isbell studies is the transition between the Cretaceous and Tertiary (Paleogene). During the Cretaceous, the ancestral Rocky Mountains were drained by numerous river systems that flowed eastward across an extensive alluvial plain before emptying into a vast shallow sea. A bolide impact, which ended the reign of the Dinosaurs, forever changed this landscape. Dr. Isbell currently works with Dr. Peter Sheehan (Milwaukee Public Museum and Adjunct Professor of Geosciences at UWM) and Dr. David Fastovsky (Univ. of Rhode Island) on rock exposures in Montana and North Dakota as part of this project. These three scientists are trying to understand how and why the landscape changed following the K-T boundary.
Concerning more recent geologic problems, Dr. William Kean (Professor of Geosciences at UWM), Dr. David Hart (Wisconsin geological and Natural History Survey) and Dr. Isbell are working to understand shifting sedimentation patterns associated with flood events in the Wisconsin River.
Dr. Isbell integrates graduate and undergraduate students into his research both in the field and by studying physical sedimentary processes using the department’s flume research facility.