Department of Earth and Atmospheric Sciences

For a number of years, Dodd has worked with Bob Stanton of Texas A&M University on using fossils and sedimentary rocks to interpret the paleoecology and sedimentologic features of Neogene strata in the Eel River and San Joaquin Basins of California. He is also co-author of a textbook on concepts and applications of paleoecology.

Evolution of fossil communities in Neogene San Joaquin Basin, California. The Neogene strata exposed in the Kettleman hills of California were deposited in an embayment of the Pacific Ocean in a series of cycles of marine through non-marine conditions. Although marine conditions were essentially the same during each cycle, the fossil communities differ in detail. This appears to be caused by recruitment and evolution of different organisms from the open Pacific coast during each cycle. This pattern of change gives us insight into the nature of change or evolution at the community level. Dodd has been studying these cycles with Bob Stanton.

In many respects, modern tropical carbonate sediments and Cenozoic tropical limestones are a poor analog for Paleozoic tropical limestones. In fact, modern and Cenozoic non-tropical carbonates are more similar to Paleozoic tropical limestones because of their similarity in original mineral composition. We can demonstrate this similarity by a comparison of Cenozic limestones on New Zealand with Mississippian limestones of Indiana. Dodd has conducted such a comparison with Campbell Nelson of the University of Waikato in New Zealand. He continues to have interest in non-Tropical limestones as a diagenetic analog to Paleozoic tropical limestones.

Depositional processes, environments, and diagenesis of the Ste. Genevieve Limestone. The Ste. Genevieve contains several intervals of eolian carbonates and several exposure surfaces. Dodd has been investigating the origin of these eolian units, their geographic and stratigraphic distribution, and their relationship to subaereal exposure surfaces. The presence of unconformities within the section allow application of the methods of sequence stratigraphy to study of this unit. He is working on this project with Patty Merkley, a former IU student (now with Exxon), and Ralph Hunter of the USGS. Graduate students Charles Zuppann, Clay Harris, and Karl Leonard worked on an early part of this project.

Depositional processes producing the Salem Limestone and relation of petrographic features of the Salem to sedimentary structures in the unit. The Salem is well exposed in numerous quarries in the Bloomington area. The development and extensive use of a chain saw-like quarrying method has resulted in beautiful exposure of sedimentary structures. These allow a more detailed view of depositional processes than has previously been possible. Current work centers on determining the source and distribution of cements and porosity in these rocks. Dodd is working on this project with Todd Thompson of the Indiana Geological Survey and Dan Petzold of the Indiana Department of Environmental Management. The work is being supported by the Marathon Oil Company.

Dodd investigates the petrology and the diagenesis of carbonate rocks to understand processes and environmental conditions leading to their deposition. Specifically, he studies optical, luminescence, and SEM petrographic, and, oxygen and carbon isotopic properties of these rocks to attain these goals. A major part of his petrologic research is carried out on the Mississippian rocks of southern Indiana and neighboring states and is supported from industrial grants.