The transformative power of chemostratigraphy for bedrock studies in the Illinois Basin
Dr. Patrick McLaughlin, Indiana Geological and Water Survey, Bloomington, Indiana
Chemostratigraphy is resolving many longstanding uncertainties about bedrock stratigraphy of the Illinois Basin through the generation of robust time-rock (i.e., chronostratigraphic) frameworks fundamental to accurate sequence stratigraphic interpretation. Mapping of regional carbonate carbon isotope trends identifies isochroneity and diachroneity of unconformity-bound packages of strata (defining chronostratigraphic strike and dip). Portable X-ray fluorescence (pXRF) enables rapid, nondestructive elemental analysis, providing additional insights into facies characterization, local correlation, depositional processes and economic assessment.
Our work in the basin is currently focused on the Maquoketa Group. Despite an abundance of high-quality subsurface samples, chronostratigraphic study of the Maquoketa Group was little developed. Our work has not only generated a robust chemostratigraphic analysis of most of the available cores in the basin, but uncovered rich graptolite and chitinozoan records and conducted targeted conodont studies that greatly enhance our new chronostratigraphic foundation. These results show that the Maquoketa is highly diachronous through certain parts of the basin, clarifying inconsistent compositional patterns identified by previous studies.
Chemostratigraphic studies in the Illinois Basin are making tangible improvements to the fundamental understanding of bedrock geology. These new studies provide opportunities for regional collaboration and advancement of multiple initiatives within the basin.
About the speaker
Dr. McLaughlin is an Indiana University research scientist with the Geological and Water Survey and an adjunct professor in the Department of Earth and Atmospheric Sciences. His research is focused on Earth systems history, particularly deciphering the recorded interactions of the lithosphere, biosphere and hydrosphere. He obtained his B.Sc. degree from Illinois State University (1999) and M.Sc. (2002) and Ph.D. (2006) degrees at the University of Cincinnati where he studied sequence and event stratigraphy as a doctoral fellow. An NSF-funded post-doctoral study led to a specialization in chemostratigraphy, particularly new applications of C-isotopes and elemental abundances (via portable XRF). His field- and subsurface-based studies span the Proterozoic to Pliocene on three continents, with an emphasis on the lower Paleozoic of eastern North America.