Late Ordovician-Early Silurian delta C-13 chemostratigraphy in the Upper Mississippi Valley: implications for chronostratigraphy and depositional interpretations
A pioneer study of the previously unknown delta C-13 chemostratigraphy in the Ordovician/Silurian boundary interval in eastern Iowa and northeastern Illinois resulted in the discovery of the Hirnantian Isotope Carbon Excursion (HICE). The presence of this major isotope excursion in the Mosalem Formation in Iowa and the Wilhelmi Formation in Illinois, which indicates that the excursion interval in