The purpose of this site is to make current information about geologic names that are recognized by the Indiana Geological Survey (IGS) available to a broad spectrum of users. You may access information about specific units by either (1) entering a formal stratigraphic name here on the page, or (2) using the advanced search. Using the advanced search, you can select units by specifying system and stratigraphic rank to retrieve data for more than one unit and view the data in alphabetic or approximate stratigraphic order. The results will show IGS nomenclature for the selected unit(s), names of equivalent correlative units, miscellaneous and abandoned names, and applicable higher-rank stratigraphic terms. The Web coverage includes each of the five Indiana regions delineated in the Midwestern Basin and Arches Region chart (American Association of Petroleum Geologists [AAPG] COSUNA Chart, 1984) and provides information on the geographic changes in rank, lithic term, and assignment to higher-ranked unit.