Unlike the original compendium, the present revision treats only of Paleozoic rock units. Classification of Quaternary rock units has been in a state of flux, and a number of ongoing (at the time of this writing) glacial stratigraphic studies in Indiana, including production of a new Quaternary map of Indiana, suggest that a Quaternary supplement to the revised compendium would have greater value if produced at a later time when greater stability in Quaternary nomenclature has been achieved.

The main body of the revised compendium, headed "Rock-Unit Names," is arranged alphabetically and consists of historical, bibliographic, descriptive, and correlative information for each of the Paleozoic rock-unit names that the Geologic Names Committee has approved as of March 31, 1985, for general Indiana use in Indiana Geological Survey-sponsored publications. For some of the names treated here in primary fashion, the compendium represents the first Survey use of preexisting names, or it serves to make slight classificatory changes, for example, changes in surnames whether a rank or a lithologic change. The compendium also establishes some new reference sections.

Names not recommended by the Geologic Names Committee for general use in Indiana are not treated in primary fashion, but they are listed in the alphabetically arranged index and shown on Plate 2. Bionomenclatural terms are treated in the same manner, but Plate 2A and B includes special columns for some of the most important Carboniferous biozones for regional and interregional correlation of Indiana rocks. The key to inclusion of these two groups of terms is their use by authors in the text, but some fossils named in the text do not appear in the bionomenelature columns of Plate 2 because the authors' notations are only in the sense of lithologic character. The listing here, therefore, is not exhaustive for Indiana. Nor are time and time-rock terms given primary treatment, but as already noted the terms recommended for general use are shown on Plate 2.

The general locations of type sections, localities, and areas for rock units named for Indiana places are shown on Plate 1. Exact locations, however, are stated only in the text for some, but not all, names.

The compendium is not intended as a direct statement of stratigraphic policy, although the Indiana Geological and Water Survey has adopted most of the principal provisions of the North American Stratigraphic Code (North American Commission on Stratigraphic Nomenclature, 1983).

Because they have much first-hand experience, authors of the compendium were encouraged to be somewhat authoritative rather than merely compilatory in their presentation, so that primary authorship of each article is indicated by initials. An example of correct bibliographic citation of a single compendium article follows: Rexroad, C. B. , 1986, Brassfield Limestone, in Shaver, R. H. , and others, Compendium of Paleozoic rock-unit stratigraphy in Indiana C A revision: Indiana Geological Survey Bulletin 59, p. 20-21.

Many modern reports provide detail on individual Indiana rock units that the compendium does not; they are cited in the appropriate articles. Several modern summary-type reports and maps complement the compendium by provision of similar information ranging in scope from that of individual units to groups or larger sequences of units. They include: For surficial distribution the eight sheets in the 1/ X 2/ Regional Geologic Maps series and the single-sheet 1:500,000-scale "Bedrock Geologic Map of Indiana" (Gray, Ault, and Keller, in preparation) for overall distribution (including subsurface), major lithology, thickness, and regional to interregional correlation C Shaver and others, 1985; for regional to interregional thickness, correlation, and paleoenvironments of lower through middle Paleozoic units C Droste and Shaver, 1983; for thickness and distribution maps of major groups of Indiana rocks C Rupp, in preparation; and for relationships with physiographic provinces C Malott, 1922.