Type section: The Salamonie Dolomite was named for exposures of dolostone in the headwaters area of the Salamonie River near Portland, Jay County, Indiana (Pinsak and Shaver, 1964, p. 24; Shaver, 1970; Droste and Shaver, 1986). The type section is the exposure near Portland in the Meshberger Bros. Stone Corp. quarry (formerly the Rockledge Products, Inc., quarry) and the rocks penetrated by Indiana Geological Survey drill hole 44 (Indiana Geological Survey Petroleum Database Management System No. 161686), cored from the floor of that quarry in the NW¼NW¼ sec. 30, T 23 N., R. 14 E. (Shaver, 1970; Droste and Shaver, 1986).
History of usage:
The name was originally applied only in northern Indiana to dolomitic rocks that were then considered to lie above the Brassfield Limestone and below the Waldron Formation except in the northern two to three tiers of counties, where it underlay the Salina Formation, and in far western counties, where it underlay (and still does) the Louisville Limestone (Droste and Shaver, 1986). In 1967 (French, p. 18) recognition of the unit was extended to the southeastern Indiana outcrop area, where it was assigned two preexisting formations reduced to member status, the Osgood Member below and the Laurel Member above (Droste and Shaver, 1986). In 1974 (Becker, p. 17-18) nearly statewide recognition was completed with description of the unit in the subsurface of southwestern Indiana (Droste and Shaver, 1986). In 1976 (Droste and Shaver, p. 4) the formation name Limberlost Dolomite was assigned to what had been the unnamed upper brown fine-grained dolostone member of the Salamonie (Droste and Shaver, 1986). This unit was later reduced to member rank and assigned to the Pleasant Mills Formation of the Salina Group (Droste and Shaver, 1982, p. 11; Droste and Shaver, 1986). In 1980 (Rexroad, p. 12) the lower, approximately Osgood equivalent of the Salamonie in the parts or whole of 17 northeastern Indiana counties was assigned to the Stroh Member of the Cataract Formation (Droste and Shaver, 1986). With assignment of what was originally the upper Salamonie to the Limberlost Dolomite (later becoming part of the Pleasant Mills), the Portland quarry section (see above) became very nearly a single, complete type section for the Salamonie Dolomite, exhibiting about 140 ft (48 m) of this formation, from which possibly only a very few feet of rocks have been eroded at the top (Droste and Shaver, 1986).
The Salamonie has two principal lithologies. Lower Salamonie rocks are generally impure, especially in southern Indiana, and include finer grained argillaceous limestone and dolomitic limestone (as well as dolostone) and shale (Osgood Member in the south) (Droste and Shaver, 1986). The upper rocks are much purer and consist of whitish coarser grained bioclastic vuggy dolostone in much of the state (Droste and Shaver, 1986). Such dolostone of great purity dominates the upper Salamonie especially in northern Indiana (Droste and Shaver, 1986). Chert is present sporadically within the Salamonie but mostly in the upper Laurel rocks in part of southeastern Indiana (Droste and Shaver, 1986). The upper Salamonie has a pure carbonate reef facies in many places in Indiana, from the Illinois Basin to northeastern Indiana outcrop (Becker and Droste, 1978; Shaver and others, 1978; Droste and Shaver, 1980; Droste and Shaver, 1986).
The Salamonie has these boundaries with other units: In northern Indiana it variably overlies the Brassfield Limestone, the Sexton Creek Limestone, and the Cataract Formation; further, in northern Indiana, a lower part of the Salamonie has a vertical cutoff boundary with the upper part of the Cataract, so that the oldest Salamonie rocks in northern Indiana are in western counties, there lying on the Sexton Creek (Droste and Shaver, 1986). In southern Indiana the Salamonie overlies the Brassfield and Sexton Creek Limestones and, in small areas, Ordovician rocks. In southwestern Indiana the Salamonie has a vertical cutoff boundary with the approximate lower half of the St. Clair Limestone (Droste and Shaver, 1986). In most of northern Indiana the Salamonie underlies the Pleasant Mills Formation, and in the rest of state, including far western counties in northern Indiana, it underlies variably the Waldron Shale (Formation) and the Louisville Limestone (Droste and Shaver, 1986). The upper contact is conformable; the lower one is unconformable except in far northwestern Indiana and in northeastern Indiana where the Salamonie overlies the Stroh Member of the Cataract (Droste and Shaver, 1986). Present criteria for recognition of the lower boundary (for example, those of Rexroad  and Rexroad and Droste ) differ in some detail from those originally proposed by Pinsak and Shaver (1964) (Droste and Shaver, 1986).
As noted above, lower Salamonie rocks in northwestern Indiana are equivalent to the upper Cataract rocks of northeastern Indiana, and in southwestern Indiana the entire Salamonie equates with lower St. Clair rocks of the Illinois Basin (Droste and Shaver, 1986). The Salamonie also correlates closely to approximately with these rocks in adjacent states: central Kentucky, the Osgood Formation and the Laurel Limestone; western Ohio, the Dayton Formation through the middle part of the Lockport Group or through the Cedarville Dolomite; in southern Ohio, the Estill Shale through the Peebles Dolomite; Michigan, the Clinton and Niagara Groups; and northern Illinois and southeastern Wisconsin, the Joliet Dolomite except for the lowermost few feet (Droste and Shaver, 1986).
Regional Indiana usage:
Illinois Basin (COSUNA 11)
Geologic Map Unit Designation:
Note: Hansen (1991, p. 52) in Suggestions to authors of the reports of the United States Geological Survey noted that letter symbols for map units are considered to be unique to each geologic map and that adjacent maps do not necessarily need to use the same symbols for the same map unit. Therefore, map unit abbreviations in the Indiana Geologic Names Information System should be regarded simply as recommendations.
COSUNA areas and regional terminology
Names for geologic units vary across Indiana. The Midwestern Basin and Arches Region COSUNA chart (Shaver, 1984) was developed to strategically document such variations in terminology. The geologic map (below left) is derived from this chart and provides an index to the five defined COSUNA regions in Indiana. The regions are generally based on regional bedrock outcrop patterns and major structural features in Indiana. (Click the maps below to view more detailed maps of COSUNA regions and major structural features in Indiana.)
COSUNA areas and numbers that approximate regional bedrock outcrop patterns and major structural featuers in Indiana.
Major tectonic features that affect bedrock geology in Indiana.
Droste, J. B., and Shaver, R. H., 1980, Recognition of buried Silurian reefs in southwestern Indiana: Journal of Geology, v. 88, p. 567-587.
Droste, J. B., and Shaver, R. H., 1986, Salamonie Dolomite, in Shaver, R. H., Ault, C. H., Burger, A. M., Carr, D. D., Droste, J. B., Eggert, D. L., Gray, H. H., Harper, Denver, Hasenmueller, N. R., Hasenmueller, W. A., Horowitz, A. S., Hutchison, H. C., Keith, B. D., Keller, S. J., Patton, J. B., Rexroad, C. B., and Wier, C. E., Compendium of Paleozoic rock-unit stratigraphy in Indiana–a revision: Indiana Geological Survey Bulletin 59, p. 130-132.
Hansen, W. R., 1991, Suggestions to authors of the reports of the United States Geological Survey (7th ed.): Washington, D.C., U.S. Geological Survey, 289 p.
Rexroad, C. B., and Droste, J. B., 1982, Stratigraphy and conodont paleontology of the Sexton Creek Limestone and the Salamonie Dolomite (Silurian) in northwestern Indiana: Indiana Geological Survey Special Report 25, 29 p.
Shaver, R. H., 1970, Salamonie Dolomite, in Shaver, R. H., Burger, A. M., Gates, G. R., Gray, H. H., Hutchison, H. C., Keller, S. J., Patton, J. B., Rexroad, C. B., Smith, N. M., Wayne, W. J., and Wier, C. E., Compendium of rock-unit stratigraphy in Indiana: Indiana Geological Survey Bulletin 43, p. 150-152.
Shaver, R. H., Ault, C. H., Ausich, W. I., Droste, J. B., Horowitz, A. S., James, W. C., Okla, S. M., Rexroad, C. B., Suchomel, D. M., and Welch, J. R., 1978, The search for a Silurian reef model–Great Lakes area: Indiana Geological Survey Special Report 15, 36 p.
Shaver, R. H., coordinator, 1984, Midwestern basin and arches region–correlation of stratigraphic units in North America (COSUNA): American Association of Petroleum Geologists Correlation Chart Series.
For additional information, contact:
Nancy Hasenmueller (firstname.lastname@example.org)Date last revised: June 14, 2017