Type locality: The Maquoketa Shale was named by White (1870, p. 180-182) for exposures of blue and brown shale that aggregate 80 ft (25 m) in thickness along the Little Maquoketa River in Dubuque County, Iowa (Gray and Shaver, 1986).
History of usage:
Since its first use, the term has spread gradually eastward, in the process becoming a group that embraces several formations (Gray and Shaver, 1986). It is now used throughout Illinois (Willman and Buschbach, 1975, p. 84-85), was extended into northwestern Indiana by Gutstadt (1958), and was adopted for use in a group sense throughout Indiana by Gray (1972; Gray and Shaver, 1986).
As described by Gray (1972), the Maquoketa Group in Indiana is a westward-thinning wedge, 1,000 ft (300 m) thick in southeastern Indiana and 200 ft (60 m) thick in northwestern Indiana (Gray and Shaver, 1986). It consists principally of shale (about 80 percent); limestone content is minimal throughout most of Indiana but increases prominently in the southeast, so that parts of the group are in places dominantly limestone (Gray and Shaver, 1986). The lower part of the group is everywhere almost entirely shale, and the lower part of the shale is dark brown to nearly black (Gray and Shaver, 1986).
The upper contact of the Maquoketa Group, which marks the top of the Ordovician System, is disconformable throughout Indiana (Gray and Shaver, 1986). The immediately overlying rocks, all of which are Silurian in age, include different formations in different areas. In most of the outcrop area in southeastern Indiana the Maquoketa Group is overlain by the Brassfield Limestone, but in small areas the Brassfield is absent, and the shaly Osgood Member of the Salamonie Dolomite, which elsewhere overlies the Brassfield, directly overlies the Maquoketa (Foerste, 1904a; Brown and Lineback, 1966; Nicoll and Rexroad, 1968; Gray and Shaver, 1986). The Brassfield also overlies the Maquoketa in the subsurface of east-central Indiana, but in western Indiana, where rocks that are laterally equivalent to the Brassfield are assigned to the characteristically cherty Sexton Creek Limestone, that formation overlies the Maquoketa. In northeastern Indiana the Maquoketa is overlain by the Manitoulin Dolomite Member of the Cataract Formation (Rexroad, 1980; Gray and Shaver, 1986).
Regional Indiana usage:
Illinois Basin (COSUNA 11)
Eden Group, Maysville Group, Richmond Group
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.)
Black, D. F. B., Cressman, E. R., and MacQuown, W. C., Jr., 1965, The Lexington Limestone (Middle Ordovician) of central Kentucky: U.S. Geological Survey Bulletin 1224-C, p. 1-29.
Brown, G. D., Jr., and Lineback, J. A., 1966, Lithostratigraphy of Cincinnatian Series (Upper Ordovician) in southeastern Indiana: American Association of Petroleum Geologists Bulletin, v. 50, p. 1,018-1,023.
Caster, K. E., Dalve, E. A., and Pope, J. K., 1955, Elementary guide to the fossils and strata of the Ordovician in the vicinity of Cincinnati, Ohio, revised: Cincinnati Museum of Natural History, 47 p.
Cumings, E. R., 1903, The morphogenesis of Platystrophia; a study of the evolution of a Paleozoic brachiopod: American Journal of Science, ser. 4, v. 15, p. 1-48 and 121-136.
Cumings, E. R., 1908, Stratigraphy and paleontology of the Cincinnati Series of Indiana: Indiana Department of Geology and Natural Resources Annual Report 32, p. 605-1,190.
Cumings, E. R., and Galloway, J. J., 1913, The stratigraphy and paleontology of the Tanner's Creek section of the Cincinnati Series of Indiana: Indiana Department of Geology and Natural Resources Annual Report 37, p. 353-479.
Foerste, A. F., 1904, The Ordovician-Silurian contact in the Ripley Island area of southern Indiana, with notes on the age of the Cincinnati Geanticline: American Journal of Science, v. 4, p. 321-342.
Ford, J. P., 1967, Cincinnatian geology in southwest Hamilton County, Ohio: American Association of Petroleum Geologists Bulletin, v. 51, p. 918-936.
Fox, W. T., 1962, Stratigraphy and paleoecology of the Richmond Group in southeastern Indiana: Geological Society of America Bulletin, v. 73, p. 621-642.
Gray, H. H., 1970, Maquoketa Shale, 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. 105-106.
Gray, H. H., 1972, Geologic map of the 1° x 2° Louisville quadrangle, Indiana, showing bedrock and unconsolidated deposits: Indiana Geological Survey Regional Geologic Map No. 6, Part A [bedrock units].
Gray, H. H., and Shaver, R. H., 1986, Maquoketa Group, 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. 88-89.
Gray, H. H., Forsyth, J. L., Schneider, A. F., and Gooding, A.M., 1972, Geologic map of the 1° x 2° Cincinnati quadrangle, Indiana and Ohio, showing bedrock and unconsolidated deposits: Indiana Geological Survey Regional Geologic Map No. 7, Part A [bedrock units].
Gutstadt, A. M., 1958, Upper Ordovician stratigraphy of the eastern interior region: American Association of Petroleum Geologists Bulletin, v. 42, p. 513-547.
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.
Hay, H. B., 1981, Lithofacies and formations of the Cincinnatian Series (Upper Ordovician), southeastern Indiana and southwestern Ohio: Oxford, Ohio, Miami University, Ph.D. thesis, 238 p.
McEwan, E. D., 1920, A study of the brachiopod genus Platystrophia: U.S. National Museum Proceedings, v. 56, p. 383-448.
Nickles, J. M., 1902, The geology of Cincinnati: Cincinnati Society of Natural History Journal, v. 20, no. 2, p. 49-100.
Nicoll, R. S., and Rexroad, C. B., 1968, Stratigraphy and conodont paleontology of the Salamonie Dolomite and Lee Creek Member of the Brassfield Limestone (Silurian) in southeastern Indiana and adjacent Kentucky: Indiana Geological Survey Bulletin 40, 73 p.
Rooney, L. F., 1966, Evidence of unconformity at top of Trenton Limestone in Indiana and adjacent states: American Association of Petroleum Geologists Bulletin, v. 50, p. 533-546.
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.
Templeton, J. S., and Willman, H. B., 1963, Champlainian Series (Middle Ordovician) in Illinois: Illinois State Geological Survey Bulletin 89, 260 p.
Weiss, M. P., and Sweet, W. C., 1964, Kope Formation (Upper Ordovician)—Ohio and Kentucky: Science, v. 145, p. 1,296-1,302.
White, C. A., 1870, Report on the geological survey of the State of Iowa: Des Moines, Mills and Co., v. 1, 391 p.
Willman, H. B., and Buschbach, T. C., 1975, Ordovician System, in Willman, H. B., Atherton, Elwood, Buschbach, T. C., Collinson, Charles, Frye, J. C., Hopkins, M. E., Lineback, J. A., and Simon, J. A., Handbook of Illinois stratigraphy: Illinois State Geological Survey Bulletin 95, p. 47-87.
For additional information contact:
Nancy Hasenmueller (firstname.lastname@example.org)Date last revised: July 25, 2014