Age:

Ordovician

Type designation:

Type area: Weiss and Sweet (1964) proposed the name "Kope Formation" for 240 ft (75 m) of shale and minor interbedded limestone that "lies between the Point Pleasant formation and shaly limestones equivalent to the Fairmount and MacMillan formations" in the Maysville area of Kentucky and Ohio (Burger, 1970; Gray, 1986). The name was taken from Kope Hollow north of Levanna, Ohio (Burger, 1970; Gray, 1986).

History of usage:

Former names: The Kope Formation includes the lowermost Cincinnatian rocks, rocks that were formerly for the most part assigned to the Eden Shale or the Eden Group (Gray, 1986). Gray (1986) noted that those terms had acquired a chronostratigraphic connotation and that the name “Kope Formation” is intended to be strictly lithographic.

Extension: Brown and Lineback (1966, p. 1,020) extended the use of the name Kope Formation into Indiana, in part to replace several names that had been applied more in the sense of biostratigraphic zones than as lithostratigraphic units (Gray, 1986). The former names (Patton, Perry, and Wayne, 1953) included the Eden Group and its component formations, in descending order, the McMicken, Southgate, and Economy Formations. Brown and Lineback (1966) and later Gray (1972) also expanded the concept of the Kope to include shale below the classic Eden.

Description:

The Kope Formation includes not only the bluish- to brownish-gray shale that is exposed at many places in the classic outcrop area in southeastern Indiana but also a thick basal dark-brown to nearly black shale that is known only in the subsurface, the Utica Shale of drillers' old terminology (Gray, 1986). As illustrated and described by Gray (1972), more than 95 percent of the formation is shale, and in places as much as two-thirds of the shale is brown (Gray, 1986).

These contact relationships make a statement regarding thickness of the Kope Formation difficult to formulate. Because there is a tendency to step the upper contact of the Kope Formation upward in a northwesterly direction, reflecting a corresponding westward diminution in limestone content of the overlying Dillsboro Formation (Gray, 1972, fig. 5), the Kope might be expected to thicken northwestward counteracting this trend, however, is a general westward thinning of all parts of the Maquoketa Group (Gray, 1986). Over most of the area in which it can be recognized, therefore, the Kope Formation is 300 to 400 ft (90 to 120 m) thick (Gray, 1986). At its southeastern most extent, however, where the basal dark shale is missing and the Kope rests conformably on the Lexington Limestone, the Kope is about 200 ft (60 m) thick and contains more limestone and less shale than it does elsewhere (Gray, 1972, fig. 9).

Distribution: As presently defined, the Kope Formation is restricted in Indiana to the area in which the overlying Dillsboro Formation can be discriminated (Gray, 1986). Thus the Kope can be identified only in the outcrop area of southeastern Indiana and in the near subsurface in core holes and other drill holes for which excellent records were kept, so that the upward increase in limestone content, which is the basis for determination of the Kope-Dillsboro contact, can be adequately evaluated (Gray, 1986).

Boundaries:

The upper contact of the Kope Formation is apparently conformable but is picked at different horizons in different places because the criterion that distinguishes the Kope from the overlying Dillsboro Formation is the dominance of shale in the Kope as contrasted to a significant, though not dominant, amount of limestone in the Dillsboro (Gray, 1986). In many places this contact must be arbitrarily placed in a transitional sequence (Gray, 1986). The basal contact of the Kope is more complex (Gray, 1986). In southeastern most Indiana the Kope conformably overlies the Lexington Limestone, but limestone of that formation gives way northwestward and interfingers with dark shale of the basal Kope (Gray, 1972, fig. 9). In a narrow linear area that extends from southern Franklin County to northern Harrison County, basal dark shale of the Kope Formation overlies the Plattin Formation of the Black River Group (Keith, 1985). Northwest of that area, and to the limit of its recognition, the Kope Formation overlies the Trenton Limestone along a time-transgressive discontinuity (Brian D. Keith, oral communication, 1984; Gray, 1986).

Correlations:

The greater part of the body of rocks now assigned to the Kope Formation was once explicitly assigned to the Eden Group; this part of the formation is now considered to be Edenian in age (Gray, 1986). The dark shale that forms the basal part of the Kope, however, is in part late Champlainian in age (Sweet and Bergstrom, 1971, fig. 2), and to the extent that the upper contact of the formation steps upward to the northwest, some of the Kope in that area may be Maysvillian in age (Gray, 1986).

The Kope Formation is laterally continuous with part of the Scales Shale of central and western Indiana, but a boundary between areas of application of these names has not been defined (Gray, 1986). The age equivalent of the Kope, however, is at least in part found in the Trenton Limestone in western Indiana and Illinois, a consequence of the time-transgressive nature of the boundary between these formations, as explained above (Gray, 1986).

Regional Indiana usage:

Cincinnati Arch (COSUNA 13)
Supergroup: none
Group: Maquoketa Group
Formation: Kope Formation

Misc/Abandoned Names:

Eden Group, Eden Shale, Utica Shale

Geologic Map Unit Designation:

Ok

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 features in Indiana.

Major tectonic features that affect bedrock geology in Indiana.

References:

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.

Burger, A. M., 1970, Kope Formation, 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. 85–86.

Gray, H. H., 1972, Lithostratigraphy of the Maquoketa Group (Ordovician) in Indiana: Indiana Geological Survey Special Report 7, 31 p.

Gray, H. H., 1986, Kope Formation, 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. 72–73.

Hansen, W. R., 1991, Suggestions to authors of the reports of the United States Geological Survey (7^th ed.): Washington, D.C., U.S. Geological Survey, 289 p.

Keith, B. D., 1985, Map of Indiana showing thickness, extent, and oil and gas fields of Trenton and Lexington Limestones: Indiana Geological Survey Miscellaneous Map 45, scale 1:500,000.

Patton, J. B., Perry, T. G., and Wayne, W. J., 1953, Ordovician stratigraphy, and physiography of part of southeastern Indiana: Indiana Geological Survey Field Conference Guidebook 6, 29 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.

Sweet, W. C., and Bergstrom, S. M., 1971, The American Upper Ordovician standard–[Pt.] 13, A revised time-stratigraphic classification of North American upper Middle and Upper Ordovician rocks: Geological Society of America Bulletin, v. 82, p. 613–627.

Weiss, M. P., and Sweet, W. C., 1964, Kope Formation (Upper Ordovician)—Ohio and Kentucky: Science, v. 145, p. 1,296–1,302.