Age:

Ordovician

Type designation:

Type locality: According to reviews by Templeton and Willman (1963) and Buckley and Buehler (1904, p. 111), the name "Plattin" was originally proposed, but not published, by E. O. Ulrich for exposures along Plattin Creek, Jefferson County, Missouri (Droste and Patton, 1986).

History of usage:

Reclassification: After long use of the term “Plattin Limestone or Formation” in the upper Mississippi Valley area, the rocks of this unit were reclassified as a subgroup in the Platteville Group of Illinois (Templeton and Willman, 1963, p. 78; Droste and Patton, 1986). In Illinois they were underlain by the Pecatonica Formation of the Platteville Group (Droste and Patton, 1986).

Extension: From Illinois, the Plattin Subgroup was traced without subdivision into the Indiana subsurface by Droste, Abdulkareem, and Patton (1982) (Droste and Patton, 1986). In Indiana, the Plattin overlies the Pecatonica Formation and with the Pecatonica makes up the Black River Group (Droste and Patton, 1986).

Description:

In gross aspect the Plattin is made up of the lithographic limestone that characteristically is associated with Black River rocks in many places in the eastern United States; dolostone is an abundant component of the Plattin only in northwestern Indiana and northeastern Illinois (Droste and Patton, 1986). The Plattin ranges in thickness from less than 100 ft (30 m) in northwestern Indiana to more than 400 ft (120 m) in southwestern Indiana (Droste and Patton, 1986).

Distribution: Except for faulted blocks of the Plattin in the Kentland structure, Newton County, Indiana, the Plattin is known only in the subsurface of Indiana (Gutschick, 1983; Droste and Patton, 1986).

Boundaries:

The Plattin Formation is overlain with minor unconformity by the more coarsely bioclastic rock of the Trenton Limestone except for places in southern Indiana where rocks of the Kope Formation (Maquoketa Group) or of the Lexington Limestone lie above (Droste and Patton, 1986).

Correlations:

The Plattin Formation in Indiana is correlated with the Plattin Subgroup of Illinois, the Plattin Formation of western Kentucky and the upper part of the High Bridge Group elsewhere in Kentucky, and the upper parts of the Black River Group of Michigan and of the Black River Limestone of Ohio (Droste and Patton, 1986). Some named subdivisions of these units in adjacent states are recognized in some wells in Indiana (Droste and Patton, 1986). For example, marker bed I of Stith (1979) in the Black River Limestone of Ohio is recognized in many wells in Indiana (Droste and Patton, 1986). These same rocks in Indiana correspond essentially to the uppermost member (Briton Member) of the Mifflin Formation, Plattin Subgroup, of northern Illinois (Droste and Patton, 1986). The Brickeys Member of the Mifflin Formation of Illinois has a characteristic lithology that can be identified in wells in Indiana in the lower part of the Plattin Formation (Droste and Patton, 1986). K-bentonite deposits called the Mud Cave and Pencil Cave Bentonite Beds in Kentucky and several K-bentonite units noted by Stith (1979) in Ohio are recognized in some wells in Indiana (Droste and Patton, 1986).

Regional Indiana usage:

Illinois Basin (COSUNA 11)
Supergroup: none
Group: Black River Group
Formation: Plattin Formation
Illinois Basin Margin (COSUNA 12)
Supergroup: none
Group: Black River Group
Formation: Plattin Formation
Cincinnati Arch (COSUNA 13)
Supergroup: none
Group: Black River Group
Formation: Plattin Formation
Kankakee Arch (COSUNA 14)
Supergroup: none
Group: Black River Group
Formation: Plattin Formation
Michigan Basin (COSUNA 15)
Supergroup: none
Group: Black River Group
Formation: Plattin Formation

Misc/Abandoned Names:

None

Geologic Map Unit Designation:

Op

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:

Buckley, E. R., and Buehler, H. A., 1904, Quarrying industry of Missouri: Missouri Bureau of Geology and Mines, 2nd Series, v. 2, 371 p.

Droste, J. B., Abdulkareem, T. F., and Patton, J. B., 1982, Stratigraphy of the Ancell and Black River Groups (Ordovician) in Indiana: Indiana Geological Survey Occasional Paper 36, 15 p.

Droste, J. B., and Patton, J. B., 1986, Plattin 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. 113–114.

Gutschick, R. C., 1983, Geology of the Kentland Dome structurally complex anomaly–northwestern Indiana (Field Trip 5), in Shaver, R. H., and Sunderman, J. A., eds., Field trips in midwestern geology: Bloomington, Indiana, Geological Society of America, Indiana Geological Survey, and Indiana University Department of Geology, v. 1., p. 105–138.

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.

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.

Stith, D. A., 1979, Chemical composition, stratigraphy, and depositional environments of the Black River Group (Middle Ordovician), southwestern Ohio: Ohio Geological Survey Report of Investigations 113, 36 p.

Templeton, J. S., and Willman, H. B., 1963, Champlainian Series (Middle Ordovician) in Illinois: Illinois State Geological Survey Bulletin 89, 260 p.