Age:

Ordovician

Type designation:

Type section: The Dutchtown Limestone was named by McQueen (1937, p. 12) for an exposure 1 mile (1.6 km) east of Dutchtown, Cape Girardeau County, Missouri (Droste, Patton, and Rexroad, 1986).

History of usage:

Extended: The Dutchtown was traced through subsurface methods and designated with the surname "Formation" in Indiana by Droste, Abdulkareem, and Patton (1982) (Droste, Patton, and Rexroad, 1986).

Description:

The Dutchtown Formation is composed generally of light-gray and brown, partly argillaceous dolostone and some interbeds of green shale (Droste, Patton, and Rexroad, 1986). In southwestern Indiana, the Dutchtown also contains sandy to argillaceous dolostone and some limestone. The rocks there are dark gray, dark brown, or black and are interbedded with dark-brown shale (Droste, Patton, and Rexroad, 1986). Everywhere in Indiana the uppermost Dutchtown rocks are light gray and brown (Droste, Patton, and Rexroad, 1986).

The thickness of the Dutchtown ranges from more than 150 ft (46 m) in southwestern Indiana to zero at its depositional or facies limits (Droste, Patton, and Rexroad, 1986).

Distribution: Within the area where the Dutchtown is generally present, the unit is completely absent because of nondeposition around and over high hills on the Knox erosion surface that were formed before Ancell deposition (Droste, Abdulkareem, and Patton, 1982; Droste, Patton, and Rexroad, 1986).

Boundaries:

The Dutchtown Formation grades into the overlying Joachim Dolomite. The Dutchtown overlies the Everton Dolomite or Shakopee Dolomite with unconformity (Droste and Shaver, 1983, fig. 2; Droste, Patton, and Rexroad, 1986).

Correlations:

The lower part of the Dutchtown of Indiana interfingers with that part of the St. Peter Sandstone that contains Chazyan conodonts of the same age as the Dutchtown of Missouri (Rexroad, Droste, and Ethington, 1982), but uppermost Dutchtown rocks are earliest Blackriverian in age (Droste, Patton, and Rexroad, 1986). The Dutchtown of Indiana is correlated with the Dutchtown Limestone of Missouri and Illinois, with the Wells Creek Formation of Ohio, and with the Wells Creek Dolomite of Kentucky (Droste, Patton, and Rexroad, 1986). It has facies equivalency with the lower part of the St. Peter Sandstone of Indiana and Illinois and with the St. Peter Sandstone of Ohio and Kentucky (Droste, Patton, and Rexroad, 1986).

Ethington, Droste, and Rexroad (1986) described the conodonts and the depositional setting of the Dutchtown Formation from cores in Rush, Fayette, Franklin, and Decatur Counties, Indiana. They (1986, p. 9) noted that the correlation of the Dutchtown of southeastern Indiana with the Dutchtown Formation of Missouri is supported by the presence of the conodont species ?Coleodus simplex and ?C. delicatus.

Regional Indiana usage:

Illinois Basin (COSUNA 11)
Supergroup: none
Group: Ancell Group
Formation: Dutchtown Formation
Illinois Basin Margin (COSUNA 12)
Supergroup: none
Group: Ancell Group
Formation: Dutchtown Formation
Cincinnati Arch (COSUNA 13)
Supergroup: none
Group: Ancell Group
Formation: Dutchtown Formation
Kankakee Arch (COSUNA 14)
Supergroup: none
Group: Ancell Group
Formation: Dutchtown Formation

Misc/Abandoned Names:

None

Geologic Map Unit Designation:

Odt

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:

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 Shaver, R. H., 1983, Atlas of early and middle Paleozoic paleogeography of the southern Great Lakes area: Indiana Geological Survey Special Report 32, 32 p.

Droste, J. B., Patton, J. B., and Rexroad, C. B., 1986, Dutchtown 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. 40.

Ethington, R. L., Droste, J. B., and Rexroad, C. B., 1986, Conodonts from subsurface Champlainian (Ordovician) rocks of eastern Indiana: Indiana Geological Survey Special Report 37, 32 p.

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.

McQueen, H. S., 1937, Dutchtown, a new Lower Ordovician formation in southeastern Missouri: Missouri Geological Survey and Water Resources 59th Biennial Report, 1935-36, 27 p.

Rexroad, C. B., Droste, J. B., and Ethington, R. L., 1982, Conodonts from the Everton Dolomite and the St. Peter Sandstone (lower Middle Ordovician) in a core from southwestern Indiana: Indiana Geological Survey Occasional Paper 39, 13 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.