Age:

Pennsylvanian

Type designation:

Type area: The term “Lead Creek Limestone” was applied by Crider (1913, p. 279) to exposures of limestone, shaly limestone, and shale along Lead Creek in Hancock County, Kentucky, and to similar exposures elsewhere in the Kentucky parts of the Tell City and Owensboro quadrangles (Shaver, 1986).

Reference sections:

Kentucky: Shaver and Smith (1974) designated two reference sections for the Lead Creek Limestone in the Kentucky type area.

(1) Road cut along both sides of a north-south county road, on the south wall of a small stream valley, and 0.75 miles (1.2 km) south of Shaver and Smith’s locality 30, Tell City quadrangle, Hancock County, Kentucky (Shaver and Smith, 1974, p. 6-7).

(2) Road cut on both sides of a north-south county road immediately south of a junction where a benchmark is at 435 ft (132.6 m) of elevation, 1 mile (1.6 km) south of Hilldale Church, 4 miles (6.4 km) west of Hawesville, Hancock County, Kentucky (Shaver and Smith, 1974, p. 34, collecting locality 30).

Indiana: Shaver and Smith (1974) designated three Indiana reference sections in Spencer and Parke Counties, Indiana.

(1) The Ohio River bluff immediately north of Indiana Highway 66 in the SE¼SW¼NW¼ sec. 20, T. 6 S., R. 4 W., in Spencer County, Indiana (Shaver and Smith, 1974, p. 8).

(2) A clay pit in the SW¼SW¼NW¼ sec. 9, T. 6 S., R. 4 W., immediately east of county road, Spencer County, Indiana (Shaver and Smith, 1974, p. 8 and 33, collecting locality 24).

(3) The exposure at the falls in Wapalo Creek, 0.25 miles (0.4 km) downstream (northwest) from Shaver and Smith’s locality 11, in the NE¼SW¼SW¼ sec. 25, T. 17 N., R. 7 W., in Parke County (Shaver and Smith, 1974, p. 9). Shaver and Smith (1974, p. 9) designated this exposure as a Lead Creek reference section for the northern part of their study area.

History of usage:

Crider (1913) referred to three or four ledges ranging in thickness from 8 to 10 ft (2.4 to 3.0 m) through an interval of 30 to 40 ft (9 to 12 m) (Shaver, 1986). The Lead Creek of Kentucky was later described by Chisholm (1931, p. 224-225) as 5 to 11 ft (1.5 to 3.4 m) of shaly limestone (above) and hard limestone (below) that lies 85 ft (26 m) below the Lewisport Limestone (Shaver, 1986).

Extended: Shaver and Smith (1974, p. 5-6) applied the name “Lead Creek” to the limestone and shale interval in Dubois, Spencer, and Perry Counties, Indiana, and assigned these rocks member rank in the upper part of the Mansfield Formation. They followed Chisholm's description of the Lead Creek as consisting of two ledges of limestone (Shaver, 1986).

Description:

In the southernmost Indiana outcrop area of Mansfield rocks, the Lead Creek Limestone Member characteristically consists of a 15- to 24-foot (5- to 7-m) interval made up of three lithologic units: a lower dark dense shaly or argillaceous limestone that has a shaly parting in some places, (2) a middle shale and siltstone that generally is 10 to 15 ft (3 to 4.6 m) thick and that has thin coal and clay in some sections, and (3) an upper massive limestone that is light colored, fine grained, and cherty and that becomes nearly all chert in some places (Shaver, 1986). The two limestones, ranging from less than 1 foot (0.3 m) to nearly 5 ft (1.5 m) in thickness, are named the Fulda Bed and the Ferdinand Bed (Shaver, 1986).

North of Dubois County, Indiana, the full Lead Creek, exhibiting two limestone ledges, is rarely seen, and physical continuity is questionable (Shaver, 1986). Nevertheless, a single thin impure limestone bed and, less commonly, two closely spaced beds have been tentatively identified as the Lead Creek member in upper Mansfield rocks as far north as Warren County (Shaver, 1986).

Boundaries:

The Lead Creek is overlain and underlain by clastic rocks in the approximately upper 50 to 60 ft (15 to 18 m) of the Mansfield Formation and in places is much nearer the top of the formation (Shaver, 1986).

Correlations:

At times in the past, the ledges of limestone in Indiana and Kentucky that are now called the Lead Creek have been confused, either as presumably traceable correlatives or more strictly in the age sense, with limestones now called the Lewisport and Curlew Limestone Members (Tradewater Formation) in Kentucky and the Perth Limestone Member (Brazil Formation) in Indiana and with what was once called the Curlew Limestone Member of Illinois, all of which are now known to be younger than the Lead Creek (Shaver, 1986).

According to Hopkins and Simon (1975, p. 182), the Boskydell Marine Zone of southern Illinois is a possible correlative of the Lead Creek, but other than this possibility, no other direct correlative is known in the Illinois Basin (Shaver, 1986).

The Lead Creek has an abundant and key microfauna that has both regional and global significance in correlating Pennsylvanian rocks ranging stratigraphically on either side of the Morrowan-Atokan boundary and of the Bashkirian-Moscovian boundary (in global terms not quite the same as the Morrowan-Atokan boundary) (Shaver, 1986). The ostracod fauna, however, belongs to the Zone of Amphissites rothi and has long been described in many formations and members in Oklahoma especially, but also in Colorado, that classically have been considered to be late Morrowan in age (Shaver, 1986). The same fauna is now known more widely, including in southwestern states, in the Poverty Run Limestone Member (Pottsville Formation) of the Appalachian Basin (Ohio), and in upper type Morrowan rocks of Arkansas (Shaver, 1986). (See discussions in Shaver and Smith, 1974; Knox, 1975; and Shaver, coordinator,1984, for names of potentially correlative units and sources of literature on this subject.)

On the basis of conodont paleontology, Rexroad and others (1999) recognized the Lead Creek as Atokan in age. They reported that the Lead Creek conodont fauna was of low diversity and was dominated by Idiognathodus and Idiognathoides. The presence of Idiognathoides and Neognathodus atokaensis distinguishes the fauna from that of the next overlying named carbonate unit, the Desmoinesian Perth Limestone Member of the Staunton Formation (Rexroad and others, 1999). Rexroad and others (1999) felt that it was not possible to correlate the Lead Creek with any of the minor marine intervals in its approximate position in Illinois.

Regional Indiana usage:

Illinois Basin (COSUNA 11)
Supergroup: none
Group: Raccoon Creek Group
Formation: Mansfield Formation
Member: Lead Creek Limestone Member
Illinois Basin Margin (COSUNA 12)
Supergroup: none
Group: Raccoon Creek Group
Formation: Mansfield Formation
Member: Lead Creek Limestone Member

Misc/Abandoned Names:

None

Geologic Map Unit Designation:

*mlc

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:

Chisholm, D. B., 1931, The geology of Hancock County, Kentucky: Kentucky Geological Survey Bulletin, ser. 6, v. 41, p. 213–247.

Crider, A. F., 1913, Economic geology of Tell City and Owensboro quadrangles: Kentucky Geological Survey, ser. 4, v. 1, p. 263–317.

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.

Hopkins, M. E., and Simon, J. A., 1975, Pennsylvanian 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. 163–201.

Knox, Larry, 1975, Ostracods from the type rocks of the Morrowan Series (Lower Pennsylvanian), Arkansas and Oklahoma: Bloomington, Indiana University, Ph.D. thesis, 130 p.

Rexroad, C. B., Brown, L. M., and Wilke, N. A., 1999, Conodont paleontology of the Lead Creek Limestone Member of the Mansfield Formation (Pennsylvanian) in Indiana: American Association of Petroleum Geologists Bulletin, v. 83, p. 1,372.

Shaver, R. H., 1986, Lead Creek Limestone Member, 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. 74–75.

Shaver, R. H., and Smith, S. G., 1974, Some Pennsylvanian kirkbyacean ostracods of Indiana and midcontinent series terminology: Indiana Geological Survey Report of Progress 31, 59 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.