Age:

Devonian

Type designation:

Type section: The Morgan Trail Member of the New Albany Shale was named by Lineback (1968, 1970) for a roadside park 1 mile (1.6 km) southwest of the type section in the NW¼ sec. 16, T. 3 N., R. 8 E., Scott County, Indiana (Blocher quadrangle) (Burger and Hasenmueller, 1986).

Description:

At the type section the Morgan Trail consists of brownish-black to olive-black fissile siliceous shale containing pyritic calcareous laminae and beds (Burger and Hasenmueller, 1986). The thin hard pyritic beds are characteristic of this member, which is recognizable throughout the southern Indiana and northern Kentucky outcrop area but cannot be readily traced in the subsurface in southwestern Indiana (Burger and Hasenmueller, 1986). It lies above the Selmier Member and below the Camp Run Member of the New Albany Shale and ranges from 22 to 38 ft (6.7 to 11.6 m) in thickness in the shallow subsurface and in the outcrop area in southeastern Indiana (Hasenmueller, 1982; Burger and Hasenmueller, 1986). Fossils include linguloid brachiopods, Tasmanites, and silicified logs of the genus Callixylon (Burger and Hasenmueller, 1986).

Correlations:

The Morgan Trail Member is considered to be stratigraphically equivalent to the lower part of the Grassy Creek Shale of Illinois, to part of the Antrim Shale of Michigan and northern Indiana, and to the lower part of the Gassaway Member of the Chattanooga Shale of Tennessee (Lineback, 1968, 1970; Burger and Hasenmueller, 1986).

The Morgan Trail Members contains the early Famennian faunas of the Early and Middle triangularis and Early crepida Zones (conodont) (Sandberg, Hasenmueller, and Rexroad, 1994).

Regional Indiana usage:

Illinois Basin Margin (COSUNA 12)
Supergroup: none
Group: none
Formation: New Albany Shale
Member: Morgan Trail Member
Cincinnati Arch (COSUNA 13)
Supergroup: none
Group: none
Formation: New Albany Shale
Member: Morgan Trail Member

Misc/Abandoned Names:

None

Geologic Map Unit Designation:

Dnamt

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:

Burger, A. M., and Hasenmueller, N. R., 1986, Morgan Trail 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. 96.

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.

Hasenmueller, N. R., 1982, Resource assessment of the New Albany Shale (Devonian and Mississippian) in southeastern Indiana–preliminary report, in Eastern Oil Shale Symposium Proceedings, 1981: Lexington, University of Kentucky and Institute for Mining and Minerals Research, p. 173–180.

Lineback, J. A., 1968, Subdivisions and depositional environments of New Albany Shale (Devonian-Mississippian) in Indiana: American Association of Petroleum Geologists Bulletin, v. 52, p. 1,291–1,303.

Lineback, J. A., 1970, Stratigraphy of the New Albany Shale in Indiana: Indiana Geological Survey Bulletin 44, 73 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.