Type section: The name "Bridge Junction Sandstone Member" was used by Friedman (1989) in describing a sandstone exposed at Bridge Junction in Coal Creek valley in the NE¼ sec. 29, T. 13 N., R. 9 W., 3.75 miles (6.0 km) southwest of New Goshen, Vigo County, Indiana. This exposure was designated the type section because it shows the thickest sandstone and typical bedding of the rock (Hasenmueller, 1986).
The Bridge Junction Sandstone Member is a light-brown sandstone that is massive, thick bedded to cross bedded, and fine grained to medium grained (Hasenmueller, 1986). The unit weathers red brown. The brown color of fresh samples of sandstone is typical of channel deposits. In places, this sandstone is slightly calcareous. The sandstone averages 30 ft (9 m) in thickness; however, it is as much as 90 ft (27 m) thick in sec. 26, T. 13 N., R. 9 W., Vigo County (Hasenmueller, 1986; Friedman, 1989).
The Bridge Junction Sandstone Member is overlain by a thin noncalcareous to calcareous gray shale, which is overlain by the Universal Limestone Member of the Dugger Formation (Hasenmueller, 1986). In the absence of both the shale and the limestone, the sandstone is overlain by underclay (Hasenmueller, 1986).
Although he did not use the name "Bridge Junction," Friedman (1960, p. 28) stated that the sandstone in the New Goshen Channel, which is now recognized as the Bridge Junction sandstone, was in the same stratigraphic position as a thick sandstone that lay below the Danville Coal Member of the Dugger Formation in Sullivan and Knox Counties. The New Goshen Channel sandstone was also equated with the Anvil Rock sandstone of Illinois and Kentucky by Friedman (1960). Anvil Rock-filled channels were mapped in southern Illinois, southwestern Indiana, and western Kentucky by Hopkins (1958), and in 1986 Ault formally introduced the name "Anvil Rock Sandstone Member of the Dugger Formation" for use in Posey, Gibson, and Knox Counties in southwestern Indiana. Although the Anvil Rock and the Bridge Junction are at the same stratigraphic position, further study is needed to determine if they belong to one body of rock and to establish definitive correlation (Ault, 1986; Hasenmueller, 1986).
Regional Indiana usage:
Illinois Basin (COSUNA 11)
Geologic Map Unit Designation:
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 featuers in Indiana.
Major tectonic features that affect bedrock geology in Indiana.
Ault, C. H., 1986, Anvil Rock Sandstone 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. 6.
Hansen, W. R., 1991, Suggestions to authors of the reports of the United States Geological Survey (7th ed.): Washington, D.C., U.S. Geological Survey, 289 p.
Hasenmueller, N. R., 1986, Bridge Junction Sandstone 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. 21-22.
Hopkins, M. E., 1958, Geology and petrology of the Anvil Rock Sandstone of southern Illinois: Illinois State Geological Survey Circular 256, 49 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.
For additional information contact:
Nancy Hasenmueller (firstname.lastname@example.org)Date last revised: July 28, 2017