Type area: A sequence of thick-bedded buff granular magnesian limestones exposed around Little Traverse Bay in the northwestern part of the Lower Peninsula of Michigan was named the "Little Traverse Group" by N. H. Winchell (1871, p. 26-33) (Burger, 1970; Droste and Shaver, 1986).
History of usage:
Lane (1895, p. 24) shortened the name “Little Traverse Group” to the Traverse Group, and this terminology is now used in the type area and in the Michigan Basin subsurface (Cohee, 1944, 1947), where the term "Traverse Limestone" is also used (Droste and Shaver, 1986). (See Shaver, 1984.)
The Traverse consists of a variety of limestones, some dolostone, and thin shale beds (Droste and Shaver, 1986). These are recognized as making up three stratigraphic units (unnamed to member in Indiana) (Droste and Shaver, 1986). In ascending order, they are: (1) 9 to 15 ft (2.8 to 4.6 m) of interbedded light-gray dense limestone (pellmicrite), light-yellow-brown micritic very fossiliferous (corals, stromatoporoids, and brachiopods) limestone, and crinoidal calcarenite (biosparite); (2) in northwestern Indiana, as much as 50 ft (15 m) of light-colored, highly fossiliferous limestone (including crinoidal, stromatoporoidal, and coralline limestones, partly in bioherms) and lithographic and sublithographic limestones and, in northeastern Indiana, more than 30 ft (9 m) of dark very fossiliferous calcareous shale and argillaceous limestone; and (3) 15 to 50 ft (4.6 to 15 m) of light-colored dense to medium-grained, somewhat cherty dolostone (Droste and Shaver, 1986). Sandy (quartz), brecciated, and oolitic rocks are present in some places and are characteristic of given stratigraphic intervals (Droste and Shaver, 1986). (See Shaver and others, 1971, p. 50-53; Lazor, 1971; Orr, 1971, p. 8-9 and appendix sections; and Doheny, Droste, and Shaver, 1975, p. 35 and appendix sections.)
The Traverse of Indiana overlies the Detroit River Formation unconformably wherever Detroit River rocks are present (Droste and Shaver, 1986). This relationship is an overlapping one, so that in updip areas along the north flank of the Kankakee and Cincinnati Arches the Traverse rests on differing parts of the Detroit River and in some places extends past the eroded (pre-Traverse) edge of Detroit River rocks (Droste and Shaver, 1986). In these places, therefore, the Traverse rests with major unconformity on Silurian rocks of the Wabash Formation. In northwestern Indiana the Traverse continues onto the crestal area of the Kankakee Arch and coextends with the North Vernon Limestone of central and southern Indiana (Droste and Shaver, 1986). (See Doheny, Droste, and Shaver, 1975, p. 33-34.) The Traverse is overlain by the Antrim Shale, both conformably and with modest unconformity according to Orr (1971, fig. 4 and p. 21) and Shaver (1984) (Droste and Shaver, 1986).
The Traverse Formation physically extends into the North Vernon Limestone across the crestal area of the Kankakee Arch in Jasper County and adjacent counties (Droste and Shaver, 1986). Droste and Shaver (1986) note that for the crestal area all across northern Indiana, however, it is a moot point as to which of the many pre-1970 references in the literature to Devonian rocks should have been to the Traverse and which should have been to the North Vernon rather than to the often erroneously identified Jeffersonville Limestone (= Detroit River). North or south of the crestal area, most of the Middle Devonian carbonate rocks of historical record in that area are readily identifiable with the Traverse, whether directly as that formation or in a correlative sense (Droste and Shaver, 1986). See a history of these misidentifications of Traverse-North Vernon rocks in Doheny, Droste, and Shaver, 1975, p. 4-6; see also the North Vernon Limestone article and Orr, 1971, p. 9, for now-obsolete names applied to these rocks (Droste and Shaver, 1986).
Regional Indiana usage:
Kankakee Arch (COSUNA 14)
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 features in Indiana.
Major tectonic features that affect bedrock geology in Indiana.
Burger, A. M., 1970, Traverse Formation, in Shaver, R. H., Burger, A. M., Gates, G. R., Gray, H. H., Hutchison, H. C., Keller, S. J., Patton, J. B., Rexroad, C. B., Smith, N. M., Wayne, W. J., and Wier, C. E., Compendium of rock-unit stratigraphy in Indiana: Indiana Geological Survey Bulletin 43, p. 178-179.
Cohee, G. V., 1944, Thickness and character of the Traverse Group and Dundee Formation in southwestern Michigan: U.S. Geological Survey Oil and Gas Investigations (Preliminary) Chart 4.
Cohee, G. V., 1947, Lithology and thickness of the Traverse Group in the Michigan Basin U.S. Geological Survey Oil and Gas Investigations (Preliminary) Chart 28.
Droste, J. B., and Shaver, R. H., 1986, Traverse 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. 156-157.
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.
Indiana University Paleontology Seminar, 1980, Stratigraphy, structure, and zonation of large Silurian reef at Delphi, Indiana: American Association of Petroleum Geologists Bulletin, v. 64, p. 115-131.
Janssens, Adriaan, 1970, Middle Devonian formations in the subsurface of northwestern Indiana: Ohio Geological Survey Report of Investigations 78, 22 p.
Klapper, Gilbert, and Johnson, J. G., 1980, Endemism and dispersal of Devonian conodonts: Journal of Paleontology, v. 54, p. 400-455.
Lane, A. C., 1895, The Traverse Group [edited from notes of C. E. Wright]: Michigan Geological Survey Report, v. 5, pt. 2, p. 24-25.
Lazor, J. D., 1971, Petrology and subsurface stratigraphy of the Traverse Formation (Middle Devonian) in northern Indiana: Bloomington, Indiana University, Ph.D. thesis, 143 p.
Orr, R. W., 1969, Stratigraphy and correlation of Middle Devonian strata in the Logansport Sag, north-central Indiana: Indiana Academy of Science Proceedings, v. 78, p. 333-341.
Schneider, A. F., and Keller, S. J., 1970, Geologic map of the 1° x 2° Chicago quadrangle, Indiana, Illinois, and Michigan, showing bedrock and unconsolidated deposits: Indiana Geological Survey Regional Geologic Map No. 4, Part A [bedrock units].
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.
Shaver, R. H., Doheny, E. J., Droste, J. B., Lazor, J. D., Orr, R. W., Pollock, C. A., and Rexroad, C. B., 1971, Silurian and Middle Devonian stratigraphy of the Michigan Basin–a view from the southwest flank, in Forsyth, J. L., Geology of the Lake Erie islands and adjacent shores: Michigan Basin Geological Society Guidebook, p. 37-59.
Shaver, R. H., with contributions by Gray, H. H., Pinsak, A. P., Sunderman, J. A., Thornbury, W. D., and Wayne, W. J., 1961, Stratigraphy of the Silurian rocks of northern Indiana: Indiana Geological Survey Field Conference Guidebook 10, 62 p.
Winchell, N. H., 1871, Report of progress of the State Geological Survey of Michigan: Michigan Geological Survey, 64 p.
For additional information, contact:
Nancy Hasenmueller (firstname.lastname@example.org)Date last revised: November 22, 2016