IGNIS
Limberlost Dolomite Member

Age:

Silurian

Type designation:

Type section: The name “Limberlost Dolomite” was originally used by Droste and Shaver (1976, p. 4) for exposures of dolostone in the Limberlost area near Geneva in Adams and Jay Counties, Indiana (Droste and Shaver, 1986). They designated the type section in the John W. Karch Stone Co. quarry 4.5 miles (7.2 km) east-southeast of Geneva, Adams County (SW¼SW¼ sec. 31, T. 25 N., R. 15 E.) (New Corydon quadrangle).

Principal reference section: The principal reference section is in the Meshberger Bros. Stone Corp. quarry 1.25 miles (2 km) southeast of Fairview, Randolph County (SW¼NW¼ sec. 11, T. 21 N., R. 12 E.) (Droste and Shaver, 1976) (Redkey quadrangle) (Droste and Shaver, 1986).

Reference sections:

(1) A reference section is in the Meshberger Bros. Stone Corp. quarry 3 miles (4.8 km) south of Pleasant Mills, Adams County (center sec. 4, T. 26 N., R. 15 E.) (Droste and Shaver, 1976) (Willshire quadrangle).

(2) A subsurface reference section consists of rocks penetrated by Indiana Geological Survey drill hole 72 (Indiana Geological Survey Petroleum Database Management System No. 140455) in the abandoned Markland Avenue Quarry in Kokomo, Howard County (SW¼SW¼ LaFountain Res., T. 24 N., R. 3 E.) (Droste and Shaver, 1976).

History of usage:

Change in rank: The Limberlost Dolomite Member was originally ranked as a formation by Droste and Shaver (1976, p. 4) (Droste and Shaver, 1986). In 1982, Droste and Shaver reduced the Limberlost Dolomite to member status and designated it as the bottommost unit in the Pleasant Mills Formation (Droste and Shaver, 1986).

Description:

The Limberlost is made up of several subtly different carbonate facies, the dominant one consisting of light-brown micritic to fine-grained rather pure dolostone (Droste and Shaver, 1986). Variations include fine-grained, faintly to strongly laminated and color-banded dolostone, oolitic dolostone, coarser grained bioclastic vuggy dolostone, and bluish-gray mudstone dolostone (the latter two lithologies in association with reef-flank and reef-core rocks) (Droste and Shaver, 1986).

In general, granularity decreases and laminated appearance increases northward and eastward toward the Michigan and Appalachian Basins, in that the Limberlost takes on typical characters of the basin carbonate facies of the Salina Group in those directions (Droste and Shaver, 1986). Oolites are conspicuous to dominant in many places in the central and eastern parts of northern Indiana, and dolostone containing molds of euhedral gypsum crystals is present in some places (Droste and Shaver, 1986). The Limberlost is a relatively unfossiliferous unit, and it represents a restricted environment in which many reefs, growing upward from within the underlying Salamonie sediments, became aborted (Droste and Shaver, 1986). Generally westward from eastern Indiana and western Ohio, reefs were less adversely affected, so that in places the Limberlost is made up entirely of its reef facies that is variably flanked by other facies, including the oolitic and coarser bioclastic facies (Droste and Shaver, 1986). The range in such relationships is well illustrated in quarries near Celina, Ohio, and New Corydon (the type quarry), Pleasant Mills, and Montpelier, Indiana (Droste and Shaver, 1986).

Distribution: The Limberlost has the same defined southern and southwestern boundaries in Indiana as do the Pleasant Mills Formation and the Salina Group, including an eroded limit in central eastern Indiana and a practically recognizable depositional wedge edge extending northwestward from Shelby County and thence northward to southern Lake County (Droste and Shaver, 1986.) A northern practical limit extends approximately across the second tier of northern Indiana counties (Droste and Shaver, 1986). In part of this area and northward, the Limberlost becomes indistinguishable because it is involved with the lower part of hundreds of feet of reef facies (the Fort Wayne Bank) and because the Waldron lithology, normally seen above the Limberlost, is hardly recognizable anywhere north of the Fort Wayne Bank (Droste and Shaver, 1986).

In this distribution the Limberlost ranges in thickness from zero along both eroded and depositional edges to more than 70 ft (21 m) in a few northern locales (Droste and Shaver, 1976, fig. 1, and 1982, appendix, secs. O-Z) (Droste and Shaver, 1986).

Boundaries:

The Limberlost is underlain by the Salamonie Dolomite and is overlain by the Waldron Member of the Pleasant Mills Formation (Droste and Shaver, 1986). Both the lower and the upper Limberlost contacts appear to be conformable, but there probably is minor unconformity in some places along the lower contact, for example, possibly in the reference-section quarry in Randolph County (Droste and Shaver, 1986).

Correlations:

A common late Llandoverian-middle Wenlockian (late Alexandrian-middle Niagaran) guide fossil, the brachiopod Pentamerus oblongus, is found at its highest stratigraphic range in the Limberlost (Droste and Shaver, 1986). It is followed closely above in middle Pleasant Mills and Louisville rocks by species of the pentamerid genus Rhipidium (late Wenlockian-early Ludlovian) (Droste and Shaver, 1986).

The lower Limberlost boundary and at least lower Limberlost-equivalent rocks can be correlated by physical tracing and by sequential position throughout much of the Great Lakes region, possibly including even western New York and western Ontario (Droste and Shaver, 1986). The Limberlost is a key unit, representing onset of restricted, near-evaporitic conditions that followed deposition of a great, widespread blanket of light-colored coarse-grained bioclastic carbonate rocks of the Niagara and Lockport Groups, the Salamonie Dolomite, and the Joliet Formation (Droste and Shaver, 1986). In those areas (for example, western Ohio) where Lockport rocks extend stratigraphically higher than they do in most places, the Limberlost position is within an upper part of the Lockport Group, that is, just below or within what is called the Guelf Dolomite in some places (Droste and Shaver, 1986). Closely equivalent units include the Greenfield Dolomite (Salina Group) of western Ohio, brown carbonate rocks of the Michigan Basin that have been variably assigned to the upper part of the Niagara Group and to the lower part of the A unit of the Salina Group, and the Sugar Run Formation of northeastern Illinois (Droste and Shaver, 1986). In each of these examples, however, the upper Limberlost boundary can hardly be coordinated precisely because the Waldron, present in Indiana, is mostly lacking beyond the borders of the state (Droste and Shaver, 1986).

Droste and Shaver (1986) noted that the Limberlost is likely a time-transgressive unit, particularly between what were basin- and shelf-depositional areas. For example, the depositional wedge in northern Indiana is thought to be the same age as upper Salamonie (Laurel) rocks of southern Indiana, but the relationship is expressed as a wedge and not as a vertical cutoff (Droste and Shaver, 1986).

Regional Indiana usage:

Illinois Basin Margin (COSUNA 12)
Supergroup: none
Group: Salina Group
Formation: Pleasant Mills Formation
Member: Limberlost Dolomite Member
Cincinnati Arch (COSUNA 13)
Supergroup: none
Group: Salina Group
Formation: Pleasant Mills Formation
Member: Limberlost Dolomite Member
Kankakee Arch (COSUNA 14)
Supergroup: none
Group: Salina Group
Formation: Pleasant Mills Formation
Member: Limberlost Dolomite Member
Michigan Basin (COSUNA 15)
Supergroup: none
Group: Salina Group
Formation: Pleasant Mills Formation
Member: Limberlost Dolomite Member

Misc/Abandoned Names:

None

Geologic Map Unit Designation:

Spml

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.)

Map showing the COSUNA areas (heavy black line) that approximate regional bedrock outcrop patterns and major structural features in Indiana, and the COSUNA numbers (large bold font) for these areas. The COSUNA boundaries are limited to state and county boundaries that facilitate coding.

COSUNA areas and numbers that approximate regional bedrock outcrop patterns and major structural features in Indiana.

Map showing major tectonic features that affect bedrock geology in Indiana.

Major tectonic features that affect bedrock geology in Indiana.

References:

Droste, J. B., and Shaver, R. H., 1976, The Limberlost Dolomite of Indiana, a key to the great Silurian facies in the southern Great Lakes area: Indiana Geological Survey Occasional Paper 15, 21 p.

Droste, J. B., and Shaver, R. H., 1982, The Salina Group (Middle and Upper Silurian) of Indiana: Indiana Geological Survey Special Report 24, 41 p.

Droste, J. B., and Shaver, R. H., 1986, Limberlost Dolomite 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. 79-80.

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.

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 (hasenmue@indiana.edu)
Date last revised: June 13, 2017

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