Mansfield Formation
  

(HCH & WAH)

Raccoon Creek Group,

Pennsylvanian System


Type area and use of name: The Mansfield Formation was originally named the Mansfield Sandstone by Hopkins (1896, p. 199-200) for rocks exposed at Mansfield, Parke County, Ind. Cumings (1922, p. 527-528) amended the Mansfield to include all the rocks between the base of the Pennsylvanian System and the base of the Lower Block Coal Member, and this is the current definition. Kottlowski (1959), recognizing that the unit contains much shale and thin beds of coal, clay, and limestone, designated the unit as the Mansfield Formation.

Description and related nomenclature: The Mansfield rests unconformably, with as much as 150 feet (46 m) of local relief, on Mississippian rocks that are generally progressively older northward. Progressive northward overlap is also suggested by the 50- to 300-foot (15- to 91-m) range in thickness of the exposed Mansfield. The lowermost part of the Mansfield commonly consists of sandstone, generally crossbedded and containing a quartz-pebble and chert conglomerates in places, but it also includes dark carbonaceous shale in many places. The quartz-pebble conglomerate is also found in higher parts of the formation.

In the Shoals area of southwestern Indiana, the Mansfield has two broad, more or less distinct, vertically separate divisions the lower consists mostly of sandstone, and the upper consists dominantly of shale and mudstone (Gray, Jenkins, and Weidman 1960, p. 23). The divisional boundary is at the position, or inferred position, of the Pinnick Coal Member, which near Shoals lies 50 to 185 feet (15 to 56 m) above the base and 200 feet (61 m) below the top of the formation. Three lithologies, passing laterally into one another, also have been recognized in southwestern Indiana (Gray, 1962, p. 28-33). The Cannelton Lithofacies, nearest the Ohio River, consists dominantly of siltstone and mudstone the Shoals Lithofacies, well exposed near Shoals, Martin County, has many cross-stratified sandstones and the Bloomfield Lithofacies, named for that town in Greene County, is characterized by an abundance of gray shales.

The seven named members of the Mansfield in ascending order are the French Lick, St. Meinrad, Pinnick, Blue Creek, and Mariah Hill Coal Members the Lead Creek Limestone Member and the Shady Lane Coal Member.

Other member and bed names having limited, colloquial, or outdated use are the Cannelton Sandstone, which was the name applied by Hopkins (1896, p. 314) to the massive sandstone that crops out in the bluff of the Ohio River behind Cannelton, Perry County; the Cannelton Coal of Logan (1922, p. 623), which was probably applied to both the Upper and Lower Cannelton Coals, especially the upper nearer Tell City and the lower near Cannelton, Perry County; the Lower Huntingburg Coal, which is Franklin and Wanless's (1944, p. 87) designation for what is also the Mariah Hill Coal Member; the Shoals Coal (Logan, 1922, p. 623), which is near the base of Pennsylvanian rocks in the railroad cut west of Shoals, Martin County; the Kirksville Coal (Logan,1922, p. 623-624), which is found in the southwestern part of Monroe County near Kirksville; and the Grandview Limestone of Franklin and Wanless (1944, p. 89-90), which is probably coextensive with the Ferdinand Limestone Bed.

The term Coal I was intended to apply to the lowest Mansfield coalbed, but as used by Ashley (1899) it actually refers to the lowest commercial coal at any given place. The name, therefore, applied to more than one bed, and it has not been widely used. The French Lick Coal Member is the lowest named member and is overlain by about 50 feet (15 m) of mudstone, siltstone, and fine-grained sandstone of remarkably even bedding. These silty rocks, best exhibited and formerly quarried near French Lick in Orange County, were called the Hindostan Whetstone Beds as early as 1838 by Owen (1859, p. 16) and were described in detail by Cox (1876, p. 6-8). The Pinnick Coal Member lies some 50 feet (15 m) above the French Lick in the French Lick area. The Upper and Lower Cannelton Coals were extensively mined near Cannelton, Perry County, and were first described by Lesley (1862, p. 343-344). Apparently, these coals are the same coals described as the Troy Coal and the Upper Troy Coal at Troy, Perry County, by Franklin and Wanless (1944, p. 86-87).

The Upper Troy Coal of Franklin and Wanless (1944, p. 88) appears to be the same as the St. Meinrad Coal Member, which is sufficiently thick to be extensively mined near St. Meinrad, Spencer County, and throughout northwestern Perry County.

North of southern Parke County the Lower Block Coal Member (Brazil Formation) is absent or unidentifiable, so that it is nearly impossible to separate the Brazil and Mansfield Formations in southern Indiana, in Daviess (Hutchison, 1971a), Dubois (Hutchison, 1964), and Spencer (Hutchison, 1959) Counties, coalbeds believed to be the equivalent of the block coals are present over most of the area but are difficult to distinguish from coals in the upper Mansfield,

Correlation: The rocks assigned to the Mansfield Formation are equivalent to the Caseyville Formation and the lower part of the Abbott Formation of Illinois, the Caseyville Formation and the lower part of the Tradewater Formation of western Kentucky, part of what has commonly been called the Pottsvillian Series of the Appalachian area, and to the Morrowan Series of the midcontinent area. The Hindostan flora was described by Read (1947) as early Pottsvillian in age. Unnamed Mansfield limestones in Parke County are in the ostracod Zone of Amphissites rothi, and unnamed Mansfield limestones near Troy and Cannelton, Spencer and Perry Counties, contain the fusulinid Profusulinella, the Amphissites rothi fauna, and the ostracod Cavellinella casei, all of which are thought to indicate a Morrowan age. (See Thompson and Shaver, 1964, Shaver and Smith, 1974, and Shaver, 1984, and for additional faunal evidence see the article on the Lead Creek Limestone Member.)






 
 
 
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