Historical:Hall Limestone Member
M. E. Hopkins and J. A. Simon
The Hall Limestone Member of the Modesto Formation (Willman, in Cooper, 1946, p. 12) is named for Hall Township, Bureau County.
The type section consists of exposures in a ravine west of the coal mine refuse pile in the western part of the town of Spring Valley (NW SW 33, 16N-11E) (Wanless, 1956, p. 12).
The Hall is correlated with the Macoupin Limestone of southern and eastern Illinois.
Extent and Thickness
The Hall is recognized only in northern Illinois.
In the type section it lies about 45 feet below the La Salle Limestone Member.
At the type section, it consists of a 3-foot ledge of fine-grained, green, gray, and red limestone containing numerous brachiopods, crinoid columnals, and bryozoans. It is underlain by a persistent black shale.
COOPER, C. L., 1946, Pennsylvanian ostracodes of Illinois: Illinois State Geological Survey Bulletin 70, 177 p. WANLESS, H. R., 1956, Classification of the Pennsylvanian rocks of Illinois as of 1956: Illinois State Geological Survey Circular 217, 14 p.
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