Historical:Trowbridge Coal Member
M. E. Hopkins and J. A. Simon
The Trowbridge Coal Member of the Mattoon Formation (Cady, 1948, p. 5, footnote 4) is named for Trowbridge, Shelby County.
The type locality consists of outcrops about 1 mile northeast of the town (S line 11, 10N-6E).
Extent and Thickness
The Trowbridge attains a maximum thickness of 2.5-3 feet. It has not been traced far from the type area.
It occurs about 150-180 feet above the Omega Limestone.
The Trowbridge is a normally banded coal that is high in ash.
CADY, G. H., 1948, Analyses of Illinois coals: Illinois State Geological Survey Supplement Bulletin 62, 77 p.
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