Historical:Howardton Limestone Member
Lithostratigraphy: Hunton Limestone Megagroup >>Lingle Formation
Chronostratigraphy: Paleozoic Erathem >>Devonian System >>Middle Devonian Series
Allostratigraphy: Kaskaskia Sequence
Charles Collinson and Elwood Atherton
The Howardton Limestone Member of the Lingle Formation (North, 1969, p. 22-25) is named for Howardton, Jackson County, 2 miles east of the type section.
The type section of the Howardton Limestone Member is located in a quarry in the Backbone ridge north of Grand Tower (NE NE SE 23, 10S-4W), where it is 33 feet thick.
Extent and Thickness
The Howardton extends throughout much of the area of the Lingle, but it is overlapped by the Tripp Member in the northern part. It is as much as 110 feet thick in southeastern Illinois and generally thins northward and westward.
The Howardton Limestone Member of the Lingle Formation (North, 1969, p. 22-25) is the basal member of the Lingle Formation.
The Howardton is gray, fine-grained, slightly silty, argillaceous limestone, most of which has thin, shaly partings. The base of the Howardton is the original Grand Tower-Lingle contact of Savage (1920). The top of the Howardton is charaterized by a thin intraformational microbreccia with light-colored limestone fragments in a dark matrix.
The basal few feet of the Howardton is characterized by a small, button-shaped coral, Microcyclus.
NORTH, W. G., 1969, Middle Devonian strata of southern Illinois: Illinois State Geological Survey Circular 441, 45 p.
SAVAGE, T. E., 1920, Devonian formations of Illinois: American Journal of Science, v. 49, p. 169-182.
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