Elwood Atherton, Charles Collinson, and Jerry A. Lineback
The Hannibal Shale (Keyes, 1892, p. 289) is named for Hannibal, Missouri.
The type section of the Hannibal Shale is located near Hannibal, Missouri, where about 75 feet of sandy shale between the Louisiana Limestone (below) and the Burlington Limestone (above) was included in the formation. The formation is now defined as the shale overlying the "Glen Park" Formation and underlying the Chouteau Limestone, both of which are absent in the Hannibal type section. It is included in the New Albany Group.
The Hannibal Shale was called Maple Mill by Workman and Gillette (1956), but Collinson (1961) found that the Maple Mill Shale in Iowa correlates with the Saverton Shale of the Upper Devonian, and the original name was reinstated.
Extent and Thickness
The Hannibal Shale is widely exposed in the Mississippi and Illinois Valleys in western Illinois, and it extends eastward in subsurface across the state. It has a maximum thickness of about 100 feet in Calhoun County, but it thins eastward and is difficult to differentiate from the underlying Devonian shale in the deeper part of the basin.
The Hannibal, as exposed in the McCraney North Section, Pike County (NE NE 15, 4S-7W), is almost entirely a green to gray, argillaceous siltstone in the northern part of the outcrop area (Collinson, 1964). The lower part becomes increasingly argillaceous southward and consists of silty shale in Calhoun and Jersey Counties- for example, at Teneriffe School, Jersey County (NW cor. 9, 7N-13W). In the southern part of the outcrop area, the Hannibal contains a lens of black shale as much as 40 feet thick that is differentiated as the Nutwood Member. A siltstone facies formerly called the English River Formation (Workman and Gillette, 1956) is well developed in the upper part of the Hannibal in Adams and Hancock Counties.
The Hannibal Shale contains abundant conodonts, which show that the upper part of the formation is equivalent to the Chouteau Limestone in the area where the Chouteau and the North Hill Group are absent. Megafossils are scarce, but the brachiopod Chonopectus is abundant in some beds of the siltstone facies. "Roostertail" markings (Taonurus caudagalli) and irregular tubular markings (Scalarituba missouriensis) are common features, and they are the reason the Hannibal Shale was originally known as the "Vermicular Sandstone and Shales."
COLLINSON, CHARLES, 1961, Kinderhookian Series in the Mississippi Valley, in Northeastern Missouri and west-central Illinois: Kansas Geological Society Guidebook, 26th Annual Field Conference, Missouri Geological Survey Report of Investigations 27, p. 100-109; Illinois State Geological Survey Reprint 1961-U.
COLLINSON, CHARLES, 1964, Western Illinois: 28th Annual Tri-State Field Conference, Quincy, Illinois, Illinois State Geological Survey Guidebook Series 6, 30 p.
KEYES, C. R., 1892, Principal Mississippian section: Geological Society of America Bulletin, v. 3, p. 283-300.
WORKMAN, L. E., and TRACEY GILLETTE, 1956, Subsurface stratigraphy of the Kinderhook Series in Illinois: Illinois State Geological Survey Report of Investigations 189, 46 p.
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