Boles Member

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Lithostratigraphy: Ottawa Limestone Megagroup >>Ancell Group >>Joachim Dolomite >>Boles Member
Chronostratigraphy: Paleozoic Erathem >>Ordovician System >>Champlainian Series >>Blackriveran Stage
Allostratigraphy: Tippecanoe Sequence

Primary source

Willman, H. B., Elwood Atherton, T. C. Buschbach, Charles Collinson, John C. Frye, M. E. Hopkins, Jerry A. Lineback, and Jack A. Simon, 1975, Handbook of Illinois Stratigraphy: Illinois State Geological Survey Bulletin 95, 261 p.

Contributing author(s)

H. B. Willman and T. C. Buschbach

Name

Original description

The Boles Member of the Joachim Dolomite (Templeton and Willman, 1963, p. 60).

Derivation

Named for Boles, Franklin County, Missouri, 6 miles southwest of the type section.

Other names

History/background

Type section

Type location

The type section of the Boles Member is located in a quarry on the north side of the Missouri Valley 1 mile southwest of Matson, St. Charles County (NE cor. SE NE SW 4, 44N- 2E), where the member is 19.1 feet thick.

Type author(s)

Type status

Reference section

Reference location

Reference author(s)

Reference status

Stratigraphic relationships

The Boles Member overlies the Augusta Member of the Joachim Dolomite.

Extent and thickness

The Boles Member is commonly about 20 feet thick, ranging from 15-30 feet.

Lithology

It consists largely of thin to medium beds of dense silty dolomite and vuggy pure dolomite, separated by layers of dark red-brown to gray-green shale as much as 5 inches thick. Many bedding surfaces are ripple marked, and mud cracks are common. It contains several bands of white to black chert nodules and is the only persistent chert zone in the outcropping Joachim. However, chert is absent in places, and in subsurface in Illinois it occurs in other members of the Joachim. The Boles is distinguished from both the Augusta below and the Defiance above by its thin bedding, abundance of shale, and the chert bands.

Core(s)

Photograph(s)

Contacts

Well log characteristics

Fossils

Age and correlation

Environments of deposition

Economic importance

Remarks

References

TEMPLETON, J. S., and H. B. WILLMAN, 1963, Champlainian Series (Middle Ordovician) in Illinois: Illinois State Geological Survey Bulletin 89, 260 p.

ISGS Codes

Stratigraphic Code Geo Unit Designation
8270
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