Matson Member

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Lithostratigraphy: Ottawa Limestone Megagroup >>Ancell Group >>Joachim Dolomite >>Matson 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


Original description

The Matson Member of the Joachim Dolomite (Templeton and Willman, 1963, p. 61).


Named for Matson, St. Charles County, Missouri, just east of the type section.

Other names


Type section

Type location

The type section of the Matson Member is located in the north bluff of the Missouri Valley (NE NE NE 4, projected, 44N-2E), where the member is 29.8 feet thick.

Type author(s)

Type status

Reference section

Reference location

Reference author(s)

Reference status

Stratigraphic relationships

The Matson Member overlies the Defiance Member of the Joachim Dolomite.

Extent and thickness

The Matson Member persists throughout the area of the Joachim. In Illinois it is exposed only at West Point Landing in Calhoun County, where it is 21 feet thick. It is about 30 feet thick in the outcrop area, but in subsurface in Illinois it commonly is 15-40 feet thick.


The Matson Member differs from the other Joachim Members in being relatively pure, brown, finely porous dolomite that generally appears to be massive but is finely laminated, the laminae separated by thin films of dark brown clay. Locally it contains a few thin beds of the lithologic types common in the Defiance and Augusta Members. The Matson appears to be largely algal in origin.




Well log characteristics


In the Matson Member ostracodes occur locally in the basal beds, and a marine fauna with corals, brachiopods, and trilobites has been observed in the basal beds at one locality near Zell, Missouri.

Age and correlation

Environments of deposition

Economic importance



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