- Usage in publication:
-
- Mackinaw Member
- Modifications:
-
- Original reference
- Dominant lithology:
-
- Sand
- Gravel
- AAPG geologic province:
-
- Illinois basin
Summary:
Pg. 71-72; Illinois Bull., no. 95, p. 226, 1975. Mackinaw Member of Henry Formation. Well-sorted, regularly bedded sand, pebbly sand, and gravel deposited as outwash valley trains leading outward from Wisconsinan glacier fronts. Thickness 30 to 100+ feet. Rests on Wedron Formation and older rocks. In area of Wisconsinan glaciation, generally overlain by Richland Loess; elsewhere overlain by Peoria Loess. Present along many valleys throughout Illinois. Age is Pleistocene (Wisconsinan Age; Altonian Subage).
Type section: gravel pit on southwest side of Mackinaw, in NE/4 NW/4 sec. 19, T. 24 N., R. 2 W., Tazewell Co., central IL. Named from village of Mackinaw, Tazewell Co., central IL.
Source: Publication; Hdbk Illinois stratigraphy (Illinois Geol. Survey Bull. 95, p. 226); US geologic names lexicon (USGS Bull. 1520, p. 189).
- Usage in publication:
-
- Mackinaw facies (informal)*
- Modifications:
-
- Revised
- AAPG geologic province:
-
- Illinois basin
Summary:
Pg. 16, 18, 56, 57. Mackinaw facies (informal) in Henry Formation of Mason Group. The lithogenetic-defined Mackinaw Member of Willman and Frye is retained as an informal sedimentary facies useful in understanding glacial history and in mapping glacial deposits. [Age is considered Pleistocene (Wisconsinan Age; Woodfordian Subage), based on age of Henry Formation.]
Source: Publication.
For more information, please contact Nancy Stamm, Geologic Names Committee Secretary.
Asterisk (*) indicates published by U.S. Geological Survey authors.
"No current usage" (†) implies that a name has been abandoned or has fallen into disuse. Former usage and, if known, replacement name given in parentheses ( ).
Slash (/) indicates name conflicts with nomenclatural guidelines (CSN, 1933; ACSN, 1961, 1970; NACSN, 1983, 2005, 2021). May be explained within brackets ([ ]).