Usage:
Hennepin Member of Pecatonica Formation of Platteville Group (IL)
Hennepin Member of Glenwood Formation of Ancell Group (IA?,WI)
(†Hennepin not used by the MN Geol. Survey; type locality in MN. Rocks incl. in unnamed upper part of Glenwood Formation. See Glenwood.)
Geologic age:
Late Ordovician (Mohawkian; Turinian)
Type section, locality, area and/or origin of name:
Type section: bluff on west side of Mississippi River at Lock and Dam No. 1, Minneapolis, in NE/4 SW/4 NW/4 sec. 17, T. 28 N., R. 23 W., [approx. Lat. 44 deg. 54 min. 54 sec. N., Long. 93 deg. 12 min. 11 sec. W., St. Paul West 7.5-min quadrangle], Hennepin Co., eastern MN (Templeton and Willman, 1963, Illinois Geol. Survey Bull., no. 89, p. 75; Willman and Buschbach, 1975, Illinois Geol. Survey Bull., no. 95, p. 47-87).
Named from Hennepin Co., eastern MN (Templeton and Willman, 1963, p. 75; Willman and Buschbach, 1975).
Notable exposures in Dixon-Oregon area, northern IL (Templeton and Willman, 1952).
AAPG geologic province:
Iowa shelf
Wisconsin arch
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 ([ ]).