Environmental Assessment. Wing Dam Improvements at Johnson Island Pool 18, Mississippi River, Des Moines County, Iowa

1992 ◽  
Author(s):  
ARMY ENGINEER DISTRICT ROCK ISLAND IL
Keyword(s):  
Environmental Assessment ◽  
Mississippi River ◽  
Des Moines

Provenance, age, and environment of mid-wisconsinan slackwater lake sediment in the St. Louis Metro East Area, USA

2006 ◽  
Vol 65 (1) ◽  
pp. 108-122 ◽  
Author(s):  
B. Brandon Curry ◽  
David A. Grimley
Keyword(s):  
Lake Sediment ◽  
Mississippi River ◽  
Lake Michigan ◽  
Fine Sand ◽  
River Valley ◽  
Green Bay ◽  
Mississippi River Valley ◽  
Des Moines ◽  
Last Glaciation ◽  
Superior Lobe

AbstractValleys tributary to the Mississippi River contain fossiliferous slackwater lake sediment (Equality Formation) deposited in response to aggradation of the Mississippi River valley during the last glaciation. In the St. Louis Metro East area, the lower part of the Equality Formation is primarily laminated, fossiliferous silt and clay deposited from about 44,150 to 24,310 14C yr B.P. The upper Equality Formation is primarily very fine sand to silt deposited from about 21,200 to 17,000 14C yr B.P. Among the four cores that sample this succession in the St. Louis Metro East area, core MNK-3 (38.64EN, 90.01EW) was selected for detailed study. Three sources are distinguished by the following characteristics: (1) gray smectite-quartz-Se-rich, feldspar-poor material of the Des Moines, Wadena, and James lobes; (2) reddish brown kaolinite–Cu–Fe-rich sediment of the Superior and Rainy lobes; and (3) brown illite–dolomite–Sr-rich sediment of the Lake Michigan and Green Bay lobes. The earliest sediments (44,150 to 41,700 14C yr B.P.) were derived from the central and western provenances and are chronocorrelative with the lower Roxana Silt. A hiatus occurred from about 41,700 to 29,030 14C yr B.P. when much of the middle Roxana Silt (Meadow Member) was deposited on adjacent uplands. The youngest sediment includes evidence of heightened activity of the Superior Lobe at about 29,000 14C yr B.P., the Lake Michigan and Green Bay lobes from about 25,000 to 24,000 14C yr B.P., and the Wadena-Des Moines-James lobes at about 21,000 14C yr B.P.

Sign in / Sign up

Export Citation Format

Share Document