Pleistocene drainage incision in the upper Mississippi Valley Driftless Area

Conference · Tue Jan 01 04:00:00 EST 1985 · Geol. Soc. Am., Abstr. Programs; (United States)

OSTI ID:6463250

Knox, J C

The deep dissection of the Wisconsin Driftless Area and topographically similar, but glaciated areas in adjacent states is generally acknowledged to have occurred during the Pleistocene, but the precise chronology has been poorly understood. The distribution of pre-Illinoian glacial outwash gravels on uplands and valley side benches near the Mississippi River, on the western margin of the Wisconsin Driftless Area, indicates that the major incision (50-60 m) of drainage had occurred during the very early Pleistocene. Deposits in cut-off valley meanders, a common feature in the lower reaches of Driftless Area rivers, provide a basis for relative dating of the valley incision. The cut-offs appear to have evolved episodically when, at various times during the Pleistocene, glacial debris blocked the drainages of the Mississippi and Wisconsin Rivers causing massive alluviation of side valley tributaries. A radiocarbon date of 21,910 +/- 350 year B.P., representing a buried soil horizon at 22 m depth and about 9 m above the bedrock floor of a cut-off valley meander and 18 m above the bedrock floor of the adjacent present-day valley, supports stratigraphic interpretations that suggest modest valley incision into bedrock probably occurred during the Illinoian and may have also occurred during the early Wisconsinan.

• Research Organization: Univ. of Wisconsin, Madison (USA)
• OSTI ID: 6463250
• Report Number(s): CONF-8510489-
• Conference Information: Journal Name: Geol. Soc. Am., Abstr. Programs; (United States) Journal Volume: 17
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580100* -- Geology & Hydrology-- (-1989)
AGE ESTIMATION
ALLUVIAL DEPOSITS
CENOZOIC ERA
DEPOSITION
DRAINAGE
FEDERAL REGION V
GEOLOGIC AGES
GEOLOGIC DEPOSITS
GEOLOGIC HISTORY
GEOLOGY
GEOMORPHOLOGY
GLACIERS
ISOTOPE DATING
MORAINES
NORTH AMERICA
PLEISTOCENE EPOCH
QUATERNARY PERIOD
TOPOGRAPHY
USA
WATERSHEDS
WISCONSIN