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Missouri River Alluvial Aquifer

Geology of the Missouri River Alluvial Aquifer

The floodplains of the Missouri River, Kansas River, Blue River, Little Blue River, and Fishing River are underlain by Quaternary age alluvial deposits consisting of clay, silt, sand, gravel, cobbles, and boulders. These deposits lie atop shale, limestone and sandstone bedrock and form the alluvial aquifer that is the focus of this investigation. The nature and extent of the alluvial deposits have been greatly influenced by glacial processes that caused numerous changes in discharge, sediment load, and course of these rivers over time. The present course of the Missouri River approximates the southern-most limit of continental glaciation.

Several abandoned alluvial channels are hydraulically connected to the Missouri River alluvial aquifer and exist as a result of changes in the course of the Missouri River and its tributaries during previous glacial and interglacial periods. The largest abandoned channel is located in the eastern part of the study area near the Lake City Army Ammunition Plant and is now occupied by the Little Blue River and Fire Prairie Creek. (plate 1). This abandoned channel is connected to a buried alluvial channel that extends north from Buckner, then divides with one arm extending northeast to the Missouri River alluvial aquifer near Sibley and the other arm extending northwest to the Missouri River alluvial aquifer near the Little Blue river.

Bedrock Altitude of Missouri River Alluvial Aquifer  Bedrock and valley walls (14.9 kb)

The alluvial deposits lie atop thin units of Pennsylvanian-age shale, limestone, sandstone, siltstone, conglomerate, coal and clay. These rocks define the bottom and walls of the alluvial aquifer (Gentile and others, 1994). The altitude of the bedrock surface below the alluvial aquifer as determined from existing borehole and well data (Kelly and Blevins, 1995), is bowl-shaped in cross-section with steeply sloping sides, a relatively flat bottom, and several deeply incised narrow channels. The incised channels probably were formed by erosion of the relatively soft bedrock clay and shale when glacial ice dams melted and released large quantities of water. (McCourt and others, 1917; Fischel, 1948; Hasan and others, 1988).

Alluvial deposits

The uppermost finer-grained clays, silty clays and clayey silts are recent (Holocene) alluvial deposits and the lower coarser sands, gravels, cobbles, and boulders are believed to be Wisconsinian-age alluvial deposits of glacial origin (Hasan and others, 1988). Although grain size typically increases with depth, grain-size distribution in locally heterogeneous deposits can be reversed. Lithologic sections for 13 locations in the study area (plate 1) were developed from existing well-cutting descriptions and borehole log data to illustrate the shape of the alluvial aquifer and the extent and lithology of the alluvial deposits.

Missouri River Alluvial Aquifer Lithologic Section (12.1 kb)

Lithologic sections A-A', B-B', E-E', F-F', G-G', and I-I', show the alluvial deposits of the Missouri River. The typical grain-size distribution includes several meters of fine-grained clays and silts at shallow depths, a thick layer of sand and gravelly sand in the middle depths, and a thin layer of sandy-gravel, gravel, and boulders in the deepest parts of the aquifer. Lithologic sections E-E' and F-F' illustrate the depth and shape of deeply-incised bedrock channels.

Cross-Section locations

Lithologic sections C-C' and D-D', show the alluvial deposits of the Kansas River. These deposits are similar to those of the Missouri River. Lithologic section C-C' illustrates a heterogeneous grain size distribution containing more silts and silty sands than the Missouri River alluvium, and the presence of a deep bedrock channel at the mouth of the Kansas river. Lithologic section D-D' reveals a grain-size distribution and bowl-shaped bedrock surface more like that of the Missouri River alluvium.

Cross-Section locations

Lithologic sections H-H', J-J', K-K', and L-L', show the alluvial deposits of the Little Blue river and an abandoned channel near Lake City Army Ammunition Plant. The grain-size distribution is similar to that found in the Missouri and Kansas river deposits except that thicker clay and silty clay deposits are present at shallow depths and fewer sandy gravels and gravels are present at depth.

Cross-Section locations

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Contact address:

Brian P. Kelly, Hydrologist
U.S. Geological Survey
401 NW Capital Drive
Lee's Summit, MO 64086
PHONE: 816-554-2414
FAX: 816-554-9273
EMAIL: bkelly@usgs.gov

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