RedN NAWQA
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Red River of the North Basin
National Water-Quality Assessment Program
Brigham, M.E., 1996, Elemental chemistry of bottom sediments of the Red
River of the North and its tributaries in North Dakota, Minnesota, and
Manitoba: Geologic Association of Canada Program with Abstracts, v. 21,
May 27-29, 1996, Winnipeg, Manitoba, p. A-11.
Abstract
The Red River of the North (Red River) is a major sediment source to southern
Lake Winnipeg. This river and its tributaries drain several distinct, major
geomorphic terrains characterized mainly by glacial deposits that vary in
thickness and composition. The morainal region of Minnesota and the glaciated
plains of North Dakota are composed of clayey till and glaciofluvial deposits.
The Lake Agassiz Plain, in the center of the Red River Basin, is composed of
clay-rich glaciolacustrine, beach, and deltaic deposits; similar deposits
exist in the lake-washed till plain of northwestern Minnesota. Bedrock is
exposed in some areas-Cretaceous shales, for example, crop out in the Pembina
River Basin. From 1992-94, 29 bottom sediment samples were collected from the
Red River and its major U.S. tributaries. These samples (<63 micrometer
fraction) were analyzed for 46 chemical elements, including major, minor,
trace, and rare-earth elements. Principal component analysis of the
standardized data produced sensible groupings of analytes: The first two
principal components, which account for 69 percent of the total variance in
the standardized data set, show groupings of elements primarily associated
either with carbonates (Ca, Mg, Na, Eu, inorganic carbon), organic carbon
(with P and S), glaciolacustrine clay (Al, Ti, Fe, K, and several associated
rare-earth elements), or several trace elements (Pb, Ag, Hg, As, Se, Sb, Cd,
Cu, V, Ni). Site scores, based on the first two principal components, tend to
group in four areas that directly relate to the elemental groupings listed
above, and are presented in the same order. Streams in the morainal region of
Minnesota form a group that is close to, but separate from streams in the
glaciated plains. Streams in the Lake Agassiz Plain and sites in the Pembina
River Basin also form separate groups. Given that these terrains have chemically distinct stream sediments, it may be possible to use lake- and stream-sediment geochemistry, coupled with other data (e.g., sediment mineralogy), to ascribe relative amounts of southern Lake Winnipeg sediments to principal terrains in its catchment. Sampling from additional sites was conducted in 1995 to obtain sediment-chemistry data that may increase the precision of a mass balance model. Lake Winnipeg sediments may hold a valuable record of variations in sediment sources from the Red River Basin. This research, which integrates data from the U.S. Geological Survey's National Water-Quality Assessment Program and the Geological Survey of Canada's Lake Winnipeg Project, may help answer questions relating to human-influenced changes in sediment erosion rates over the past century, an important water-quality concern in the region.
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U.S. Department of the Interior |
U.S. Geological Survey