CGRG Bibliography of Canadian Geomorphology
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Author : Brigham, M.E.
Date : 1996
Title : Elemental chemistry of bottom sediments of the Red River of the North and its tributaries in North Dakota, Minnesota, and Manitoba
Publication : Geologic Association of Canada Program with Abstracts, v. 21, May 27-29, 1996, Winnipeg, Manitoba,
Issue :
Page(s) : A11
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.
Bibliography of Canadian Geomorphology