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The clay plain on the south shore of Lake Superior in Ontonagon County, Mich., is underlain by glacial deposits of Valders and post-Valders age consisting of till interbedded with finegrained glaciolacustrine sediments. The surface of the plain is strongly grooved by glacial flutings parallel to the direction of ice motion. The grooves have a regular wavelength that averages 380 feet. In places the grooves are buried by lacustrine sediments of glacial Lake Duluth. Seven or more glacial lake shorelines cross the plain, in places interrupting the grooves. Six shorelines between 650 and 1,200 feet above sea level are attributed to glacial Lake Duluth. One ancient shoreline at about 615 feet altitude is attributed to Lake Nipissing. Lake Duluth was short lived. It formed and withdrew completely between 10,300 and 9,500 before present. More conspicuous shore features were formed by Lake Nipissing at its stand only 15 feet above the level of present Lake Superior. As Lake Duluth withdrew from the Ontonagon Plain, a drainage network formed. The streams followed the grooves that extended downslope toward the lake. The resulting drainage pattern is strongly attenuated downslope, but, except for the attenuation, is similar in its geometry to drainage patterns in well-graded landscapes. The evidence available supports the theory that the spacing of stream bifurcations or junctions in a typical drainage network is random and that stream lengths tend to be proportional to the six-tenths power of the drainage area because of the random arrangement of channels. Very little change has taken place in the Ontonagon drainage pattern as a result of piracies or headward migration of divides. The depth of incision of the present valleys is roughly proportional to a function of the drainage area and there is little or no evidence to support the idea of nickpoints that migrate upstream. Instead, the valleys are cut to depths proportional to, the available discharge. The longitudinal profiles of the larger streams' are slightly concave. The streams are adjusted to the bed and bank materials and those in bedrock have steeper gradients than those in unconsolidated deposits. Most of the streams have intricate meander patterns, both of their channels and their valleys. Streams flowing in bedrock, however, have straighter courses. Meander wavelength increases in a regular manner as average discharge increases, and is also affected by the materials in the valley; streams in bedrock have meanders about four times the wavelength of streams in till. It is concluded that the evolution of the drainage system in the Ontonagon area has proceeded in response to upstream factors, such as available discharge and the geology of the drainage basin. Changes in base level have affected the streams mainly by changing the relief and the available potential energy in the landscape.

Postglacial drainage evolution and stream geometry in the Ontonagon area, Michigan