Successive glacial advances dammed and diverted existent streams during the Pleistocene Epoch in North Dakota causing meltwater to cut a complex system of trenches and change the drainage pattern from northeast- to southeast-trending. Most of the Pleistocene and pre-Pleistocene drainage channels in North Dakota are buried beneath glacial drift, but many buried preglacial valleys can be distinguished from buried glacial diversion trenches by a study of their width, shape, trend, and contents. Some of the diversion trenches are composite features comprised of segments ranging in age from preglacial to late Wisconsinan. The best example of such a trench in North Dakota is the modern Missouri River Valley.

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