Roseau Lake in northwestern Minnesota occupies a conspicuous, circular depression in a level plain of glacial drift. A detailed gravity survey of the lake was made to determine if the Precambrian bed rock under the thin cover of glacial drift exhibited the low-density, fractured character of an impact crater or if the feature was confined solely to the drift. Although a sharp local gravity minimum was found in the vicinity, it is displaced to the northwest in association with a positive magnetic anomaly. Roseau Lake therefore is interpreted to be an exceptionally large glacial kettle.

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