Introduction to the bedrock geology of Minnesota



Geoterrane map

Bedrock exposure map

Minnesota's geologic framework is moderately well known from a combination of outcrop mapping where exposure permits, and interpretation of high resolution geophysical data and drilling where it does not. The state is underlain by rocks of Precambrian age that are covered in part by veneers of Paleozoic and Mesozoic (Phanerozoic) marine strata and rather extensively by Quaternary glacial deposits. The Late Archean rocks of the Superior Province and the Early Proterozoic rocks of the Penokean orogen are southwestern extensions of counterparts in southern Ontario that are noteworthy for their abundance of metallic mineral deposits. The mafic igneous rocks within the Middle Proterozoic Midcontinent Rift System trend obliquely across the regional east-northeast strike of the older rocks and separate the Minnesota segments of some lithotectonic belts from their equivalents to the east and northeast in Wisconsin, Upper Michigan, and Ontario. Nevertheless, the geological continuity of Late Archean and Early Proterozoic belts from Ontario into Minnesota is well established.

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