Eon of geologic time approximately 2.5 billion to 542 million years ago.

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Digital Geologic Map of the Penokean Continental Margin, Northern Michigan and Wisconsin

The data on this CD consist of geographic information system (GIS) coverages and tabular data on the geology of Early Proterozoic and Archean rocks in part of the Early Proterozoic Penokean orogeny. The map emphasizes metasedimentary and metavolcanic rock