New map reveals origin and geology of North American mid-continent rift


  • W. F. Cannon,

    1. USGS, MS954, Reston, Va., 20192, USA
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  • D. L. Daniels,

  • S. W. Nicholson,

  • J. Phillips,

  • L. G. Woodruff,

  • Val W. Chandler,

  • G. B. Morey,

  • T. Boerboom,

  • K. R. Wirth,

  • M. G. Mudrey Jr.


New aeromagnetic data from the north central United States are helping geophysicists and geologists better understand the 1.1-billion-year-old mid-continent rift, one of the fundamental components of the Precambrian basement of North America.

A detailed geologic map of part of the rift is being made and a myriad of new details concerning the history of rift subsidence, volcanism, sedimentation, and inversion are being deciphered. The data are also helping to establish a link between well-known parts of the rift in the Lake Superior region, where exposures of rift-related rocks are abundant and where a comprehensive geophysical data base has existed for more than a decade, and the buried extension of the rift to the southwest. Scientists from the U.S. Geological Survey (USGS), the Minnesota Geological Survey the Wisconsin Geological and Natural History Survey and Macalester College are using the new data in conjunction with field and laboratory investigations in a joint study that promises to produce new insights into the history and formation of the rift.