Similarity of east-striking magnetic anomalies in east-central Minnesota and northwestern Wisconsin, on opposite sides of the Midcontinent Rift System, implies that Archean and lower Proterozoic rocks in these areas are correlative and have been offset by middle Proterozoic rifting. The anomalies are displaced about 60 km along a direction perpendicular to the rift axis. This distance is regarded as a minimum estimate of crustal spreading associated with rifting. This model provides improved constraints on the magnitude and direction of crustal separation associated with the Midcontinent Rift System.

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