Publication 23

North American Central Plains Conductivity Anomaly goes East

Alan G. Jones and Peter J. Savage


The North American Central Plains electrical conductivity (NACP) anomaly has been known for almost two decades, and its influence on palaeotectonic models of the North American continent has been significant. Magnetometer array studies have located the structure in a gross sense, but there has not been, until now, a comprehensive magnetotelluric (MT) survey of it. In this letter we report on the preliminary interpretation of data from thirty-five MT sites recorded along a 400 km East-West profile just north of the US-Canadian border. We show that the anomaly at this latitude is 75 km farther east of the location previously mapped by the array studies. Modelling indicates that the conductive body has its top surface at about 10 km depth and appears to be anticlinal in shape. The profile also extends sufficiently east that it traverses another previously known electrical structure, referred to herein as the TOBE anomaly. We consider briefly other geophysical and geological data for the region, and tentatively infer that the NACP structure is terminated to the east by the interpreted southern extension of the Tabbernor fault/fold system, and that the TOBE anomaly is an expression of the known southern extension of the Thompson nickel belt, both beneath Phanerozoic sediments of the Williston Basin.


Geophysical Research Letters, 13, 685-688, 1986.

Request reprint of publication 23

MTNet Home Page Alan's Home Page

Alan G Jones / 10 June 2004 /