A 250 km long east-west geological and geophysical transect has been constructed at about 66 degrees 40'N latitude, from near the Yukon-Alaska border, across the Eagle Plains and Richardson Mountains Anticlinorium (RMA), to the Interior Platform in northwestern Canada. It includes reprocessed industry seismic reflection profiles, regional gravity data and drill hole information. The north trending RMA is interpreted as a contractional (pop-up) structure, bounded on the east and west by post-Carboniferous, pre- or syn-Cretaceous thrust faults, that is cored by lower Paleozoic and Proterozoic rocks. The location of the pop-up may have been controlled by a pre-existing west-facing crustal scale ramp at the top of the crystalline basement, because horizontal displacement required to accommodate the pop-up, about 33 km, probably occurred above regional detachment(s) which project westward beneath the Eagle Plains. Contractional deformation in the Eagle Plain fold belt is probably the same age.
