Seismic and borehole data at Dumas, Saskatchewan (T. 11, R.1 & 2, W2M) and surface geology and well control at Eagle Butte, Alberta (T. 8 & 9, R. 4 & 5, W4M) reveal structural features that suggest hyper–velocity impact during late Cretaceous time.

In both instances, the anomaly consists of a pronounced, highly disturbed central uplift, a rim syncline, and the suggestion of a positive outer lip. Although some deformation persists into Paleozoic strata, the majority of the relief involves Mesozoic rocks.

Subsurface information appears to rule out any possibility of explaining these features by means of deep–seated tectonic activity and/or solution collapse phenomena.

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