Glacioeustatic sea level fall marking the base of supercycle TA-1 at 66.5Â Ma recorded by the kaolinization of the Whitemud Formation and the Colgate Member of the Fox Hills Formation

The Colgate Member of the Fox Hills Formation in Montana is an exact correlative of the Whitemud, and kaolinization of the Colgate is due to the same sea level fall from the International Boundary to central North Dakota. The age correlates to the sea level cycle marking the base of supercycle TA-1, and the short duration indicates that this sea level cycle was glacioeustatic.