The heavy minerals from surface exposures in the Fox Hills, Hell Creek, Ludlow, and Cannonball formations, Morton and Sioux Counties, North Dakota, are studied. Nine mineral zones are established on the basis of heavy mineral frequencies. The first three correspond to lithologic units in the Fox Hills, the third extending to the base of the Breien marine member of the Hell Creek. Zone 4, in the Cannonball River sections, is the lower bed of brown sands in the Breien. Zones 5 and 8 are local. Zone 6 begins in a bentonitic sand in the Breien and extends above the Breien. Zone 7 is in the upper Hell Creek and Ludlow. Zone 9 corresponds to the Cannonball. The Fox Hills and the Cannonball are characterized by a high percentage of green amphibole. The Hell Creek is differentiated by its epidote, garnet, and sphene content.

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