A study, extending from western Mississippi across Louisiana and into East Texas, of the surface stratigraphy of the Vicksburg (Oligocene) equivalent in Louisiana reveals that five units comprise the sequence from upper Jackson (Eocene) to lower Catahoula (Miocene): (5) massive quartzose sandstone; Cassels Hill Member of the Catahoula Formation (20-50 feet); (4) clays and silts, fossiliferous and calcareous; east of Sabine Parish designated Rosefield Formation and in Sabine Parish and farther westward called Nash Creek Formation (25-70 feet); (3) well sorted quartzose sand; Sandel Formation (20 feet); (2) chocolate clays and lenticular quartzose sands; Mosley Hill Formation (80 feet); (1) khaki-colored fossiliferous clays; Danville Landing Beds (100+feet).

These units remain consistent and persistent along strike across Louisiana. The three middle units represent the original Mosley Hill group thought to be Oligocene by Murray, but in this paper the Mosely Hill is restricted to the lower unit which is present at the type locality. The names Sandel and Rosefield are new. The maximum thickness of the total sequence is 180 feet in Catahoula Parish. The Cassels Hill Formation is separated from the Rosefield Formation by a disconformity beneath which the Rosefield decreases in thickness from 70 feet in Catahoula Parish to 7 feet in western Louisiana and East Texas.

The Mint Spring Marl of the lower Vicksburg sequence in Mississippi is subdivided into the underlying marl facies which extends westward and the overlying carbonate facies which extends eastward. The Rosefield Formation of Louisiana is thought to correlate with the entire Vicksburg sequence at Vicksburg plus the uppermost 15 feet of the Forest Hill of Mississippi. The Sandel and upper Mosley Hill represent the Forest Hill (restricted) of Mississippi and the Danville Landing is upper Yazoo equivalent. The Sandel pinches out westward into Texas so that there is no separation between the Mosley Hill and Rosefield clay and silt sequences, both of which are represented in the type Manning of Texas.

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