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Geologic units in Rockwall county, Texas

Marlbrook Marl (Late Cretaceous; Gulfian Series) at surface, covers 64 % of this area

Marlbrook Marl

Neylandville and Marlbrook Marls, undivided (Late Cretaceous; Gulfian Series) at surface, covers 12 % of this area

Neylandville and Marlbrook Marls, undivided

Neylandville Marl (Late Cretaceous; Gulfian Series) at surface, covers 10 % of this area

Neylandville Marl

Wolfe City Formation (Late Cretaceous; Gulfian Series) at surface, covers 6 % of this area

Wolfe City Formation

Alluvium (Holocene) at surface, covers 4 % of this area

Alluvium

Terrace deposits (Pleistocene and Holocene) at surface, covers 3 % of this area

Terrace deposits

Nacatoch Sand (Late Cretaceous; Gulfian Series) at surface, covers 0.6 % of this area

Nacatoch Sand

Pecan Gap Chalk (Late Cretaceous; Gulfian Series) at surface, covers 0.2 % of this area

Pecan Gap Chalk

Ozan Formation (Late Cretaceous; Gulfian Series) at surface, covers < 0.1 % of this area

Ozan Formation