El Pico Clay
(Eocene) at surface, covers 22 % of this area El Pico Clay
Leona Formation
(Pleistocene) at surface, covers 16 % of this area Leona Formation
Laredo Formation
(Middle Eocene) at surface, covers 13 % of this area Laredo Formation
Terrace deposits
(Pleistocene and Holocene) at surface, covers 9 % of this area Terrace deposits
Alluvium
(Holocene) at surface, covers 8 % of this area Alluvium
Carizzo Sand
(Eocene) at surface, covers 7 % of this area Carizzo Sand
Uvalde Gravel
(Pliocene to Pleistocene) at surface, covers 4 % of this area Uvalde Gravel
Indio Formation
(Paleocene to Eocene) at surface, covers 4 % of this area Indio Formation
Escondido Formation
(Late Cretaceous; Gulfian Series) at surface, covers 0.3 % of this area Escondido Formation
Kincaid Formation
(Paleocene) at surface, covers 0.1 % of this area Kincaid Formation