Geologic units in Starr county, Texas

Goliad Formation (Miocene) at surface, covers 53 % of this area

Goliad Formation

Jackson Group, undivided (Oligocene and Eocene) at surface, covers 17 % of this area

Jackson Group, undivided

Catahoula Formation and Frio Clay, undivided (Oligocene) at surface, covers 10 % of this area

Catahoula Formation and Frio Clay, undivided

Sand sheet deposits (Holocene) at surface, covers 6 % of this area

Sand sheet deposits

Terrace deposits (Pleistocene and Holocene) at surface, covers 4 % of this area

Terrace deposits

Alluvium (Holocene) at surface, covers 3 % of this area

Alluvium

Dune sand sheet deposits (Holocene) at surface, covers 3 % of this area

Dune sand sheet deposits

Yegua Formation (Middle Eocene) at surface, covers 2 % of this area

Yegua Formation

Uvalde Gravel (Pliocene to Pleistocene) at surface, covers 1 % of this area

Uvalde Gravel

Quaternary deposit, undivided (Quaternary) at surface, covers 0.5 % of this area

Quaternary deposit, undivided

Laredo Formation (Middle Eocene) at surface, covers 0.2 % of this area

Laredo Formation