Geologic units in Hays county, Texas

Glen Rose Limestone (Early Cretaceous) at surface, covers 50 % of this area

Glen Rose Limestone

Edwards Limestone (Early Cretaceous) at surface, covers 23 % of this area

Edwards Limestone

Pecan Gap Chalk (Late Cretaceous; Gulfian Series) at surface, covers 9 % of this area

Pecan Gap Chalk

Austin Chalk (Late Cretaceous; Gulfian Series) at surface, covers 3 % of this area

Austin Chalk

Del Rio Clay and Georgetown Limestone, undivided (Late Cretaceous; Gulfian Series) at surface, covers 3 % of this area

Del Rio Clay and Georgetown Limestone, undivided

Terrace deposits (Pleistocene and Holocene) at surface, covers 2 % of this area

Terrace deposits

Leona Formation (Pleistocene) at surface, covers 2 % of this area

Leona Formation

Navarro Group and Marlbrook Marl, undivided (Late Cretaceous; Gulfian Series) at surface, covers 2 % of this area

Navarro Group and Marlbrook Marl, undivided

Alluvium (Holocene) at surface, covers 2 % of this area

Alluvium

Eagle Ford Formation and Buda Limestone, undivided (Late Cretaceous) at surface, covers 1 % of this area

Eagle Ford Formation and Buda Limestone, undivided

Buda Limestone and Del Rio Clay, undivided (Late Cretaceous) at surface, covers 0.6 % of this area

Buda Limestone and Del Rio Clay, undivided; Eastern part of Trans-Pecos and High Plains and Western part of Trans-Pecos and North, central, and south Texas including Quaternary for all of west Texas.

Hensell Sand (Early Cretaceous; Comanchean Series) at surface, covers 0.4 % of this area

Hensell Sand

Onion Creek Marl (Pleistocene) at surface, covers 0.4 % of this area

Onion Creek Marl

Cow Creek Limestone, Hammett Shale, and Sycamore Sand, undivided (Early Cretaceous) at surface, covers 0.2 % of this area

Cow Creek Limestone, Hammett Shale, and Sycamore Sand, undivided

Ozan Formation (Late Cretaceous; Gulfian Series) at surface, covers 0.2 % of this area

Ozan Formation

High gravel deposits (Pleistocene) at surface, covers 0.2 % of this area

High gravel deposits

Quaternary deposit, undivided (Quaternary) at surface, covers < 0.1 % of this area

Quaternary deposit, undivided

Eagle Ford Formation (Late Cretaceous) at surface, covers < 0.1 % of this area

Eagle Ford Formation

Willis Formation (Pliocene) at surface, covers < 0.1 % of this area

Willis Formation