Eagle Ford Formation Wikipedia

The Eagle Ford Formation (also called the Eagle Ford Shale) is a sedimentary rock formation from the Cretaceous age underlying much of South and East Texas in United States, consisting of organic matter-rich fossiliferous marine shale.

http://en.wikipedia.org/wiki/Eagle_Ford_Formation

 

Eagle Ford DallasSchematic E-W section showing the Eagle Ford Shale among the geological strata beneath the DFW Metroplex