In east-central Texas, or the area between the Colorado
and Trinity Rivers, the Wilcox Group (lower Eocene) is divided
into three formations. Up section they are the Hooper,
Simsboro, and Calvert Bluff. At Alcoa and Butler, lower Calvert

Geologic maps that depicts the surface geology of McLennan, Limestone, and Falls Counties and parts of Bosque, Hill, Navarro, Freestone, Leon, Madison, Robertson, Milam, Bell, Lampasas, Coryell, and Hamilton Counties, Texas.

One of the basic mineral resources of Texas is abundant deposits of lignite in Eocene rocks of the Gulf Coastal Plain.

These circulars issued from the Bureau of Economic Geology contain the record of cores and cuttings from well received and described in the Bureau.