Trilobites collected during the past 20 years from the Morgan Creek, Point Peak, and San Saba Members of the Wilberns Formation comprise 89 species assigned to 45 genera belonging to zones of the upper Franconian and Trempealeauan Stages of the Upper Cambrian Croixan Series.

The Bofecillos Mountains area of Trans-Pecos Texas contains a Tertiary volcanic vent and a varied sequence of lava flows, tuff, ash-flow tuff, and associated conglomerate, sandstone, and mudrock; after most of the volcanic activity had ceased, the area was block faulled and later dissected into a

Two distinctive subaerial physiographic features that form a substantial portion, by area, of most barrier islands along the Texas coast are the washover fan and the tidal delta. Volumetrically, washover fan deposits and tidal delta deposits form a significant part of each barrier island.

This work was begun in 1964 and substantially completed in 1965; at that time conodont zones had been established in North America only for the Upper Devonian, by Clark and Becker (1960) for the Great Basin and Collinson, Scott, and Rexroad (1962) for the mid-continent.

Texas is no longer a frontier. The expansion of cities, industries, superhighways, and reservoirs, and changing land uses are fast absorbing the open spaces that once were so abundant in Texas.

The Quitman Mountains are part of a narrow mountain range that extends southeastward from near Sierra Blanca, Texas (85 miles southeast of El Paso, Texas), into northern Mexico.

This guidebook is a reprinting of a field guide prepared by Shell Development Company as part of a three-day industrial short course for full-time college teachers in geology, conducted from March 30 to April 1, 1970, by Shell Development Company, Houston, Texas, in cooperation with AGI Council o

Tertiary rocks, including sandstone, conglomerate, shale, pyroclastics, tuff, and lava, are preserved in Big Bend National Park and in a much larger area to the west and northwest. Some of the rocks have distinctive characteristics that enable recognition by their lithology.

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.

The conservation movement has grown enormously in strength and breadth during the last decade as a result of widespread concern about natural resources and the quality of the environment.