This Guidebook represents an updating of Bureau of Economic Geology Guidebook No. 5, Field Excursion-Geology of Llano Region and Austin Area. It also represents a modification of Geology of the Llano Region and Austin Area, Texas, published by the Shreveport Geological Society in 1971.

Basic geologic, hydrologic and engineering criteria on which selection of sanitary landfill sites should be based include (1) thickness, excavation characteristics, permeability, solution-holding capacity, and reactivity of host and cover materials; (2) hydrologic properties including depth to water table, season variation in position of water table, and rate of liquid movement; and (3) nature of terrain in terms of slope, topography, and surface drainage.

A study of Gum Hollow delta, a modern fan delta along the north shore of Nueces Bay, Texas, was undertaken to determine the mechanics of fan development and the relationships between sedimentary processes and structures. In addition this study provides criteria that can be utilized in recognizing ancient fan delta deposits and in making a distinction between ancient fan and bayhead deltas. Further, the study documents changes in form of the fan and relates these changes to specific geologic processes.

A resource capability unit is an environmental entity--land, water, area of active process, or biota--defined in terms of the nature, degree of activity, or use it can sustain without losing an acceptable level of environmental quality. Units are established by recognizing elements of first-order environmental significance, whether dominantly physical, biologic, or chemical.