Remotely sensed features such as linear drainages, escarpments, ridges, and aligned playas have been identified on Landsat imagery (scale 1:250,000) of the Texas Panhandle and adjacent regions to allow comparison of these features with detailed regional and site-specific geologic data. Physiographic subdivisions of this area are the High Plains, Canadian Breaks, Rolling Plains, Pecos Valley, and Raton section.

This field guide summarizes recent interpretations of the upper Cenozoic stratigraphy of parts of the Southern High Plains and Rolling Plains in northwestern Texas and eastern New Mexico. Processes that formed lacustrine basins, which pond surface water on the High Plains that is recharged to the Ogallala aquifer. are also described. Field trip stops were selected to illustrate the depositional facies and paleosols of Cenozoic formations, Cenozoic local faunas, and lacustrine basins.

This guidebook, Hydrogeology of Trans-Pecos Texas, grew out of our interest in the hydrogeology of desert environments. After we participated in Marty Mifflin and Jay Quade's 1988 field trip through eastern Nevada; we realized that, although there were many similarities, the hydrogeology of Trans-Pecos Texas was quite different from what we had observed in Nevada. Thus the seed was planted for this field trip and guidebook.

Horizontal drilling in a mature hydrocarbon province such as Texas can increase recovery from reservoirs in which a significant proportion of oil or gas in place remains unrecovered by conventional means. Such drilling has been particularly effective in increasing production where production is from natural fiactures, such as in the Pearsall field of the Austin Chalk trend in South Texas. Production can also be enhanced where the reservoir-quality

Detailed characterization of the spatial distribution of hydraulic conductivity (K) by direct measurement is usually impractical. A viable alternative is to use geologic information and geostatistics to characterize interconnectedness of critical K facies that have a dominant influence on fluid flow. Conditional simulation is introduced herein as a method for estimating aquifer interconnectedness.