This report details the occurrence, geometries, scarp morphology, and paleorupture histories of Quaternary faults of northwest Trans-Pecos Texas and northern Chihuahua, Mexico.

The Solitario is a circular, 14- to 16-krn-diameter, mid-Tertiary laccolithic dome and caldera in southern Trans-Pecos Texas; it is among the world's largest laccoliths.

The 37-Ma-old Infiernito caldera of the northern Chinati Mountains is a major eruptive center of the mid-Tertiary volcanic field of Trans-Pecos Texas. Volcanism in the Chinati Mountains began with eruption of a sequence of rhyolitic to trachytic lavas, the precollapse lavas.

The Hueco Basin of Trans-Pecos Texas, which formed in response to Cenozoic extensional tectonism, lies within the southern Rio Grande rift near the poorly defined boundary between the rift and the southern Basin and Range province.

This guidebook, Hydrogeology of Trans-Pecos Texas, grew out of our interest in the hydrogeology of desert environments.

The hydrochemical history of ground water in the arid southeastern Hueco Bolson and southwestern Diablo Plateau was investigated by collecting soil-moisture samples from unsaturated siliciclastic bolson-fill sediments and groundwater samples from the Diablo Plateau aquifer, the Hueco Bolson silt

The Hueco Basin of Trans-Pecos Texas and Chihuahua, Mexico, formed in response to Basin and Range extensional tectonism that began about 24 Ma ago and continues to the present.

Cretaceous sedimentary rocks and Tertiary intrusive, extrusive, and volcaniclastic rocks dominate the geology of the Hen Egg Mountain and Christmas Mountains quadrangles in the Big Bend region of Texas.

In the western Delaware Basin and southern Central Basin Platform of Trans-Pecos Texas, Upper Permian (Ochoan) evaporite strata host locally voluminous but notoriously unpredictable, sporadic deposits of biogenic native sulfur.