Walnut Clay
  Glen Rose Fm.

Paluxy Formation
(c. 105.6 mya to c. 108 mya)

The Geology of Tarrant County

" This sand, the westernmost outcropping formation in the county, is exposed in the valley of the West Fork, in the northwest corner of the county. It is an artesian water reservoir and consists of alternating layers of rather unconsolidated sands and compact clay, the formation being iron-stained but free from gypsum, and its water of a correspondingly good quality. On exposure the material is seen to be poorly consolidated, and readily disintegrated; it contains rounded concretions and phosphate nodules. The Paluxy sand is about 100 feet thick and contains three principal artesian layers. It is poor in fossils."

Early Cretaceous Vertebrates of Texas

" The Paluxy Formation throughout northeastern Texas consists of a series of sandstone and shale units representing fluvial meanderbelt to coastal barrier and deltaic facies (Caughey, 1977). The marine Walnut Formation of Albian age laterally replaces the Paluxy near Waco (Atlee, 1962; Boone, 1968; Caughey, 1977)."

Geology Pics:

Primary rock type: Sandstone
Paluxy Sand
 Walnut Formation
An old sand pit
 An old sand pit
 Outcrop map

These above pictures are from a large exposure of Paluxy Sand in western Tarrant County, Texas.  The Paluxy Sand is capped by the Walnut Formation [16-18 feet] which is largely a conglomerate of Gryphea shells.