SOUTHERN PACIFIC LINES = of § 
limestone lies on Austin chalk, but in its western part a sheet of 
Upson clay intervenes between them. North of the mountain are 
long slopes of Austin chalk succeeded by slabby buff Eagle Ford 
limestone, which thickens considerably to the west. About 12 
miles north of Odlaw siding is Turkey Mountain, a plug of intrusive 
igneous rock in part capping a mound of Eagle Ford, Buda, and Del 
Rio beds. The railroad is on Austin chalk from Odlaw west for sey- 
eral miles. At Chacon Creek (cha-cone’), southwest of Anacacho 
siding, Anacacho Mountain ends through a rapid thinning of the lime- 
stone or through change of its upper member into softer rocks of the 
San Miguel formation and also of its lower member into Upson clay. 
From Spofford a branch of the Southern Pacific runs to Eagle 
Pass (old Fort Duncan), an important town on the Rio Grande, 34 
miles south. The railroad here is on the broad Rio 
Spofford. Grande Plain, developed on the upper part of the 
Elevation 1,009 feet. Austin chalk, overlain by a thick deposit of sand and 
aerating miles, gravel with much caliche, a covering that extends to 
and beyond Amanda siding. The chalk is revealed 
on Pinto Creek near Pinto siding, in a quarry 3 miles beyond Pinto, 
and also in the arroyos to the south, which cut deeply to reach the 
Rio Grande. Ten miles north of Spofford, just south of Brackett- 
ville, on State highway 3, is Fort Clark, which was established in 
1852 to protect travelers on the old trail. The fort was named from 
Maj. John B. Clark, United States Army. In it have been stationed 
General Gorgas when he was a second lieutenant, General Bulks, 
General Shafter, and General Pershing. In 1931 there were 386 
soldiers and 44 officers there. The fort is near the Las Moras Springs 
(Spanish, moras, blackberries), which ordinarily have an average 
flow of about 22,000,000 gallons a day. (Meinzer.) Still farther 
north is Las Moras Mountain, due to an intrusion of igneous rock 
which has been forced up in molten condition through the Cretaceous 
strata. Other conspicuous igneous masses near by are Elm Moun- 
tain, 10 miles northwest of Pavo siding, and Pinto Mountain, 10 miles 
northwest of Brackettville. 
In the region between Spofford and Del Ric the formations trav- 
ersed are as follows: 
s Thick 
Formation Character ness 
(feet) 
Aust Chalk and soft massive limestone 
Bal Ford Shale and slab lim limestone, buff ye 
60 
Del Rio Bat, fin hard la: 
Georgetown Massive finest ayers, with many Ezogyra arietina__._....-_--.- 60 
Although the general regional dip of the strata is to the east and 
southeast, they are flexed by an anticline with about 150 feet of uplift 
