SOUTHERN PACIFIC LINES 73 
Sabinal (sah-bee-nahl’) is on a sand and gravel plain that borders 
and extends west from the Sabinal River, which is crossed by the rail- 
road a mile west of the station. On this stream there 
Sabinal. is an almost continuous succession of exposures of the 
Reutie ole whup strata of Upper Cretaceous age, beginning with low 
New Orleans 643 miles. Cliffs of Anacacho limestone south of the railroad.® 
The name of the place is derived from the word 
“sabina (sa-bee’na),” the Spanish name for juniper, misapplied by the 
Mexicans to the cypress tree, of which there is a small group on the 
Sabinal River a mile west of the station. 
The Blanco River, which is crossed 4 miles beyond the Sabinal 
River, carries but little water except in times of freshet. Just west 
of it are exposures of alluvial sand and gravel containing much caliche, 
and the ridge near Yucca is one of the numerous remnants of an old 
gravel-capped high terrace in this general region. 
A mile southwest of Knippa is a prominent knoll known as Chat- 
field Hill, caused by a mass of hard diabase which has been intruded 
in the Cretaceous strata. It is similar to many other 
Knippa. igneous masses that are more or less prominent topo- 
ee graphic features in the surrounding region and for a 
New Orleans 654 miles. long distance west. These igneous rocks have come 
in a molten condition through cracks from a deep- 
seated source and either formed irregular conical masses or spread 
out in “sills” or layers between the sedimentary strata. They lift 
the overlying beds and in many places flex or break them irregularly. 
The mass near Knippa is extensively quarried for road metal just 
south of the railroad. A notable feature seen especially in the upper 
part of the quarries is the columnar structure of the rock, such as is 
developed in many intruded igneous masses (notably in the Palisades 
of the Hudson opposite New York City). This structure is developed 
y shrinkage in cooling, both in intrusive masses and in many lava 
flows. <A portion of oneof the quarries is shownin Plate 9,C. Just 
north of Chatfield Hill the railroad crosses two main branches of the 
Frio River (free’o), which comes from the Edwards Plateau. The 
size of the bridges at this place indicates that provision is made for 
the passage of a great body of water in time of freshet. A short 
distance farther west are conspicuous limestone hills a mile or so 
north of the railroad which consist of an upfaulted block of George- 
town limestone. In the adjoining foothills are extensive outcrops of 
** The Anacacho limestone crops out | adjoining slopes 4 miles north of Sa- 
at intervals to the north for 4 miles, | bi 
with a short interruption caused by a 
low arch and fault that reveal the 
underlying Austin chalk. This chalk 
pears in the river banks and on 
152109°—33——_6 
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