54 
RIO GRANDE COAL FIELDS OF TEXAS. 
[BULL. 164. 
taining lignite beds. The actual base of the series in the positively 
known and inferred localities is sandstone. The immediately succeed- 
ing beds may be mostly sandstones, as along the Frio, or there may 
be much clay, as along the Rio Grande. The variations of the sections 
can be discovered only by very detailed mapping-. 
The coarse-grained Carrizo sandstone seems a fairly persistent mem- 
ber. It outcrops around the Chupadero ranch, between India ranch 
and San Lorenzo Creek, and extends northward on the west side of 
Carrizo Springs. A very similar sandstone outcrops in the hills 
around the Turk ranch, in the northwestern corner of Zavalla County, 
Fig. 6.— Sandstone and clays above coal horizon (Santo Tomas seam) at Santo Tomas. 
and near the Habey ranch on the Nueces. It is seen 12^ miles south 
of Uvalde, between the Leona and Nueces rivers, along the road to 
Batesville, and apparently extends southward to Loma Yista. It also 
occurs on the divide in southern Uvalde County, between the Leona 
and Frio rivers. 
Above this sandstone are alternations of finer-grained sandstones 
and clays, and it is in these sandstones and clays that most of the lig- 
nite beds occur. 
NEOCENE AND PLEISTOCENE. 
The formations of these ages have received so much attention in the 
paper entitled Geology of the Edwards Plateau and Rio Grande Plain, 
etc., 1 that it does not appear necessary to say a great deal here. 
Eighteenth Ann. Eept. U. S. Geol. Survey, Pt. II. 
