80 RIO GRANDE COAL FIELDS OF TEXAS. [bull. 164. 
The lower limit in thickness occurs over a very small area; the average thickness 
is about 2 feet. In this seam a binder occurs. The binder consists of two thin 
seams of sand, and varies in thickness from half an inch to 2 inches. Between 
the seams of sand is a thin coal seam about half an inch thick. Of this coal seam 
where examined: 
a. Upper 9-inch does not coke. 
b. Nine inches just above binder coking. 
c. Binder. 
d. Below binder, 9 inches, coal all coking. 1 
3. Carbonaceous shale 1 to 3 in. 
2. Fire clay 2 ft.'- 2 
I. Sandstone. 
This section of the coal corresponds to Nos. 13 to 6, inclusive, of the 
general section of the mountain. 
Along the side of the mountain the usual dip is 5° to 7° (though it 
may sometimes be more or less), and the strike is N. 35° to 50° E. 
Section in arroyo northeast of shaft of San Carlos Coal Company, 2 miles east of south of 
San Carlos. 
(PI. XI, fig. 25.) 
Feet. 
II. Soft yellow sandstone 10 
10. Yellow clays 10 
9. Ledge of soft yellow sandstone 15 
8. Clay. 
7. Coal, upper seam. 
6. Clay. 
5. Coal, lower seam. 
4. Soft yellow sandstone. 6 
3. Bluish clay, with fossils, Cyprimeria, Inoceramus, Exogyra, etc 35 
2. Layer of clay containing many limestone nodules and fossils 1 
1. Clay. 
Above the soft sandstone (No. 11) are two other prominent sand- 
stone ledges, about 30 feet apart, the upper of which is conglomeritic. 
The strike of the rocks at the foregoing exposure is southwest and 
northeast, dip 20° to 30° SE. 
Fossils from No. 3 {field No. 299). 
Ostrea sp. 
Exogyra costata Say var. 
Inoceramus sp., fragments of a large form. 
Trigonia sp. 
Cyprimeria sp., the same as for field Nos. 297 and 298. 
OVERTURNED FOLD NORTH OF SHAFT OF SAN CARLOS COAL COMPANY. 
A short distance north of the shaft of the San Carlos Coal Company 
there is a small overturned fold accompanied by an overthrust fault. On 
the overthrust side ol the fault a fossil if erous horizon is exposed, but it 
1 The information concerning what part of the coal seam would coke was furnished by Mr. Maloney, 
mine superintendent. Samples of the coke were furnished by the mine officials. 
2 Or more. 
